KR102715822B1 - Method for manufacturing resin-attached metal foil, resin-attached metal foil, laminate and printed circuit board - Google Patents

Abstract

Provided are: a resin-attached metal foil having excellent electrical properties and mechanical strength, and a resin layer with excellent adhesiveness useful as a printed circuit board material, which does not bend easily, a method for producing the same, and a printed circuit board. A method for producing a resin-attached metal foil having a resin layer on the surface of the metal foil, comprising: applying a powder dispersion containing a tetrafluoroethylene polymer powder, a dispersant having a mass reduction rate of 1 mass%/min or more in a temperature range of 80 to 300°C, and a solvent, to the surface of the metal foil, maintaining the metal foil at a temperature at which the mass reduction rate in the temperature range becomes 1 mass%/min or more, and firing the tetrafluoroethylene polymer at a temperature exceeding the temperature range, to form a resin layer containing the tetrafluoroethylene polymer on the surface of the metal foil.

Description

Method for manufacturing resin-attached metal foil, resin-attached metal foil, laminate and printed circuit board

The present invention relates to a method for manufacturing a resin-attached metal foil, a resin-attached metal foil, a laminate, and a printed circuit board.

A metal foil having a resin attached to the surface of the metal foil having an insulating resin layer is used as a printed circuit board by forming a transmission circuit by processing the metal foil by etching or the like.

Printed circuit boards used for transmitting high-frequency signals are required to have excellent transmission characteristics. In order to improve transmission characteristics, it is necessary to use a resin with low dielectric constant and dielectric loss tangent as the insulating resin layer of the printed circuit board. Fluoropolymers such as polytetrafluoroethylene (PTFE) are known as resins with low dielectric constant and dielectric loss tangent.

As a material for forming a resin-attached metal foil having an insulating resin layer including a fluoropolymer, a powder dispersion in which a fluoropolymer powder is dispersed in a solvent has been proposed (see Patent Documents 1 to 3). This powder dispersion has the advantage of being able to arbitrarily adjust various physical properties of the resulting resin-attached metal foil by blending other insulating resins and varnishes thereof, and the advantage of being able to form a resin-attached metal foil simply by applying the powder dispersion to the surface of the metal foil and drying it.

In addition, with the increase in the density of electronic devices, multilayering of printed circuit boards is being considered, in which printed circuit boards are bonded to each other using other substrates such as prepregs.

As a study on multilayering a printed circuit board formed of a metal foil with a resin attached thereto using a fluoropolymer as an insulating resin layer, there is a study on forming a covering layer of a silane coupling agent having silicon atoms, nitrogen atoms or sulfur atoms on the insulating resin layer of the printed circuit board, and bonding the covering layer and a prepreg having a specific fluoropolymer as a main component by thermocompression (see Patent Document 4).

International Publication No. 2017/222027 International Publication No. 2016/159102 Japanese Patent Publication No. 2017-193655 Japanese Patent Publication No. 2018-011033

In an embodiment of multilayering by laminating another substrate (prepreg, etc.) on the surface of an insulating resin layer including a fluoropolymer, or in an embodiment of packaging by laminating another substrate (coverlay film, etc.) on the surface of the insulating resin layer, the insulating resin layer and the other substrate need to be firmly laminated from the viewpoint of electrical characteristics or productivity of the resulting printed circuit board.

However, fluoropolymers are inherently hydrophobic and have low adhesiveness, and it is not easy to firmly laminate the insulating resin layer with another substrate. A method of modifying the resin layer into hydrophilicity and imparting adhesiveness by surface treatment (plasma treatment, corona treatment, electron beam treatment, etc.) is known. However, surface treatment sometimes induces temporal degeneration or shape change, thereby impairing the original electrical properties or mechanical strength of the insulating resin layer.

In this way, there is a need for a method for manufacturing a resin-attached metal foil having an insulating resin layer having particularly excellent adhesive properties while having various physical properties including a fluoropolymer, from a powder dispersion containing a fluoropolymer powder.

In addition, since fluoropolymers have inherently low adhesiveness and high thermal elasticity, it is not easy to form a multilayer printed circuit board formed with a metal foil to which a resin serving as the insulating resin layer is attached, by firmly bonding it to another substrate such as a prepreg without impairing its dimensional stability.

In the review in Patent Document 4, it is preferable to use a high-melting-point fluoropolymer in order to maintain the transmission characteristics and mechanical strength after multilayering. In this case, when multilayering, it is necessary to thermally bond the print substrate and the prepreg at a high temperature. Therefore, there is a problem that the dimensional stability of the print substrate deteriorates due to the high temperature in the thermal bonding. If the dimensional stability of the print substrate is impaired when multilayering, warping of the obtained multilayer print substrate is likely to become a problem.

In addition, in the process of mounting a printed circuit board, when a method of applying solder paste and heating it (solder reflow method) is adopted, swelling occurs at the interface between the insulating resin layer and the cured layer of the prepreg due to heating, so solder reflow resistance also becomes an issue.

In this way, when multilayering a printed circuit board using a fluoropolymer as an insulating resin layer, a printed circuit board that can be bonded at low temperatures with other substrates such as prepregs without impairing the dimensional stability of the printed circuit board and that does not easily cause swelling during a heating process such as a solder reflow method is required, and a metal foil with a resin attached that can form such a printed circuit board is required.

In addition, in the multilayer substrate described in Patent Document 4, the electrical properties of the insulating resin layer are easily reduced due to the covering layer of the silane coupling agent formed on the insulating resin layer containing the fluoropolymer. In addition, when the insulating resin layer and the prepreg are thermo-compression bonded at high temperature, it is also difficult to use a prepreg containing a matrix resin (such as a matrix resin that does not have a fluorine atom) that generally has lower heat resistance than the fluoropolymer.

In this way, a laminate having a fluoropolymer as an insulating resin layer and a metal foil in which the properties of the materials forming each layer are not impaired, each layer is firmly bonded, and has little warping is required.

The present invention provides an efficient method for manufacturing a resin-attached metal foil having a resin layer having excellent adhesive properties, including a fluoropolymer, which has excellent electrical properties and mechanical strength and is useful for manufacturing a printed circuit board.

The present invention provides a resin-attached metal foil having a resin layer having excellent adhesive properties, including a fluoropolymer, which has excellent electrical properties and mechanical strength and is useful for manufacturing a printed circuit board.

The present invention provides a laminate and a printed circuit board having excellent transmission characteristics and mechanical strength, in which each layer is firmly bonded, and with little warping.

The present invention has the following aspects.

[1] A method for manufacturing a resin-attached metal foil having a resin layer on the surface of the metal foil, comprising: applying a powder dispersion containing a tetrafluoroethylene polymer powder, a dispersant having a mass reduction rate of 1 mass%/min or more in a temperature range of 80 to 300°C, and a solvent to the surface of the metal foil; maintaining the metal foil at a temperature at which the mass reduction rate in the temperature range becomes 1 mass%/min or more; and firing the tetrafluoroethylene polymer at a temperature exceeding the temperature range to form a resin layer containing the tetrafluoroethylene polymer on the surface of the metal foil.

[2] The manufacturing method described in [1], wherein the water contact angle of the resin layer is 70 to 100°.

[3] A manufacturing method according to [1] or [2], wherein the dispersant is a polymer having a polyfluoroalkyl group or polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in the side chain.

[4] A manufacturing method according to any one of [1] to [3], wherein the temperature at which the metal foil is maintained in the above temperature range is 100 to 300°C.

[5] A manufacturing method according to any one of [1] to [4], wherein the atmosphere when maintaining the metal foil in the above temperature range is an atmosphere containing oxygen gas.

[6] A manufacturing method according to any one of [1] to [5], wherein the temperature at which the tetrafluoroethylene polymer is sintered is 330 to 380°C.

[7] A metal foil having a resin attached thereto, the metal foil having, in this order, a resin layer including a tetrafluoroethylene polymer, and an adhesive portion including a hydrophilic component having at least one selected from the group consisting of an ethereal oxygen atom, a hydroxyl group, and a carboxyl group, wherein the resin layer and the adhesive portion are in contact with each other.

[8] Metal foil with resin attached as described in [7], wherein the above-mentioned bonding portion exists in an island form.

[9] A metal foil having a resin attached thereto as described in [7] or [8], wherein the hydrophilic component is derived from a polymer having a polyfluoroalkyl group or a polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in the side chain.

[10] A method for producing a laminate, comprising bonding a metal foil to which a resin as described in any one of the above [7] to [9] is attached to another substrate by a heat press method to obtain a laminate.

[11] A laminate having a metal foil, a resin layer including a tetrafluoroethylene polymer, and a cured layer of a prepreg including a matrix resin in this order, and further having a commercial layer between the resin layer and the cured layer, the commercial layer including a component having fluorine atoms and oxygen atoms in contact with the resin layer and the cured layer.

[12] A laminate as described in [11], wherein the thickness of the commercial layer is 1 to 500 nm.

[13] A laminate as described in [11] or [12], wherein the commercial layer is derived from a polymer having a polyfluoroalkyl group or a polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in the side chain.

[14] A laminate according to any one of [11] to [13], wherein the matrix resin is at least one matrix resin that does not have a fluorine atom and is selected from the group consisting of an epoxy resin, polyphenylene oxide, polyphenylene ether, and polybutadiene.

[15] A printed circuit board having a transmission circuit, a resin layer including a tetrafluoroethylene polymer, and a cured layer of a prepreg including a matrix resin in this order, and further having a commercial layer between the resin layer and the cured layer, the commercial layer including a component having fluorine atoms and oxygen atoms in contact with the resin layer and the cured layer.

According to the manufacturing method of the present invention, it is possible to efficiently manufacture a resin-attached metal foil having a resin layer having excellent adhesive properties, including a fluoropolymer, which has electrical properties and mechanical strength and is useful for manufacturing a printed circuit board.

The metal foil with a resin attached to it of the present invention can be bonded at low temperatures to another substrate without impairing its dimensional stability, despite having a resin layer containing a fluoropolymer. In addition, when used as a printed circuit board, it has excellent heat resistance and is unlikely to cause swelling.

The laminate of the present invention has excellent transmission characteristics and mechanical strength, each layer is firmly bonded, and has little warping.

The printed board of the present invention has excellent transmission characteristics and mechanical strength, each layer is firmly bonded, and has little warping. According to the present invention, a printed board having excellent transmission characteristics and mechanical strength, each layer is firmly bonded, and has little warping can be manufactured.

Figure 1 is an image obtained by analyzing the surface of the resin layer of copper foil A to which resin is attached in Example 3-1 of the embodiment using the AFM-IR method.
Fig. 2 is a scanning electron microscope photograph of a cross-section of laminate B in Example 4-1 of the embodiment.

The following terms have the following meanings.

"Powder D50" is the cumulative 50% diameter of the powder based on the volume obtained by the laser diffraction/scattering method. In other words, the particle size distribution of the powder is measured by the laser diffraction/scattering method, the total volume of the particle group is 100%, and the cumulative curve is obtained, and it is the particle diameter of the point on the cumulative curve where the cumulative volume becomes 50%.

"Powder D90" is the cumulative 90% diameter of the powder based on the volume obtained by the laser diffraction/scattering method. In other words, the particle size distribution of the powder is measured by the laser diffraction/scattering method, the total volume of the particle group is 100%, and the cumulative curve is obtained, and it is the particle diameter of the point on the cumulative curve where the cumulative volume is 90%.

"Melt viscosity of polymer" is a value measured in accordance with ASTM D 1238 using a flow tester and a 2Φ-8L die, with a polymer sample (2 g) heated at a pre-measured temperature for 5 minutes and maintained at the measurement temperature with a load of 0.7 MPa.

The "melting point of a polymer" is the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC).

The “mass reduction rate of the dispersant” is the mass reduction amount of the dispersant when the temperature of the dispersant is increased from the lower limit to the upper limit of the temperature range, divided by the temperature increase time and the amount of dispersant sample.

"Bending rate" is a value measured by cutting a square test piece measuring 180 mm in length and width from a sample (metal foil with resin attached, laminate, etc.) and using the measurement method specified in JIS C 6471: 1995 (IEC 249-1: 1982).

The "dimensional change rate" is a value obtained as follows. Cut the sample (metal foil with resin attached, laminate, etc.) into 150 mm by 150 mm pieces, drill holes at the four corners using a 0.3 mm drill, and measure the positions of the holes with a three-dimensional measuring device. Etch away the metal foil of the resin attached metal foil, and dry at 130°C for 30 minutes. Measure the positions of the holes drilled at the four corners with a three-dimensional measuring device. The dimensional change rate is calculated from the difference in the positions of the holes before and after etching.

The "arithmetic mean roughness Ra" and "maximum height Rz" are the values measured on the surface (1 ㎛ ² range) of a sample (metal foil with resin attached, laminate, etc.) using an atomic force microscope (AFM) manufactured by Oxford Instruments under the following measurement conditions.

Probe: AC160TS-C3 (tip R < 7 nm, spring constant 26 N/m), Measurement mode: AC-Air, Scan Rate: 1 Hz.

"Permittivity (20 ㎓) and dielectric loss factor (20 ㎓)" are the values measured at a frequency of 20 ㎓ in an environment within the range of 23 ℃ ± 2 ℃, 50 ± 5% RH by the SPDR (Split Post Dielectric Resonator) method.

“Heat-resistant resin” means a polymer compound having a melting point of 280°C or higher, or a polymer compound having a maximum continuous use temperature of 121°C or higher as specified in JIS C 4003:2010 (IEC 60085:2007).

“(Meth)acrylate” is a general term for acrylate and methacrylate.

The "unit" in a polymer may be an atomic group formed directly from a monomer by a polymerization reaction, or may be an atomic group whose structure is partially converted by processing a polymer obtained by a polymerization reaction by a predetermined method. A unit based on monomer A contained in a polymer is also simply referred to as "unit A."

The method for manufacturing a metal foil having a resin attached thereto according to the present invention is a method of applying a powder dispersion containing a specific powder, a specific dispersant, and a solvent to the surface of a metal foil, and gradually heating and maintaining the dispersion in a specific temperature atmosphere to form a resin layer (hereinafter also referred to as an “F resin layer”) containing a tetrafluoroethylene polymer (hereinafter also referred to as a “TFE polymer”) on the surface of the metal foil. The powder dispersion in the present invention is a dispersion in which a powder of a TFE polymer is dispersed in a particle form.

The reason why the F resin layer of the resin-attached metal foil obtained by the manufacturing method of the present invention has excellent adhesion to other substrates is not necessarily clear, but is thought to be as follows.

The powder dispersion in the present invention contains a dispersant exhibiting a predetermined mass reduction rate (a mass reduction rate of 1 mass%/min or more in a temperature range of 80 to 300°C), and due to the high degree of interaction between the powder of the TFE-based polymer and the dispersant, the dispersion stability and the packing ability of the powder at the time of application are high. In short, when this powder dispersion is applied to the surface of a metal foil and maintained at a predetermined temperature (a temperature at which a mass reduction rate of 1 mass%/min or more in a temperature range of 80 to 300°C occurs), a highly smooth film in which specific powders are densely packed is formed as the solvent volatilizes and the dispersant decomposes. In addition, it is thought that at this time, the dispersant becomes hydrophilic and easily floats around the specific powder, thereby easily flowing to the surface. Therefore, it is also thought that by this maintenance, a state in which a hydrophilic component is segregated on the surface is formed.

In the present invention, since the F resin layer is formed from the film at a higher temperature (a temperature exceeding the above temperature range) in this state, it is thought that, as a result, the surface of the F resin layer has high hydrophilicity and smoothness, and a metal foil with a resin attached thereto having an F resin layer with excellent adhesiveness is obtained.

The metal foil to which the resin is attached in the manufacturing method of the present invention has an F resin layer on at least one surface of the metal foil. In short, the metal foil to which the resin is attached may have an F resin layer on only one surface of the metal foil, or may have an F resin layer on both surfaces of the metal foil.

The warpage ratio of the resin-attached metal foil is preferably 25% or less, and particularly preferably 7% or less. The lower limit of the warpage ratio is usually 0%. In this case, the handling properties when processing the resin-attached metal foil into a printed circuit board and the transfer properties of the resulting printed circuit board are excellent.

The dimensional change rate of the metal foil with the resin attached is preferably ±1% or less, and particularly preferably ±0.2% or less. In this case, it is easy to multilayer the printed circuit board obtained from the metal foil with the resin attached.

Examples of the material of the metal foil in the present invention include copper, copper alloy, stainless steel, nickel, nickel alloy (including 42 alloy), aluminum, aluminum alloy, titanium, titanium alloy, etc.

Examples of metal foil include rolled copper foil and electrolytic copper foil. On the surface of the metal foil, a rust-preventive layer (such as an oxide film such as chromate), a heat-resistant layer, etc. may be formed.

The 10-point average roughness of the surface of the metal foil is preferably 0.2 to 1.5 ㎛. In this case, the adhesion to the F resin layer is improved, and a printed circuit board with excellent transmission characteristics can be easily obtained.

The thickness of the metal foil may be any thickness that can function for the purpose of the metal foil to which the resin is attached. The thickness of the metal foil is preferably 2 ㎛ or more, and particularly preferably 3 ㎛ or more. In addition, the thickness of the metal foil is preferably 40 ㎛ or less, and particularly preferably 20 ㎛ or less.

The surface of the metal foil may be treated with a silane coupling agent, the entire surface of the metal foil may be treated with a silane coupling agent, or a portion of the surface of the metal foil may be treated with a silane coupling agent.

The F resin layer in the manufacturing method of the present invention is a layer formed from a powder dispersion.

As described above, the surface of the F resin layer has hydrophilicity resulting from the dispersant. The water contact angle of the surface of the F resin layer is preferably 70 to 100°, and particularly preferably 70 to 90°. When the range is below the upper limit, the adhesion between the F resin layer and another substrate is more excellent. When the range is above the lower limit, the electrical characteristics (low dielectric loss and low dielectric constant) of the F resin layer are more excellent.

The thickness of the F resin layer is preferably 1 µm or more, more preferably 2 µm or more, and particularly preferably 5 µm or more. In addition, the thickness of the F resin layer is preferably 50 µm or less, more preferably 15 µm or less, and particularly preferably less than 10 µm. In this range, it is easy to balance the transfer characteristics of the printed circuit board and the suppression of warpage of the metal foil to which the resin is attached. When the metal foil to which the resin is attached has F resin layers on both surfaces of the metal foil, the composition and thickness of each F resin layer are preferably the same from the viewpoint of suppressing warpage of the metal foil to which the resin is attached.

Specific examples of the thickness of the F resin layer include 1 to 50 ㎛, 1 to 15 ㎛, 1 ㎛ or more and less than 10 ㎛, 5 to 15 ㎛, etc.

The dielectric constant of the F resin layer is preferably 2.0 to 3.5, more preferably 2.0 to 3.0. In this case, the metal foil to which the resin is attached is preferably used for printed circuit boards, etc., where both the electrical properties and adhesive properties of the F resin layer are excellent and a low dielectric constant is required.

The Ra of the surface of the F resin layer is less than the thickness of the F resin layer, and is preferably 2.2 to 8 ㎛. In this range, it is easy to balance the adhesion and processability of other substrates.

The powder dispersion in the present invention comprises a powder having a volume-based cumulative 50% diameter of 0.05 to 6.0 µm including a TFE polymer (hereinafter also referred to as “F powder”), a dispersant having a mass reduction rate of 1 mass%/min or more in a temperature range of 80 to 300°C, and a solvent.

The TFE polymer in the manufacturing method of the present invention is a polymer containing a unit (TFE unit) based on tetrafluoroethylene (TFE). The TFE polymer may be a homopolymer of TFE, or may be a copolymer of TFE and another monomer copolymerizable with TFE (hereinafter also referred to as a comonomer). It is preferable that the TFE polymer contains 90 to 100 mol% of TFE units based on the total units contained in the polymer.

Examples of TFE polymers include polytetrafluoroethylene (PTFE), copolymers of TFE and ethylene (ETFE), copolymers of TFE and propylene, copolymers of TFE and perfluoro(alkyl vinyl ether) (PAVE) (PFA), copolymers of TFE and hexafluoropropylene (HFP) (FEP), and copolymers of TFE and chlorotrifluoroethylene.

The melting temperature of the TFE polymer is preferably 1 × 10 ² to 1 × 10 ⁶ ㎩·s at 380 ° C, preferably 1 × 10 ² to 1 × 10 ⁶ ㎩·s at 340 ° C, and preferably 1 × 10 ² to 1 × 10 ⁶ ㎩·s at 300 ° C. In this case, when the powder dispersion is applied to the surface of a metal foil and maintained at a predetermined temperature (a temperature at which a mass reduction rate within a temperature range of 80 to 300 ° C becomes 1 mass%/min or more), it is easier to form a highly smooth film in which the powder is densely packed.

A preferred embodiment of the TFE polymer is low molecular weight PTFE. The low molecular weight PTFE may be a PTFE in which only the shell portion satisfies the above melt viscosity in a core-shell structure composed of a core portion and a shell portion.

As the low-molecular-weight PTFE, it may be PTFE obtained by irradiating high-molecular-weight PTFE (having a melt viscosity of approximately 1 × 10 ⁹ to 1 × 10 ¹⁰ ㎩ s) with radiation (see International Publication Nos. 2018/026012 and 2018/026017, etc.), or PTFE obtained by reducing the molecular weight by using a chain transfer agent when manufacturing PTFE by polymerizing TFE (see Japanese Patent Application Laid-Open No. 2009-1745 and 2010/114033, etc.).

In addition, the low-molecular-weight PTFE may be a polymer obtained by polymerizing TFE alone, or may be a copolymer obtained by copolymerizing TFE with a comonomer (see International Publication No. 2009/20187, etc.). With respect to the total units included in the polymer, the TFE unit is preferably 99.5 mol% or more, more preferably 99.8 mol% or more, and still more preferably 99.9 mol% or more. When the TFE unit is in the above range, the PTFE properties can be maintained. As the comonomer, examples thereof include the fluoromonomers described below, and HFP, PAVE or FAE are preferable.

As PTFE having a core-shell structure, PTFE described in Japanese Patent Publication No. 2005-527652, International Publication No. 2016/170918, etc. can be mentioned. In order to make the melt viscosity of the shell portion within the above range, a method of lowering the molecular weight of the shell portion by using a chain transfer agent (see Japanese Patent Publication No. 2015-232082, etc.), a method of copolymerizing TFE and the above comonomer during the production of the shell portion (see Japanese Patent Publication No. 09-087334, etc.) can be mentioned.

In the latter case, the amount of comonomer used is preferably 0.001 to 0.05 mol% with respect to TFE. In addition, not only the shell portion but also the core portion may be manufactured by copolymerization. In this case as well, the amount of comonomer used is preferably 0.001 to 0.05 mol% with respect to TFE.

The standard specific gravity of low molecular weight PTFE is preferably 2.14 to 2.22, more preferably 2.16 to 2.20. The standard specific gravity can be measured in accordance with ASTM D4895-04.

A preferred embodiment of the TFE polymer is a fluoropolymer (hereinafter also referred to as “polymer F”) which is a copolymer of TFE and a comonomer and contains more than 0.5 mol% of a unit based on the comonomer based on the total units contained in the copolymer. The melting point of the polymer F is preferably 240°C or higher and less than 330°C, more preferably 260 to 320°C, and particularly preferably 295 to 310°C. In this case, the heat resistance and melt moldability of the polymer are balanced. Examples of the polymer F include ETFE, FEP, and PFA. As the polymer F, in terms of electrical properties (dielectric constant, dielectric loss tangent) and heat resistance, PFA or FEP is more preferable, and PFA is particularly preferable.

Among the TFE polymers, a TFE polymer having at least one functional group (hereinafter also referred to as “functional group”) selected from the group consisting of a carbonyl group-containing group, a hydroxyl group, an epoxy group, an amide group, an amino group, and an isocyanate group is preferable in terms of excellent adhesion between the F resin layer and the metal foil. The functional group may be provided by plasma treatment or the like.

The functional group may be included in a unit of the TFE polymer, or may be included in a terminal group of the main chain of the polymer. As the latter polymer, a polymer having the functional group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc. can be exemplified.

As the polymer F, a polymer including a unit having a functional group and a TFE unit is preferable. In addition, in this case, it is preferable that the polymer F additionally includes another unit (such as a PAVE unit or HFP unit described later).

As a functional group, a carbonyl group-containing group is preferable from the viewpoint of adhesion between the F resin layer and the metal foil. Examples of the carbonyl group-containing group include a carbonate group, a carboxyl group, a haloformyl group, an alkoxycarbonyl group, an acid anhydride residue (-C(O)O(O)C-), a fatty acid residue, and the like, and a carboxyl group and an acid anhydride residue are preferable.

The unit having a functional group is preferably a unit based on a monomer having a functional group, more preferably a unit based on a monomer having a carbonyl group-containing group, a unit based on a monomer having a hydroxyl group, a unit based on a monomer having an epoxy group, and a unit based on a monomer having an isocyanate group, and particularly preferably a unit based on a monomer having a carbonyl group-containing group.

As monomers having a carbonyl group, cyclic monomers having an acid anhydride residue, monomers having a carboxyl group, vinyl esters and (meth)acrylates are preferable, and cyclic monomers having an acid anhydride residue are particularly preferable.

As the above cyclic monomers, itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride (alias: hymic anhydride. Also referred to as “NAH” hereinafter) and maleic anhydride are preferable.

Among units other than units having functional groups and TFE units, HFP units, PAVE units and FAE units are preferable.

As the polymer F, a polymer containing a unit having a functional group, a TFE unit, and a PAVE unit or an HFP unit is preferable. A specific example of such a polymer F is the polymer (X) described in International Publication No. 2018/16644.

The proportion of TFE units in polymer F is preferably 90 to 99 mol% among the total units constituting polymer F.

The proportion of PAVE units or HFP units in polymer F is preferably 0.5 to 9.97 mol% among the total units constituting polymer F.

The proportion of units having functional groups in polymer F is preferably 0.01 to 3 mol% among the total units constituting polymer F.

The powder in the manufacturing method of the present invention (hereinafter also referred to as “F powder”) is a powder containing a TFE-based polymer. The F powder may contain components other than the TFE-based polymer within a range that does not impede the effects of the present invention, but it is preferable that the TFE-based polymer be the main component. The content of the TFE-based polymer in the F powder is preferably 80 mass% or more, and particularly preferably 100 mass%.

The D50 of the F powder is preferably 0.05 to 6.0 ㎛, more preferably 0.1 to 3.0 ㎛, and particularly preferably 0.2 to 3.0 ㎛. In this range, the fluidity and dispersibility of the F powder are improved, and the electrical properties (low permittivity, etc.) and heat resistance of the TFE polymer in the metal foil to which the resin is attached are most easily expressed.

The D90 of the F powder is preferably 8 ㎛ or less, more preferably 6 ㎛ or less, and particularly preferably 5 ㎛ or less. The D90 of the powder is preferably 0.3 ㎛ or more, and particularly preferably 0.8 ㎛ or more. In this range, the fluidity and dispersibility of the F powder are improved, and the electrical properties (low dielectric constant, etc.) and heat resistance of the F resin layer are most easily expressed.

The small charge bulk density of the F powder is preferably 0.05 g/㎖ or more, and particularly preferably 0.08 to 0.5 g/㎖.

The dense packing bulk density of the F powder is preferably 0.05 g/㎖ or more, and particularly preferably 0.1 to 0.8 g/㎖.

The method for manufacturing F powder is not particularly limited, and the methods described in [0065] to [0069] of International Publication No. 2016/017801 can be adopted. In addition, if the desired powder is commercially available, F powder may be used.

The dispersant in the manufacturing method of the present invention is a compound showing a mass reduction rate of 1 mass%/min or more in a temperature range of 80 to 300°C. It is preferable that the dispersant is a compound having a mass reduction rate of 1 mass%/min or more in a temperature range of 100 to 200°C, or a compound having a mass reduction rate of 1 mass%/min or more in a temperature range of 200 to 300°C.

The mass loss rate of the dispersant can be measured using a thermogravimetric measuring device (TG) and a thermogravimetric differential thermal analysis device (TG-DTA) under a mixed gas atmosphere (90 volume% helium and 10 volume% oxygen) at a heating pace of 10°C/min and a sample amount of the dispersant of 10 mg.

For example, the "mass reduction rate in the temperature range of 200 to 300°C of the dispersant" is obtained as a percentage value of the mass reduction amount when 10 mg of the dispersant is heated from 200°C to 300°C at a pace of 10°C/min in a mixed gas atmosphere (90 vol% helium and 10 vol% oxygen) using a thermogravimetric differential thermal analyzer (TG-DTA), divided by the heating time (10 minutes) and the amount of dispersant sample (10 mg).

The upper limit of the mass reduction rate is preferably 50 mass%/min.

The mass reduction rate is preferably 2 to 50 mass%/min, more preferably 4 to 20 mass%/min, and particularly preferably 6 to 15 mass%/min.

When the mass reduction rate is 1 mass%/min or more, it is easy to balance the hydrophilicity and smoothness of the surface of the F resin layer. When the mass reduction rate is 50 mass%/min or less, it is easy to balance the smoothness of the surface of the F resin layer and the suppression of deterioration of the metal foil due to the decomposition components of the dispersant.

The dispersant in the manufacturing method of the present invention is preferably a compound (surfactant) having a hydrophobic portion and a hydrophilic portion, and particularly preferably a compound having a fluorinated portion and a hydrophilic portion (fluorinated surfactant).

As dispersants, polyols, polyoxyalkylene glycols, polycaprolactam and polymeric polyols are preferred, and polymeric polyols are more preferred.

Polymeric polyol refers to a polymer having a unit based on a monomer having a carbon-carbon unsaturated double bond and two or more hydroxyl groups. As the polymeric polyol, polyvinyl alcohol, polyvinyl butyral and fluoropolyol are particularly preferable, and fluoropolyol is most preferable. However, fluoropolyol is a polymeric polyol having a hydroxyl group and a fluorine atom, other than an F polymer. In addition, a part of the hydroxyl groups of the polymeric polyol may be chemically modified and modified.

As a fluoropolyol, a polymeric polyol in which a main chain is composed of a carbon chain derived from an ethylenically unsaturated monomer and a side chain has a fluorinated hydrocarbon group and a hydroxyl group can be exemplified. The fluorinated hydrocarbon group is preferably a group having a tertiary carbon atom to which multiple (2 or 3) monovalent fluorinated hydrocarbon groups are bonded.

As a dispersant, a polymer having a polyfluoroalkyl group or polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in the side chain (hereinafter also referred to as “surfactant F”) is preferable, and a copolymer of a (meth)acrylate having a polyfluoroalkyl group or polyfluoroalkenyl group (hereinafter also referred to as “(meth)acrylate F”) and a (meth)acrylate having a polyoxyalkylene monool group (hereinafter also referred to as “(meth)acrylate AO”) (hereinafter also referred to as “surfactant F1”) is particularly preferable.

The polyfluoroalkyl group or polyfluoroalkenyl group in the surfactant F is preferably a group having 4 to 12 carbon atoms.

Surfactant F may have both a polyoxyalkylene group and an alcoholic hydroxyl group in the side chain, or may have only one of the groups in the side chain, and it is preferable that it has at least a polyoxyalkylene group in the side chain.

The present inventors have found that the mass reduction of the surfactant F in the above temperature range progresses due to the detachment of a polyfluoroalkyl group or a polyfluoroalkenyl group and the decomposition of an oxyalkylene unit in a polyoxyalkylene group or the presence of an alcoholic hydroxyl group. In addition, it has been found that, in the above temperature range, the polyfluoroalkyl group or the polyfluoroalkenyl group of the surfactant F is detached, whereas the polyoxyalkylene group tends to only undergo partial decomposition of the oxyalkylene unit, thereby forming a highly hydrophilic component. Since this hydrophilic component is effectively surface segregated, not only does the surface of the F resin layer become hydrophilic, but also powder falling off during powder packing is suppressed, thereby increasing the smoothness of the F resin layer, and therefore, it is thought that the adhesion of the metal foil to which the resin is attached is excellent.

R ¹ represents a hydrogen atom or a methyl group.

R ² represents a hydrogen atom or a methyl group.

The ratio of units based on (meth)acrylate F to the total units included in the surfactant F1 is preferably 20 to 60 mol%, particularly preferably 20 to 40 mol%.

The ratio of units based on (meth)acrylate AO to the total units included in the surfactant F1 is preferably 40 to 80 mol%, particularly preferably 60 to 80 mol%.

The ratio of the content of units based on (meth)acrylate AO to the content of units based on (meth)acrylate F in the surfactant F1 is preferably 1 to 5, and particularly preferably 1 to 2.

The surfactant F1 may be composed solely of units based on (meth)acrylate AO and units based on (meth)acrylate AO, or may additionally contain other units.

The fluorine content of the surfactant F1 is preferably 10 to 45 mass%, particularly preferably 15 to 40 mass%.

It is preferable that the surfactant F1 be nonionic.

The mass average molecular weight of the surfactant F1 is preferably 2,000 to 80,000, particularly preferably 6,000 to 20,000.

The solvent in the manufacturing method of the present invention is a dispersion medium, and is preferably a solvent (compound) that is liquid and inert at 25°C and does not react with the F powder, has a lower boiling point than components other than the solvent included in the powder dispersion, and can be removed by volatilization by heating or the like.

The solvent in the coating film formed by applying the powder dispersion to the surface of the metal foil is removed before the firing of the TFE-based polymer is completed. The solvent may be removed before the metal foil is maintained at a temperature at which the mass reduction rate within the temperature range is 1 mass%/min or more, may be removed while maintained at the temperature, or may be removed during firing. It is preferable that at least a part of the solvent is removed while maintained at the temperature.

Examples of the solvent include water, alcohols (methanol, ethanol, isopropanol, etc.), nitrogen-containing compounds (N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, etc.), sulfur-containing compounds (dimethyl sulfoxide, etc.), ethers (diethyl ether, dioxane, etc.), esters (ethyl lactate, ethyl acetate, etc.), ketones (methyl ethyl ketone, methyl isopropyl ketone, cyclopentanone, cyclohexanone, etc.), glycol ethers (ethylene glycol monoisopropyl ether, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.). One type of the solvent compound may be used alone, or two or more types may be used in combination.

As the solvent, a solvent that does not volatilize instantly and volatilizes while being maintained in the above temperature range is preferable, a solvent having a boiling point of 80 to 275°C is preferable, and a solvent having a boiling point of 125 to 250°C is particularly preferable. In this range, when the powder dispersion applied to the surface of the metal foil is maintained at a predetermined temperature, volatilization of the solvent and partial decomposition and flow of the dispersant effectively proceed, so that the dispersant is easily segregated on the surface.

As a solvent, an organic compound is preferable, and cyclohexane (boiling point: 81°C), 2-propanol (boiling point: 82°C), 1-propanol (boiling point: 97°C), 1-butanol (boiling point: 117°C), 1-methoxy-2-propanol (boiling point: 119°C), N-methylpyrrolidone (boiling point: 202°C), γ-butyrolactone (boiling point: 204°C), cyclohexanone (boiling point: 156°C), and cyclopentanone (boiling point: 131°C) are more preferable, and N-methylpyrrolidone, γ-butyrolactone, cyclohexanone, and cyclopentanone are particularly preferable.

The powder dispersion in the manufacturing method of the present invention may contain other materials as long as the effects of the present invention are not impaired. The other materials may or may not be dissolved in the powder dispersion.

These other materials may be non-curable or curable resins.

Non-curable resins include heat-meltable resins and non-meltable resins. Heat-meltable resins include thermoplastic polyimides, etc. Non-meltable resins include cured products of curable resins, etc.

Examples of the curable resin include polymers having a reactive group, oligomers having a reactive group, low-molecular-weight compounds, and low-molecular-weight compounds having a reactive group. Examples of the reactive group include a carbonyl group-containing group, a hydroxyl group, an amino group, and an epoxy group.

Examples of the curable resin include epoxy resins, thermosetting polyimides, polyamic acid which is a polyimide precursor, thermosetting acrylic resins, phenol resins, thermosetting polyester resins, thermosetting polyolefin resins, thermosetting modified polyphenylene ether resins, polyfunctional cyanate ester resins, polyfunctional maleimide-cyanate ester resins, polyfunctional maleimide resins, vinyl ester resins, urea resins, diallyl phthalate resins, melamine resins, guanamine resins, and melamine-urea cocondensation resins. Among these, from the viewpoint of being useful for printed circuit board applications, thermosetting polyimides, polyimide precursors, epoxy resins, thermosetting acrylic resins, bismaleimide resins, and thermosetting polyphenylene ether resins are preferable, and epoxy resins and thermosetting polyphenylene ether resins are particularly preferable.

Specific examples of epoxy resins include naphthalene type epoxy resin, cresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, alkylphenol novolac type epoxy resin, aralkyl type epoxy resin, biphenol type epoxy resin, dicyclopentadiene type epoxy resin, trishydroxyphenylmethane type epoxy compound, epoxy product of condensation of phenol and aromatic aldehyde having phenolic hydroxyl group, diglycidyl ether of bisphenol, diglycidyl ether of naphthalenediol, glycidyl ether of phenol, diglycidyl ether of alcohol, triglycidyl isocyanurate, etc.

Examples of bismaleimide resins include a resin composition (BT resin) using a bisphenol A type cyanate ester resin and a bismaleimide compound in combination, described in Japanese Patent Application Laid-Open No. Hei 7-70315, and the invention described in International Publication No. 2013/008667 and the background art thereof.

Polyamic acid usually has a reactive group that can react with the functional group of a TFE polymer.

Examples of the diamine or polycarboxylic acid dianhydride forming the polyamic acid include those described in Japanese Patent No. 5766125 [0020], Japanese Patent No. 5766125 [0019], Japanese Patent Application Laid-Open No. 2012-145676 [0055], [0057], etc. Among these, a polyamic acid formed by a combination of an aromatic diamine such as 4,4'-diaminodiphenyl ether or 2,2-bis[4-(4-aminophenoxy)phenyl]propane and an aromatic polycarboxylic acid dianhydride such as pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, or 3,3',4,4'-benzophenonetetracarboxylic dianhydride is preferable.

Examples of heat-melting resins include thermoplastic resins such as thermoplastic polyimide, and heat-melting cured products of curable resins.

Examples of thermoplastic resins include polyester resin, polyolefin resin, styrene resin, polycarbonate, thermoplastic polyimide, polyarylate, polysulfone, polyarylsulfone, aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystalline polyester, and polyphenylene ether, with thermoplastic polyimide, liquid crystalline polyester, and polyphenylene ether being preferable.

In addition, these other materials may include thixotropic agents, antifoaming agents, inorganic fillers, reactive alkoxysilanes, dehydrating agents, plasticizers, weathering agents, antioxidants, heat stabilizers, activators, antistatic agents, whitening agents, colorants, conductive agents, release agents, surface treatment agents, viscosity modifiers, flame retardants, etc.

The ratio of F powder in the powder dispersion is preferably 5 to 60 mass%, and particularly preferably 35 to 45 mass%. In this range, it is easy to control the dielectric constant and dielectric tangent of the F resin layer to be low. In addition, the uniform dispersibility of the powder dispersion is high, and the mechanical strength of the F resin layer is excellent.

The ratio of the dispersant in the powder dispersion is preferably 0.1 to 30 mass%, and particularly preferably 5 to 10 mass parts. In this range, it is easy to balance the uniform dispersibility of the F powder and the hydrophilicity and electrical properties of the surface of the F resin layer.

The ratio of the solvent in the powder dispersion is preferably 15 to 65 mass%, and particularly preferably 25 to 50 mass parts. In this range, the powder dispersion has excellent coatability, and the appearance of the resin layer is less likely to deteriorate.

In the manufacturing method of the present invention, a powder dispersion is applied to the surface of a metal foil.

As the coating method, any method may be used in which a stable wet film made of a powder dispersion is formed on the surface of the metal foil after coating, and examples thereof include a spray method, a roll coating method, a spin coating method, a gravure coating method, a micro gravure coating method, a gravure offset method, a knife coating method, a kiss coating method, a bar coating method, a die coating method, a fountain-Meyer bar method, and a slot die coating method.

In addition, before providing the metal foil in the temperature range of 80 to 300°C, the state of the wet film may be adjusted by heating the metal foil at a temperature below the above temperature range. This preparation is made to such an extent that the solvent does not completely volatilize, and is usually made to such an extent that 50 mass% or less of the solvent volatilizes.

In the manufacturing method of the present invention, after applying a powder dispersion to the surface of a metal foil, the metal foil is maintained at a temperature (hereinafter also referred to as “maintenance temperature”) at which a mass reduction rate is 1 mass%/min or more within a temperature range of 80 to 300°C. The maintenance temperature represents the temperature of the atmosphere.

Maintenance may be carried out in one step or in two or more steps at different temperatures.

Maintenance methods include using an oven, using a ventilation dryer, and irradiating heat rays such as infrared rays.

The atmosphere for maintenance may be either normal pressure or reduced pressure. In addition, the atmosphere for maintenance may be any of an oxidizing gas (oxygen gas, etc.) atmosphere, a reducing gas (hydrogen gas, etc.) atmosphere, and an inert gas (helium gas, neon gas, argon gas, nitrogen gas, etc.) atmosphere.

The maintenance atmosphere is preferably an atmosphere containing oxygen gas from the viewpoints of promoting decomposition of the dispersant and further improving the adhesion of the F resin layer. The oxygen gas concentration (by volume) at this time is preferably 1 × 10 ² to 3 × 10 ⁵ ppm, and particularly preferably 0.5 × 10 ³ to 1 × 10 ⁴ ppm. In this range, it is easy to balance the promotion of decomposition of the dispersant and the inhibition of oxidation of the metal foil.

The maintenance temperature is a temperature at which the mass reduction rate in a temperature range of 80 to 300°C is 1 mass%/min or more, and is more preferably 100 to 300°C. When a dispersant having a mass reduction rate of 1 mass%/min or more in a temperature range of 100 to 200°C is used, the maintenance temperature is more preferably 100 to 200°C, and is particularly preferably 160 to 200°C. In addition, when a dispersant having a mass reduction rate of 1 mass%/min or more in a temperature range of 200 to 300°C is used, the maintenance temperature is preferably 200 to 300°C, and is particularly preferably 220 to 260°C.

In the above temperature range, partial decomposition and flow of the dispersant effectively proceed, making it easier to segregate the dispersant on the surface.

The time for maintaining the temperature is preferably 0.1 to 10 minutes, and particularly preferably 0.5 to 5 minutes.

In the manufacturing method of the present invention, further, the TFE-based polymer is fired in a temperature range exceeding the holding temperature (hereinafter also referred to as “firing temperature”) to form an F resin layer on the surface of the metal foil. The firing temperature represents the temperature of the atmosphere. In the manufacturing method of the present invention, since the F powder is densely packed and the fusion of the TFE-based polymer progresses in a state where the hydrophilic component derived from the dispersant is effectively surface segregated, an F resin layer having excellent smoothness and hydrophilicity is formed. In addition, when the powder dispersion contains a heat-meltable resin, an F resin layer composed of a mixture of the TFE-based polymer and the soluble resin is formed, and when the powder dispersion contains a thermosetting resin, an F resin layer composed of a cured product of the TFE-based polymer and the thermosetting resin is formed.

As a heating method, a method using an oven, a method using a ventilation drying furnace, a method irradiating heat rays such as infrared rays, etc. can be mentioned. In order to increase the smoothness of the surface of the F resin layer, it may be pressurized with a heating plate, a heating roll, etc. As a heating method, a method irradiating far-infrared rays is preferable because it can be fired in a short time and the far-infrared path is relatively compact. As a heating method, infrared heating and hot air heating may be combined.

The effective wavelength of far-infrared rays is preferably 2 to 20 ㎛, more preferably 3 to 7 ㎛, from the viewpoint of promoting homogeneous fusion of TFE polymers.

The sintering atmosphere may be either normal pressure or reduced pressure. In addition, the atmosphere for the sintering may be any of an oxidizing gas (oxygen gas, etc.) atmosphere, a reducing gas (hydrogen gas, etc.) atmosphere, and an inert gas (helium gas, neon gas, argon gas, nitrogen gas, etc.) atmosphere. From the viewpoint of suppressing oxidation deterioration of each of the metal foil and the F resin layer to be formed, a reducing gas atmosphere or an inert gas atmosphere is preferable.

As the sintering atmosphere, a gas atmosphere composed of an inert gas and having a low oxygen gas concentration is preferable, and a gas atmosphere composed of nitrogen gas and having an oxygen gas concentration (by volume) of less than 500 ppm is preferable. The oxygen gas concentration (by volume) is particularly preferably 300 ppm or less. Also, the oxygen gas concentration (by volume) is usually 1 ppm or more. In this range, additional oxidative decomposition of the dispersant is suppressed, making it easy to improve the hydrophilicity of the F resin layer.

The sintering temperature is more than 300°C, preferably more than 300°C and less than or equal to 400°C, and particularly preferably 330 to 380°C. In this case, the TFE polymer is more likely to form a dense F resin layer.

The time maintained at the sintering temperature is preferably 30 seconds to 5 minutes, and particularly preferably 1 to 2 minutes.

In the case where the resin layer in the metal foil to which the resin is attached is a conventional insulating material (a cured product of a thermosetting resin such as polyimide), long-term heating is required to cure the thermosetting resin. On the other hand, in the present invention, the resin layer can be formed by short-term heating by fusion of the TFE-based polymer. In addition, when the powder dispersion contains a thermosetting resin, the firing temperature can be lowered. In this way, the manufacturing method of the present invention is a method in which the heat load on the metal foil when forming a resin layer on the metal foil to which the resin is attached is small, and is a method in which damage to the metal foil is small.

The metal foil having the resin attached thereto obtained by the manufacturing method of the present invention may be surface treated on the surface of the F resin layer in order to control the coefficient of linear expansion of the F resin layer or further improve the adhesiveness of the F resin layer. Examples of the surface treatment method include annealing treatment, corona discharge treatment, atmospheric pressure plasma treatment, vacuum plasma treatment, UV ozone treatment, excimer treatment, chemical etching, silane coupling treatment, and micro-roughening treatment.

In annealing treatment, the temperature is preferably 120 to 180°C, the pressure is preferably 0.005 to 0.015 MPa, and the time is preferably 30 to 120 minutes.

Examples of plasma irradiation devices for plasma treatment include high-frequency induction type, capacitively coupled electrode type, corona discharge electrode-plasma jet type, parallel plate type, remote plasma type, atmospheric pressure plasma type, and ICP type high-density plasma type.

Examples of gases used in plasma treatment include oxygen gas, nitrogen gas, noble gases (such as argon), hydrogen gas, and ammonia gas, with noble gases or nitrogen gas being preferred. Specific examples of gases used in plasma treatment include argon gas, a mixed gas of hydrogen gas and nitrogen gas, and a mixed gas of hydrogen gas, nitrogen gas, and argon gas.

As an atmosphere for plasma treatment, an atmosphere having a volume fraction of noble gas or nitrogen gas of 70 volume% or more is preferable, and an atmosphere having a volume fraction of 100 volume% is particularly preferable. In this range, by adjusting the Ra of the surface of the F resin layer to 2.0 ㎛ or less, it is easy to form fine roughness on the surface of the F resin layer.

The surface of the F resin layer of the resin-attached metal foil obtained by the manufacturing method of the present invention has high hydrophilicity and excellent adhesiveness, so it can be easily and firmly laminated with another substrate.

Other substrates include a heat-resistant resin film, a prepreg which is a precursor of a fiber-reinforced resin plate, a laminate having a heat-resistant resin film layer, and a laminate having a prepreg layer.

Prepreg is a sheet-shaped substrate in which a substrate (e.g., soil, woven fabric) made of reinforcing fibers (e.g., glass fibers, carbon fibers) is impregnated with a thermosetting resin or thermoplastic resin.

The heat-resistant resin film is a film containing one or more types of heat-resistant resin, and may be a single-layer film or a multi-layer film.

Heat-resistant resins include polyimide, polyarylate, polysulfone, polyarylsulfone, aromatic polyamide, aromatic polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, and liquid crystal polyester.

As a method of laminating another substrate on the surface of the F resin layer of the metal foil to which the resin is attached, an example of this method is a method of heat-pressing the metal foil to which the resin is attached and another substrate.

When the other substrate is a prepreg, the press temperature is preferably lower than the melting point of the TFE polymer, more preferably 120 to 300°C, and particularly preferably 160 to 220°C. In this range, the F resin layer and the prepreg can be firmly bonded while suppressing thermal deterioration of the prepreg.

When the substrate is a heat-resistant resin film, the press temperature is preferably 310 to 400°C. In this range, the F resin layer and the heat-resistant resin film can be firmly bonded while suppressing thermal deterioration of the heat-resistant resin film.

It is preferable to perform the heat pressing under a reduced pressure atmosphere, and it is particularly preferable to perform it under a vacuum of 20 kPa or less. In this range, the inclusion of bubbles in the interfaces of the F resin layer, the substrate, and the metal foil in the laminate can be suppressed, and deterioration due to oxidation can be suppressed.

In addition, when performing a heat press, it is preferable to raise the temperature after reaching the above vacuum level. If the temperature is raised before reaching the above vacuum level, the F resin layer is pressed in a softened state, that is, in a state with a certain degree of fluidity and adhesion, which causes bubbles.

The pressure in the heat press is preferably 0.2 MPa or more. Also, the upper limit of the pressure is preferably 10 MPa or less. In this range, the F resin layer and the substrate can be firmly adhered while suppressing damage to the substrate.

The metal foil or laminate thereof with a resin attached thereto obtained by the manufacturing method of the present invention can be used for manufacturing a printed circuit board as a flexible copper-clad laminate or a rigid copper-clad laminate.

For example, by using a method of processing the metal foil of the resin-attached metal foil of the present invention into a conductor circuit of a predetermined pattern (pattern circuit) by etching or the like, or a method of processing the metal foil of the resin-attached metal foil of the present invention into a pattern circuit by an electrolytic plating method (semi-additive method (SAP method), modified semi-additive method (MSAP method), etc.), a printed circuit board can be manufactured from the metal foil of the present invention having the resin attached thereto.

In the manufacture of a printed circuit board, after forming a pattern circuit, an interlayer insulating film may be formed on the pattern circuit, and a pattern circuit may be additionally formed on the interlayer insulating film. The interlayer insulating film may also be formed, for example, using a powder dispersion according to the present invention.

In the manufacture of a printed circuit board, a solder resist may be laminated on a pattern circuit. The solder resist can be formed using the powder dispersion of the present invention.

In the manufacture of a printed circuit board, a coverlay film may be laminated on a pattern circuit. The coverlay film can also be formed using the powder dispersion of the present invention.

The resin-attached copper foil of the present invention is a metal foil, a resin layer including a TFE-based polymer (hereinafter also referred to as an "F1 resin layer"), and a resin-attached metal foil having a specific bonding portion that comes into contact with the F1 resin layer. The reason why the resin-attached metal foil of the present invention (also includes a laminate or a printed circuit board obtained from the resin-attached copper foil of the present invention; the same applies hereinafter) can be bonded at low temperature to another substrate without impairing its dimensional stability is not necessarily clear, but is thought to be as follows.

It is thought that a specific bonding site contains a hydrophilic component having at least one selected from the group consisting of an ethereal oxygen atom, a hydroxyl group, and a carboxyl group, and that the adhesiveness is expressed by the characteristics (polarity, reactivity, etc.) of this hydrophilic component. The bonding site is formed by contacting the F1 resin layer, and it is also thought that, at the boundary between the F1 resin layer and the other substrate of the adhesive laminate of the metal foil to which the resin of the present invention is attached and the other substrate, the hydrophilic components are highly compatible with each other to form an adhesive layer. In short, it is thought that the adhesiveness of the metal foil to which the resin of the present invention is attached is mainly due to the bonding site, and specifically, it is not necessarily due to fusion adhesion of the TFE polymer by high-temperature heating. For this reason, the metal foil with the resin attached to it of the present invention can be processed into a multilayer substrate (such as a multilayer printed substrate) with little warping by bonding it to another substrate without impairing its dimensional stability even at relatively low temperatures, while using a non-adhesive and heat-elastic TFE polymer as the F1 resin layer.

The resin-attached copper foil of the present invention has a metal foil, an F1 resin layer, and an adhesive portion in contact with the F1 resin layer, in this order. As a layer configuration of the resin-attached copper foil of the present invention, examples thereof include metal foil/F1 resin layer/adhesive portion, F1 resin layer/metal foil/F1 resin layer/adhesive portion, adhesive portion/F1 resin layer/metal foil/F1 resin layer/adhesive portion, and metal foil/F1 resin layer/metal foil/F1 resin layer/adhesive portion. "Metal foil/F1 resin layer/adhesive portion" indicates that the metal foil, the F1 resin layer, and the adhesive portion are laminated in this order, and other layer configurations are the same.

The warpage ratio of the resin-attached metal foil of the present invention is preferably 25% or less, and particularly preferably 7% or less. In this case, the handleability when processing the resin-attached metal foil into a printed circuit board and the transfer characteristics of the resulting printed circuit board are excellent.

The dimensional change rate of the resin-attached metal foil of the present invention is preferably ±1% or less, and particularly preferably ±0.2% or less. In this case, it is easy to process the resin-attached metal foil into a printed circuit board and to multilayer it.

The relative permittivity (20 MHz) of the resin portion (F1 resin layer and bonding portion) of the resin-attached metal foil of the present invention is preferably 2.0 to 3.5, particularly preferably 2.0 to 3.0. In this range, the resin-attached metal foil can be preferably used for printed circuit boards or the like in which both the electrical properties (low permittivity, etc.) and the adhesiveness of the F1 resin layer are excellent, and excellent transmission properties are required.

The Ra of the surface of the resin portion (F1 resin layer and bonding portion) of the metal foil to which the resin of the present invention is attached is preferably 2 nm to 3 µm, more preferably 3 nm to 1 µm, still more preferably 4 nm to 500 nm, and particularly preferably 5 nm to 300 nm. In this range, it is easy to balance the adhesiveness with other substrates and the ease of processing of the surface of the resin portion.

The form of the metal foil in the resin-attached metal foil of the present invention, including preferred forms, is the same as the form of the metal foil in the method for producing the resin-attached metal foil of the present invention.

The F1 resin layer in the present invention contains a TFE-based polymer.

The F1 resin layer may contain inorganic fillers, resins other than TFE polymers, additives, etc., as needed, as long as the effects of the present invention are not impaired.

The thickness of the F1 resin layer is preferably 1 to 100 ㎛, more preferably 3 to 75 ㎛, and particularly preferably 5 to 50 ㎛. When the thickness of the F1 resin layer is equal to or greater than the lower limit above, the transfer characteristics as a printed circuit board are further excellent. When the thickness of the F1 resin layer is equal to or less than the upper limit above, the metal foil to which the resin is attached does not bend easily.

In the resin-attached metal foil of the present invention, the ratio of the thickness of the F1 resin layer to the thickness of the metal foil is preferably 0.1 to 5.0, and particularly preferably 0.2 to 2.5. When the ratio of the thickness of the F1 resin layer to the thickness of the metal foil is equal to or greater than the lower limit, the transfer characteristics as a printed circuit board are further excellent. Since the resin-attached metal foil of the present invention has a bonding portion, even when the ratio is large (for example, when the F1 resin layer is thick), the dimensional stability of the resin-attached metal foil of the present invention can be low-temperature bonded to another substrate without impairing the bonding, so that warping after multilayering is suppressed.

The mode of the TFE-based polymer in the resin-attached metal foil of the present invention is the same as the mode of the TFE-based polymer in the method for producing the resin-attached metal foil of the present invention, including preferred modes.

The bonding site in the metal foil to which the resin of the present invention is attached includes a hydrophilic component having at least one selected from the group consisting of an ethereal oxygen atom, a hydroxyl group, and a carboxyl group.

The bonding portion may be composed solely of a hydrophilic component, or may be composed of a hydrophilic component and a component other than a hydrophilic component (such as a TFE polymer).

As the hydrophilic component, an organic compound having at least one selected from the group consisting of an ethereal oxygen atom, a hydroxyl group, and a carboxyl group is preferable (however, excluding a TFE polymer; the same applies hereinafter), and an organic compound having at least one selected from the group consisting of an ethereal oxygen atom, a hydroxyl group, and a carboxyl group and having a water contact angle of 30° to 90° is particularly preferable. Furthermore, it is preferable that the organic compound does not have a silicon atom.

As the organic compound, a polymer having at least one selected from the group consisting of an ethereal oxygen atom, a hydroxyl group and a carboxyl group is preferable, a polymer having an ethereal oxygen atom and a hydroxyl group or a carboxyl group is more preferable, and a fluoropolymer having an ethereal oxygen atom and a hydroxyl group or a carboxyl group is particularly preferable. In this case, as described above, the compatibility of the TFE polymer and the hydrophilic component at the boundary between the F1 resin layer and the bonding portion is improved, so that the bonding strength between the F1 resin layer and the bonding portion is more likely to be improved.

As the hydrophilic component, a hydrophilic component derived from a dispersant in the method for producing a resin-attached metal foil of the present invention is preferable. As the hydrophilic component, surfactant F in the method for producing a resin-attached metal foil of the present invention is preferable, and surfactant F1 in the method for producing a resin-attached metal foil of the present invention is particularly preferable.

The bonding portion in the resin-attached metal foil of the present invention may exist in a layered form, may exist in an island form, and is preferably present in an island form. In this case, it is easy to balance the electrical characteristics (low permittivity, low dielectric constant, etc.) of the F1 resin layer of the resin-attached metal foil and the adhesiveness due to the hydrophilic component forming the bonding portion. In short, it is easy to express adhesiveness while suppressing the deterioration of the electrical characteristics due to the presence of the hydrophilic component.

The thickness of the bonding portion existing in layers and the height of the bonding portion existing in islands are preferably 1 to 1000 nm, more preferably 5 to 500 nm, still more preferably 5 to 300 nm, and particularly preferably 5 to 200 nm. In this case, it is easy to balance the electrical characteristics of the F1 resin layer of the metal foil to which the resin is attached and the adhesiveness of the bonding portion.

As a method for manufacturing the resin-attached metal foil of the present invention, (i) a method of applying a coating solution containing a hydrophilic component to the surface of the F1 resin layer of the resin-attached metal foil having the metal foil and the F1 resin layer, (ii) a method of applying a coating solution containing a TFE-based polymer and a hydrophilic component to the surface of the metal foil. Since the TFE-based polymer and the hydrophilic component at the boundary between the F1 resin layer and the bonding portion are compatible with each other, the method (ii) is preferable because the adhesion between the F1 resin layer of the resin-attached metal foil and the bonding portion is easily improved.

(ii) A specific example of the method includes a method of applying a powder dispersion containing a TFE-based polymer, a hydrophilic component, and a liquid medium to the surface of a metal foil, maintaining the metal foil at a temperature within a temperature range of 100 to 300°C, and firing the TFE-based polymer in a temperature range exceeding the temperature range, thereby forming an F1 resin layer containing a TFE-based polymer on the surface of the metal foil and simultaneously forming an adhesive portion containing a hydrophilic component on the surface of the F1 resin layer.

Specifically, the resin-attached metal foil of the present invention is preferably manufactured by the method for manufacturing the resin-attached metal foil of the present invention. The manufacturing mode in this case, including the preferred mode, is the same as the mode of the method for manufacturing the resin-attached metal foil of the present invention.

In the metal foil to which the resin of the present invention is attached, if the bonding portion exists in a layered form, the surface of the bonding portion may be surface-treated in order to further improve the adhesiveness of the bonding portion. If the bonding portion exists in an island form, the surface of the F1 resin layer and the bonding portion may be surface-treated in order to control the coefficient of linear expansion of the F1 resin layer or further improve the adhesiveness of the F1 resin layer or the bonding portion.

As surface treatment, examples thereof include annealing, corona discharge treatment, atmospheric plasma treatment, vacuum plasma treatment, UV ozone treatment, excimer treatment, chemical etching, silane coupling treatment, and micro-roughening treatment. Each aspect of the annealing treatment and the plasma treatment, including preferred aspects, is the same as that in the method for producing a resin-attached metal foil of the present invention.

Since the resin-attached metal foil of the present invention has excellent adhesiveness due to the presence of an adhesive portion on the surface of the F1 resin layer, it can be firmly bonded at low temperatures to another substrate. In short, the resin-attached metal foil of the present invention can be bonded at low temperatures to another substrate without affecting the thickness of the resin layer and the type or thickness of the metal foil, and without impairing dimensional stability, even though it uses an inherently heat-stretchable TFE-based polymer as the resin layer.

It is preferable to manufacture a laminate by bonding a metal foil to which the resin of the present invention is attached and another substrate by a heat press method.

Other aspects of the invention, including preferred aspects, are the same as those in the method for producing a metal foil having a resin attached thereto according to the present invention.

In addition, the aspect of the hot pressing method, including the preferred aspect, is the same as that in the method for producing a metal foil having a resin attached thereto of the present invention.

Since the resin-attached metal foil of the present invention uses a TFE-based polymer having excellent physical properties such as electrical properties and chemical resistance (etching resistance) as a resin layer, the resin-attached metal foil of the present invention or a laminate thereof can be used in the manufacture of printed circuit boards as a flexible copper-clad laminate or a rigid copper-clad laminate.

The mode of using the resin-attached metal foil of the present invention for the manufacture of a printed circuit board, including preferred modes, is the same as the mode of using the resin-attached metal foil obtained by the manufacturing method of the present invention for the manufacture of a printed circuit board.

The laminate of the present invention is a laminate obtained by thermo-compression bonding a metal foil, a resin layer including a TFE-based polymer (hereinafter also referred to as an "F2 resin layer"), a metal foil to which a resin having a specific commercial layer in contact with the F2 resin layer is attached, and a specific prepreg. The reason why the laminate of the present invention (also includes a printed circuit board obtained from the laminate of the present invention; the same applies hereinafter) has excellent transmission characteristics and mechanical strength, each layer is firmly bonded, and warpage is low is not necessarily clear, but is thought to be as follows.

It is thought that a specific commercial layer contains a component having fluorine atoms and oxygen atoms, and that adhesion with the F2 resin layer is expressed by the characteristics (compatibility, etc.) of the portion having fluorine atoms, and adhesion with the cured layer of the prepreg is expressed by the characteristics (polarity, reactivity, etc.) of the portion having oxygen atoms. In addition, compared to the temperature at which the heat-sealability of the TFE-based polymer included in the F2 resin layer is expressed, the adhesion by the commercial layer is expressed at a relatively low temperature. Therefore, even if the melting point of the TFE-based polymer is high, the prepreg can be firmly adhered to the resin side of the metal foil to which the resin is attached at a relatively low temperature.

Since the metal foil to which the resin is attached and the prepreg can be bonded at a relatively low temperature, the properties (electrical properties and mechanical strength) of the cured layer of the prepreg are not easily deteriorated. In addition, as the prepreg, a prepreg containing a matrix resin (such as a matrix resin not having a fluorine atom) which has excellent electrical properties, mechanical strength, etc. but generally lower heat resistance than a TFE-based polymer can be used. In addition, the F2 resin layer has excellent electrical properties because it contains a TFE-based polymer. In addition, the commercial layer, like a covering layer of a silane coupling agent, does not easily deteriorate the electrical properties of the F2 resin layer. In this way, since the cured layer has excellent electrical properties and mechanical strength, and the F2 resin layer has excellent electrical properties, and furthermore, since their properties are not easily deteriorated by heat or the commercial layer, the laminate as a whole has excellent transmission properties and mechanical strength.

In addition, by bonding the resin-attached metal foil and the prepreg at a relatively low temperature without impairing the dimensional stability of the resin-attached metal foil while using a non-adhesive and heat-elastic TFE polymer as the F2 resin layer, a laminate with low warpage is obtained.

The laminate of the present invention has a metal foil, an F2 resin layer, a commercial layer in contact with the F2 resin layer, and a cured layer in contact with the commercial layer, in this order. Examples of the layer configuration of the laminate of the present invention include metal foil/F2 resin layer/commercial layer/cured layer, and metal foil/F2 resin layer/commercial layer/cured layer/commercial layer/F2 resin layer/metal foil. “Metal foil/F2 resin layer/commercial layer/cured layer” indicates that the metal foil, the F2 resin layer, the commercial layer, and the cured layer are laminated in this order, and other layer configurations are the same.

The warpage ratio of the laminate of the present invention is preferably 5% or less, and particularly preferably 1% or less. In this case, the handling properties when processing the laminate into a printed circuit board and the transfer properties of the resulting printed circuit board are excellent.

The dielectric constant (20 ㎓) of the substrate portion (F2 resin layer, commercial layer, and cured layer) of the laminate of the present invention is preferably 5.5 or less, more preferably 4.7 or less, still more preferably 4.0 or less, and particularly preferably 3.6 or less. The dielectric loss tangent (20 ㎓) of the substrate portion is preferably 0.02 or less, more preferably 0.009 or less, still more preferably 0.005 or less, and particularly preferably 0.003 or less. In this range, the laminate can be preferably used for a printed circuit board or the like which requires excellent electrical properties (low dielectric constant, low dielectric loss tangent, etc.) and adhesiveness of the substrate portion, and excellent transmission characteristics.

The form of the metal foil in the laminate of the present invention, including preferred forms, is the same as the form of the metal foil in the method for producing a resin-attached metal foil of the present invention.

The F2 resin layer in the laminate of the present invention contains a TFE-based polymer.

The F2 resin layer may contain inorganic fillers, resins other than TFE polymers, additives, etc., as needed, as long as the effects of the present invention are not impaired.

The thickness of the F2 resin layer is preferably 1 to 100 ㎛, more preferably 3 to 75 ㎛, and particularly preferably 5 to 50 ㎛. When the thickness of the F2 resin layer is equal to or greater than the lower limit above, the transfer characteristics as a printed circuit board are further excellent. When the thickness of the F2 resin layer is equal to or less than the upper limit above, the laminate is less likely to warp.

The ratio of the thickness of the F2 resin layer to the thickness of the metal foil in the laminate of the present invention is preferably 0.1 to 5.0, and particularly preferably 0.2 to 2.5. When the ratio of the thickness of the F2 resin layer to the thickness of the metal foil is equal to or greater than the lower limit, the transfer characteristics as a printed circuit board are further excellent. Since the laminate of the present invention has a commercial layer, even when the ratio is large (for example, when the F2 resin layer is thick), when manufacturing the laminate, the resin-attached metal foil and the prepreg can be bonded at low temperatures without impairing the dimensional stability of the resin-attached metal foil, so that warping of the laminate is suppressed.

The mode of the TFE-based polymer in the laminate of the present invention, including preferred modes, is the same as the mode of the TFE-based polymer in the method for producing a metal foil having a resin attached thereto of the present invention.

The commercial layer in the laminate of the present invention contains a component having fluorine atoms and oxygen atoms.

The commercial layer may be composed only of the above components, or may be composed of the above components and components other than the above components (such as a TFE polymer).

The aspect of the above component, including a preferred aspect, is the same as that of the hydrophilic component in the resin-attached metal foil of the present invention. In a particularly preferred aspect, the compatibility of the TFE polymer and the above component at the boundary between the F2 resin layer and the commercial layer is improved, so that the adhesive strength between the F2 resin layer and the commercial layer is more likely to be improved. In addition, the compatibility or reactivity of the above component and the matrix resin of the prepreg at the boundary between the commercial layer and the cured layer of the prepreg is improved, so that the adhesive strength between the commercial layer and the cured layer of the prepreg is more likely to be improved.

The thickness of the commercial layer is preferably 1 to 500 nm, and particularly preferably 5 to 100 nm. In this case, it is easy to balance the electrical characteristics of the F2 resin layer of the resin-attached metal foil and the adhesiveness of the commercial layer.

The cured layer in the laminate of the present invention is a cured material of a prepreg containing a matrix resin. The matrix resin is preferably a matrix resin that does not have a fluorine atom.

As for prepreg, an example is a prepreg in which a matrix resin is impregnated into a reinforcing fiber sheet.

Examples of the reinforcing fiber sheet include a reinforcing fiber bundle made of a plurality of reinforcing fibers, a cloth made by weaving the reinforcing fiber bundle, a unidirectional reinforcing fiber bundle in which a plurality of reinforcing fibers are aligned in one direction, a unidirectional cloth made of the unidirectional reinforcing fiber bundle, a sheet combining these, a sheet in which a plurality of reinforcing fiber bundles are overlapped, etc.

As the reinforcing fiber, continuous long fibers having a length of 10 mm or longer are preferable. The reinforcing fibers do not need to be continuous over the entire length in the longitudinal direction or the entire width in the transverse direction of the reinforcing fiber sheet, and may be divided in the middle.

Reinforcing fibers include inorganic fibers, metal fibers, and organic fibers.

Examples of inorganic fibers include carbon fiber, graphite fiber, glass fiber, silicon carbide fiber, silicon nitride fiber, alumina fiber, silicon carbide fiber, and boron fiber.

Metal fibers include aluminum fibers, brass fibers, and stainless steel fibers.

Examples of organic fibers include aromatic polyamide fibers, polyaramid fibers, polyparaphenylenebenzoxazole (PBO) fibers, polyphenylene sulfide fibers, polyester fibers, acrylic fibers, nylon fibers, and polyethylene fibers.

The reinforcing fibers may be surface treated.

Reinforcing fibers may be used alone or in combination of two or more types.

For printed circuit board applications, glass fiber is preferred as the reinforcing fiber.

The matrix resin may be a thermoplastic resin or a thermosetting resin, with a thermosetting resin being preferred.

As the thermosetting resin, the same resin as the thermosetting resin exemplified in the description of the method for producing the metal foil having the resin attached thereto of the present invention can be exemplified.

As the thermoplastic resin, the same resin as the thermoplastic resin exemplified in the description of the method for producing the metal foil having the resin attached thereto of the present invention can be exemplified.

Matrix resins may be used alone or in combination of two or more types.

As the matrix resin of the prepreg, at least one matrix resin selected from the group consisting of epoxy resin, polyphenylene oxide, polyphenylene ether, and polybutadiene is preferable in terms of processability.

The thickness of the prepreg is preferably 10 ㎛ or more and 5 mm, more preferably 30 ㎛ or more and 3 mm or less, and particularly preferably 80 ㎛ or more and 1 mm or less. However, the thickness of the prepreg can be appropriately set depending on the intended use of the printed circuit board.

As for prepreg, the following product names can be mentioned.

The laminate of the present invention can be manufactured by bonding a resin-attached metal foil having a metal foil, an F2 resin layer, and a commercial layer, and a prepreg by a heat press method. Specifically, the resin-attached metal foil of the present invention is preferably manufactured by bonding a resin-attached metal foil of the present invention and a prepreg by a heat press method.

The commercial layer of the resin-attached copper foil in the laminate of the present invention may be present in a layered form or in an island form. When the commercial layer is present in a layered form, the resin-attached metal foil can form a strong low-temperature bond with the prepreg because the surface adhesiveness of the commercial layer is excellent. In addition, when the resin-attached metal foil forms an island form, the commercial layer is present in a F2 resin layer because the surface adhesiveness of the commercial layer is excellent, so the resin-attached metal foil can form a strong low-temperature bond with the prepreg. In short, the resin-attached metal foil of the present invention can form a low-temperature bond with the prepreg without deteriorating dimensional stability, regardless of the thickness of the resin layer and the type or thickness of the metal foil, while using an inherently heat-stretchable TFE polymer as the resin layer.

Examples of methods for manufacturing such a resin-attached metal foil include (i) a method of applying a coating solution containing a component that forms a commercial layer (such as a dispersant having a weight reduction rate of 1 mass%/min or more at 80 to 300°C as described above) to the surface of the F2 resin layer of the resin-attached metal foil having the metal foil and the F2 resin layer, and (ii) a method of applying a coating solution containing a TFE-based polymer and the above-mentioned component to the surface of the metal foil. Since the TFE-based polymer and the above-mentioned component are compatible at the boundary between the F2 resin layer and the commercial layer, and the adhesion between the F2 resin layer of the resin-attached metal foil and the commercial layer is likely to improve, method (ii) is preferable.

(ii) A specific example of the method includes a method in which a powder dispersion containing a TFE-based polymer, the dispersant (a polymer having a polyfluoroalkyl group or polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in a side chain, etc., as described above), and a liquid medium is applied to the surface of a metal foil, the metal foil is maintained in a temperature range of 80 to 300°C, and the TFE-based polymer is sintered in a temperature range exceeding the above-mentioned temperature range, thereby forming an F2 resin layer containing the TFE-based polymer on the surface of the metal foil and simultaneously forming a commercial layer on the surface of the F2 resin layer.

When manufacturing the laminate of the present invention, a method of laminating a prepreg on the surface of a commercial layer of a resin-attached metal foil or on the surface of an F2 resin layer and a commercial layer may include a method of heat-pressing a resin-attached metal foil and a prepreg.

The press temperature is preferably lower than the melting point of the TFE polymer, more preferably 120 to 300°C, and particularly preferably 160 to 220°C. In this range, the commercial layer and the prepreg can be firmly bonded while suppressing thermal deterioration of the prepreg.

It is preferable to perform the hot pressing under a reduced pressure atmosphere, and it is particularly preferable to perform it under a vacuum of 20 kPa or less. In this range, the inclusion of bubbles in the respective interfaces of the metal foil, F2 resin layer, commercial layer, and cured layer in the laminate can be suppressed, thereby suppressing deterioration due to oxidation.

In addition, when performing a heat press, it is preferable to raise the temperature after reaching the above vacuum level. If the temperature is raised before reaching the above vacuum level, the F2 resin layer is pressed in a softened state, that is, in a state with a certain degree of fluidity and adhesion, which causes bubbles.

The pressure in the heat press is preferably 0.2 to 10 MPa. In this range, the commercial layer and the prepreg can be firmly bonded while suppressing damage to the prepreg.

Since the laminate of the present invention uses a TFE-based polymer having excellent physical properties such as electrical properties and chemical resistance (etching resistance) as a resin layer, the laminate of the present invention can be used in the manufacture of printed circuit boards as a flexible copper-clad laminate or a rigid copper-clad laminate.

For example, a printed circuit board can be manufactured from the laminate of the present invention by a method of processing the metal foil of the laminate of the present invention into a conductor circuit (transmission circuit) of a predetermined pattern by etching, or by a method of processing the metal foil of the laminate of the present invention into a transmission circuit by an electrolytic plating method (semi-additive method (SAP method), modified semi-additive method (MSAP method), etc.).

A printed circuit board manufactured from the laminate of the present invention has a transmission circuit, an F2 resin layer, and a cured layer in this order, and further has a commercial layer in contact with the F2 resin layer and the cured layer between the F2 resin layer and the cured layer. Examples of the layer configuration of the printed circuit board of the present invention include transmission circuit/F2 resin layer/commercial layer/cured layer, and transmission circuit/F2 resin layer/commercial layer/cured layer/commercial layer/F2 resin layer/transfer circuit.

In the manufacture of a printed circuit board, after forming a transmission circuit, an interlayer insulating film may be formed on the transmission circuit, and a transmission circuit may be additionally formed on the interlayer insulating film. The interlayer insulating film may also be formed, for example, using a powder dispersion according to the present invention.

In the manufacture of a printed circuit board, a solder resist may be laminated on a transmission circuit. The solder resist can be formed using the powder dispersion of the present invention.

In the manufacture of a printed circuit board, a coverlay film may be laminated on a transmission circuit. The coverlay film can also be formed using the powder dispersion of the present invention.

Example

Hereinafter, the present invention will be described in detail by examples, but the present invention is not limited to these.

Various measurement methods are shown below.

<Melt viscosity of polymer>

In accordance with ASTM D 1238, a polymer sample (2 g) heated at a pre-measured temperature for 5 minutes was measured using a flow tester and a die of 2Φ-8L, and then maintained at the measurement temperature with a load of 0.7 MPa.

<Melting point of polymer>

The TFE polymer was heated at a rate of 10°C/min using a differential scanning calorimeter (DSC-7020, manufactured by Seiko Instruments).

<D50 and D90 of Powder>

A laser diffraction-scattering particle size distribution measuring device (LA-920 measuring device manufactured by Horiba, Ltd.) was used, and the powder was dispersed in water for measurement.

<Smoothness of the resin layer>

The light-irradiated resin layer was visually observed from an oblique angle and evaluated using the following criteria.

A: The shape cannot be confirmed.

B: No stripes are confirmed, but a bumpy surface shape is confirmed.

C: Stripes are confirmed.

<Water contact angle of the resin layer>

When pure water (approximately 2 ㎕) was placed on the surface of the resin layer of a metal foil to which resin was attached at 25°C, the angle formed between the water droplet and the surface of the resin layer was measured using a contact angle meter (CA-X type manufactured by Kyowa Interface Science Co., Ltd.), and evaluated according to the following criteria.

A: The water contact angle is between 70° and 90°.

B: The water contact angle is greater than 90° and less than 100°.

C: The water contact angle is greater than 100°.

<Bending rate of resin layer>

A square test piece measuring 180 mm in length and width was cut from the laminate. For this test piece, the bending rate was measured according to the measurement method specified in JIS C 6471: 1995.

<Ra and Rz of the surface of the resin layer>

Using an AFM manufactured by Oxford Instruments, Ra and Rz of the surface of the resin layer in the range of 1 ㎛ ² were measured under the following measurement conditions.

Probe: AC160TS-C3 (tip R < 7 nm, spring constant 26 N/m), Measurement mode: AC-Air, Scan Rate: 1 ㎐.

<Peeling strength of laminate>

A square test piece measuring 100 mm in length and 10 mm in width was cut from the laminate. The copper foil and the cured product of the prepreg to which the resin was attached were peeled off from one end of the test piece in the longitudinal direction to a position of 50 mm. Then, a position 50 mm from one end of the test piece in the longitudinal direction was set as the center, and a 90-degree peel was performed at a tensile speed of 50 mm/min using a tensile tester (manufactured by Orientec Co., Ltd.), and the maximum load was taken as the peel strength (N/cm).

<Permittivity and dielectric tangent>

For the substrate portion (resin layer, commercial layer, and cured layer) of the printed circuit board, the relative permittivity (20 GHz) and dielectric loss tangent (20 GHz) were measured at a frequency of 20 GHz in an environment within the range of 23 ℃ ± 2 ℃, 50 ± 5% RH by the SPDR (split post dielectric resonator) method.

The materials used are listed below.

[Powder]

Powder 1: Powder (D50: 1.7 ㎛, D90: 3.8 ㎛) composed of a copolymer (melting point: 300°C) having an acid anhydride group containing TFE units, NAH units, and PPVE units in that order at 97.9 mol%, 0.1 mol%, and 2.0 mol%, respectively.

Polymer 2: A powder (D50: 0.3 μm, D90: 0.6 μm) substantially composed of a homopolymer of TFE (melt viscosity at 380°C: 1.4 × 10 ⁴ ) containing 99.5 mol% or more of TFE units.

[Dispersant]

Dispersant 1: A copolymer of a (meth)acrylate having a perfluoroalkenyl group and a (meth)acrylate having a polyoxyethylene group (nonionic surfactant, a mass reduction rate at 100 to 200°C of less than 1 mass%/min and a mass reduction rate at 200 to 300°C of 6 mass%/min.).

Dispersant 2: Copolymer of methacrylate having a perfluoroalkyl group and hydroxybutyl methacrylate (nonionic surfactant, mass loss rates at 100 to 200°C and 200 to 300°C are each less than 1 mass%/min.)

Dispersant 3: Copolymer of CH ₂ =CHC(O)O(CH ₂ ) ₄ OCF(CF ₃ )C(CF(CF ₃ ) ₂ )(=C(CF ₃ ) ₂ ) and CH ₂ =CHC(O)O(CH ₂ CH ₂ O) ₁₀ H (mass loss rate at 100 to 200 ℃ is less than 1 mass%/min and mass loss rate at 200 to 300 ℃ is 6 mass%/min).

[Metal foil]

Copper foil 1: Ultra-low-light electrolytic copper foil (manufactured by Fukuda Metal Foil Industry Co., Ltd., CF-T4X-SV, thickness: 18 ㎛).

[Prepreg]

Prepreg 1: FR-4 (Hitachi Chemical Company, GEA-67N 0.2t (HAN), Reinforcing fiber: glass fiber, Matrix resin: epoxy resin, Thickness: 0.2 mm).

(Example 1) Manufacturing example of copper foil with resin attached

(Example 1-1) Manufacturing example of copper foil 1 with resin attached

A powder dispersion was prepared by mixing 50 parts by mass of powder 1, 5 parts by mass of dispersant 1, and 45 parts by mass of N-methylpyrrolidone.

A powder dispersion was applied onto the surface of copper foil 1 using a die coater, and the copper foil 1 was passed through a ventilation drying furnace (atmosphere temperature: 230°C, atmosphere gas: nitrogen gas having an oxygen gas concentration of 8000 ppm) and maintained for 1 minute, and further passed through a far-infrared furnace (temperature: 340°C, gas: nitrogen gas having an oxygen gas concentration of less than 100 ppm) and maintained for 1 minute, thereby obtaining copper foil 1 having a resin layer of polymer 1 (having a thickness of 5 μm) attached thereto on the surface of the copper foil 1.

(Example 1-2) ∼ (Example 1-6) Manufacturing examples of copper foils 2 to 6 with resin attached

Copper foils 2 to 6 with a resin attached were obtained in the same manner as in Example 1, except that the types of powder and dispersant, the atmospheric temperature of the ventilation dryer, and the oxygen gas concentration of the atmospheric gas of the ventilation dryer were changed.

The properties (water contact angle and smoothness) of the resin layer of the copper foil to which each resin was attached were evaluated. The results are summarized and shown in Table 1 below.

(Example 2) Example of manufacturing a laminate

(Example 2-1) Manufacturing example of laminate 1

The surface of the resin layer of the copper foil 1 to which the resin was attached was subjected to vacuum plasma treatment. The treatment conditions were as follows: output: 4.5 kW, introduction gas: argon gas, introduction gas flow rate: 50 cm3/min, pressure: 50 mTorr (6.7 ㎩), and treatment time: 2 min.

Prepreg 1 was overlapped on the surface of the resin layer of copper foil 1 to which resin was attached after treatment, and vacuum heat pressing was performed under the conditions of 185°C and 3.0 MPa of pressure for 60 minutes to obtain laminate 1.

(Example 2-2) ∼ (Example 2-4) Manufacturing examples of laminates 2 to 4

Laminates 2 to 4 were manufactured in the same manner as Example 2-1, except that the copper foil to which the resin was attached was changed.

The peel strength of each laminate was measured. The results are summarized and shown in Table 2 below.

(Example 3) Manufacturing example of laminate A

A powder dispersion containing 50 parts by mass of powder 1, 5 parts by mass of dispersant 3, and 45 parts by mass of N-methylpyrrolidone was applied onto the surface of copper foil 1 using a die coater. The copper foil 1 to which the powder dispersion was applied was passed through a ventilation drying furnace (atmosphere temperature: 230°C, atmosphere gas: nitrogen gas having an oxygen gas concentration of 8000 ppm), maintained for 1 minute, and further passed through a far-infrared furnace (temperature: 340°C, gas: nitrogen gas having an oxygen gas concentration of less than 100 ppm) and fired for 1 minute. Copper foil A having a resin layer F of polymer 1 (thickness: 5 μm) attached thereto was obtained.

The surface of the F resin layer and the bonding portion of the copper foil A to which the resin was attached was subjected to vacuum plasma treatment. The treatment conditions were as follows: output: 4.5 kW, introduction gas: argon gas, introduction gas flow rate: 50 cm3/min, pressure: 50 mTorr (6.7 ㎩), and treatment time: 2 min.

As a result of analyzing the surface of the F resin layer of the resin-attached copper foil A by the atomic reflection-infrared absorption spectrum method (ATR-IR analysis method), an absorption peak of a carboxyl group was confirmed. In addition, the surface of the F resin layer of the resin-attached copper foil A was analyzed by the AFM-IR method. An image obtained by analyzing the surface of the resin-attached copper foil A by the AFM-IR method is shown in Fig. 1. The white dot portion (12) in Fig. 1 is an island-shaped convex portion in contact with the F resin layer (10), and an infrared absorption spectrum derived from ethereal oxygen atoms, carboxyl groups, and a -CF- structure was detected in the convex portion. That is, the white dot portion (12) in Fig. 1 is an island-shaped bonding portion dotted on the surface of the F resin layer (10), and the bonding portion contains a hydrophilic component having ethereal oxygen atoms and carboxyl groups derived from the dispersant 3.

After vacuum plasma treatment, prepreg 1 was overlapped on the surface of the F resin layer and the bonding portion of copper foil A to which resin was attached, and vacuum hot pressing was performed at 185°C and 3.0 MPa for 60 minutes to obtain a laminate A. The bending rate of laminate A was 0.3%, and the peel strength was 12 N/cm.

In addition, as a result of subjecting laminate A to a soldering heat resistance test in which it was floated in a solder bath, in the case of laminate A, swelling did not occur even when it was floated in 288°C solder for 5 seconds five times. On the other hand, in the case of a laminate having no island-shaped convex portions, swelling occurred at the stage of being floated in 288°C solder for 5 seconds twice.

(Example 4) Manufacturing example of laminate B

A powder dispersion containing 50 parts by mass of powder 1, 5 parts by mass of dispersant 3, and 45 parts by mass of N-methylpyrrolidone was applied onto the surface of copper foil 1 using a die coater. The copper foil 1 to which the powder dispersion was applied was passed through a ventilation drying furnace (atmosphere temperature: 230°C, atmosphere gas: nitrogen gas having an oxygen gas concentration of 8000 ppm), maintained for 1 minute, and further passed through a far-infrared furnace (temperature: 340°C, gas: nitrogen gas having an oxygen gas concentration of less than 100 ppm) and fired for 1 minute. Copper foil B having a resin portion (thickness of 5 μm) attached to the surface of copper foil 1 was obtained.

The surface of the resin portion of the copper foil B to which the resin was attached was subjected to plasma treatment. As a plasma treatment device, AP-1000 from NORDSON MARCH was used. The plasma treatment conditions were as follows: RF output: 300 W, inter-electrode gap: 2 inches, introduction gas: argon gas, introduction gas flow rate: 50 cm3/min, pressure: 13 Pa, and treatment time: 1 minute. The surface Ra of the resin portion after plasma treatment was 14.5 nm, and Rz was 195 nm.

After plasma treatment, prepreg 1 was overlapped on the surface of the resin portion of copper foil B to which resin was attached, and vacuum heat pressing was performed under the conditions of press temperature: 185°C, press pressure: 3.0 MPa, and press time: 60 minutes, thereby obtaining a laminate B having copper foil 1, resin portion, and cured layer of prepreg in this order.

As a result of observing the cross-section of laminate B by a scanning transmission electron microscope, as shown in Fig. 2, a commercial layer (12') having a thickness of 60 nm was formed between the F resin layer (10') and the cured layer (14'). As a result of analyzing by energy dispersive X-ray analysis, it was confirmed that the commercial layer (12') contained oxygen atoms and fluorine atoms. The bending rate of laminate B was 0.3%, and the peel strength was 12 N/cm.

The dielectric constant (20 ㎓) of the printed board obtained by forming a transmission circuit on laminate B was 4.32 and the dielectric loss tangent (20 ㎓) was 0.01568.

(Example 5) Manufacturing example of laminate B'

A laminate B' was obtained in the same manner as Example 4, except that dispersant 3 was not included in the powder dispersion. Laminate B' did not have a commercial layer, and the F resin layer and the cured layer were in direct contact, and its peel strength was 6 N/cm.

Industrial applicability

The method for producing a resin-attached metal foil of the present invention is a method suitable for producing a resin-attached metal foil having a resin layer having excellent adhesive properties, including a fluoropolymer, and is useful for producing printed circuit boards and the like.

The metal foil and laminate having the resin of the present invention attached thereto are useful as a material for a printed circuit board.

In addition, the entire contents of the specification, claims, abstract and drawings of Japanese Patent Application No. 2018-104011 filed on May 30, 2018, Japanese Patent Application No. 2018-134926 filed on July 18, 2018 and Japanese Patent Application No. 2018-134927 filed on July 18, 2018 are incorporated herein by reference and are incorporated herein as the disclosure of the specification of the present invention.

10 F resin layer
12. Baekjeombu
10' F resin layer
12' commercial floor
14' hardened layer

Claims (15)

A method for manufacturing a resin-attached metal foil having a resin layer on the surface of the metal foil, comprising: applying a powder dispersion containing a tetrafluoroethylene polymer powder, a dispersant having a mass reduction rate of 1 mass%/min or more in a temperature range of 200 to 300°C, and a solvent to the surface of the metal foil, maintaining the metal foil at a temperature at which the mass reduction rate in the temperature range becomes 1 mass%/min or more, and firing the tetrafluoroethylene polymer at a temperature exceeding the temperature range, thereby forming a resin layer containing the tetrafluoroethylene polymer on the surface of the metal foil. In the first paragraph,
A method for manufacturing a metal foil having a resin attached thereto, wherein the water contact angle of the resin layer is 70 to 100°. In claim 1 or 2,
A method for producing a resin-attached metal foil, wherein the dispersant is a polymer having a polyfluoroalkyl group or a polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in the side chain. In claim 1 or 2,
A method for manufacturing a metal foil with a resin attached thereto, wherein the temperature when the metal foil is maintained in the above temperature range is 200 to 300°C. In claim 1 or 2,
A method for manufacturing a metal foil with a resin attached thereto, wherein the atmosphere when maintaining the metal foil in the above temperature range is an atmosphere containing oxygen gas. In claim 1 or 2,
A method for producing a metal foil having a resin attached thereto, wherein the temperature at which a tetrafluoroethylene polymer is sintered is 330 to 380°C. A resin-attached metal foil manufactured by the manufacturing method of claim 1, comprising: a metal foil; a resin layer including a tetrafluoroethylene polymer; and an adhesive portion including a hydrophilic component having at least one selected from the group consisting of an ethereal oxygen atom, a hydroxyl group, and a carboxyl group, in this order, wherein the resin layer and the adhesive portion are in contact. In paragraph 7,
A metal foil with a resin attached thereto, wherein the above-mentioned bonding portion exists in the form of an island. In clause 7 or 8,
A metal foil having a resin attached thereto, wherein the hydrophilic component is derived from a polymer having a polyfluoroalkyl group or a polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in the side chain. A method for producing a laminate, comprising bonding a metal foil to which a resin as described in claim 7 or claim 8 is attached to another substrate by a heat press method to obtain a laminate. A laminate comprising a metal foil to which a resin is attached, manufactured by the manufacturing method of claim 1, having a metal foil, a resin layer comprising a tetrafluoroethylene polymer, and a cured layer of a prepreg comprising a matrix resin in that order, and further having a commercial layer between the resin layer and the cured layer, the commercial layer being in contact with the resin layer and the cured layer, and containing a component derived from the dispersant and having fluorine atoms and oxygen atoms. In Article 11,
A laminate having a thickness of the commercial layer of 1 to 500 nm. In clause 11 or 12,
A laminate, wherein the commercial layer is derived from a polymer having a polyfluoroalkyl group or a polyfluoroalkenyl group and a polyoxyalkylene group or an alcoholic hydroxyl group in the side chain. In clause 11 or 12,
A laminate, wherein the matrix resin is at least one matrix resin that does not have a fluorine atom and is selected from the group consisting of epoxy resin, polyphenylene oxide, polyphenylene ether, and polybutadiene. A printed circuit board including a transmission circuit processed from a metal foil manufactured by the manufacturing method of claim 1, comprising a transmission circuit, a resin layer including a tetrafluoroethylene polymer, and a cured layer of a prepreg including a matrix resin in this order, and further comprising a commercial layer between the resin layer and the cured layer, in contact with the resin layer and the cured layer, the commercial layer containing a component derived from the dispersant and having fluorine atoms and oxygen atoms.