JP6275200B2 - Double-sided circuit board suitable for high-frequency circuits - Google Patents

Description

  The present invention relates to a double-sided circuit board that is excellent in high-frequency transmission characteristics and adhesion between a copper foil and a resin layer, and suitable for a high-frequency circuit having a low linear expansion coefficient and elastic modulus in the Z-axis direction.

  In general, epoxy resins and polyimide resins are widely used for printed wiring boards, but for printed wiring boards used for high frequency applications of several tens of gigahertz, copper foil is used from the viewpoint of dielectric properties and hygroscopicity. A laminate in which a fluororesin insulating layer is formed is mainly used.

  In general, since the fluororesin does not have high adhesive strength with a metal, it is necessary to roughen the surface of the metal in order to improve the adhesion. However, it is known that the signal easily propagates on the surface of the metal at a high frequency of 1 gigahertz or more (skin effect). When the unevenness of the surface of the metal foil that becomes the transmission line is large, the electric signal is not inside the conductor. Since it propagates around the surface of the uneven part, there arises a problem that transmission loss increases. Examples of Patent Document 1 illustrate a laminate using a metal foil having a surface roughness (Rz) of 0.6 to 0.7 μm. However, in a high-frequency circuit, for example, in the case of 15 GHz, it is said that an electric signal travels a depth of 0.5 μm from the metal surface, and as the frequency increases, the depth becomes shallower. The degree is not enough.

  In addition, a fluororesin generally has a high coefficient of linear expansion of 100 ppm / ° C. or higher, and there is a problem in dimensional stability. Patent Documents 2 and 3 describe a method of combining a fluororesin film and a glass cloth. In Patent Document 2, a copper foil with an adhesive is used in order to improve the adhesiveness. However, since the adhesive is generally an epoxy resin having inferior dielectric properties, it is not suitable for high frequency applications. In the example of Patent Document 3, a copper foil 3EC (thickness 18 μm) manufactured by Mitsui Kinzoku Co., Ltd. is used. The surface roughness (Rz) of this copper foil is 5 μm or more according to the company's technical data. Therefore, it is not suitable for use in a high frequency region. In the example of Patent Document 4, a copper foil having a surface roughness (Ra) of 0.2 μm and not roughened on both sides is used, but for adhesion to an insulating substrate made of fluororesin, tetrafluoro is used. An adhesive resin film that is a composite film of a blend of ethylene-perfluoroalkyl vinyl ether and a liquid crystal polymer resin is used.

  Patent Document 5 describes that the transmission loss of a copper-clad laminate composed of a low-roughness copper foil, a fluororesin film subjected to a special surface treatment, and a glass cloth is sufficiently low. In this structure, XY Although the linear expansion coefficient in the direction is as low as around 15 ppm / ° C., the linear expansion coefficient in the Z-axis direction is very high at around 250 ppm / ° C. at room temperature. In the case of such a substrate with a high coefficient of linear expansion in the Z-axis direction, if the through-hole of the substrate is plated and the front surface and the back surface of the substrate are made conductive, then a heat shock test from -45 ° C to 125 ° C is performed. There may be a failure that the through hole breaks around 1000 cycles. Moreover, the general copper clad laminated board using a glass reinforcing material has the tendency for the elasticity modulus of a dielectric material layer to become high, so that the ratio of a reinforcing material increases. On the other hand, when mounting a semiconductor chip on a high-frequency board, it is common not to use an underfill material made of an epoxy resin with a high dielectric constant to suppress an increase in dielectric constant, but when the elastic modulus of the board is high In this case, unless an underfill material is used, the stress generated between the substrate and the semiconductor chip cannot be sufficiently relaxed, and there is a problem that the semiconductor chip is broken or dropped off. Therefore, a substrate having a sufficiently low elastic modulus is required for a high-frequency circuit substrate.

JP 2009-246201 A JP-A-1-317727 JP-A-5-269918 JP 2007-98692 A WO2016 / 021666

  The present invention has been made in view of the above points, and can reduce electrical signal transmission loss in a high-frequency circuit, and at the same time has high adhesion between a copper foil having a low surface roughness and a fluororesin, An object of the present invention is to provide a substrate for a double-sided circuit that has a sufficiently low linear expansion coefficient in the Z-axis direction as well as a surface direction and a sufficiently low elasticity.

  In the double-sided circuit board that is a laminate of copper foil, fluororesin, and glass nonwoven fabric (glass paper), the present inventors set the two-dimensional roughness Ra of the surface in contact with the fluororesin of the copper foil to a specific value or less. In addition, by making the presence ratio of oxygen atoms on the surface in contact with the copper foil of the fluororesin more than a specific value, the adhesiveness is high even for a copper foil having a low surface roughness, resulting in a transmission loss at a high frequency. It was found that a double-sided circuit board having a low linear expansion coefficient in the Z-axis direction in addition to the surface direction and having a sufficiently low elastic modulus was obtained.

That is, the present invention
(1) A double-sided circuit board, which is a laminate including two copper foils and a composite material made of a glass nonwoven fabric with a front surface and a back surface covered with a fluororesin provided between the two copper foils. The two-dimensional roughness Ra of the surface in contact with the composite material of the two copper foils is 0.2 μm or less, and the presence ratio of oxygen atoms observed by ESCA on the surface in contact with the copper foil of the composite material is 1. A double-sided circuit board that is 0% or more,
(2) The double-sided circuit board according to (1), wherein the composite material is a surface-modified composite material;
(3) Both surfaces which are laminated bodies including two copper foils and alternating layers in which n sheets of fluororesin and n-1 glass nonwoven fabrics are alternately provided between the two copper foils. A circuit board, wherein n is an integer of 2 to 10, the two-dimensional roughness Ra of the surface of the two copper foils in contact with the fluororesin film is 0.2 μm or less, and the fluororesin A substrate for a double-sided circuit, wherein the existence ratio of oxygen atoms observed by ESCA on the surface in contact with the copper foil of the film is 1.0% or more;
(4) The substrate for a double-sided circuit according to the above item (3), wherein the film made of the fluororesin is a film whose surface in contact with the copper foil is surface-modified.
(5) The double-sided circuit board according to any one of (1) to (4) above, wherein the content of the glass nonwoven fabric in the insulator layer obtained by removing two copper foils from the double-sided circuit board is 10 A substrate for a double-sided circuit that is at least mass%,
(6) Any of (1) to (5) above, wherein the component of the fluororesin is a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) or a tetrafluoroethylene / hexafluoropropylene copolymer (FEP). The double-sided circuit board as described,
(7) The double-sided circuit board according to any one of (1) to (6), wherein the peel strength of the copper foil in the 90-degree direction with respect to the board is 0.8 N / mm or more,
About.

  Since the circuit board of the present invention uses a copper foil having an extremely low surface roughness, the transmission loss is extremely small even in a high frequency band, and the adhesion between the fluororesin film layer and the metal and dimensional stability are excellent.

  The copper foil used for the double-sided circuit board of the present invention preferably has a surface roughness (Ra) of the surface in contact with the fluororesin in the range of 0.2 μm or less, and in the range of 0.15 μm or less. It is more preferable. If the surface roughness exceeds 0.2 μm, the transmission loss increases, and the practical performance of the double-sided circuit board may not be satisfied. There are electrolytic foils and rolled foils as the types of copper foils, but both copper foils can be used for the double-sided circuit board of the present invention. The thickness of the copper foil is preferably 5 to 50 μm, more preferably 8 to 40 μm.

  The surface of the copper foil in contact with the fluororesin may be untreated or surface-treated. Specific examples of the surface treatment include, for example, plating treatment with one or more metals selected from nickel, iron, zinc, gold, silver, aluminum, chromium, titanium, palladium, or tin. Nickel, iron, zinc, gold Or the plating process by 1 or more types chosen from aluminum is preferable, the plating process by nickel or aluminum is more preferable, and the 1 or more types of metal plating process chosen from nickel, iron, zinc, gold | metal | money, or tin in some cases is preferable. Alternatively, the surface of the copper foil that has not been treated or the surface of the copper foil that has been plated with the above metal may be subjected to surface modification with a chemical such as a silane coupling agent.

  The glass nonwoven fabric used for the double-sided circuit board of the present invention is obtained by fixing glass short fibers with a small amount of a binder compound (resin or inorganic material) or by entanglement of glass short fibers without using a binder compound. A commercially available product can be used. The diameter of the short glass fiber is preferably 0.5 to 30 μm, and the fiber length is preferably 5 to 30 mm. Specific examples of the binder compound include resins such as epoxy resin, acrylic resin, cellulose, polyvinyl alcohol, and fluorine resin, and inorganic substances such as silica compound. The usage-amount of a binder compound is 3-15 mass% normally with respect to a glass short fiber. Examples of the material for the short glass fiber include E glass, C glass, A glass, S glass, D glass, NE glass, and low dielectric constant glass. The thickness of the glass nonwoven fabric is usually 50 μm to 1000 μm, preferably 100 μm to 900 μm. In addition, the thickness of the glass nonwoven fabric in this application means the value measured using digital gauge DG-925 (load 110 grams, surface diameter 10mm) by Ono Sokki Co., Ltd. according to JISP8118: 1998. In order to increase the affinity with the fluororesin, the glass nonwoven fabric may be treated with a silane coupling agent.

  Since most of the glass nonwoven fabrics have a very high porosity of 80% or more, it is preferable to use a material thicker than a film made of a fluororesin described later and compress it with pressure.

  Examples of fluororesins include polytetrafluoroethylene [PTFE], polychlorotrifluoroethylene [PCTFE], ethylene-TFE copolymer [ETFE], ethylene-chlorotrifluoroethylene [ECTFE] copolymer, and CTFE-TFE copolymer. Preferably, it is at least one selected from the group consisting of a polymer, a TFE-HFP copolymer [FEP], a TFE-PAVE copolymer [PFA], and a polyvinylidene fluoride [PVdF]. From the viewpoint of dielectric constant / dielectric loss tangent) and heat resistance, PFA and / or FEP are more preferable, and PFA is more preferable.

PFA is a copolymer including polymerized units based on TFE (TFE units) and polymerized units based on PAVE (PAVE units).
In the PFA, PAVE is not particularly limited, and for example, the following general formula (1):
CF ₂ = CF-ORf ¹ (1)
The perfluoro unsaturated compound represented by these is mentioned. In the formula, Rf ¹ represents a perfluoro organic group.

  In the present specification, the “perfluoro organic group” means an organic group in which all of the hydrogen atoms bonded to the carbon atom are substituted with fluorine atoms, and the perfluoro organic group is an ether-bonded oxygen atom. You may have.

As the PAVE, for example, in the general formula (1), Rf ¹ is preferably a perfluoroalkyl group having 1 to 10 carbon atoms, more preferably a perfluoroalkyl group having 1 to 5 carbon atoms. preferable.

  The PAVE is selected from the group consisting of perfluoro (methyl vinyl ether) [PMVE], perfluoro (ethyl vinyl ether) [PEVE], perfluoro (propyl vinyl ether) [PPVE], and perfluoro (butyl vinyl ether). It is more preferably at least one, more preferably at least one selected from the group consisting of PMVE, PEVE and PPVE, and particularly preferably PPVE in terms of excellent heat resistance.

  The PFA preferably has 1 to 10 mol% of PAVE units, and more preferably 3 to 6 mol%. The PFA preferably has a total of 90 to 100 mol% of TFE units and PAVE units with respect to all polymerized units.

The PFA may be a copolymer including TFE units, PAVE units, and polymerized units based on monomers copolymerizable with TFE and PAVE. As monomers copolymerizable with TFE and PAVE, hexafluoropropylene, CX ₁ X ₂ = CX ₃ (CF ₂ ) nX ₄ (wherein X ₁ , X ₂ and X ₃ are the same or different) And represents a hydrogen atom or a fluorine atom, X ₄ represents a hydrogen atom, a fluorine atom or a chlorine atom, n represents an integer of 2 to 10, and CF ₂ = CF At least one selected from the group consisting of alkyl perfluorovinyl ether derivatives represented by —OCH ₂ —Rf ² (wherein Rf ² represents a perfluoroalkyl group having 1 to 5 carbon atoms) is preferable.

As the alkyl perfluorovinyl ether derivative, those in which Rf ² is a perfluoroalkyl group having 1 to 3 carbon atoms are preferable, and CF ₂ ═CF—OCH ₂ —CF ₂ CF ₃ is more preferable.

  When PFA has polymerized units based on monomers copolymerizable with TFE and PAVE, PFA has 0 to 10 monomer units derived from monomers copolymerizable with TFE and PAVE. Preferably, the total amount of TFE units and PAVE units is 90 to 100 mol%. More preferably, the monomer units derived from monomers copolymerizable with TFE and PAVE are 0.1 to 10 mol%, and the total of TFE units and PAVE units is 90 to 99.9 mol%. .

  FEP is a copolymer containing polymerized units based on tetrafluoroethylene (TFE units) and polymerized units based on hexafluoropropylene (HFP units).

  The FEP is not particularly limited, but is preferably a copolymer having a molar ratio of TFE units to HFP units (TFE units / HFP units) of 70 to 99/30 to 1, preferably 80 to 97/20 to 3. A copolymer is more preferred. When there are too few TFE units, there exists a tendency for a mechanical physical property to fall, and when too much, melting | fusing point becomes high too much and there exists a tendency for a moldability to fall.

  FEP has a monomer unit derived from a monomer copolymerizable with TFE and HFP in an amount of 0.1 to 10 mol%, and a total of 90 to 99.9 mol% of TFE units and HFP units. A polymer is also preferred. Examples of monomers copolymerizable with TFE and HFP include PAVE and alkyl perfluorovinyl ether derivatives.

The content of each monomer of the copolymer described above can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and fluorescent X-ray analysis depending on the type of monomer.
The fluororesin preferably has a melt flow rate (MFR) of 1.0 g / 10 min or more, more preferably 2.5 g / 10 min or more, and further preferably 10 g / 10 min or more. . The upper limit of MFR is, for example, 100 g / 10 minutes.
The MFR is a value that can be measured under conditions of a temperature of 372 ° C. and a load of 5.0 kg in accordance with ASTM D3307.

  The melting point of the fluororesin is preferably 320 ° C. or lower, and more preferably 310 ° C. or lower. The melting point is preferably 260 ° C. or higher and more preferably 265 ° C. or higher in view of heat resistance and workability in producing a double-sided substrate.

  The melting point is a temperature corresponding to a melting peak when the temperature is raised at a rate of 10 ° C./min using a DSC (Differential Scanning Calorimetry) apparatus.

  When a film is used as the material form of the fluororesin, the melt-processable fluororesin or a composition containing the fluororesin is molded by a known method such as a melt extrusion molding method, a solvent casting method, or a spray method. can get. The thickness of one film made of a fluororesin is preferably 10 to 100 μm, more preferably 20 to 80 μm.

As the composite material used for the double-sided circuit board of the present invention, a glass nonwoven fabric whose front and back surfaces are covered with a fluororesin can be used. As a method of obtaining a composite material from a fluororesin and a glass nonwoven fabric, for example,
I. A method in which a fluororesin film and a glass nonwoven fabric that have been pre-formed and surface-treated are pressure-bonded under heating,
II. A method of compounding and molding under heat with a fluororesin melt extruded from a die or the like and a glass nonwoven fabric,
In view of productivity, the method I is preferable.

  In the case of pressure bonding under heat (thermocompression bonding), the pressure can be usually within a range of 250 to 400 ° C. for 1 to 20 minutes at a pressure of 0.1 to 10 megapascals. Regarding the thermocompression bonding temperature, there is a concern that the resin may ooze out or the thickness may become non-uniform at a high temperature, and is preferably less than 350 ° C., more preferably 340 ° C. or less. Thermocompression bonding can be performed batch-wise using a press machine, or can be performed continuously using a high-temperature laminator. In the case of using a press machine, it is preferable to use a vacuum press machine in order to prevent air from being caught and to improve the impregnation property of the fluororesin into the glass nonwoven fabric. When the impregnation property of the fluororesin into the glass nonwoven fabric is low, the problem that the plating solution permeates into the glass cloth and forms a short between the through holes when the through holes are formed is likely to occur. However, in this specification, the film made of a fluororesin is sufficiently impregnated with respect to the glass nonwoven fabric, regardless of whether it is not sufficiently impregnated, an alternating layer composed of the fluororesin film and the glass nonwoven fabric, One form of the composite material is used.

  In the film made of the composite material and the fluororesin used for the double-sided circuit board of the present invention, the oxygen atom existence ratio observed by ESCA on the surface in contact with the copper foil is 1.0% or more. The proportion of oxygen atoms observed by ESCA on the surface in contact with the copper foil is preferably 1.2% or more, more preferably 1.8% or more, and even more preferably 2.5% or more. The upper limit is not particularly specified, but it is preferably 15% or less in view of the influence on productivity and other physical properties. The proportion of nitrogen atoms observed by ESCA on the surface in contact with the copper foil is not particularly defined, but is preferably 0.1% or more.

  Modification of the surface of the composite material (the surface of the fluororesin) and the surface of the film made of the fluororesin is necessary in order to make the oxygen atom existing ratio observed by ESCA on the surface in contact with the copper foil 1.0% or more. It is. In the case of a composite material, a film made of a fluororesin whose surface has been modified in advance can be pressure-bonded to a glass nonwoven fabric by the above method to obtain a composite material whose surface has been modified.

  For the surface modification, a conventionally known discharge treatment such as corona discharge treatment, glow discharge treatment, plasma discharge treatment, or sputtering treatment can be employed. For example, surface free energy can be controlled by introducing oxygen gas, nitrogen gas, hydrogen gas, etc. into the discharge atmosphere, and inert gas containing organic compounds (eg nitrogen gas, helium gas, argon gas, etc.) The surface to be modified is exposed to the atmosphere, and a high frequency voltage is applied between the electrodes to cause discharge, thereby generating active species on the surface, and then introducing a functional group of the organic compound or graft polymerization of the polymerizable organic compound. Thus, surface modification can be performed.

  The organic compound used here is a polymerizable or non-polymerizable organic compound containing an oxygen atom. For example, vinyl esters such as vinyl acetate and vinyl formate; acrylic acid esters such as glycidyl methacrylate; vinyl ethyl ether and vinyl Ethers such as methyl ether and glycidyl methyl ether; Carboxylic acids such as acetic acid and formic acid; Alcohols such as methyl alcohol, ethyl alcohol, phenol and ethylene glycol; Ketones such as acetone and methyl ethyl ketone; Carboxes such as ethyl acetate and ethyl formate Acid esters; acrylic acids such as acrylic acid and methacrylic acid; Of these, vinyl esters, acrylate esters, and ketones are preferred from the viewpoint that the modified surface is not easily deactivated (long life) and easy in terms of safety, and particularly vinyl acetate, Glycidyl methacrylate is preferred.

The concentration of the organic compound varies depending on the fluorine resin to be surface-modified, the kind of the organic compound, and the like, but is usually 0.1 to 3.0% by volume, preferably 0.1 to 1.0% by volume. The discharge conditions may be appropriately selected depending on the desired degree of surface modification, the type of fluororesin, the type and concentration of the organic compound, etc. Usually, the charge density is 0.3 to 9.0 W · sec / cm ² , The discharge treatment is preferably performed in the range of 0.3 to 3.0 W · sec / cm ² . The treatment temperature can be any temperature in the range of 0 to 100 ° C.

  Next, a method for producing the double-sided circuit board of the present invention will be described.

As a method for obtaining the double-sided circuit board of the present invention, for example, method A; two copper foils and the above composite material are used, and a copper foil surface having a two-dimensional roughness of 0.2 μm or less is opposed to the composite material. A method in which a copper foil-composite material-copper foil is laminated in this order to form a laminate, followed by pressure bonding under heating,
Method B: After alternately laminating n sheets of fluororesin and n-1 glass nonwoven fabrics to obtain alternating layers of fluororesin films and glass nonwoven fabrics, from the top layer fluororesin of the laminate Laminate and laminate the copper foil on the top and bottom layers of the fluororesin film so that the copper foil surface with a two-dimensional roughness of 0.2 μm or less faces the fluororesin film. Examples of the method include a method of performing pressure bonding under heating after forming a body.

  The method A is the simplest preparation method using a single composite material, but a double-sided circuit board may be prepared using a plurality of composite materials between two copper foils. In the case of using a plurality of composite materials, as long as the oxygen atom existence ratio observed by ESCA on the surface in contact with the copper foil of the composite material is 1.0% or more, the surface is inspected by ESCA on the surface in contact with another composite material. The existing proportion of oxygen atoms may be less than 1.0%.

  In addition, although said A method is a preparation method of the double-sided circuit board which provided the copper foil only on both surfaces, it has a multilayered board of three or more layers obtained using three or more copper foils, and a copper foil on both surfaces A circuit board having a structure in which a fluororesin layer (and a glass nonwoven fabric) is further laminated on the copper foil of the two-layer board is also included in the category of the double-sided circuit board of the present invention.

  The B method will be described more specifically. For example, when a double-sided circuit board is prepared using two fluororesin films and one glass nonwoven fabric, the two-dimensional roughness of the copper foil is 0.00. Copper foil-film made of fluororesin-glass nonwoven fabric-fluororesin so that the surface of 2 μm or less and the surface of the film made of fluororesin observed by ESCA have a proportion of oxygen atoms of 1.0% or more After the film-copper foil consisting of the above is superposed in this order, it is pressure-bonded under heating. In this case, the proportion of oxygen atoms observed by ESCA on the surface facing the glass nonwoven fabric of the fluororesin film may be less than 1.0%. For example, when a double-sided circuit board is prepared using a film made of three fluororesins and two glass nonwoven fabrics, the copper foil has a surface having a two-dimensional roughness of 0.2 μm or less and a fluororesin. Copper foil-film made of fluororesin-glass nonwoven fabric-film made of fluororesin-glass nonwoven fabric-fluororesin so that the surface of the film observed with ESCA has an oxygen atom content of 1.0% or more. After the film-copper foil consisting of the above is superposed in this order, it is pressure-bonded under heating.

  The above-mentioned method B is a method for preparing a double-sided circuit board provided with copper foil on both sides, and a fluororesin layer (and glass nonwoven fabric) is further laminated on the copper foil of a two-layer board having copper foil on both sides. The multilayer circuit board of the structure which laminated | stacked copper foil through the film board | substrate which carried out, the film which consists of n sheets of fluororesin, and the n-1 glass nonwoven fabric is also contained in the category of the board | substrate for double-sided circuits of this invention.

  The thermocompression bonding in the A method and the B method may be performed by a method according to the thermocompression bonding conditions described in the method for obtaining a composite material.

  The film made of a fluororesin that has been subjected to the above surface treatment cannot have a sufficient adhesive strength with respect to a copper foil having a surface roughness of 0.2 μm or less by itself, and it exudes from the copper foil at the time of thermocompression bonding. Although uniformization cannot be achieved, by using a glass nonwoven fabric in combination or by using a composite material with a glass nonwoven fabric, the linear expansion coefficient is sufficiently lowered, and the resin exudation is reduced, and the surface roughness Ra is 0. High adhesiveness is expressed even for copper foil of 2 μm or less.

  The number n of films made of fluororesin used for the double-sided circuit board of the present invention is usually an integer of 2 to 10, preferably an integer of 2 to 8, and more preferably an integer of 2 to 6. . The linear expansion coefficient in the XY direction of the dielectric layer of the present invention can be changed by changing the thickness of the fluororesin film, the type and thickness of the glass nonwoven fabric, and the value of n. It is preferably in the range of 50 ppm / ° C., more preferably in the range of 10 to 40 ppm / ° C. When the linear expansion coefficient of the dielectric layer exceeds 50 ppm / ° C., the adhesion between the copper foil and the dielectric layer is lowered, and problems such as warping and undulation of the substrate are likely to occur after the copper foil etching.

The elastic modulus of the insulator layer excluding the copper foil from the double-sided circuit board of the present invention is preferably 5 GPa or less at room temperature, more preferably 4 GPa or less. In order to prevent deterioration of dielectric characteristics in a high-frequency substrate, an underfill that is a stress relaxation agent is often not added between the semiconductor chip and the substrate. In such a case, if the elastic modulus of the substrate exceeds 5 GPa, The stress generated in the semiconductor chip cannot be sufficiently relaxed, and the semiconductor chip is likely to be damaged.
The content of the glass nonwoven fabric in the insulator layer excluding the copper foil from the double-sided circuit board of the present invention is usually 10 to 90% by mass, preferably 15 to 85% by mass.

  In the present invention, the high-frequency circuit is not only a circuit that transmits only a high-frequency signal, but also a transmission path that converts a high-frequency signal into a low-frequency signal and outputs the generated low-frequency signal to the outside, or a high-frequency circuit. A transmission path for transmitting a signal that is not a high-frequency signal, such as a transmission path for supplying power to drive the corresponding component, is also included.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. In addition, the measurement and evaluation in an Example were performed with the apparatus and method as described below.

(Two-dimensional roughness Ra of the copper foil surface)
Measurement was performed by a stylus method using SE-500 manufactured by Kosaka Laboratory.

(ESCA analysis of fluororesin surface)
It was measured with an X-ray photoelectron spectrometer (ESCA-750 manufactured by Shimadzu Corporation).

(Adhesive strength between copper foil and fluororesin)
In accordance with JIS C5016-1994, the peel strength of the copper foil was measured by a tensile tester while peeling the copper foil at a rate of 50 mm per minute in the direction of 90 ° with respect to the copper foil removal surface. The obtained value was defined as the adhesive strength.

(Elastic modulus of insulator layer)
After etching the copper foil of the produced double-sided substrate, it was measured with a tensile tester (AGS-X manufactured by Shimadzu Corporation).

(Dielectric constant, dielectric loss tangent of double-sided circuit board)
After etching the copper foil of the produced double-sided substrate, it was measured at 1 GHz with a cavity resonator (manufactured by Kanto Electronics Application Development Co., Ltd.) and analyzed with a network analyzer (manufactured by Agilent Technology Co., Ltd., model 8719ET).

(Transmission loss of double-sided circuit board)
A 10 cm long microstrip line was produced by etching, and the transmission loss at 40 GHz was measured using a network analyzer.

(Linear expansion coefficient of the insulator layer in the Z-axis direction)
It measured with the laser thermal dilatometer (LIX-2M; Advance Riko Co., Ltd. product).

Example 1
Surface treatment on 2 sides of non-roughened electrolytic copper foil (product name CF-T9DA-SV-18 manufactured by Fukuda Metal Foil Powder Co., Ltd.) having a surface roughness Ra of 0.08 μm and a thickness of 18 μm and 50 μm in thickness (A nitrogen gas containing 0.13% by volume of vinyl acetate is passed in the vicinity of the discharge electrode and the roll-shaped ground electrode of the corona discharge device, and the film is continuously passed along the roll-shaped ground electrode to obtain a charge density of 1 A tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) film in which both sides of the film were subjected to corona discharge treatment at 7 w · s / cm ² ) and the proportion of O present by ESCA surface analysis was 2.62%. (TFE / PPVE = 98.5 / 1.5 (mol%), MFR: 14.8 g / 10 min, melting point: 305 ° C.) 2 sheets, a glass nonwoven fabric (Olive) having a thickness of 423 μm (Sys Co., Ltd., SYS053), and the matte surface of the copper foil is inside (that is, the matte surface is in contact with the PFA film), and the copper foil / PFA film / nonwoven glass / PFA film / It laminated | stacked in order of copper foil. This laminated body was hot-pressed at 325 ° C. for 30 minutes using a vacuum press machine, thereby producing a double-sided substrate 1 of the present invention having a thickness of 125 μm.

Example 2
In Example 1, the thickness of the two PFA films was set to 50 μm on one side and 25 μm on the other side, and then the same as in Example 1, and a double-sided substrate 2 of the present invention having a thickness of 100 μm was produced.

Example 3
In Example 1, the double-sided substrate 3 having a thickness of 125 μm was prepared in the same manner except that the two PFA films were changed to FEP films and the same double-sided treatment as in Example 1 was used. did.

Comparative Example 1
A double-sided substrate 4 having a thickness of 120 μm is prepared in the same manner as in Example 1 except that a glass cloth having a thickness of 43 μm (IPC style name 1078 manufactured by Arisawa Manufacturing Co., Ltd.) is used instead of the glass nonwoven fabric. did.

  Using the double-sided substrates 1, 2, 3, and 4, the peel strength between the copper foil and the fluororesin layer was measured. Further, the copper foil was etched, and the elastic modulus, dielectric constant, dielectric loss tangent, and linear expansion coefficient in the Z-axis direction of the insulating layer were measured. Furthermore, a microstrip line was produced and the transmission loss at 40 GHz was measured.

According to the present invention, a double-sided circuit board having a low linear expansion coefficient, a strong copper foil peeling strength, and a low transmission loss at high frequencies can be easily manufactured, and thus it is extremely useful industrially.

Claims (7)

A double-sided circuit board that is a laminate including two copper foils and a composite material made of a glass nonwoven fabric having a front surface and a back surface covered with a fluororesin provided between the two copper foils, The two-dimensional roughness Ra of the surface of the copper foil in contact with the composite material is 0.2 μm or less, and the proportion of oxygen atoms observed by ESCA on the surface of the composite material in contact with the copper foil is 1.0% or more der Ri, Z-axis direction of the linear expansion coefficient in the range of 30 ° C. to 40 ° C. is not more than 120 ppm / ° C., the substrate double-sided circuit.   The double-sided circuit board according to claim 1, wherein the composite material is a surface-modified composite material. A double-sided circuit board, which is a laminate including two copper foils and alternating layers in which n sheets of fluororesin and n-1 glass nonwoven fabrics are alternately provided between the two copper foils And n is an integer of 2 to 10, the two-dimensional roughness Ra of the surface in contact with the film made of fluororesin of two copper foils is 0.2 μm or less, and the copper of the film made of fluororesin the proportion of oxygen atoms observed by ESCA surface in contact with the foil Ri der least 1.0%, Z-axis direction of the linear expansion coefficient in the range of 30 ° C. to 40 ° C. is not more than 120 ppm / ° C., double-sided circuit Substrate.   The double-sided circuit board according to claim 3, wherein the film made of a fluororesin is a film having a surface modified with a surface in contact with the copper foil.   The double-sided circuit board according to any one of claims 1 to 4, wherein the content of the glass nonwoven fabric in the insulator layer obtained by removing two copper foils from the double-sided circuit board is 10% by mass or more. A double-sided circuit board. The fluorine resin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer containing (FEP), both surfaces of any one of claims 1 to 5 Circuit board. Double-sided circuit board according to any one of claims 1 to 6 peeling strength of the copper foil is 0.8N / mm or more in the direction of 90 degrees with respect to the double-sided circuit board.