JP7645638B2 - Circuit board interlayer adhesive and laminate - Google Patents

Description

The present invention relates to a circuit board interlayer adhesive and a laminate.

Conventionally, wired circuit boards are provided in various electronic devices. Wired circuit boards are manufactured, for example, by the following method.

That is, first, a first-layer circuit is formed on the copper foil of the carrier-attached copper foil. Next, the first-layer circuit is embedded in a resin layer. Next, a second-layer circuit is formed on the resin layer. After that, the carrier is peeled off to expose the first-layer circuit. In addition, epoxy resin and polyimide resin have been proposed as such a resin layer (see, for example, Patent Document 1).

In recent years, printed circuit boards are being required to handle high-frequency signals. As a result, it has been proposed to use fluororesin, which has a lower dielectric constant than epoxy resin and polyimide resin, as the resin layer (see, for example, Patent Document 2).

JP 2014-225650 A JP 2019-065061 A

However, when the resin layer of the wiring circuit board contains a fluororesin, there is a problem in that the adhesion between the resin layer and the conductor layer is low. In addition, when the resin layer of the wiring circuit board contains a fluororesin, there is a problem in that the resin layer has low conformability to the irregularities of the conductor layer.

The present invention relates to a circuit board interlayer adhesive that has a relatively low dielectric constant and excellent adhesion and conformability to irregularities, and a laminate obtained using the circuit board interlayer adhesive.

The present invention [1] includes a circuit board interlayer adhesive that contains a polyolefin resin.

The present invention [2] further includes the circuit board interlayer adhesive described in [1] above, which contains a fluorine-based resin and/or a polyphenylene ether-based resin.

The present invention [3] includes a laminate comprising a first conductor layer, a second conductor layer disposed opposite the first conductor layer, and an adhesive layer disposed between the first conductor layer and the second conductor layer and adhering the first conductor layer and the second conductor layer, the adhesive layer being made of the circuit board interlayer adhesive described in [1] or [2] above.

The present invention [4] includes a laminate comprising an insulating layer, a conductor layer disposed opposite the insulating layer, and an adhesive layer disposed between the insulating layer and the conductor layer and adhering the insulating layer and the conductor layer, the adhesive layer being made of the circuit board interlayer adhesive described in [1] or [2] above.

The circuit board interlayer adhesive of the present invention contains a polyolefin resin, so it has a relatively low dielectric constant and is excellent in adhesion and conformability to irregularities.

The laminate of the present invention has an adhesive layer made of the above-mentioned circuit board interlayer adhesive. Therefore, in the laminate, the adhesive layer has a relatively low dielectric constant and is excellent in adhesion and conformability to irregularities.

FIG. 1 is a process diagram for manufacturing a circuit board as a first embodiment of a laminate, in which FIG. 1A shows a process for preparing a copper foil with a carrier, FIG. 1B shows a process for forming a first resist layer, and FIG. 1C shows a process for forming a first conductor layer. FIG. 2 is a process diagram for manufacturing a multilayer circuit board following FIG. 1, in which FIG. 2D shows a process for removing the first resist layer, FIG. 2E shows a process for removing the copper foil exposed from the first conductor layer, FIG. 2F shows a process for laminating an adhesive layer, and FIG. 2G shows a process for laminating a copper foil with a carrier onto the adhesive layer. 3 is a process diagram for manufacturing a multilayer circuit board following FIG. 2, in which FIG. 3H shows a process for peeling off the carrier layer, FIG. 3I shows a process for forming a via hole, FIG. 3J shows a process for forming a via fill, and FIG. 3K shows a process for forming a second resist layer. Figure 4 is a process diagram for manufacturing a multilayer circuit board following Figure 3, in which Figure 4L shows the process of forming a second conductor layer, Figure 4M shows the process of removing the second resist layer, Figure 4N shows the process of removing the copper foil exposed from the second conductor layer, and Figure 4O shows the process of peeling off the carrier layer 3. FIG. 5 is a schematic diagram showing a copper-clad laminate as a second embodiment of the laminate. FIG. 6 is a schematic diagram showing a circuit board as a third embodiment of the laminate.

Circuit board interlayer adhesives are adhesives used in the manufacture of laminates (described below). Note that laminates (described below) refer to circuit boards or circuit board materials that can be processed into circuit boards.

The circuit board interlayer adhesive contains a polyolefin resin.

Polyolefin-based resins are homopolymers of olefins or copolymers of olefins. Olefin copolymers are copolymers of olefins and copolymerizable monomers that can be copolymerized with olefins. More specifically, polyolefin-based resins include unmodified polyolefin-based resins and modified polyolefin-based resins.

Examples of unmodified polyolefin resins include polyethylene, polypropylene, polyisobutylene, poly-1-butene, poly-4-methylpentene, polyvinylcyclohexane, polystyrene, poly-p-methylstyrene, poly-α-methylstyrene, ethylene-propylene copolymer, propylene-butene copolymer, styrene-ethylene-propylene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, ethylene-butene copolymer, ethylene-4-methyl-1-pentene copolymer, propylene-4-methyl-1-pentene copolymer, butylene-4-methyl-1-pentene copolymer, ethylene-hexene copolymer, and ethylene-vinyl acetate copolymer. Examples of copolymers include random copolymers and block copolymers (same below). These can be used alone or in combination of two or more types.

Modified polyolefin resins are modified versions of unmodified polyolefin resins.

Examples of modified polyolefin resins include halogenated polyolefin resins, acid-modified polyolefin resins, and halogenated acid-modified polyolefin resins.

Halogenated polyolefin resins are obtained by halogen-modifying unmodified polyolefin resins using known methods. Examples of halogens include fluorine, chlorine, bromine, and iodine. These can be used alone or in combination of two or more. Chlorine is a preferred halogen.

That is, examples of halogenated polyolefin resins include fluorinated polyolefin resins, chlorinated polyolefin resins, brominated polyolefin resins, and iodized polyolefin resins. These can be used alone or in combination of two or more. A preferred example of the halogenated polyolefin resin is a chlorinated polyolefin resin.

Examples of chlorinated polyolefin resins include chlorinated polyethylene, chlorinated polypropylene, chlorinated polyisobutylene, chlorinated poly 1-butene, chlorinated poly 4-methylpentene, chlorinated polyvinylcyclohexane, chlorinated ethylene-propylene copolymer, chlorinated propylene-butene copolymer, chlorinated styrene-ethylene-propylene-styrene copolymer, chlorinated styrene-ethylene-butylene-styrene copolymer, chlorinated ethylene-butene copolymer, chlorinated ethylene-4-methyl-1-pentene copolymer, chlorinated propylene-4-methyl-1-pentene copolymer, chlorinated butylene-4-methyl-1-pentene copolymer, chlorinated ethylene-hexene copolymer, and chlorinated ethylene-vinyl acetate copolymer. These can be used alone or in combination of two or more.

In addition, the halogenation ratio of halogenated polyolefin resins is not particularly limited and is set appropriately depending on the purpose and application.

The acid-modified polyolefin resin is obtained by acid-modifying an unmodified polyolefin resin by a known method. Examples of the acid include unsaturated acids. Examples of the unsaturated acid include maleic acid, fumaric acid, itaconic acid, and (meth)acrylic acid. Examples of the unsaturated acid include anhydrides of these acids. These can be used alone or in combination of two or more kinds. A preferable example of the unsaturated acid is maleic acid.

That is, examples of acid-modified polyolefin resins include maleic acid-modified polyolefin resins, fumaric acid-modified polyolefin resins, itaconic acid-modified polyolefin resins, and (meth)acrylic acid-modified polyolefin resins. These can be used alone or in combination of two or more. A preferred example of the acid-modified polyolefin resin is maleic acid-modified polyolefin resin.

Examples of maleic acid-modified polyolefin resins include maleic acid-modified polyethylene, maleic acid-modified polypropylene, maleic acid-modified polyisobutylene, maleic acid-modified poly 1-butene, maleic acid-modified poly 4-methylpentene, maleic acid-modified polyvinylcyclohexane, maleic acid-modified ethylene-propylene copolymer, maleic acid-modified propylene-butene copolymer, maleic acid-modified styrene-ethylene-propylene-styrene copolymer, maleic acid-modified styrene-ethylene-butylene-styrene copolymer, maleic acid-modified ethylene-butene copolymer, maleic acid-modified ethylene-4-methyl-1-pentene copolymer, maleic acid-modified propylene-4-methyl-1-pentene copolymer, maleic acid-modified butylene-4-methyl-1-pentene copolymer, maleic acid-modified ethylene-hexene copolymer, and maleic acid-modified ethylene-vinyl acetate copolymer. These can be used alone or in combination of two or more.

In acid-modified polyolefin resins, the modification ratio is not particularly limited and is set appropriately depending on the purpose and application.

For example, the amount of acid is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and, for example, 20 parts by mass or less, preferably 10 parts by mass or less, per 100 parts by mass of the total amount of the acid-modified polyolefin resin.

The acid value of the acid-modified polyolefin resin is, for example, 0.1 mgKOH/g or more, preferably 0.5 mgKOH/g or more, and, for example, 100 mgKOH/g or less, preferably 60 mgKOH/g or less.

The acid value is measured in accordance with JIS K 2501 (2003).

The halogenated acid-modified polyolefin resin can be obtained, for example, by halogenating an acid-modified polyolefin resin by a known method. The halogenated acid-modified polyolefin resin can be obtained, for example, by acid-modifying a halogenated polyolefin resin by a known method.

These polyolefin resins can be used alone or in combination of two or more types.

As the polyolefin resin, preferably, a modified polyolefin resin is used, more preferably, an acid-modified polyolefin resin is used, even more preferably, a maleic acid-modified polyolefin resin is used, and particularly preferably, a maleic acid-modified propylene-butene copolymer is used.

The weight average molecular weight of the polyolefin resin is, for example, 10,000 or more, preferably 50,000 or more, and, for example, 500,000 or less, preferably 300,000 or less.

The weight average molecular weight of polyolefin resins is measured using gel permeation chromatography in terms of standard polystyrene.

The melting point of the polyolefin resin is, for example, 30°C or higher, preferably 50°C or higher, and typically 150°C or lower.

The melting point is measured in accordance with JIS K 7122 (2012).

The heat of fusion of the polyolefin resin is, for example, 0 J/g or more, preferably 5 J/g or more. The heat of fusion of the polyolefin resin is, for example, 100 J/g or less, preferably 60 J/g or less.

The heat of fusion is measured in accordance with JIS K 7122 (2012).

The circuit board interlayer adhesive may contain a polyolefin resin and may not contain other resins. In other words, the circuit board interlayer adhesive may contain, for example, only a polyolefin resin.

The circuit board interlayer adhesive contains a polyolefin resin and may also contain other resins.

The other resins are resin components other than polyolefin-based resins. Examples of the other resins include fluorine-based resins, polyphenylene ether-based resins, and (meth)acrylic resins.

Examples of fluorine-based resins include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-ethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroethylene copolymer, and tetrafluoroethylene-hexafluoropropylene-perfluoroethylene-chlorotrifluoroethylene copolymer.

Fluorine-based resins are also available on the market. Examples of commercially available products include Fluon+ series (registered trademark, manufactured by AGC), Lumiflon series (registered trademark, manufactured by AGC), PTFE dispersion NS series (manufactured by Nagoya Gosei Co., Ltd.), and PTFE dispersion (manufactured by uni).

These fluororesins can be used alone or in combination of two or more types.

Examples of polyphenylene ether resins include known polyphenylene ether resins. In addition, modified polyphenylene ether resins in which polyphenylene ether resins are alloyed with other resins (such as polystyrene) are also included.

In addition, examples of polyphenylene ether resins include commercially available products. Examples of commercially available products include Zylon S201A and Zylon S202A (both manufactured by Asahi Kasei), Noryl SA9000 and Noryl SA90 (both manufactured by SABIC), Bestran 1900NC (manufactured by Daicel-Evonik), and Iupiace LN23 and NX700 (both manufactured by Mitsubishi Engineering Plastics).

These polyphenylene ether resins can be used alone or in combination of two or more types.

Examples of (meth)acrylic resins include (meth)acrylic homopolymers and (meth)acrylic copolymers. Note that (meth)acrylic refers to acrylic and/or methacrylic.

Examples of (meth)acrylic homopolymers include homopolymers of (meth)acrylic acid esters. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, and phenyl (meth)acrylate. These can be used alone or in combination of two or more.

The (meth)acrylic copolymer may be, for example, a copolymer of the above-mentioned (meth)acrylic acid ester and a copolymerizable monomer. The copolymerizable monomer is a monomer that can be copolymerized with the (meth)acrylic acid ester. The copolymerizable monomer is not particularly limited, and may be any known copolymerizable monomer. More specifically, the copolymerizable monomer may be, for example, a carboxy group-containing copolymerizable monomer, a hydroxy group-containing copolymerizable monomer, an amino group-containing copolymerizable monomer, a cyano group-containing copolymerizable monomer, a styrene-based monomer, and a vinyl ester-based monomer. These may be used alone or in combination of two or more kinds. The copolymerizable monomer may preferably be a carboxy group-containing copolymerizable monomer.

Examples of carboxyl group-containing copolymerizable monomers include maleic acid, fumaric acid, itaconic acid, and (meth)acrylic acid. Examples of carboxyl group-containing copolymerizable monomers also include anhydrides of these. These can be used alone or in combination of two or more types.

These (meth)acrylic resins can be used alone or in combination of two or more kinds. As the (meth)acrylic resin, a (meth)acrylic copolymer is preferable, and a copolymer of a (meth)acrylic acid ester and a carboxy group-containing copolymerizable monomer is more preferable.

These other resins can be used alone or in combination of two or more. Preferred examples of the other resins include fluorine-based resins and polyphenylene ether-based resins.

In other words, the circuit board interlayer adhesive preferably contains a polyolefin resin and a fluorine-based resin and/or a polyphenylene ether resin. When the circuit board interlayer adhesive contains a polyolefin resin and a fluorine-based resin and/or a polyphenylene ether resin, an adhesive layer is obtained that has a lower dielectric constant, is highly flexible, and is easily softened quickly when heated.

When the circuit board interlayer adhesive contains other resins, the content of the other resins is, for example, 10% by mass or more, preferably 20% by mass or more, and, for example, 95% by mass or less, preferably 90% by mass or less, relative to the total amount of the circuit board interlayer adhesive. Also, the content of the polyolefin resin is, for example, 5% by mass or more, preferably 10% by mass or more, and, for example, 90% by mass or less, preferably 80% by mass or less, relative to the total amount of the circuit board interlayer adhesive.

In addition, the circuit board interlayer adhesive can contain known additives.

Examples of additives include plasticizers, defoamers, leveling agents, mildew inhibitors, rust inhibitors, matting agents, flame retardants, thixotropic agents, tackifiers, thickeners, lubricants, antistatic agents, surfactants, reaction retarders, antioxidants, UV absorbers, hydrolysis inhibitors, weather stabilizers, heat stabilizers, dyes, inorganic pigments, organic pigments, hardeners, crosslinking agents, silane coupling agents, tack inhibitors, inorganic particles, and organic particles. These can be used alone or in combination of two or more types. The proportion and timing of addition of the additives are appropriately set depending on the purpose and application.

The circuit board interlayer adhesive can also be prepared as a solution. More specifically, the polyolefin resin and other resins that are added as necessary can be dissolved or dispersed in an organic solvent. The organic solvent is not particularly limited, and examples include known organic solvents.

In such a case, the solid content concentration of the circuit board interlayer adhesive is, for example, 5% by mass or more, preferably 10% by mass or more. Also, the solid content concentration of the circuit board interlayer adhesive is, for example, 50% by mass or less, preferably 30% by mass or less.

And because this type of circuit board interlayer adhesive contains polyolefin resin, it has a relatively low dielectric constant and is excellent in adhesion and conformability to uneven surfaces.

Therefore, circuit board interlayer adhesives are suitable for use in the manufacture of laminates.

The laminate is a circuit board or a circuit board material. The circuit board is, for example, a laminate having a conductor layer with a circuit pattern. The circuit board material is, for example, a laminate having a conductor layer without a circuit pattern, in which a circuit pattern can be formed by processing.

The laminate is manufactured by using a circuit board interlayer adhesive. The method of manufacturing a circuit board as a laminate using a circuit board interlayer adhesive is described in detail below.

Figures 1 to 4 are cross-sectional views showing the steps for manufacturing a circuit board as a first embodiment of the laminate.

In the following, the upper side of the paper will be referred to as one side, and the lower side of the paper will be referred to as the other side.

In Figures 1 to 4, the circuit board 1 is a multilayer circuit board having at least two conductor layers. More specifically, as shown in Figure 4O, the circuit board 1 includes a first conductor layer 6, a second conductor layer 16 disposed opposite the first conductor layer 6, and an adhesive layer 11 disposed between the first conductor layer 6 and the second conductor layer 16 and bonding the first conductor layer 6 and the second conductor layer 16 together.

In addition, in the circuit board 1, the adhesive layer 11 is formed from the above-mentioned circuit board interlayer adhesive.

To manufacture such a circuit board 1, first, a carrier-attached copper foil 2 is prepared as shown in FIG. 1A. The carrier-attached copper foil 2 includes a carrier layer 3 and a copper foil 4 laminated on one side of the carrier layer 3.

The carrier layer 3 is not particularly limited, and may be a known release sheet. The copper foil 4 is laminated to the carrier layer 3 by a known method. The thickness of the copper foil 4 is appropriately set depending on the purpose and application. Furthermore, the copper foil 4 is surface-treated as necessary. Examples of surface treatments include roughening treatments.

Next, in this method, as shown in FIG. 1B, a first resist layer 5 having a predetermined shape is formed on one surface of the copper foil 4. The first resist layer 5 is formed, for example, by applying a known resist liquid, exposing it to light, and developing it. The first resist layer 5 can also be formed by exposing and etching a dry film resist.

Next, in this method, as shown in FIG. 1C, the first conductor layer 6 is formed. The first conductor layer 6 is formed, for example, by electrolytic plating. In electrolytic plating, for example, the carrier layer 3, the copper foil 4, and the first resist layer 5 are immersed in an electrolytic plating solution, and then the copper foil 4 is powered. As a result, the first conductor layer 6 is formed on one surface of the copper foil 4 in the reverse pattern of the first resist layer 5. In other words, the first conductor layer 6 has a circuit pattern.

Then, in this method, as shown in FIG. 2D, the first resist layer 5 is removed by a known method. Then, in this method, as shown in FIG. 2E, the copper foil 4 exposed from the first conductor layer 6 is removed by a known method.

Next, in this method, as shown in Figure 2F, an adhesive layer 11 made of a wiring circuit interlayer adhesive is laminated onto the carrier layer 3, the first conductor layer 6, and the copper foil 4.

More specifically, in this method, for example, a cast film of a wiring circuit interlayer adhesive is created. The cast film is then pressed onto the carrier layer 3, the first conductor layer 6, and the copper foil 4. As a result, the cast film covers the first conductor layer 6 and the copper foil 4. The cast film also forms an adhesive layer 11.

On the other hand, in this method, the carrier-attached copper foil 12 is prepared separately. The carrier-attached copper foil 12 includes a carrier layer 13 and a copper foil 14 laminated on the other side of the carrier layer 13. Then, in this method, the copper foil 14 of the carrier-attached copper foil 12 is laminated on the adhesive layer 11, as shown in FIG. 2G.

Next, in this method, as shown in FIG. 3H, the carrier layer 13 of the carrier-attached copper foil 12 is peeled off. Next, in this method, as shown in FIG. 3I, the copper foil 14 and the adhesive layer 11 are opened by a known method to form a via hole 18. Also, the first conductor layer 6 is exposed from the via hole 18. Next, in this method, as shown in FIG. 3J, the via hole 18 is filled with a conductive material to form a via fill 19. Note that an example of the conductive material is copper.

Next, in this method, as shown in FIG. 3K, a second resist layer 15 of a predetermined shape is formed on one surface of the copper foil 14. The second resist layer 15 is formed, for example, by applying a known resist liquid, exposing it to light, and developing it. Similarly to the first resist layer 5, the second resist layer 15 can also be formed from a dry film resist.

Next, in this method, as shown in FIG. 4L, the second conductor layer 16 is formed. The second conductor layer 16 is formed, for example, by electrolytic plating. As a result, the second conductor layer 16 is formed on one surface of the copper foil 14 in the reverse pattern of the second resist layer 15. In other words, the second conductor layer 16 has a circuit pattern.

Then, in this method, as shown in FIG. 4M, the second resist layer 15 is removed by a known method. Then, in this method, as shown in FIG. 4N, the copper foil 14 exposed from the second conductor layer 16 is removed by a known method.

Then, the method includes peeling off the carrier layer 3, as shown in FIG. 4O, thereby exposing the copper foil 4. As a result, the circuit board 1 is formed.

In the circuit board 1, the first conductor layer 6 and the second conductor layer 16 are bonded together by the adhesive layer 11.

In other words, the circuit board 1 has an adhesive layer 11 made of the above-mentioned circuit board interlayer adhesive. Therefore, in the circuit board 1, the adhesive layer 11 has a relatively low dielectric constant and is excellent in adhesion and conformability to irregularities.

The manufacturing method of the circuit board is not limited to the above description. In other words, the circuit board can be manufactured using the circuit board interlayer adhesive by other known methods.

In the above description, a circuit board is given as an example of a laminate, but other examples of laminates include circuit board materials that can be processed into circuit boards. Examples of circuit board materials include copper-clad laminates.

The cross section is a schematic cross section showing a copper-clad laminate as a second embodiment of the laminate.

In FIG. 5, the copper-clad laminate 21 includes an insulating layer 22, a conductor layer 24 disposed opposite the insulating layer 22, and an adhesive layer 23 disposed between the insulating layer 22 and the conductor layer 24 and bonding the insulating layer 22 and the conductor layer 24. In the copper-clad laminate 21, the adhesive layer 23 is formed from the above-mentioned circuit board interlayer adhesive.

The insulating layer 22 is an insulating layer containing a known dielectric. Examples of the dielectric include polyimide resin, epoxy resin, fluororesin, and liquid crystal polymer. These can be used alone or in combination of two or more types. The thickness of the insulating layer 22 is set appropriately depending on the purpose and application.

The conductor layer 24 is a thin film made of a conductive material. An example of the conductive material is copper. The conductor layer 24 is formed by a known film formation method. The thickness of the conductor layer 24 is adjusted to be, for example, relatively thin. This allows the circuit pattern to be formed by a subtractive method. The thickness of the conductor layer 24 is, for example, 50 μm or less.

The adhesive layer 23 is interposed between the insulating layer 22 and the conductor layer 24. The adhesive layer 23 is a dried product of the above-mentioned circuit board interlayer adhesive.

When manufacturing the copper-clad laminate 21, for example, first, the insulating layer 22 and the conductor layer 24 are prepared. Next, a circuit board interlayer adhesive is applied to one side of the insulating layer 22. Thereafter, the conductor layer 24 is adhered to one side of the circuit board interlayer adhesive, and the circuit board interlayer adhesive is dried. In this way, the copper-clad laminate 21 is obtained. Note that the copper-clad laminate 21 can also be manufactured in the reverse order described above. That is, in this method, the circuit board interlayer adhesive is applied to one side of the conductor layer 24. Then, the insulating layer 22 is adhered to one side of the circuit board interlayer adhesive, and the circuit board interlayer adhesive is dried. In this way, the copper-clad laminate 21 is obtained.

In the copper-clad laminate 21, the insulating layer 22 and the conductor layer 24 are bonded together by the adhesive layer 23.

In other words, the copper-clad laminate 21 has an adhesive layer 23 made of the above-mentioned circuit board interlayer adhesive. Therefore, in the copper-clad laminate 21, the adhesive layer 23 has a relatively low dielectric constant and is excellent in adhesion and conformability to irregularities.

In the above description, the adhesive layer 23 and the conductor layer 24 are formed only on one side of the insulating layer 22, but the adhesive layer 23 and the conductor layer 24 may be formed on both sides of the insulating layer 22.

The copper-clad laminate 21 may not have an insulating layer 22. In other words, the conductor layer 24 may be formed on both sides of the adhesive layer 23. In other words, the two conductor layers 24 may be bonded together by the adhesive layer 23. In such a case, the adhesive layer 23 also serves as the insulating layer 22.

The copper-clad laminate 21 can also be processed to form a circuit board. More specifically, the conductor layer 24 of the copper-clad laminate 21 can be etched by a known method to form a circuit. As a result, a circuit board is formed as the third embodiment of the laminate, as shown in FIG. 6.

In such a circuit board, the insulating layer 22 and the circuit consisting of the conductor layer 24 are bonded together by the adhesive layer 23.

In other words, such a circuit board also has an adhesive layer 23 made of the above-mentioned circuit board interlayer adhesive. Therefore, the adhesive layer 23 has a relatively low dielectric constant and is excellent in adhesion and conformability to irregularities.

Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are by mass unless otherwise specified. In addition, the specific numerical values of the compounding ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit value (a numerical value defined as "equal to or less than") or lower limit value (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding compounding ratio (content ratio), physical property value, parameter, etc. described in the above "Form for carrying out the invention".

<Resin>
Production Example 1 (Unmodified Propylene-Butene Copolymer (PBR): Resin (A-1))
A 2-liter autoclave that had been thoroughly purged with nitrogen was charged with 900 mL of hexane and 90 g of 1-butene. Next, 1 mmol of triisobutylaluminum was added to the autoclave, and the temperature was raised to 70° C. Next, propylene was supplied to the autoclave, and the total pressure was adjusted to 7 kg/cm ² G. Next, methylaluminoxane and rac-dimethylsilylene-bis{1-(2-methyl-4-phenylindenyl)}zirconium dichloride were added to the autoclave. The amount of methylaluminoxane was 0.30 mmol. The amount of rac-dimethylsilylene-bis{1-(2-methyl-4-phenylindenyl)}zirconium dichloride was 0.001 mmol in terms of Zr.

Thereafter, propylene was continuously supplied to the autoclave, and the total pressure was maintained at 7 kg/cm ² G, and 1-butene and propylene were polymerized for 30 minutes. After polymerization, the mixture was degassed and the reaction product was recovered in a large amount of methanol. The reaction product was then dried under reduced pressure at 110° C. for 12 hours. As a result, an unmodified propylene-1-butene copolymer (resin (A-1)) was obtained.

The melting point of resin (A-1) was 78.3°C, the heat of fusion was 29.2 J/g, the weight average molecular weight (Mw) was 330,000, and the propylene content was 67.2 mol%.

Production Example 2 (Unmodified Propylene-Butene Copolymer: Resin (A-2))
A 2-liter autoclave that had been thoroughly purged with nitrogen was charged with 900 mL of hexane and 80 g of 1-butene. Next, 1 mmol of triisobutylaluminum was added to the autoclave, and the temperature was raised to 70° C. Next, propylene was supplied to the autoclave, and the total pressure was adjusted to 7 kg/cm ² G. Next, methylaluminoxane and rac-dimethylsilylene-bis{1-(2-methyl-4-phenylindenyl)}zirconium dichloride were added to the autoclave. The amount of methylaluminoxane was 0.30 mmol. The amount of rac-dimethylsilylene-bis{1-(2-methyl-4-phenylindenyl)}zirconium dichloride was 0.001 mmol in terms of Zr.

Thereafter, propylene was continuously supplied to the autoclave to maintain the total pressure at 7 kg/cm ² G, and 1-butene and propylene were polymerized for 30 minutes. After polymerization, the mixture was degassed and the reaction product was recovered in a large amount of methanol. The reaction product was then dried under reduced pressure at 110° C. for 12 hours. As a result, an unmodified propylene-1-butene copolymer (resin (A-2)) was obtained.

The melting point of resin (A-2) was 89.2°C, the heat of fusion was 31.5 J/g, the Mw was 330,000, and the propylene content was 73.5 mol%.

Production Example 3 (Unmodified Propylene/4-methyl-1-pentene Copolymer: Resin (A-3))
300 mL of hexane and 450 mL of 4-methyl-1-pentene were charged into a 1.5-liter autoclave that had been thoroughly purged with nitrogen. Then, 0.75 mmol of triisobutylaluminum was added to the autoclave, and the temperature was raised to 60°C. Then, propylene was supplied to the autoclave, and the total pressure was adjusted to 0.40 MPa (gauge pressure). Then, methylaluminoxane and diphenylmethylene(1-ethyl-3-t-butyl-cyclopentadienyl)(2,7-di-t-butyl-fluorenyl)zirconium dichloride were added to the autoclave. The amount of methylaluminoxane was 1 mmol in terms of Al. Also, the amount of diphenylmethylene(1-ethyl-3-t-butyl-cyclopentadienyl)(2,7-di-t-butyl-fluorenyl)zirconium dichloride was 0.01 mmol.

Propylene was then continuously fed into the autoclave, and 4-methyl-1-pentene and propylene were polymerized for 60 minutes. After polymerization, the reaction was stopped, and the autoclave was depressurized to atmospheric pressure. The reaction product was then recovered with acetone. The reaction product was then dried under reduced pressure at 100°C for 12 hours. This resulted in the production of an unmodified propylene-4-methyl-1-pentene copolymer (resin (A-3)).

The melting point of resin (A-3) was not observed. In addition, the Mw of resin (A-3) was 320,000, and the propylene content was 28 mol%.

Production Example 4 (Maleic Acid Modified Propylene-Butene Copolymer: Resin (A-4))
3 kg of resin (A-2) was added to 10 L of toluene and heated to 145°C under a nitrogen atmosphere. This resulted in a toluene solution of the resin. Next, 382 g of maleic anhydride and 175 g of di-tert-butyl peroxide were fed to the solution over 4 hours, and the mixture was reacted at 145°C for 2 hours. Thereafter, acetone was added to the reaction solution to precipitate the reaction product. The precipitate was filtered, washed, and vacuum dried. This resulted in a maleic acid-modified propylene-1-butene copolymer (resin (A-4)).

The melting point of resin (A-4) was 85.9°C, the heat of fusion was 29.9 J/g, the Mw was 110,000, and the proportion of maleic anhydride was 1 part by mass per 100 parts by mass of the total amount of resin (A-4).

Production Example 5 (Mixture of Maleic Acid Modified Propylene-1-butene Copolymer and Maleic Acid Modified SEPS: Resin (A-5))
1.5 kg of resin (A-1) and 1.5 kg of Septon 2002 (product name, styrene-ethylene-propylene-styrene copolymer (SEPS), manufactured by Kuraray) were added to 10 L of toluene, and the temperature was raised to 145°C under a nitrogen atmosphere. This resulted in a toluene solution of the resin. Next, 382 g of maleic anhydride and 175 g of di-tert-butyl peroxide were supplied to the solution over 4 hours, and the reaction was carried out at 145°C for 2 hours. Thereafter, acetone was added to the reaction liquid to precipitate the reaction product. The precipitate was filtered, washed, and vacuum dried. This resulted in a mixture of maleic acid-modified propylene-1-butene copolymer and maleic acid-modified styrene-ethylene-propylene-styrene copolymer (resin (A-5)).

The melting point of resin (A-5) was 75.6°C, the heat of fusion was 14.7 J/g, the Mw was 98,000, and the proportion of maleic anhydride was 1 part by mass per 100 parts by mass of the total amount of resin (A-5).

Production Example 6 (Maleic Acid Modified Styrene-Ethylene-Butylene-Styrene Copolymer: Resin (A-6))
3 kg of Kraton G1652M (product name, styrene-ethylene-butylene-styrene copolymer (SEBS), manufactured by Kuraray) was added to 10 L of toluene and heated to 145°C under a nitrogen atmosphere. This resulted in a toluene solution of a resin. Next, 382 g of maleic anhydride and 175 g of di-tert-butyl peroxide were fed to the solution over 4 hours, and the mixture was reacted at 145°C for 2 hours. Thereafter, acetone was added to the reaction liquid to precipitate the reaction product. The precipitate was filtered, washed, and vacuum dried. This resulted in a maleic acid-modified styrene-ethylene-butylene-styrene copolymer (resin (A-6)).

The melting point of resin (A-6) was not observed. Furthermore, the heat of fusion of resin (A-6) was not observed. Resin (A-6) had an Mw of 100,000, and the proportion of maleic anhydride was 2 parts by mass per 100 parts by mass of the total amount of resin (A-6).

Production Example 7 (Maleic Acid Modified Propylene/4-Methyl-1-Pentene Copolymer: Resin (A-7))
3 kg of resin (A-3) was added to 10 L of toluene and heated to 145°C under a nitrogen atmosphere. This resulted in a toluene solution of the resin. Next, 382 g of maleic anhydride and 175 g of di-tert-butyl peroxide were fed to the solution over 4 hours, and the mixture was reacted at 145°C for 2 hours. Thereafter, acetone was added to the reaction solution to precipitate the reaction product. The precipitate was then filtered, washed, and vacuum dried. This resulted in a maleic acid-modified propylene/4-methyl-1-pentene copolymer (resin (A-7)).

The melting point of resin (A-7) was not observed. In addition, the Mw of resin (A-7) was 100,000, and the proportion of maleic anhydride was 1 part by mass per 100 parts by mass of the total amount of resin (A-7).

Production Example 8 (Ethylene-propylene copolymer (Resin A-8))
Into a continuous polymerization reactor equipped with an agitator and thoroughly purged with nitrogen, 1 L of dehydrated and purified hexane was added.

Then, a hexane solution of 96 mmol/L ethylaluminum sesquichloride was continuously fed into the reactor at a flow rate of 500 mL/h for 1 hour.

Then, 500 mL/h of a hexane solution of 16 mmol/L VO(OC ₂ H ₅ )Cl ₂ as a catalyst and 500 mL/h of hexane were continuously fed to the reactor.

Next, 47 L/h of ethylene gas, 47 L/h of propylene gas, and 20 L/h of hydrogen gas were supplied to the reactor using a bubbling tube. A coolant was circulated through the jacket outside the reactor. Meanwhile, the reaction liquid was extracted from the top of the reactor and adjusted so that the reaction liquid was always at 1 L.

The reaction solution was deashed with hydrochloric acid and poured into a large amount of methanol. The precipitated reaction product was then dried under reduced pressure at 130°C for 24 hours.

This resulted in the production of ethylene-propylene copolymer (EPR) (resin A-8).

The ethylene content of resin (A-8) was 55.9 mol% and the Mw was 14,000.

<Interlayer adhesive for circuit boards>
Reference Example 1
100 g of resin (A-5) was dissolved in 400 g of toluene under heating to prepare circuit board interlayer adhesive A.

Reference Example 2
80 g of resin (A-4) and 20 g of resin (A-8) were dissolved in 400 g of toluene with heating to prepare circuit board interlayer adhesive B.

Reference Example 3
100 g of resin (A-4) was dissolved in 400 g of toluene under heating to prepare circuit board interlayer adhesive C.

Reference Example 4
50 g of resin (A-7) was dissolved in 450 g of toluene under heating to prepare circuit board interlayer adhesive D.

Reference Example 5
15 parts by mass of n-propyl acetate was mixed with 4 parts by mass of methylcyclohexane to prepare a mixed solvent of methylcyclohexane and n-propyl acetate.

Next, 63 g of Kraton G1652M (product name: styrene-ethylene-butylene-styrene copolymer (SEBS), manufactured by Kuraray) was dissolved in 152 g of the mixed solution by heating.

Meanwhile, 46.3 g of methyl methacrylate, 2.5 g of n-butyl acrylate, 11.7 g of n-butyl methacrylate, 2.5 g of methacrylic acid, 0.76 g of Perbutyl O (manufactured by NOF Corp.), and 107 g of n-propyl acetate were mixed uniformly to prepare a monomer solution.

The monomer solution was then added dropwise to the Kraton G1652M solution over a period of 2 hours and polymerized at 95°C. After that, 114 g of n-propyl acetate was added to the reaction solution. This resulted in the preparation of circuit board interlayer adhesive E.

Reference Example 6
100 g of resin (A-6) was dissolved in 400 g of toluene under heating to prepare circuit board interlayer adhesive F.

Reference Example 7
A fluorine-based resin solution (product name Fluon+EA-2000, manufactured by AGC) was prepared.

Next, 30 g of resin (A-8) was added to 70 g of fluororesin (solid content).

Toluene was then added to adjust the total amount to 500 g. This produced circuit board interlayer adhesive G.

Reference Example 8
A fluororesin solution was prepared. Next, 30 g of polyisobutylene (trade name: Himol 4H, manufactured by Petrochemical Co., Ltd.) was added to 70 g of the fluororesin (solid content).

Toluene was then added to adjust the total amount to 500 g. This produced circuit board interlayer adhesive H.

Example 9
A fluororesin solution was prepared. Next, the circuit board interlayer adhesive A was added to 50 g of the fluororesin (solid content) so that the resin component of the circuit board interlayer adhesive A was 50 g.

Toluene was then added to adjust the total amount to 500 g. This resulted in the preparation of circuit board interlayer adhesive I.

Example 10
A fluororesin solution was prepared. Next, the circuit board interlayer adhesive B was added to 50 g of the fluororesin (solid content) so that the resin component of the circuit board interlayer adhesive B was 50 g.

Toluene was then added to adjust the total amount to 500 g. This resulted in the preparation of circuit board interlayer adhesive J.

Example 11
A fluororesin solution was prepared. Next, the circuit board interlayer adhesive C was added to 50 g of the fluororesin (solid content) so that the resin component of the circuit board interlayer adhesive C was 50 g.

Toluene was then added to adjust the total amount to 500 g. This produced circuit board interlayer adhesive K.

Example 12
A fluororesin solution was prepared. Next, the circuit board interlayer adhesive D was added to 50 g of the fluororesin (solid content) so that the resin component of the circuit board interlayer adhesive D was 50 g.

Toluene was then added to adjust the total amount to 500 g. This produced circuit board interlayer adhesive L.

Comparative Example 1
A fluorine-based resin solution was prepared. Toluene was then added to adjust the total amount to 500 g. Thus, a circuit board interlayer adhesive M was prepared.

<Evaluation>
(1) Dielectric constant and dielectric loss tangent A predetermined amount of the circuit board interlayer adhesive was applied onto a 100 μm-thick release PET film and dried at 100° C. for 3 minutes. This resulted in a coating film with a dry thickness of about 60 μm. The coating film was then formed into a rectangular shape.

Then, the cavity resonator method was used to measure the relative dielectric constant and dielectric tangent of the coating film at a frequency of about 10 GHz. The measurement device used was a vector network analyzer HP8510B (manufactured by Keysight Technologies). The measurement method was in accordance with JIS R 1641 (2007).

(2) Adhesion A predetermined amount of the circuit board interlayer adhesive was applied to an aluminum foil and dried at 100°C for 1 minute. This resulted in a coating film with a dry thickness of about 3 μm. The coating film was then thermocompressed to a copper plate. The thermocompression conditions were 180°C, 0.3 MPa, and 1 second.

The coating was then cooled and a 15 mm wide cut was made into the aluminum foil.

Then, the peel strength between the aluminum foil and the copper plate was measured using a universal tensile tester. The crosshead speed was 50 mm/min. The peel angle was 180°.

(3) Contourability A predetermined amount of the circuit board interlayer adhesive was applied to an aluminum foil and dried for 2 minutes at 100° C. This resulted in a coating film having a dry thickness of about 30 μm.

On the other hand, a circuit board with an exposed conductor layer (see FIG. 2E) was prepared. The coating film was then thermocompression bonded to the conductor layer. The thermocompression conditions were 180°C, 0.3 MPa, and 3 seconds. The cross section of the bonded portion was then observed with a digital microscope. The conformability to irregularities was evaluated according to the following criteria.

〇: No gaps were observed between the coating and the circuit.

×: Gaps were observed between the coating and the circuit.

Details of the abbreviations in the table are given below.

Maleated PBR: maleic acid modified propylene-butene copolymer Maleated C3-4MP: maleic acid modified propylene-4-methyl-1-pentene copolymer Maleated SEPS: maleic acid modified styrene-ethylene-propylene-styrene copolymer Maleated SEBS: maleic acid modified styrene-ethylene-butylene-styrene copolymer EPR: ethylene-propylene copolymer SEBS: styrene-ethylene-butylene-styrene copolymer Acrylic resin: methyl methacrylate/n-butyl acrylate/n-butyl methacrylate/methacrylic acid copolymer Fluorine resin: trade name Fluon+EA-2000, manufactured by AGC

Reference Signs List 1 Multilayer circuit board 2 Copper foil with carrier 3 Carrier layer 4 Copper foil 5 Resist layer 6 First conductor layer

Claims (4)

Contains a polyolefin resin and a fluorine-based resin ,
The circuit board interlayer adhesive, wherein the polyolefin resin contains an acid-modified polyolefin resin. For the total amount of circuit board interlayer adhesive,
The proportion of the polyolefin resin is 5% by mass or more and 90% by mass or less,
2. The circuit board interlayer adhesive according to claim 1, wherein the proportion of the fluorine-based resin is 10% by mass or more and 95% by mass or less. A first conductor layer;
A second conductor layer disposed opposite the first conductor layer;
an adhesive layer disposed between the first conductor layer and the second conductor layer and adhering the first conductor layer and the second conductor layer;
A laminate, wherein the adhesive layer comprises the circuit board interlayer adhesive according to claim 1 or 2. An insulating layer;
a conductor layer disposed opposite the insulating layer;
an adhesive layer disposed between the insulating layer and the conductor layer and adhering the insulating layer and the conductor layer;
A laminate, wherein the adhesive layer comprises the circuit board interlayer adhesive according to claim 1 or 2.

Images