JPS61183374A - Adhesive composition for flexible printed circuit board - Google Patents

Abstract

PURPOSE:To obtain an adhesive having excellent adhesion, resistance to heat and deterioration by heat, flame retardance and processability, by blending an acrylic elastomer, a novolak resin, an epoxy resin, a curing accelerator and an inorg. filler. CONSTITUTION:An adhesive compsn. contains an acrylic elastomer (A) contg. a functional group selected from among epoxy, carboxyl and hydroxyl groups, a novolak resin (B) contg. p-xylene linkage, an epoxy resin (C), a curing accelerator (D) and an inorg. filler (E). As the acrylic elastomer, those contg. epoxy group are preferred, because they are reacted a a low temp. Pref. the acrylic elastomer (A) is used in a quantity of 30-70% based on that of the resin component. Pref. the novolak resin (B) is used in such a quantity as to give an equivalent ratio of the phenolic hydroxyl group (b) to the epoxy group (c) in the epoxy resin of 0.6-1.1.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides strong adhesion between a metal foil and a thin synthetic resin material in a flexible printed wiring board, excellent heat resistance and heat deterioration resistance, as well as moisture resistance and resistance to heat deterioration. Flexible printing arrangement with flammability and excellent processing characteristics! The present invention relates to an adhesive composition for reversal.

[Technical background of the invention and its problems 1 In recent years, as electronic devices have become denser, lighter, thinner, and smaller, the demand for lightweight flexible printed wiring boards that can be mounted in three-dimensional wiring and functions has increased. There is. In addition, in consumer electronics, demands for flame retardant materials and adhesive properties after heat deterioration are becoming stronger, particularly from the standpoint of safety. Adhesives for flexible printed circuit boards are used not only to bond thin synthetic resin materials and the treated surface of metal foil, but also to insulate and protect circuits on the shine surface (polished surface) of the metal foil of patterned wiring boards. It is desirable that it can be used to bond lay films. In particular, adhesives for cover lay films can firmly adhere to the shine surface of metal foil, and can suppress flow to the land area to a small extent, and can be used to bond pattern circuits. There must be good embedding properties between the parts.
Moreover, the shelf life is required to be at least one month at room temperature and three months or more at 5°C. Furthermore, in order to improve productivity and not deteriorate dimensional accuracy, heating is performed at low temperature and between MRs.
Processability such as crimping is required.

However, even when polyimide film, which has excellent heat resistance and flame retardancy, is used as a thin base material, in addition to the above-mentioned processing properties of the flexible printed wiring board, there are also problems in adhesiveness, heat resistance, line insulation resistance, heat deterioration resistance, and It was extremely difficult to provide flame retardancy and other properties. Conventionally, nitrile rubber adhesives (JP-A-51-135936, JP-A-57-3877) have been used as adhesives for flexible printed wiring boards.
No.), polyamide adhesive (Japanese Patent Application Laid-open No. 125285
No.), polyester adhesive (JP-A-50-16866
A number of proposals have been made, including JP-A No. 54-7441) and polyacrylic adhesives (Japanese Patent Application No. 12993-1982). However, the nitrile rubber type has the disadvantage that it has poor heat deterioration resistance and tends to become extremely hard after a 10-day air deterioration test at 150° C., and the polyamide type has the disadvantage of slightly high hygroscopicity. Polyester-based films have the disadvantage of weak adhesive strength compared to polyimide films, and polyacrylic-based films require high temperatures and long periods of time for heat molding.
Lowering the molding temperature and shortening the molding time had the disadvantage of poor moisture resistance.

[Object of the Invention] The object of the present invention was to solve the above-mentioned difficulties and disadvantages, and to provide an adhesive that has excellent adhesive properties, heat deterioration resistance, flame retardance, and moisture resistance, and which can be used as a coverlay adhesive. The present invention aims to provide an adhesive composition for flexible printed wiring boards that has good processing properties.

[Summary of the Invention] As a result of extensive studies aimed at achieving the above object, the present inventors have discovered that the adhesive composition described below is suitable as an adhesive for flexible printed wiring boards, and have accomplished the present invention. This is what led to this.

That is, the present invention provides (A) an acrylic elastomer having one or more functional groups selected from the group of epoxy groups, carboxyl groups, and hydroxyl groups, (B) a novolak resin containing a paraxylene bond, (C This is an adhesive composition for a flexible printed wiring board, which contains as essential components: ) an epoxy resin, (D) a curing accelerator, and (E) an inorganic filler.

Examples of the acrylic elastomer (A) having one or more functional groups selected from the group of epoxy groups, carboxyl groups, and hydroxyl groups used in the present invention include Arontac S-1511L, S-1511X, and S-1.
015,8-1017 (manufactured by Toagosei Kagaku Co., Ltd., trade name)
, AR-51 (manufactured by Nippon Zeon Co., Ltd., trade name), Noxtite PA-501, PA-502 (manufactured by Nippon Mektron Co., Ltd., trade name), Tissant Resin WSO23,8G51.5
Examples include G80.5G90 (manufactured by Teikoku Kagaku Sangyo Co., Ltd., trade name), and these may be used alone or in combination of two or more.

This acrylic elastomer may have any functional group such as an epoxy group, a carboxyl group, or a hydroxyl group, but among these, those having an epoxy group are particularly used because they react at low temperatures. The blending amount of the acrylic elastomer is preferably 30 to 70% by weight based on the resin component of the adhesive composition.

If the blend M is less than 30% by weight, the flexibility is poor;
If it exceeds % by weight, the flexibility will be improved, but the heat resistance during the second half of humidification and the flame retardance will be poor, which is not preferable.

Examples of the (B) novolak resin containing a paraxylene bond used in the present invention include Millex XL-225 (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name). It has been found that the paraxylene bond-containing novolak resin has a larger molecular weight than a normal novolak resin, and that the resin after curing has better adhesion after heat-resistant deterioration than when a normal novolak resin is used. Similar to novolac resins, it has crosslinking properties with epoxy resins due to the action of hydroxyl groups at the ortho position, and because of its large molecular weight, the apparent reaction with epoxy resins is rapid and is thought to result from the plasticizing effect. The blending amount of the novolak resin containing a xylene bond is the phenolic hydroxyl group (b) and the epoxy group (C) of the epoxy resin.
It is desirable that the equivalent ratio ((b)/(C)) is within the range of 0.6 to 1.1. This is because if the equivalence ratio is less than 0.6, the solder heat resistance after humidification will decrease, and if it exceeds 1.1, the moisture resistance will decrease, which is not preferable.

The epoxy resin (C) used in the present invention is not particularly limited, and all epoxy resins can be used. Examples include bisphenol A type epoxy resins, novolac epoxy resins, and brominated epoxy resins thereof, and these may be used alone or in combination of two or more. When making flame retardant with an epoxy resin, the bromination rate is preferably 8% by weight or more based on the resin component of the adhesive composition. If it is less than 8% by weight, it is not effective for flame retardancy (unpreferable).

Examples of the curing accelerator (E) used in the present invention include dicyandiamide, Ebicure YPH201 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name), BFg imidazole complex AC
-4B series (manufactured by Maruzen Oil Co., Ltd., trade name), imidazole, etc., which may be used alone or together with 28H
Mix and use on X. Crosslinking of epoxy resin is carried out by a paraxylene bond-containing novolac resin and an acrylic elastomer, so depending on the molding conditions, an epoxy resin curing accelerator may not be necessary. It is necessary to use The amount to be added is determined depending on the desired molding conditions or shelf life.

Examples of the inorganic filler (E) used in the present invention include ultrafine anhydrous silica and aluminum hydroxide, which are used alone or in combination of two or more. The effect of the inorganic filler is to adjust the surface tack (viscosity S>) and to moderate the expansion and contraction of the adhesive composition at high temperatures such as during soldering.The amount of the inorganic filler to be added depends on the adhesive composition. It is desirable that the amount is 3 to 65% by weight based on the solid content of the product.If the amount is less than 3% by weight, the surface tack will be strong and the processability will be poor, and if it exceeds 65% by weight, the base thin material will deteriorate. It is undesirable because it has poor wettability with other materials, resulting in poor adhesion.

As the solvent for the adhesive composition containing each of the above components as essential components, methyl ethyl ketone, acetone, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, dioxane, methyl cellosolve acetate, and mixtures thereof can be used. The adhesive composition is dissolved in a solvent and applied in a solution state, but the resin component can also be prepared by mixing the respective raw materials or by proceeding with preliminary curing.

Lamination of a synthetic resin thin material and metal foil via an adhesive composition is performed by applying the adhesive composition to at least either the synthetic resin thin material or the metal foil in a solution state, and then applying the adhesive composition to the synthetic resin thin material or the metal foil in a hot air oven. Dry to evaporate the solvent or perform preliminary curing. Next, any method can be used, such as applying heat and pressure using a heated press, or continuously coating and drying, continuously passing through heated rolls, applying heat and pressure, winding up, and post-heat curing. can be adopted.

Examples of thin synthetic resin materials include polyimide films and ultra-thin laminates, and examples of metal foils include copper foil, aluminum foil, nichrome foil, and the like. On the other hand, in order to use it for adhesion of Burley film, apply the above-mentioned solvent onto the surface of the synthetic resin thin film material using a normal coating device to a film thickness of 15 to 35 μm, dry it to volatilize the solvent, or use a preliminary coating method. Perform curing. Thereafter, a pattern is punched out to fit the flexible printed wiring board, and then the printed circuit board is overlapped with the wiring board and bonded and laminated by heating and pressing at a temperature of 150 to 180° C. and a pressure of 20 to 40 kMc1.

[Embodiments of the invention] Next, the present invention will be specifically explained with reference to Examples.

In Examples and Comparative Examples, "parts" means "parts by weight."

Example 1 Acrylic elastomer 5G90 (manufactured by Teikoku Kagaku Sangyo Co., Ltd.,
368.6 parts of a 20% solution of (trade name) dissolved in methyl ethyl ketone/toluene = 1/1 mixed solvent, WSO23
(manufactured by Teikoku Kagaku Sangyo Co., Ltd., trade name) dissolved in a mixed solvent of ethyl acetate/toluene - 1/1 24% 11 20 parts of solution, YDB-400 (manufactured by Tobu Kasei Co., Ltd., trade name) dissolved in toluene 60 40 parts of % solution, 3.8 parts of Epicote 828 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name), and 28 parts of a 50% solution in which 3.8 parts of MiLzx XL-225 (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name) were dissolved in dioxane. 96 parts, ginandiamide 1.11 parts, Curesol C17Z (manufactured by Shikoku Kasei Co., Ltd., trade name) 0.07 parts, H-43M (manufactured by Showa Light Metal Co., Ltd., trade name) 118 parts, Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd., Product name) 2.8 parts, Ethylce O Solve 200
193 parts of dioxane and 193 parts of dioxane were weighed, charged, sufficiently stirred using a high-speed stirrer, and filtered through a 100-mesh wire gauze to prepare an adhesive solution having a bromine content of 9 to 10% by weight as a resin component.

Next, the adhesive solution was applied to Kapton (manufactured by DuPont, trade name of polyimide film) with a thickness of 25 μm, and after drying,
Apply to a thickness of 5μ■ and heat at 120℃ for 5 minutes.
After drying at 150°C for 2 minutes, it was superimposed on the shine side of etched copper foil for evaluation on Kapton base copper clad board (copper foil 35 μm) of UL standard -0, and pressed at a pressing temperature using a hot pressure press. 165±2℃, pressure 30k
It was laminated and covered with a coverlay under the conditions of g/co+2 and heating time of 45 minutes. The resulting coverlay coating was tested for peel strength, adhesion after heat deterioration, solder heat resistance, flame resistance, processability, and solder resistance after humidification.

The results are shown in Table 1.

Comparative Example 1 In Practical IIM Example 1, phenol novolac resin TO-2093 (manufactured by Dainippon Ink Chemical Industries, Ltd.,
Product name) All the same as Example 1 except that 8.48 parts were used.
The adhesive solution was obtained in the same manner as above and then the coverlay coating was obtained. The obtained coverlay coating was subjected to the same test as in Example 1 and is shown in Table 1.

Comparative Example 2 An adhesive solution was prepared in the same manner as in Example 1 except that the inorganic fillers H-43M (mentioned above) and Aerosil 200 (mentioned above) were not added in the formulation of Example 1. A coverlay coating was applied.

The same test as in Example 1 was conducted on the obtained coverlay coating. The results obtained are shown in Table 1.

Table 1 *1: After being left in an atmosphere of 40℃ x 95%RH for 30 minutes 2
Example 2: Floating on a solder bath at 60°C for 20 seconds to check for abnormalities such as peeling and flaking. Acrylic elastomer AR-51 (manufactured by Nippon Zeon Co., Ltd., trade name) was mixed in a mixed solvent of methyl ethyl ketone/toluene = 1/1. 200 parts of a 25% solution dissolved in Arontac S
-5.9 parts of a 20% solution of -1511L (manufactured by Toagosei Kagaku Co., Ltd., trade name) dissolved in toluene, 53 parts of a 60% solution of YDB-400 (mentioned above) dissolved in toluene, 3 parts of Epicote 828 (mentioned above) .8 parts, 30.76 parts of a 50% solution of Mirex XL-225 (mentioned above) dissolved in dioxane,
1.07 parts of dicyandiamide, Curazole C17Z
Weighed and prepared 0.09 parts (as above), 7.1 parts of 8-43M (as above), 100 parts of ethyl cellosolve, and 44 parts of dioxane, respectively, and stirred thoroughly with a high-speed stirrer to prepare 100 parts of
Bromine content in the resin component is 15 after filtering through mesh wire mesh.
A ~16% by weight adhesive solution was prepared.

Next, the adhesive solution was applied to Kapton (described above) with a thickness of 50 μm so that it would have a thickness of about 22 μm after drying.
After drying at 00°C for 5 minutes and at 150°C for 2 minutes, a 35 μm electrolytic copper foil (Shuide Metal Industry Co., Ltd. vJ) was overlaid on this coated surface, and a hot press was used to press at a temperature of 170°C.
Lamination was carried out under conditions of 2° C., pressure of 30 kg/c12, and heating time of 45 minutes to produce a flexible printed wiring board substrate. This board was tested for peel strength, heat-resistant deterioration adhesiveness, soldering heat resistance, and flame resistance, which are shown in Table 2.

Table 2 Example 3 Acrylic elastomer AR-51 (described above) was dissolved in a mixed solvent of methyl ethyl ketone/toluene-1/1.
% solution 308 parts, Arontac S-15111 (mentioned above)
8.15 parts of a 20% solution of YDB-
40 parts of a 60% solution of 400 (mentioned above) dissolved in toluene, 11.4 parts of a 50% solution of BREN (manufactured by Nihon Koyaku Co., Ltd., trade name) dissolved in dioxane, 3.8 parts of Epicote 828 (mentioned above), 38 parts of a 50% solution of Mirex XL-225 (mentioned above) dissolved in dioxane, 1.34 parts of dicyandiamide, CUREZOL 2PH2C (manufactured by Shikoku Kasei Co., Ltd.,
Product name) 0.08 part, H-43M (mentioned above) 87.5
parts, 200 parts of methyl cellosolve and 181 parts of dioxane
Weigh each portion, mix thoroughly with a high-speed stirrer, and add 1
An adhesive solution having a bromine content of 10 to 11% by weight in the resin component was prepared by filtration through a 00 mesh wire mesh.

Next, the adhesive solution was applied to Kapton (mentioned above) with a thickness of 25 μm so as to have a thickness of about 35 μm after drying.
After drying at 20°C for 5 minutes and at 150°C for 2 minutes, it was superimposed on the shine side of etched copper foil for evaluation in UL standard -0 Kapton base copper clad board (copper foil 35μm), and hot-press pressed. Using press temperature 165±2
℃, pressure 40 ka/am2, and heating time 45 minutes to create a coverlay coating. The resulting coverlay coatings were tested for peel strength, adhesion after heat deterioration, solder heat resistance, flame resistance, workability, and solder resistance after humidification, which are shown in Table 3.

Table 3 *1: After being left in an atmosphere of 40℃ x 95%RH for 30 minutes 2
The adhesive composition for flexible printed wiring boards of the present invention has excellent adhesive properties and heat resistance. Since it has excellent deterioration resistance, moisture resistance, flame resistance, and processability, it is suitable as an adhesive for flexible printed wiring boards or as an adhesive for coverlay coating.

Claims (1)

[Scope of Claims] 1 (A) an acrylic elastomer having one or more functional groups selected from the group of epoxy groups, carboxyl groups, and hydroxyl groups, (B) a novolak resin containing paraxylene bonds, (C 1.) An adhesive composition for a flexible printed wiring board, comprising an epoxy resin, (D) a curing accelerator, and (E) an inorganic filler. 2 Resin component of adhesive composition ((A) + (B) + (C)
), (A) acrylic elastomer is 30 to 70
% by weight of the adhesive composition for flexible printed wiring boards according to claim 1. 3 (B) Phenolic hydroxyl equivalent of novolac resin (
Claim 1 or 2, wherein the equivalent ((b)/(c)) between b) and the epoxy group equivalent (c) of the epoxy resin (C) is within the range of 0.6 to 1.1. The adhesive composition for flexible printed wiring boards according to item 2. 4. The adhesive composition for a flexible printed wiring board according to any one of claims 1 to 3, which contains 3 to 65% by weight of (E) an inorganic filler based on the solid content of the adhesive composition. . 5. The adhesive composition for a flexible printed wiring board according to any one of claims 1 to 4, wherein the bromination rate of the resin component of the adhesive composition is 8% by weight or more.