JPS61108678A - Adhesive and flexible printed circuit board - Google Patents

Abstract

PURPOSE:To provide an adhesive having high bonding strength and excellent heat resistance and suitable for fabrication of a flexible printed circuit board, etc., prepared by adding a specified acrylic resin and a hardener to an epoxy resin. CONSTITUTION:The adhesive is prepared by blending (A) 100pts.wt. acrylic resin consisting of 15-35wt% acrylonitrile, 55-83wt% (meth)acrylate of a 5C or lower alcohol and 2-10wt% (meth)acrylic acid, (B) 15-80pts.wt. epoxy resin (e.g. Epicote 828 made by Yuka Shell Co.) and (C) 30-150pts.wt. hardener consisting of a compd. containing a urethane bond and having primary amino group on both terminals.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an adhesive that provides excellent adhesive strength and heat resistance and is used in the manufacture of 7-lexiple printed circuit boards, and a printed circuit having this adhesive layer. It is related to the board.

[Prior art]

BACKGROUND ART In recent years, with the development of the electronic and electrical industry, there has been a demand for simpler, smaller, more reliable, and higher performance mounting methods for equipment for communications, consumer use, etc., and the use of printed wiring boards has become desirable. In particular, it is advantageous to use a 7 lexiple printed wiring board with a 2 plastic film substrate, which is lightweight and can be mounted three-dimensionally (6F).
,Attention has been paid.

BACKGROUND ART Acrylic adhesives have been known as adhesives for flexible printed wiring boards that have excellent heat deterioration resistance of adhesive strength, soldering heat resistance, and solvent resistance. However, since the curing agent is an isocyanate type, there is a drawback that the adhesive life after application and drying (B stage) is extremely short.

[Purpose of the invention]

The present inventors have conducted extensive research to resolve the above-mentioned drawbacks of acrylic adhesives that use isocyanate as a crosslinking agent, and have found that by using a specific amine curing agent as a crosslinking agent for acrylic adhesives, acrylic The present inventors have discovered that it is possible to maintain the characteristics of adhesives and to significantly improve the life of the adhesive after application and drying.

[Structure of the invention]

The present invention is obtained by copolymerizing (a) 15 to 35% by weight of acrylonitrile, 55 to 83% by weight of an ester of an alcohol having 5 or less carbon atoms with acrylic acid or methacrylic acid, and 2 to 10% by weight of acrylic acid or methacrylic acid. 100 parts by weight of acrylic resin, Φ) epoxy resin 15
~80 parts by weight, (C) 30 to 150 parts by weight of a compound having a urethane bond in the molecule and having primary amines at both ends; and for flexible printed circuits having the adhesive layer. It is related to the board.

In order to obtain good results in the present invention, it is essential to mix the adhesive components in the above-mentioned proportions.

For each component (a), 15% of acrylonitrile is contained in component (a).
It is necessary to set the content to 35% by weight. If it is less than 15% by weight, adhesive strength and soldering heat resistance will decrease.

As the acrylonitrile component increases, adhesive strength and soldering heat resistance improve, but when the weight exceeds 35 weight jlX, flexibility decreases. In order to achieve sufficient adhesive strength, solder heat resistance, and flexibility, the content is preferably 15 to 35% by weight. Examples of esters of alcohols having 5 or less carbon atoms and acrylic acid or methacrylic acid include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, etc. can be given. The amount of acrylic acid or methacrylic acid must be 2 to 10% by weight. If it is less than 2% by weight, adhesive strength and soldering heat resistance will decrease.

If it exceeds 10% by weight, flexibility decreases. As the epoxy resin of component (b), usual ones such as bisphenol-based, resol-based, novolak-based, ether ester-based glycidyl ethers and cycloaliphatic epoxy compounds, and their brominated products can be used. If the epoxy resin is less than 15 parts by weight, the 70% of the entire adhesive will be small and it will be difficult to bond uniformly with metal foil by hot press bonding, especially roll lamination, making adhesive strength and soldering heat resistance unstable. . If it exceeds 80 parts by weight, flexibility will decrease.

The curing agent is a compound with a urethane bond in the molecule and a general amine at both ends, and the amine value is 300 to 150.
It is desirable to set it to 0. When the amine value is 300 or less, heat resistance is excellent, but flexibility and adhesive strength are reduced. Also 15
If it is more than 00, the heat resistance will be reduced. The amount added is such that the equivalent ratio of curing agent/epoxy is 0.6 to epoxy resin.
It is necessary to set it to 1.2. If the equivalence ratio is outside this range, the soldering heat resistance will decrease. Wrapping using general aromatic amines, acid anhydrides, dicyandiamide, and other curing agents other than this compound has excellent heat resistance, but flexibility and
Adhesive strength is low and lacks practicality as a flexible copper clad board.

Furthermore, a curing accelerator such as 4-midazole, BP, -monoethylamine complex, wax, or tertiary amines may be added.

Furthermore, the adhesive of the present invention includes flame-retardant inorganic compounds such as antimony trioxide, aluminum hydroxide, and barium borate, silica, alumina, mica, titanium oxide, zirconia, calcium silicate, magnesium hydroxide, magnesium oxide, and magnesium oxide. Inorganic fillers such as iron, calcium carbonate, and silicon carbide may be contained in an amount of 45 parts by weight or less based on 100 parts by weight of the adhesive. If the amount of these inorganic fillers exceeds 45 parts by weight, adhesive flow will be small, roll lamination properties will be deteriorated, and adhesive strength will further decrease.

In addition to these, glass cloth impregnated may also be used.

Furthermore, all the various commonly used additives such as fillers, stabilizers, surfactants, etc. other than these may be blended according to the purpose.

In the printed circuit board of the present invention, the plastic films used include polyimide films, polyester films, polyethylene filtrate polypropylene films, polyvinyl chloride films, etc., and the metal foils used include copper foils and steel alloys (e.g. brass). , aluminum, iron, nichrome, etc. may be used. In addition to flexible steel clad plates obtained by heat-pressing these plastic films and metal foils using different adhesives (a) to (C), there are also insulating coverlays for flexible printed circuits and multiple laminations of flexible printed circuits. , and further includes a printed circuit board using the above adhesive for adhesion to a hard reinforcing plate.

〔Effect of the invention〕

By using the adhesive according to the present invention, it is possible to maintain the heat aging resistance of adhesive strength, which is a characteristic of acrylic adhesives, and to significantly improve the life of the adhesive after application and drying, which is disadvantageous with conventional adhesives.

〔Example〕

Prepare the adhesive varnish according to the recipe in Table 1 and apply it to a thickness of 2.
After drying, it was coated on a polyimide film (L) (Kapton, manufactured by Upont) to a thickness of 30 x m and heated to 130°C.
It was dried in the oven for 5 minutes. This film with adhesive was placed in an atmosphere at a temperature of 20°C and a relative temperature of 65% for 3 days and 10
After storage for 20 days, 30 days, 60 days, the thickness is 35μ
A flexible steel clad plate was created by pasting it on a copper foil of 500 mm and heat-pressing it using a press method. The pressing conditions were a temperature of 150°C,
The pressure was 20 kgf/an" and the heating time was 70 minutes. From the copper foil peeling strength of the obtained flexible steel clad plate,
The adhesive life was evaluated. The characteristics are shown in Table 2 and Figure 1.

Claims (2)

[Claims] (1) An adhesive containing the following (a) to (c). (a) Acrylic system obtained by copolymerizing 15 to 35% by weight of acrylonitrile, 55 to 83% by weight of an ester of an alcohol having 5 or less carbon atoms with acrylic acid or methacrylic acid, and 2 to 10% by weight of acrylic acid or methacrylic acid. 100 parts by weight of a resin; (b) 15 to 80 parts by weight of an epoxy resin; (c) 30 to 150 parts by weight of a compound having a urethane bond in the molecule and having primary amines at both ends. (2) A flexible printed wiring board having an adhesive layer including the following (a) to (c). (a) Acrylic system obtained by copolymerizing 15 to 35% by weight of acrylonitrile, 55 to 83% by weight of an ester of an alcohol having 5 or less carbon atoms with acrylic acid or methacrylic acid, and 2 to 10% by weight of acrylic acid or methacrylic acid. 100 parts by weight of a resin; (b) 15 to 80 parts by weight of an epoxy resin; (c) 30 to 150 parts by weight of a compound having a urethane bond in the molecule and having primary amines at both ends.