JP2006165495A - Adhesive resin composite and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive resin composite with sufficient fire retardancy without including insoluble flame retarder in solvent, and further in detail to provide the adhesive resin composite with superior fire retardancy, adhesiveness, and thermal resistance for a flexible printed circuit board. <P>SOLUTION: Glass transition temperature after curing is 100°C or more, and peel strength of a resin layer made of resin composite with thickness of 10 μm and the copper foil is 0.8 N/mm or more. In the resin composite for the flexible printed circuit board, a peel strength retention ratio after heating of 240 hour at 150°C is 50% or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin composition for a flexible circuit board and its use. More specifically, the present invention relates to an adhesive for a flexible printed circuit board, which can reduce the thickness of an adhesive layer and is excellent in flame retardancy, adhesiveness, and heat resistance.

  A flexible printed circuit board is produced by laminating a metal foil typified by copper foil and a synthetic resin film typified by polyimide resin with an adhesive to form a circuit of the metal foil.

  In recent years, flexible printed circuit boards have been widely used as electronic devices such as digital cameras, camcorders, hard disk drives, printers and mobile phones become lighter and thinner. Along with this, the demands on characteristics have increased further. High flame resistance, thin plate, high flexibility, high heat resistance that can withstand lead-free solder from the environmental point of view, and long-term high-temperature environment due to increase in operating temperature of equipment The maintenance performance of the adhesive strength below is required. Conventionally used adhesives include acrylonitrile-butadiene rubber / epoxy resin, etc., but have the problem of reduced adhesive strength in high-temperature atmospheres, and flame retardant to ensure the safety of electronic equipment The performance was bad. In order to solve this problem, Japanese Patent Laid-Open No. 61-76579 discloses a brominated epoxy resin / antimony trioxide-based flame retardant adhesive composition, and Japanese Patent Publication No. 58-13039 contains a halogen compound and an inorganic flame retardant. Adhesiveness, soldering heat resistance, flame retardancy, and adhesive composition containing an epoxy resin / carboxyl group-containing ethylene acrylic copolymer and a filler and a flame retardant are disclosed in JP-A-2-301186. Attempts to improve sex have been made. However, these adhesives cause protrusions on the metal surface as the adhesive layer becomes thinner as the flame retardant particles added to impart flame retardancy, causing wiring breaks and shorts during circuit formation. In the case of straddling the gap, the insulation resistance between the wirings is lowered, and further, an adhesive layer having a non-uniform distribution is formed, and the non-uniformity of flame retardancy is caused.

Japanese Patent Laid-Open Nos. 05-315743 and 2002-69414 propose attempts to remove this flame-retardant particle component. JP-A No. 05-315743 discloses an adhesive composition comprising an acrylic elastomer, a phenol aralkyl resin, and an epoxy resin, but the acrylic elastomer used is highly hygroscopic and susceptible to hydrolysis. There is a problem that the adhesive strength retention rate is likely to be decomposed at a high temperature, and the adhesive strength retention rate is lowered at a long time. Japanese Patent Application Laid-Open No. 2002-69414 discloses an adhesive composition comprising an ethylene / acrylate copolymer rubber, a curing agent, and an epoxy resin, but the presence of a non-reactive ethylene / acrylate copolymer rubber. Has a problem of causing a transition at a high temperature for a long period of time and causing a decrease in adhesive strength.
JP-A 61-76579 Japanese Patent Publication No.58-13039 JP-A-2-301186 JP 05-315743 A JP 2002-69414 A

  The problem to be solved by the present invention is to solve the above-mentioned problems of the prior art, and to provide an adhesive resin composition that can sufficiently obtain flame retardancy even without containing an inorganic flame retardant insoluble in a solvent. There is to do. More specifically, the object is to provide an adhesive resin composition for a flexible printed circuit board that is excellent in flame retardancy, adhesiveness, and heat resistance.

The inventors of the present invention completed the present invention as a result of intensive studies on the adhesive resin composition for the above purpose.
That is, the present invention is firstly a resin composition for a flexible printed circuit board, having a glass transition temperature after curing of 100 ° C. or higher, and a 10 μm-thick resin layer comprising the resin composition, a copper foil, Is a resin composition for a flexible printed circuit board having a peel strength retention of 50% or more after heating at 150 ° C. for 240 hours.
In view of flame retardancy, the resin composition contains (A) an epoxy resin, (B) an elastomer having a carboxyl group, (C) a compound having a phenolic hydroxyl group, and (D) a compound having an imidazole group. This is a preferred embodiment.
Furthermore, it is heat resistant that the (B) carboxyl group-containing elastomer is an ethylene / acrylic rubber containing no unsaturated bond, and the (C) compound having a phenolic hydroxyl group is a resin having an aralkyl group (aralkyl resin). This is a preferred embodiment in terms of aging properties.

  The second invention is a thin film having a thickness of 1 to 15 μm produced from the adhesive resin composition, and the third invention is a flexible printed circuit board bonded by the thin film.

  Even if the adhesive layer made of the composition of the present invention is thinned, there is no fear that the flame retardant particles straddle the protrusions or the lines. Therefore, the adhesive layer can be thinned, has a high glass transition temperature, excellent heat aging resistance, excellent flame retardancy and adhesiveness, and is particularly useful as an adhesive for flexible printed circuit boards.

The present invention will be described in detail below.
The resin composition of the present invention has a glass transition temperature after curing of 100 ° C. or higher, an adhesive strength retention after heating at 150 ° C. for 240 hours, of 50% or higher, and a resin layer comprising the resin composition And the copper foil have a peel strength of 0.8 N / mm or more.

When the glass transition temperature after curing is 100 ° C. or higher, more preferably 120 ° C. or higher, and the adhesive retention after heating for 240 hours at 150 ° C. after curing is 50% or higher, reliability in solder heat resistance and the like This is preferable.
Since the resin composition of the present invention can provide a sufficiently flame-retardant effect without containing an inorganic filler, the thickness of the adhesive layer after drying can be reduced to 1 to 15 μm.
The peel strength between the 10 μm-thick resin layer composed of the adhesive composition of the present invention and the copper foil is 0.8 N / mm or more, more preferably 1.0 N / mm or more.

  The epoxy resin that can be used in the present invention is not particularly limited as long as it exhibits the above-described properties, and those conventionally containing one or more epoxy groups in one molecule are used. Specifically, epoxy resins such as glycidyl ether type epoxy resins such as bisphenol type epoxy resins and phenol novolak resins, glycidyl ethers of xylylene type phenol compounds, polyglycidyl ethers of trisphenol or tetraphenol, and aromatic amine type epoxy resins. And bromides thereof. Preferred are glycidyl ether type epoxy resins such as bisphenol type epoxy resins and phenolic novolak resins, glycidyl ethers of xylylene type phenolic compounds and brominated products thereof, and more preferred are glycidyl such as bisphenol type epoxy resins and phenolic novolak resins. Ether type epoxy resins and brominated products thereof. These epoxy resins can be used alone or in admixture of two or more.

  In the present invention, using only brominated epoxy resin in order to ensure the bromine content necessary to achieve flame retardancy is a combination of epoxy resin with high bromination rate and non-brominated epoxy resin. In comparison, it is a particularly preferable aspect in terms of reliability because it can improve the toughness of the cured product, improve the adhesiveness at high temperature, and further reduce the water absorption rate.

  In the present invention, it is preferable to use the bromine-containing epoxy resin so that the bromine content is 20 parts by weight or more and 40 parts by weight or less with respect to the total amount of (1) epoxy resin and (2) carboxyl group-containing elastomer. . More preferably, it is 24-30 weight part. If it is less than 20 parts by weight, flame retardancy may not be achieved. Moreover, when it exceeds 40 weight part, adhesive force may fall.

  The elastomer having a carboxyl group generally includes carboxylated ethylene / acrylic rubber, carboxylated nitrile / butadiene rubber, carboxylated acrylic rubber, etc., but in the present invention, carboxylated ethylene / acrylic rubber containing no unsaturated bond is used. Acrylic rubber can be preferably used. The amount used is preferably 20 to 100 parts by weight, more preferably 25 to 70 parts by weight, based on 100 parts by weight of the total epoxy resin. Particularly preferred is 30 to 60 parts by weight. If it is less than 20 parts by weight, the adhesive strength is reduced, and if it exceeds 100 parts by weight, flame retardancy may not be exhibited. As the carboxylated ethylene / acrylic rubber containing no unsaturated bond for use in the present invention, Bamac GLS (manufactured by DuPont) is most preferable.

  As the compound having a phenolic hydroxyl group, one containing two or more hydroxyl groups in one molecule is preferable, and obtained by reacting the phenols shown below with an aralkyl compound represented by the general formula (1). A resin having an aralkyl group (aralkyl resin) is particularly preferable. Examples of phenols include phenol, o-cresol, m-cresol, p-cresol, resorcinol, hydroquinone, catechol, bisphenol A, biphenol, α-naphthol, β-naphthol, and more preferably phenol, α-naphthol. , Β-naphthol.

_{X-H 2 C-A-} CH 2 -X (1)
In general formula (1), A includes a phenylene group, an alkyl-substituted phenylene group, a diphenylene group, a diphenyl ether group, or a naphthylene group, and X includes a halogen atom such as chlorine or bromine, or a hydroxyl group.
The addition amount of the compound having a phenolic hydroxyl group is preferably 5 to 50 parts by weight, more preferably 7 to 30 parts by weight with respect to 100 parts by weight of the epoxy resin. More preferably, it is 10 to 25 parts by weight. If the amount added is too large or too small, the adhesiveness in hot-pressure curing may be reduced. The hydroxyl equivalent of the compound having a phenolic hydroxyl group is preferably 100 to 300 g / eq, more preferably 140 to 250 g / eq. Adhesive performance may be reduced whether the hydroxyl equivalent is small or large.

  Examples of the compound having an imidazole group include 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2- Methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2- Phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')] -Ethyl-s-tri Gin, 2,4-diamino-6- [2'-undecylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid addition Products, 2-methylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-dihydroxymethylimidazole and the like. Preferred is 2,4-diamino-6- [2'-undecylimidazolyl- (1 ')]-ethyl-s-triazine.

The imidazole compound is preferably used in an amount of 0.7 to 4 parts by weight based on 100 parts by weight of the epoxy resin. More preferably, it is 1.5 to 3.0 parts by weight. If it is less than 0.7 parts by weight or more than 4 parts by weight, the adhesive strength may be lowered, which may be undesirable.
In addition to the above components, a curing accelerator may be added to adjust the reaction rate. Examples of the curing accelerator include imidazole compounds, acid anhydrides, amine complexes of boron trifluoride, 1,8-diazabicyclo (5,4,0) -undecene-7, and the like.

  The resin composition of the present invention is usually dissolved in a solvent and applied to an adherend as an adhesive. Usable solvents include methyl ethyl ketone, methyl isobutyl ketone, dioxane, ethanol, methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, N-methylpyrrolidone, N, N-dimethylformamide, toluene, xylene These may be used alone or in combination at any ratio depending on the application. Among these, methyl ethyl ketone, propylene glycol monomethyl ether, N, N-dimethylformamide, toluene, and xylene are preferable from the viewpoint of solubility.

  The adhesive resin composition of the present invention is usually used as a single solution dissolved in a solvent, but it is more preferable that the adhesive resin composition is divided into solutions such as a main agent and a curing agent and mixed immediately before use. The amount of the solvent is preferably adjusted to an optimum coating thickness by a coating machine so that the nonvolatile content is in the range of 15 to 60% by weight so that drying can be performed. The adhesive resin composition has excellent characteristics by being applied to an adherend such as a polyimide film or a polyester film, B-staged, and then crimped to a metal foil such as a copper foil by hot pressing or hot roll laminating. A printed circuit board is obtained.

  As for the thickness of the adhesive bond layer which consists of a resin composition of this invention, 0.5-25 micrometers is preferable, More preferably, it is 1-15 micrometers. The adhesive comprising the resin composition of the present invention has excellent adhesive strength, and even when the thickness of the adhesive layer is set to 10 μm, the peel strength from the copper foil is 0.8 N / mm or more, and it is 240 hours at 150 ° C. Even after heating, the peel strength retention is 50% or more.

  The bonding temperature is preferably 50 to 200 ° C. and a pressure of 0.1 to 10 MPa. In order to obtain better adhesive strength, the pressure is 80 to 200 ° C. and the pressure of pressure 0.5 to It is particularly preferable to carry out in the range of 8 MPa. The curing temperature is preferably 100 to 190 ° C, more preferably 130 to 180 ° C. Thus, the board | substrate adhere | attached by the adhesive bond layer which consists of the resin composition of this invention manufactured is useful as a printed circuit board, especially a flexible printed circuit board.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the contents of the present invention are not limited to the following examples.

(Evaluation methods)
The adhesive resin composition is applied to a polyimide film (Kapton H (thickness 25 μm)) using a multi-coater so as to have a dry coating thickness of 10 μm, and dried at 140 ° C. for 2 minutes to form a B stage. For surface state observation, coating is performed so as to have respective dry coating thicknesses of 15 μm, 12 μm, 9 μm, 7 μm, 5 μm, and 3 μm. The flame retardant test piece is similarly coated on both sides with a dry coating thickness of 25 μm. The B stage product and the matte surface of the rolled copper foil (thickness 18 μm) were bonded together with a laminator under conditions of linear pressure 0.5 kg / cm, 100 ° C., 0.6 m / min, and then 160 ° C., 5.88 MPa. , Heat-pressure curing in 60 minutes. The flame retardant test piece is hung in an oven without bonding a copper foil and cured at 160 ° C. for 60 minutes. The test piece produced as described above is evaluated by the following method.
Adhesiveness: 90 ° peel strength (copper drawing) is measured in accordance with JIS C 6481.
Adhesion retention: A test piece similar to the adhesive evaluation is subjected to heat treatment at 150 ° C. for 240 hours, and then measured in the same manner as the adhesive evaluation. Expressed as a percentage of the adhesive strength before processing.
Tg: B stage products are stacked and cured under the same curing conditions as described above to produce a test piece with a thickness of 3 mm. Tg is measured for this test piece using a dynamic viscoelasticity testing apparatus (temperature rising rate of 5 ° C./min).
Solder heat resistance: After a test piece cut out to 3 cm × 3 cm is immersed in a solder bath at 340 ° C. for 10 seconds, the adhesive layer is peeled off and the swelling state is visually confirmed.
Flame retardancy: Compliant with UL standard 94 (V-0 evaluated as ○).
Surface state observation: Visual observation of the presence of blisters, aggregates, etc. from the polyimide film side.

Raw materials used in Examples and Comparative Examples
[Carboxyl group-containing elastomer]
・ Carboxylated nitrile butadiene rubber,
Nipol 1072B made by Nippon Zeon
・ Carboxylated ethylene acrylic rubber,
BEIMAC GLS (registered trademark) made by Mitsui DuPont Polychemicals
[Epoxy resin]
・ Brominated bisphenol type epoxy resin (bromine content 48% by weight)
ESB-400T manufactured by Sumitomo Chemical
・ Brominated bisphenol type epoxy resin (bromine content: 21% by weight)
Epicoat 5046B80 made by Japan Epoxy Resin
・ Brominated phenol novolac epoxy resin (bromine content 35% by weight)
Nippon Kayaku BREN-S
・ Bisphenol type epoxy resin (bromine content 0% by weight)
Epicoat 1001 made by Japan Epoxy Resin
[Compounds having phenolic hydroxyl groups]
・ Phenol / p-xylylene glycol dimethyl ether polycondensate (hydroxyl equivalent 175 g / eq)
Millex XLC-LL (registered trademark) made by Mitsui Chemicals
・ Phenol novolak (Hydroxyl equivalent 105g / eq)
PSM-4326 made by Gunei Chemical
[Curing (acceleration) agent]
・ Imidazole-based compound Shikoku Kasei C11Z-A
・ Imidazole-based compound Shikoku Kasei Co., Ltd.
・ Dicyandiamide Japan Epoxy Resin EpiCure DYCY15
・ Aromatic amine Cure Hard MED manufactured by Ihara Chemical Industry
[Inorganic filler]
・ Talc Asada Flour FFF
・ Aerosil Japan Aerosil R972
[Flame retardants]
-Antimony trioxide NIPPON SEIKO PATOX-S
・ Phosphate ester amide Shikoku Kasei SP-703

Example 1
Adjustment of adhesive resin composition: Bamac GLS 40 g, ESB-400T 55 g, Epicoat 5046 B80 45 g, Millex XLC-LL 15 g, C11Z-A 2 g and methyl ethyl ketone / propylene glycol monomethyl ether = 2/1 366 g (calculated non-volatile content 30%) Into a 1000 ml glass separable flask and stirred vigorously at room temperature for 1 hour. After completion of stirring, the adhesive resin composition was prepared by normal pressure filtration with a 325 mesh wire mesh filter. The obtained adhesive resin composition was evaluated by the method described above. The evaluation results are shown in Table 2.

(Examples 2-5 and Comparative Examples 1-5)
The adhesive resin composition was prepared in the same manner as in Example 1 with the composition shown in Table 1 (calculated non-volatile content 30%), and evaluated in the same manner as in Example 1. The evaluation results are summarized in Table 2.

Claims (5)

A resin composition for a flexible printed circuit board, having a glass transition temperature after curing of 100 ° C. or higher, and a peel strength between a 10 μm-thick resin layer comprising the resin composition and a copper foil is 0.8 N / mm The resin composition for a flexible printed circuit board as described above, wherein the peel strength retention after heating at 150 ° C. for 240 hours is 50% or more. The resin composition comprises (A) 100 parts by weight of a brominated epoxy resin, (B) 10 to 100 parts by weight of an elastomer having a carboxyl group, (C) 5 to 50 parts by weight of a compound having a phenolic hydroxyl group, and (D) The resin composition for a flexible printed circuit board according to claim 1, comprising 0.7 to 4 parts by weight of a compound having an imidazole group. (B) The elastomer having a carboxyl group in the resin composition is an ethylene / acrylic rubber containing no unsaturated bond, and (C) the compound having a phenolic hydroxyl group is a resin having an aralkyl group. The resin composition for flexible printed circuit boards according to claim 2. A thin film having a thickness of 1 to 15 µm produced from the resin composition according to any one of claims 1 to 3. A flexible printed circuit board, which is adhered by the thin film according to claim 4.