JPH0747725B2 - Adhesive for flexible printed circuit boards - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an adhesive for flexible printed circuit boards, and more particularly to an adhesive used in the production of flexible printed circuit boards, which comprises a support plastic film (polyimide) for the substrate. The present invention relates to an epoxy resin-based adhesive capable of exhibiting excellent adhesive strength and heat resistance when a metal foil (copper foil) is bonded to a film.

2. Description of the Related Art Problems to be Solved by the Prior Art and Invention A flexible printed circuit board is one in which a metal foil (copper foil) is adhered on a support plastic film, and by forming a conductor circuit on the metal foil, it is widely used in industrial equipment. ,
Used as printed wiring boards and wiring cables for electronic devices. By using the flexible polymer film as described above, it is possible to realize a mounting which is lightweight and can be bent and three-dimensionally wired. However, for a heat-resistant type flexible printed circuit board using a film such as polyimide (PI) and a copper foil, an adhesive that can achieve both required solder heat resistance and copper foil adhesive strength has not yet been known.

Conventionally, epoxy resin / rubber-based and phenol resin / rubber-based adhesives have been mainly used as this type of adhesive. Therefore, in order to achieve the above performances, the type of epoxy resin or phenol resin itself or Although the compounding ratio with rubber has been examined, the result has not been satisfactory.

The present inventors have made extensive studies to provide an adhesive capable of exhibiting excellent adhesive strength and heat resistance, particularly to a polyimide film and a copper foil. The inventors have found that the intended adhesive can be obtained by combining a curing agent with the main agent component containing the rubber fine particles described above, and have completed the present invention.

Structure and effect of the invention That is, the present invention, the rubber grafted with an epoxy group-containing polymerizable monomer (hereinafter, referred to as graft-modified rubber) 10 to 40 to 100 parts (parts by weight, the same below) of the epoxy resin.
The present invention provides an adhesive for a flexible printed circuit board, which comprises a curing agent and a main agent component containing 1 part to 20 parts of vulcanized rubber fine particles and a curing agent.

As the epoxy resin in the present invention, usual bisphenol A type, phenol novolak type, cresol novolak type, ester type, ether type, urethane modified type,
Although various amine-based or other liquids or solids at room temperature can be used, those at room temperature are preferable from the standpoint of preventing tack after coating and drying the adhesive. Further, when more excellent heat resistance is desired, a polyfunctional epoxy resin such as a novolak type is advantageous.

The graft-modified rubber in the present invention is obtained by grafting a rubber with an epoxy group-containing polymerizable monomer to modify the rubber. As the rubber to be used, various ones can be mentioned, but those having good compatibility with the epoxy resin, for example, polar rubbers such as acrylonitrile-butadiene copolymer rubber (NBR) and urethane rubber are preferable. Examples of the monomer to be grafted include glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether.

The above grafting can be performed by a usual method. For example, the above rubber is used as an organic solvent [methyl ethyl ketone (ME
K), acetone, methyl isobutyl ketone, toluene,
Xylene, ethyl acetate, butyl acetate, or the like, or a mixture thereof, and then a polymerization initiator (benzoyl peroxide, azobisisobutyronitrile, quinene hydroperoxide, t-butyl hydroperoxide, etc.) and a monomer Is added and mixed, and graft polymerization is carried out for about 3 to 6 hours while heating under reflux at 60 to 80 ° C.
In such a graft, the ratio of the rubber to the monomer is usually selected so as to be 5 to 30 parts of the monomer per 100 parts of the rubber.

The vulcanized rubber fine particles in the present invention are solid substantially spherical fine particles obtained by uniformly dispersing liquid rubber in an epoxy resin of a liquid solvent or solid solvent solution type at room temperature and vulcanizing it. Vulcanized rubber is designated. Examples of the epoxy resin used include bisphenol A
Type, cyclohexane oxide type, cyclopentane oxide type, epoxy resin derived from other polymer or copolymer of di- or polyolefin, epoxy resin obtained by copolymerization of glycidyl methacrylate and vinyl compound and highly unsaturated fatty acid An epoxy resin obtained from glyceride and the like are included. The liquid rubber to be dispersed in the epoxy resin, urethane rubber, polysulfide rubber, butadiene rubber, acrylonitrile butadiene rubber, chloroprene rubber, isoprene rubber, styrene butadiene rubber and the like and carboxyl modification, hydroxyl modification, amino Examples thereof include modified rubbers, and particularly desirable ones are polymers or copolymers of diene hydrocarbons having a functional group that bonds with an epoxy resin at the terminal or in the molecular chain. The liquid rubber does not necessarily have a chemical bonding property with the epoxy resin, but a functional group that bonds with the epoxy resin, for example, one having a carboxyl group, a hydroxyl group, an amino group or the like at the terminal as described above is partially epoxied simultaneously with vulcanization. It seems to bind to the resin.

The above vulcanization is carried out by using a vulcanizing agent (sulfur, sulfur compound, other inorganic vulcanizing agent, oxime, nitroso compound, organic peroxy compound, resin vulcanizing agent, etc.) and, if necessary, a vulcanization accelerator (thiazole type, thiuram). System, guanidine-based, xanthate-based, thiourea-based, dithiocarbamate-based, etc.) and heated under high speed stirring. Thus, the vulcanized rubber fine particles are produced in a state of being dispersed in the epoxy resin, but usually they are used as they are without being isolated. Therefore, the epoxy resin used here can be replaced with a part of the previous epoxy resin component.

The adhesive for a flexible printed circuit board according to the present invention is composed of a main component containing the above-mentioned epoxy resin, graft modified rubber and vulcanized rubber fine particles, and a curing agent.

The blending ratio of each component in the main component is 10 to 40 parts (preferably 15 to 30 parts) of graft modified rubber and 1 to 20 parts (preferably 3 to 10 parts) of vulcanized rubber fine particles to 100 parts of epoxy resin. So that If the amount of graft-modified rubber is less than 10 parts, the adhesive layer tends to be too hard and the flexibility of the flexible printed circuit board tends to be impaired. If so, the peel adhesion strength is increased, but the solder heat resistance is slightly reduced (it is improved because it is an epoxy graft reaction type). If the amount of vulcanized rubber particles is less than 1 part, the peel adhesive strength will be reduced, making it difficult to balance the heat resistance and the peel adhesive strength. If it exceeds 20 parts, the adhesive strength will also increase, but the adhesive viscosity will increase. Rises and the workability decreases.

On the other hand, as the curing agent to be combined with the main component, either a room temperature curing type or a heat curing type can be adopted, and specifically, methyl nadetic acid anhydride, dodecenyl succinic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride. , Methylcondomethylenetetrahydrophthalic anhydride, chlorendic anhydride, ethylene glycol trimellitic anhydride ester, methyltetrahydrophthalic anhydride,
Acid anhydrides such as methylhexahydrophthalic anhydride, imidazole, 2-methylimidazole, 2-ethyl-4-
Methylimidazole, 2-phenylimidazole, 2-
Undecyl imidazole, 2-heptadecyl imidazole, 1-benzyl-2-methyl imidazole, 1-cyanoethyl-2-methyl imidazole, 1-cyanoethyl-2-phenyl imidazole, 1-cyanoethyl-2-
Ethyl-4-methylimidazole, 1-cyanoethyl-
2-undecylimidazole, 1-cyanoethyl-2-
Methylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6- [2'-methylimidazolyl- (1) ']
-Ethyl-S-triazine, 2,4-diamino-6-
(2'-Undecylimidazole- (1) ']-ethyl-
S-triazine, 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1) ']-ethyl-S
-Triazine, 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate, 1-cyanoethyl-
2-Undecylimidazole trimellitate, 1-dodecyl-2-methyl-3-benzimidazolium chloride, imidazole derivatives such as 1,3-dibenzyl-2-methylimidazolium chloride, dicyandiamide or its derivative, sebacic acid dihydrazide, etc. Organic acid dihydrazide of 3- (3,4-dichlorophenyl) -1,1-
Examples thereof include urea derivatives such as dimethylurea, polyamidoamine, and modified polyamine.

In the adhesive of the present invention, the solid content may be adjusted by adding the organic solvent exemplified in the above graft polymerization, if necessary, and a usual filler, a thermoplastic resin / rubber, a dye / pigment, a silane compound, etc. Adhesion promoters, anti-aging agents and the like may be added in appropriate amounts.

Next, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 (1) graft-modified rubber component unit NBR (Zeon Co., hikers ♯1032) 20% of
(% By weight, the same applies hereinafter) MEK solution …… 100 glycidyl methacrylate …… 3 benzoyl peroxide …… 0.1 MEK …… 30 The above ingredients were charged in a four-necked flask equipped with a reflux condenser, and N ₂ was added.
After gas replacement, the mixture is heated to 70 to 75 ° C. in a hot water bath and stirred for 6 hours to carry out graft polymerization to obtain a pale yellow viscous liquid (graft modified rubber content 17.4%).

(2) Vulcanized rubber fine particle component part Bisphenol A type liquid epoxy resin (manufactured by Yuka Shell Co., Ltd., Epicoat # 828) …… 80 Liquid NBR containing terminal carboxyl groups (manufactured by Ube Industries, Ltd.,
Hiker CTBN1300 × 31) …… 20 Sulfur …… 2 Vulcanization accelerator Dibenzothiazole disulfide …… 0.8 Tetramethylthiuram disulfide …… 1 Zinc white …… 0.8 Stearic acid (vulcanization modifier) …… 1.2 “ Hiker CTBN1300 × 31 ”was blended with sulfur, vulcanization accelerator, zinc white and stearic acid, well dispersed, and then stirred into a high-speed“ Epicoat # 828 ”heated to 120 ° C with a homomixer (3000 ˜5000 rpm) and continue stirring for 3 hours to obtain a brownish viscous liquid (vulcanized rubber fine particle content 24.4%).

(3) Adhesive 50 parts of the graft-modified rubber viscous liquid of (1) above, (2) above
15 parts of viscous liquid containing vulcanized rubber fine particles of bisphenol A type solid epoxy resin (Yukaka Shell Co., Ltd., Epicoat #
1001) 50% MEK solution 60 parts, acid anhydride (manufactured by Shin Nippon Rika Co., Ltd., liquid acid anhydride curing agent MTA-18) 25 parts and MEK1
An adhesive is obtained by thoroughly mixing 0 parts of the mixture.

Comparative Example 1 40 parts of 20% MEK solution of NBR (Hiker # 1032), 50% of bisphenol A type solid epoxy resin (Epicoat # 1001)
MEK solution 30 parts, acid anhydride (liquid acid anhydride curing agent MTA-18) 1
Mix 6 parts and 44 parts of MEK thoroughly to obtain an adhesive.

<Adhesion test> An adhesive is applied to a 35μ thick electrolytic copper foil so that the dry thickness is about 20μ, and dried in a hot air dryer at 100 ° C for 15 minutes. A 25μ thick polyimide film is overlaid on the adhesive layer of the resulting copper foil, and hot pressing is performed at 120 ° C. and 10 kg / cm ² .
Further, heat curing is performed at 150 ° C. for 30 minutes.

The obtained copper-clad sheet is cut into 1 cm width to make a test piece, and subjected to various performance tests. The results are shown in Table 1.

Continuation of the front page (56) Reference JP 61-195115 (JP, A) JP 61-213277 (JP, A) JP 61-254680 (JP, A) JP 58-57776 (JP , A) JP-A 63-376 (JP, A) JP-A 64-16885 (JP, A)

Claims (2)

[Claims] 1. A main agent component containing 10 to 40 parts by weight of a rubber grafted with an epoxy group-containing polymerizable monomer and 1 to 20 parts by weight of vulcanized rubber fine particles to 100 parts by weight of an epoxy resin, and a curing agent. An adhesive for flexible printed circuit boards, characterized by being formed. 2. The adhesive according to claim 1, wherein the vulcanized rubber fine particles are dispersed in an epoxy resin.