JPH04370996A - Bonding sheet - Google Patents

Abstract

PURPOSE:To form a bonding sheet having excellent processability with solder resistance at a low temperature for a short time by coating a mold release film with special adhesive, and drying it to remove solvent to set the adhesive to a semicured state. CONSTITUTION:A heat resistant adhesive layer of a semicured state and a mold release film are laminated to form a bonding sheet. The adhesive contains 100 pts.wt. of epoxy resin, 40-150 pts.wt. of nitrile rubber containing carboxyl group, l-50 pts.wt. of curing agent, and 0.1-5 pts.wt. of curing accelerator of one or more types selected from imidazole compound, tetraphenyl boride of third amine, and boron fluoride of zinc, tin, nickel. The epoxy resin includes, for example, epoxy resin bromide, etc. The rubber made of Hycar CTBN, etc., of Goodrich Co. is used. The curing agent includes, for example, diethyltriamine, etc. The accelerator includes, for example, 2-alkyl-4- methylimidazole, etc., thereby performing a predetermined purpose and effect.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to adhesives for bonding sheets for flexible printed circuit boards.

0002

BACKGROUND OF THE INVENTION In recent years, as electrical products have become lighter, thinner, smaller, and more sophisticated, the demand for printed circuit boards has increased, and in particular, the range of use of flexible circuit boards has expanded. In particular, as high-density packaging progresses and demands for multilayer flexible printed circuit boards increase, the bonding sheets used to bond each layer are expected to have improved performance such as adhesion, heat resistance, and processability. It is rare.

0003

[Problems to be solved by the invention] Conventional products lack adhesion, resulting in poor adhesion, poor heat resistance, which causes blistering during soldering, and poor processability, requiring long-term processing at high temperatures. There were some difficulties. Most of the causes of these difficulties are thought to be due to the adhesive, and so far the adhesives for bonding sheets have been NBR/phenolic resin, epoxy phenol/NBR, and NBR/phenol resin.
BR/epoxy resin, epoxy/polyester, epoxy/acrylic resin, acrylic resin, etc. have been used, but these adhesives have advantages and disadvantages. For example, NBR
At present, we have not yet found a fully satisfactory product, as the thermal deterioration of systems is large, the adhesion of epoxy systems is low, and acrylic systems require high temperatures, long periods of heating, and pressure bonding, resulting in poor workability. be. The present invention aims to eliminate the above-mentioned drawbacks and provide a bonding sheet with excellent adhesiveness, heat resistance, and processability.

0004

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the present inventors have completed the present invention as a result of intensive research focusing on adhesive compositions. That is, the present invention
A bonding sheet formed by laminating a semi-cured heat-resistant adhesive layer and a release film, characterized in that the adhesive has the following composition. a) epoxy resin 100 parts by weight, b) carboxyl group-containing nitrile rubber 40 to 150 parts by weight, c) curing agent 1 to 50 parts by weight, d) imidazole compound, tetraphenyl borate of tertiary amines and zinc, 0.1 to 5 parts by weight of one or more hardening accelerators selected from tin and nickel fluorides. The main points are as follows.

[0005] The present invention will be explained in detail below.
First, the adhesive composition for bonding sheets of the present invention will be described. b) The epoxy resin may be one having two or more epoxy groups in one molecule, such as bisphenol type epoxy resin, glycidyl ether type such as novolak resin, cycloaliphatic epoxy resin, aromatic type epoxy resin. , halogenated epoxy resins, etc. can be used alone or in combination of two or more. Further, among the above-mentioned epoxy resins, an adhesive having excellent flame retardancy can be obtained by using a halogenated epoxy resin, preferably a brominated epoxy resin.

[0006] This brominated epoxy resin may be of any type as long as it has an epoxy group and a bromine atom in one molecule, and examples thereof include bisphenol type brominated epoxy resin, novolak type brominated epoxy resin, etc. . Specifically, Epicoat 5045 manufactured by Yuka Shell Epoxy Co., Ltd. (Br%: 19% by weight (hereinafter % is % by weight)
), 5046 (Br%: 21%), 5048
(Br%: 25%), 5049 (Br%: 26%), 5
050 (Br%: 49%), B manufactured by Nippon Kayaku Co., Ltd.
There are REN-S (Br%: 35%) and the like. These Br
Brominated epoxy resins having different contents can be used alone or in combination of two or more. Note that the Br content is 21
% to 51% of bromine epoxy resin is preferred from the viewpoint of flame retardancy.

[0007] As the carboxyl group-containing nitrile rubber of component (b), there may be mentioned an acrylonitrile-butadiene copolymer rubber obtained by copolymerizing acrylonitrile and butadiene, and the terminals of which are carboxylated. Specifically, Goodrich's Hiker CTBN, Hiker CTBN
X, Hiker 1072, Nipole 1072J, Nipole 1072, Nipole DN manufactured by Nippon Zeon Co., Ltd.
612, Nipaul DN631, Nipaul DN601
etc. These carboxyl group-containing nitrile rubbers can be used alone or in combination of two or more. The content of carboxyl groups is preferably 2 to 8% by weight.

c) The curing agent is not particularly limited as long as it is used as a curing agent for ordinary epoxy resins, and examples thereof include diethyltriamine, triethylenetetramine, metaxylene diamine, diaminodiphenylmethane, and diaminodiphenylsulfone. amine compounds, phthalic anhydride, hexahydrophthalic anhydride,
Examples include acid anhydrides such as tetrahydrophthalic anhydride and trimellitic anhydride, dicyandiamide, and boron trifluoride amine complex compounds. These can be used alone or in combination of two or more. These curing agents can be added in a wide range of amounts, usually 1 to 50 parts by weight per 100 parts by weight of the epoxy resin component (a), but the amount used depends on the type of curing agent and the type of each resin. It is selected appropriately depending on the amount.

As the curing accelerator component (d), imidazoles such as 2-alkyl-4-methylimidazole, 2-alkyl-4-ethylimidazole, 1-(2-cyanoethyl)-2-alkylimidazole, and 2-phenylimidazole are used. and tetraphenylborate salts of tertiary amines such as triethylammonium tetraphenylborate, zinc borofluoride, tin borofluoride, and nickel borofluoride, which may be used alone or in combination of two or more. It is used as The appropriate amount of these additives to be added is 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight. Also,
Among the above imidazole compounds, tetraphenyl borates of tertiary amines, and fluorides of zinc, tin, and nickel, tetraphenyl borates of tertiary amines and fluorides of zinc, tin, and nickel are oxides are preferred, and fluorides of zinc, tin, and nickel are more preferred.

[0010] Furthermore, fine particulate inorganic powder can be added to the above adhesive if necessary. As fine particle inorganic powder,
Metal hydroxides such as aluminum hydroxide and magnesium hydroxide, oxides such as zinc oxide, magnesium oxide, and antimony trioxide, carbonates such as calcium carbonate and magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, etc. silicates, silicic acid and boron nitride. These can be used alone or in combination of two or more.

[0011] Recently, flexible printed circuits have become finer, and patterns of several tens of micrometers have been put into practical use.
The particle size of the inorganic powder is 10 μm or less, preferably 5 μm or less.
A value of μm or less is appropriate. In order to improve the adhesion of these particulate inorganic powders to the resin matrix and water resistance, it is desirable to perform hydrophobization treatment. A processing agent such as a ring agent is used.

[0012] The present invention provides the above a), b), c) and d).
The desired desired effect can be achieved by an adhesive having a composition consisting of each of the above components, and if the composition is outside the above range, the following disadvantages will occur. In other words, the epoxy resin of component (a)
If the carboxyl group-containing nitrile rubber of component (b) is less than 40 parts by weight relative to 100 parts by weight, the peel strength will decrease, and if it exceeds 150 parts by weight, the soldering heat resistance will decrease. If the amount of curing agent in the component (c) is less than 1 part by weight, curing will be insufficient and the soldering heat resistance will decrease, and if it exceeds 50 parts by weight, the life of the adhesive will be shortened and the soldering heat resistance and peel strength will decrease. descend. If the curing accelerator component (d) is less than 0.1 parts by weight, the soldering heat resistance will decrease, the flow of the adhesive will become too large, and long-term processing at high temperatures will be required; if it exceeds 5 parts by weight, the adhesive will deteriorate. As the life of the agent becomes shorter, the peel strength decreases.

[0013] As the release film used in the present invention,
Plastic films such as PE film, PP film, TPX film, PET film with silicone release agent, polyolefin films such as PE and PP, vinylidene chloride film, TPX film, etc. are coated on one or both sides of base paper. Examples include release paper such as paper.

Next, the method for manufacturing the bonding sheet of the present invention will be described. The adhesive is applied to a release film to a thickness of 20 to 60 μm in a dry state, and dried to remove the solvent and semi-cure the adhesive. In this case, it can be heated to about 100° C. for a short time if necessary. Furthermore, a release film is applied to this using a roll laminator at 30 to 100°C and a linear pressure of 2 to 10 kg/cm.
It is manufactured by pressing and laminating at a line speed of 2 m/min and winding it up into a roll.

[0015]

[Examples] Next, specific embodiments of the present invention will be explained with reference to Examples, but the present invention is not limited thereto. Note that all parts and percentages in the specific examples are based on the weight of solid content. (Examples 1 to 6, Comparative Examples 1 to 6) A 30% MEK solution was prepared using the adhesive composition shown in Table 1, and the solution was uniformly dispersed using a ball mill to obtain an adhesive solution. Next, these adhesive solutions were applied to a 25 μm PET film, one side of which had been treated with silicone mold release, so that the coating thickness after drying was 30 μm, and the film was dried by heating at 80°C for 2 minutes and at 120°C for 5 minutes. The solvent was removed and the adhesive was left in a semi-cured state. A release paper coated with TPX film on both sides was laminated onto this using a roll laminator at a temperature of 50° C., a linear pressure of 5 kg/cm 2 , and a speed of 2 m/min to produce a bonding sheet. Next, in order to measure the physical properties of this bonding sheet, the adhesive sheet from which the release PET film and release paper had been removed was set on a 25 μm polyimide film, laminated on the glossy surface of a 35 μm electrolytic copper foil, and pressed under the following conditions. A laminated film was produced by pressing at 160° C., 50 kg/cm 2 , and 15 minutes. The properties of the flexible laminated film thus obtained are also listed in Table 1.

The physical properties of the flexible laminated film shown in Table 1 were measured as follows. (Flexible laminate film physical property measurement method) 1) Peel strength: Measured in accordance with JIS C6481. The copper foil was peeled off at a speed of 50 mm/min in a 90° direction from a sample with a width of 10 mm. 2) Solder heat resistance: Float the sample in a solder bath for 30 seconds, then measure the temperature at which no blistering occurs. For moisture-absorbing solder, the sample is made to absorb moisture under the conditions of 40° C. x 90% RH x 1 hr, then floated in a solder bath for 30 seconds, and checked for appearance, blisters, etc.

[0017]

[Table 1]

[0018]

Effects of the Invention According to the present invention, it is possible to provide a bonding sheet with excellent adhesiveness, soldering heat resistance, and processability at low temperatures and in a short time, and its practical value is extremely high.

Claims (1)

[Claims] 1. A bonding sheet comprising a semi-cured heat-resistant adhesive layer and a release film laminated, wherein the adhesive has the following composition. b) Epoxy resin

100 parts by weight, b) Carboxyl group-containing nitrile rubber 4
0 to 150 parts by weight, c) curing agent

1 to 50 parts by weight, d) one or more curing accelerators selected from imidazole compounds, tetraphenyl borates of tertiary amines, and fluorides of zinc, tin, and nickel;

0.1 to 5 parts by weight.