JPH06322324A - Bonding sheet - Google Patents

Abstract

PURPOSE:To provide a bonding sheet having a heat-resistant adhesive layer of a specific composition and suitable for the production of a multilayer flexible printed circuit board owing to its excellent adhesiveness, thermal deterioration resistance, soldering heat-resistance and processability. CONSTITUTION:The bonding sheet is produced by laminating a semicured heat- resistant adhesive layer to a releasing film. The adhesive is composed of (A) 100 pts.wt. of an epoxy resin, (B) 10-40 pts.wt. of a carboxyl-containing nitrile rubber (e.g. obtained by carboxylating the terminal of an acrylonitrile-butadiene copolymer rubber), (C) 1-50 pts.wt. of a curing agent (e.g. diethyltriamine), (D) 0.1-5 pts.wt. of a cure accelerator selected from an imidazole compound, a tetraphenylboric acid salt of a tert-amine and borofluoride of Zn, Sn or Ni (preferably borofluoride of Zn, Sn or Ni) and (E) 0.1-10 pts.wt. of a silane coupling agent (e.g. vinyltrimethoxysilane).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive for a bonding sheet for flexible printed circuit boards.

[0002]

2. Description of the Related Art In recent years, the demand for printed circuit boards has increased as electric products have become smaller and smaller and have higher functionality, and the range of use of flexible boards has expanded. In particular, as the mounting of high density advances and the demand for multilayering of flexible printed circuit boards increases, the bonding sheet used for bonding each layer or bonding rigid and flexible printed circuit boards has better adhesiveness than before. It is desired to improve performance such as heat resistance and workability.

[0003]

Since the conventional bonding sheet has insufficient adhesiveness, it causes poor adhesion between the layers of the flexible printed circuit board, and poor heat resistance causes blistering and the like during soldering, resulting in poor workability. Since it was bad, there was a problem that processing at high temperature for a long time was required. It is believed that most of these problems are caused by adhesives. So far, adhesives for bonding sheets have been NBR / phenol resin, epoxy / phenol / NBR, NBR / epoxy resin, epoxy / polyester, epoxy. / Acrylic resin, acrylic resin, etc. have been used, but these adhesives have advantages and disadvantages. For example, NBR type has large thermal deterioration, epoxy type has low adhesiveness, and acrylic type has high temperature and long time. In the present situation, it is not possible to find a sufficiently satisfactory one in that it requires heating and pressure bonding and is inferior in workability.
The present invention aims to provide a bonding sheet excellent in adhesiveness, heat deterioration, heat resistance and workability in order to solve the above-mentioned drawbacks and to make a flexible printed circuit board into a multilayer board or the like.

[0004]

Means for Solving the Problems The present inventors have completed the present invention as a result of earnestly researching the adhesive composition in order to achieve the above object. That is, the present invention is a bonding sheet obtained by laminating a semi-cured heat-resistant adhesive layer and a release film, wherein the adhesive has the following composition. A) 100 parts by weight of epoxy resin, b) 10 to 40 parts by weight of carboxyl group-containing nitrile rubber, c) 1 to 50 parts by weight of curing agent, d) imidazole compound, tetraphenylborates of tertiary amines and zinc, The gist of the present invention is 0.1 to 5 parts by weight of one or more curing accelerators selected from tin and nickel borofluorides, and (e) 0.1 to 5 parts by weight of a silane coupling agent.

The present invention will be described in detail below.
First, the bonding sheet adhesive composition will be described. A) Any epoxy resin may be used as long as it has two or more epoxy groups in one molecule. For example, bisphenol type epoxy resin, glycidyl ether type epoxy resin such as novolac resin, cycloaliphatic type epoxy resin, and aromatic resin. Type epoxy resins, halogenated epoxy resins and the like can be used alone or in combination of two or more. Among the epoxy resins exemplified above, a halogenated epoxy resin,
Preferably, a brominated epoxy resin is used to obtain an adhesive having excellent flame retardancy.

The brominated epoxy resin may be any one having an epoxy group and a bromine atom in one molecule, and examples thereof include bisphenol type brominated epoxy resin and novolac type brominated epoxy resin. .
Specifically, Epicoat manufactured by Yuka Shell Epoxy Co., Ltd.
5045 (Br%: 19% by weight (hereinafter% represents% by weight)), 50
46 (Br%: 21%), 5048 (Br%: 25%), 5049 (Br%:
26%), 5050 (Br%: 49%), BREN manufactured by Nippon Kayaku Co., Ltd.
-S (Br%: 35%) etc. These brominated epoxy resins having different Br contents can be used alone or in combination of two or more. A brominated epoxy resin having a Br content of 21% to 51% is preferable from the viewpoint of flame retardancy.

Examples of the nitrile rubber containing a carboxyl group as the component (b) include those obtained by carboxylating an acrylonitrile-butadiene copolymer rubber in which acrylonitrile and butadiene are copolymerized. Specifically, Hiker CTBN, Hiker CTBNX, Hiker 1072 manufactured by Goodrich, Nipol 1072J and Nipol manufactured by Nippon Zeon Co., Ltd.
There are 1072, Nipol DN612, Nipol DN631, Nipol DN601 and so on. These carboxyl group-containing nitrile rubbers may be used alone or in combination of two or more. The content of the carboxyl group 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, metaxylenediamine, diaminodiphenylmethane and diaminodiphenylsulfone. Amine compounds, phthalic anhydride, hexahydrophthalic anhydride,
Examples thereof include acid anhydrides such as tetrahydrophthalic anhydride and trimellitic anhydride, dicyandiamide, and boron trifluoride amine complex compounds. These may be used alone or in combination of two or more. These curing agents are usually
The component (a) can be added in a wide range of 1 to 50 parts by weight per 100 parts by weight of the epoxy resin, and the amount used is appropriately selected depending on the type of curing agent and the type and amount of each resin.

As the curing accelerator of component d), imidazole such as 2-alkyl-4-methylimidazole, 2-alkyl-4-ethylimidazole, 1- (2-cyanoethyl) -2-alkylimidazole, 2-phenylimidazole and the like. System compounds, tetraphenylboronates of tertiary amines such as triethylammonium tetraphenylborate and zinc borofluoride, tin borofluoride and nickel borofluoride, which may be used alone or in combination of two or more. Used. The addition amount of these is appropriately 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight. Further, among the imidazole compounds, tetraphenylborates of tertiary amines and zinc, tin, borofluoride of nickel, among tetraphenylborates of tertiary amines and zinc,
Bromides of tin and nickel are preferable, and bromides of zinc, tin and nickel are more preferable.

Examples of the silane coupling agent (e) include vinyl-based silanes, amino-based silanes, mercapto-based silanes, epoxy-based silanes, and acryl-based silanes. Specifically, vinyltrimethoxysilane, vinyltriethoxysilane. Such as vinylsilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and other amino-based silanes, 3-mercaptopropyltrimethoxysilane, etc. Mercapto-based silanes, 3-glycidoxypropyltrimethoxysilane, 3
-Epoxy silanes such as glycidoxypropyltriethoxysilane, acrylic silanes such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and the like, but are not particularly limited to these. Absent.

If desired, a fine-particle inorganic powder can be added to the adhesive. 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 may be used alone or in combination of two or more. Since the flexible printed circuits have become finer and patterns of several tens of μm have been put into practical use recently, the inorganic powder particles have a particle size of 10 μm or less, preferably for adhesives for bonding sheets for making the flexible printed circuit board into a multilayer board or the like. Is preferably 5 μm or less. In order to improve the fixability and water resistance of these finely divided inorganic powders to the resin matrix, hydrophobizing treatment is desirable. Chlorosilane such as dimethyldichlorosilane, silicone oil, silane cup such as alkyltriethoxysilane, and methyltriethoxysilane. A treating agent such as a ring agent is used. Incidentally, the hydrophobic treatment is 0.
The inorganic powder may be added to an aqueous solution obtained by mixing 5 to 1.0% by weight of the above silane coupling agent with an alcoholic aqueous solution, and the mixture may be heated and stirred, and then separated and dried.

The present invention relates to the above a), b), c), d),
The objective effect is achieved by the adhesive composed of the respective components (e), and the following inconveniences occur outside the above composition range. That is, component a) epoxy resin 1
If the amount of the nitrile rubber containing the carboxyl group of component (b) is less than 10 parts by weight with respect to 00 parts by weight, the peel strength will decrease, and
If it exceeds the weight part, the thermal deterioration becomes large and the peel strength after long-term heat resistance decreases. If the curing agent of component (c) is 1 part by weight at the end, the curing will be insufficient and the solder heat resistance will decrease, and if it exceeds 50 parts by weight, the life of the adhesive will be shortened and the solder heat resistance and peel strength will decrease. . D) The curing accelerator of component is 0.1
If it is less than 5 parts by weight, the solder heat resistance will decrease and the exudation of the adhesive during pressing will become too large, and processing at high temperature for a long time will be required. If it exceeds 5 parts by weight, the life of the adhesive will become shorter and the peel strength will increase. Is reduced. If the silane coupling agent of component (e) is less than 0.1 parts by weight, the peel strength will be reduced, and if it exceeds 10 parts by weight, the solder heat resistance will be reduced.

The adhesive composition comprising the above components (a) to (e) is dissolved in an organic solvent such as methyl ethyl ketone, methanol, ethanol or toluene to give an adhesive.

The release film used in the present invention includes:
Plastic films such as PE film, PP film, TPX film, PET film with silicone release agent, and
Examples include release papers such as film-coated papers obtained by coating a polyolefin paper such as PE or PP, a vinylidene chloride film, a TPX film or the like on one side or both sides of a base paper.

Next, a method of manufacturing the bonding sheet of the present invention will be described. The release film is coated with the adhesive so as to have a thickness of 20 to 60 μm, and dried at a temperature of 80 to 120 ° C. to remove the solvent, thereby semi-curing the adhesive. In this case, if necessary, it can be heated to about 100 ° C for a short time. Further, a release film is pressure-bonded and laminated on this using a roll laminator, and wound into a roll.

[0016]

EXAMPLES Next, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these. The parts and percentages in the specific examples are all based on the weight of the solid content. (Examples 1 to 6 and Comparative Examples 1 to 8) Using the adhesive compositions shown in Tables 1 and 2, a 30% MEK solution was prepared and uniformly dispersed by a ball mill to obtain adhesive solutions. Next, these adhesive solutions were applied to a 25 μm PET film with silicone release treatment on one side so that the coating thickness after drying would be 30 μm, and dried by heating at 80 ° C. for 2 minutes and 120 ° C. for 5 minutes. The solvent was removed and the adhesive was semi-cured. Release paper with both sides coated with TPX film was pressure-laminated with a roll laminator at a temperature of 50 ° C, a linear pressure of 5 kg / cm, and a speed of 2 m / min.
A bonding sheet was produced. Next, in order to measure the physical properties of this bonding sheet, the release PET film and the adhesive sheet from which the release paper had been removed were set on a 25 μm polyimide film, laminated on the glossy surface of electrolytic copper foil 35 μm, and pressed. It was pressed at 160 ° C. and 50 kg / cm ² for 15 minutes to produce a laminated film. The characteristics of the flexible laminated film thus obtained are also shown in Tables 1 and 2.

[0017]

[Table 1]

[0018]

[Table 2]

The methods for measuring the physical properties of the flexible laminated films shown in Tables 1 and 2 are as follows. (Method for measuring physical properties of flexible laminated film) 1) Peel strength: Measured according to JIS C6481. A 10 mm wide sample is peeled off the copper foil in 90 directions at a speed of 50 mm / min. 2) Solder heat resistance: After the sample is floated in a solder bath for 30 seconds, the temperature at which blistering does not occur is measured. Moisture absorbing solder absorbs moisture under the condition of 40 ℃ × 90% RH × 1hr, and then floats the sample in the solder bath for 30 seconds.
Check the appearance and blisters.

[0020]

According to the present invention, it becomes possible to provide a bonding sheet excellent in adhesiveness, heat deterioration, solder heat resistance and workability at low temperature in a short time, and its utility value is extremely high in practical use.

Claims (1)

[Claims] 1. A bonding sheet obtained by laminating a semi-cured heat-resistant adhesive layer and a release film, wherein the adhesive has the following composition. A) 100 parts by weight of epoxy resin, b) 10 to 40 parts by weight of carboxyl group-containing nitrile rubber, c) 1 to 50 parts by weight of curing agent, d) imidazole compound, tetraphenylborates of tertiary amines and zinc, 0.1 to 5 parts by weight of one or more curing accelerators selected from tin and nickel borofluorides, and (e) 0.1 to 10 parts by weight of silane coupling agent.