JP3031795B2 - Bonding sheet - Google Patents

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 a flexible printed circuit board.

[0002]

2. Description of the Related Art In recent years, the demand for printed circuit boards has been increasing in accordance with the miniaturization of electronic products and the increasing functionality thereof, and in particular, the range of use of flexible substrates has been expanding. In particular, as high-density mounting has progressed and the demand for multi-layer flexible printed circuit boards has increased, the bonding sheets used for laminating each layer and for bonding rigid boards and flexible printed circuit boards have more adhesive properties than before. Improvements in performance such as heat resistance and workability are desired.

[0003]

The conventional product of the bonding sheet is insufficient in adhesiveness, resulting in poor adhesion between the multilayers of the flexible printed circuit board, and inferior heat resistance, causing blisters and the like at the time of soldering, resulting in poor workability. There were difficulties, such as the necessity of high-temperature and long-time processing because it was bad. It is considered that these difficulties are almost entirely caused by adhesives. Until now, adhesives for bonding sheets include NBR / phenolic resin, epoxy phenol / NBR, NBR / epoxy resin, epoxy / polyester, epoxy / Acrylic resin, acrylic resin, etc. have been used, but these adhesives have their advantages and disadvantages. For example, NBR type has large thermal degradation, epoxy type has low adhesiveness, and acrylic type has high temperature and long time. In the present situation, it is necessary to perform heating and pressure bonding, and the workability is inferior.
An object of the present invention is to provide a bonding sheet excellent in adhesiveness, heat resistance deterioration, heat resistance and workability in order to eliminate the above-mentioned drawbacks and make a flexible printed circuit board into a multilayer board or the like.

[0004]

Means for Solving the Problems The present inventors have made intensive studies with a focus on the adhesive composition in order to achieve the above object, and as a result, completed the present invention. That is, the present invention provides a bonding sheet obtained by laminating a heat-resistant adhesive layer in a semi-cured state and a release film, wherein the adhesive has the following composition. A) 100 parts by weight of an epoxy resin, b) 10 to 40 parts by weight of a carboxyl group-containing nitrile rubber, c) 1 to 50 parts by weight of a curing agent, d) imidazole compound, tetraphenylborate 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 fluorides, and 0.1 to 5 parts by weight of a silane coupling agent.

Hereinafter, the present invention will be described in detail.
First, the adhesive composition for a bonding sheet will be described. A) The epoxy resin may be any resin having two or more epoxy groups in one molecule. For example, glycidyl ether type epoxy resin such as bisphenol type epoxy resin and novolak resin, cycloaliphatic type epoxy resin, aromatic resin Epoxy resins, halogenated epoxy resins and the like can be used alone or in combination of two or more. Further, among the epoxy resins exemplified above, a halogenated epoxy resin,
Preferably, by using a brominated epoxy resin, an adhesive having excellent flame retardancy can be obtained.

The brominated epoxy resin may be any one having an epoxy group and a bromine atom in one molecule, such as a bisphenol-type brominated epoxy resin and a novolak-type brominated epoxy resin. .
Specifically, Epicoat made by Yuka Shell Epoxy Co., Ltd.
5045 (Br%: 19% by weight (hereinafter% means weight%)), 50
46 (Br%: 21%), 5048 (Br%: 25%), 5049 (Br%:
26%), 5050 (Br%: 49%), BREN manufactured by Nippon Kayaku Co., Ltd.
-S (Br%: 35%). 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 preferred from the viewpoint of flame retardancy.

Examples of the carboxyl group-containing nitrile rubber (b) include acrylonitrile-butadiene copolymer rubber in which acrylonitrile and butadiene are copolymerized and carboxylated at the terminal. Specifically, hiker CTBN, hiker CTBNX and hiker 1072 manufactured by Goodrich, Nipol 1072J and Nipol manufactured by Zeon Corporation
1072, Nipol DN612, Nipol DN631, Nipol DN601 and the like. These carboxyl group-containing nitrile rubbers can 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 usual curing agent for epoxy resins. 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 compound. These can be used alone or in combination of two or more. These curing agents are usually
A) The epoxy resin of the component can be added in a wide range of 1 to 50 parts by weight per 100 parts by weight of the epoxy resin. The amount used is appropriately selected depending on the type of the curing agent and the type and amount of each resin.

As the curing accelerator of the component (d), imidazoles such as 2-alkyl-4-methylimidazole, 2-alkyl-4-ethylimidazole, 1- (2-cyanoethyl) -2-alkylimidazole and 2-phenylimidazole are used. Tertiary amines such as triethylammonium tetraphenylborate, and the like, and zinc borofluoride, tin borofluoride, and nickel borofluoride, which may be used alone or in combination of two or more. Used. The appropriate amount of these additives is 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight. Further, among the above imidazole compounds, tertiary amines tetraphenylborate and zinc, tin, and nickel borofluoride, tertiary amines tetraphenylborate and zinc;
Preferred are tin and nickel borofluorides, more preferably zinc, tin and nickel borofluorides.

Examples of the silane coupling agent (e) include vinyl silanes, amino silanes, mercapto silanes, epoxy silanes, and acrylic silanes. Specifically, vinyl trimethoxy silane, vinyl triethoxy silane Such as vinylsilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and the like, 3-mercaptopropyltrimethoxysilane, etc. Mercapto silane, 3-glycidoxypropyltrimethoxysilane, 3
Epoxy silanes such as -glycidoxypropyltriethoxysilane, acrylic silanes such as 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane, and the like. Absent.

Further, fine particles of inorganic powder can be added to the adhesive if necessary. As the fine 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 and the like Silicates, silicates and boron nitride. These can be used alone or in combination of two or more. In recent years, flexible printed circuits have become finer, and patterns of several tens of μm have also been put into practical use. Is suitably 5 μm or less. In order to improve the fixability and water resistance of these fine inorganic powders to the resin matrix, a hydrophobic treatment is desirable. Chlorosilane such as dimethyldichlorosilane, silicone oil, silane cup such as alkyltriethoxysilane, methyltriethoxysilane, etc. A treating agent such as a ring agent is used. In addition, the hydrophobizing treatment is applied to the inorganic powder in an amount of 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 aqueous alcohol solution or the like, heated and stirred, and then separated and dried.

The present invention relates to the above-mentioned a), b), c), d),
The intended effect is achieved by the adhesive having the composition of each component e), and the following inconvenience occurs outside the above composition range. That is, the epoxy resin of component b) 1
If the amount of the nitrile rubber containing a carboxyl group of component (b) is less than 10 parts by weight per 100 parts by weight, the peel strength decreases, and
When the amount exceeds the weight part, thermal deterioration increases, and peel strength after long-term heat resistance decreases. C) If the component curing agent is 1 part by weight at the end, curing becomes insufficient and solder heat resistance decreases. If it exceeds 50 parts by weight, solder heat resistance and peel strength decrease in addition to shortening the life of the adhesive. . D) The curing accelerator of the component is 0.1
If the amount is less than 5 parts by weight, the heat resistance of the solder is reduced, and the exudation of the adhesive during press working becomes too large. At the same time, high temperature and long time processing is required. Decrease. E) When the amount of the silane coupling agent is less than 0.1 part by weight, the peel strength decreases, and when it exceeds 10 parts by weight, the solder heat resistance decreases.

The adhesive composition comprising the components (a) to (e) is dissolved in an organic solvent such as methyl ethyl ketone, methanol, ethanol and toluene to form 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
Release paper such as film-coated paper in which a polyolefin film such as PE or PP, a vinylidene chloride film, a TPX film or the like is coated on one side or both sides of a base paper.

Next, a method for manufacturing the bonding sheet of the present invention will be described. The adhesive is applied to a release film so as to be 20 to 60 μm in a dry state, dried at a temperature of 80 to 120 ° C. to remove the solvent, and the adhesive is brought into a semi-cured state. In this case, it can be heated to about 100 ° C. for a short time if necessary. Furthermore, a release film is pressure-bonded and laminated using a roll laminator on this, and it is manufactured by winding 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 thereto. All parts and percentages in the specific examples are based on the weight of the solid content. (Examples 1 to 6, 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 an adhesive solution. Next, these adhesive solutions were applied to a 25 μm PET film that had been silicone-released on one side to a coating thickness of 30 μm after drying, and heated and dried at 80 ° C. × 2 minutes and 120 ° C. × 5 minutes. The solvent was removed, leaving the adhesive in a semi-cured state. Then, release paper coated on both sides with TPX film is press-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 prepared. 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 was removed were set on a 25 μm polyimide film, laminated on a glossy surface of electrolytic copper foil 35 μm, and pressed. Press processing was performed at 160 ° C. and 50 kg / cm ² for 15 minutes to produce a laminated film. The properties of the thus obtained flexible laminated film are 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. (Measurement method for physical properties of flexible laminated film) 1) Peel strength: Measured in accordance with JIS C6481. The copper foil is peeled off from a 10 mm wide sample in a 90 direction at a speed of 50 mm / min. 2) Solder heat resistance: After a sample is floated in a solder bath for 30 seconds, a temperature at which blistering or the like does not occur is measured. After absorbing the sample under the conditions of 40 ° C. × 90% RH × 1 hr, the sample is floated in the solder bath for 30 seconds.
Check the appearance, blisters, etc.

[0020]

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

Continuation of the front page (56) References JP-A-4-370996 (JP, A) JP-A-60-226582 (JP, A) JP-A-56-49780 (JP, A) JP-A-5-154857 (JP) JP-A-2-60193 (JP, A) JP-A-4-197746 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 7/00 C09J 163/00 H05K 3/38

Claims (1)

(57) [Claims] 1. A bonding sheet comprising a heat-resistant adhesive layer in a semi-cured state and a release film laminated on each other, wherein the adhesive has the following composition. A) 100 parts by weight of an epoxy resin, b) 10 to 40 parts by weight of a carboxyl group-containing nitrile rubber, c) 1 to 50 parts by weight of a curing agent, d) imidazole compound, tetraphenylborate of tertiary amines and zinc, 0.1 to 5 parts by weight of one or more hardening accelerators selected from tin and nickel fluorides; 0.1) to 10 parts by weight of a silane coupling agent.