JPH08181418A - Coverlay film - Google Patents

Abstract

PURPOSE: To improve reliability on resistance to wet heat, soldering heat resistance and adhesion property by making an adhesive composition and resin of a coverlay film a specified element. CONSTITUTION: A coverlay film is constituted of a lamination body of thermosetting type adhesive and a release film. An essential element is 100 pts.wt. of epoxy resin, 20 to 100 pts.wt. of carboxyl group-containing acrylonitrile-butadiene rubber, 0.01 to 50 pts.wt. of setting agent, a block having a functional group which enables chemical bond with one or both of epoxy group and carboxyl group, or 2 to 60 pts.wt. of graft copolymer. Thereby, it is possible to acquire a coverlay film of good wet heat resistant reliability, soldering heat resistance and adhesion property and to improve reliability and economy of a flexible printed substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel coverlay film which is used for protection of printed circuit boards and which is excellent in moisture and heat resistance, solder heat resistance and adhesiveness.

[0002]

2. Description of the Related Art In recent years, electronic devices have become smaller and higher in density, and the role of a flexible printed circuit board has become important for mounting components in a narrow space. Therefore, a coverlay film is generally used to protect the flexible printed circuit board. Therefore, even with respect to the coverlay film, improvement in performance such as adhesiveness, solder heat resistance, wet heat reliability, insulation, and bending durability is strongly desired. In addition, it is necessary to be able to deal with the bonding work accompanying the finer circuit pattern, particularly the improvement of workability of alignment. Conventionally, a coverlay film is one side of an insulating plastic film such as polyimide or polyester, a thermosetting resin such as epoxy resin and / or phenol resin, acrylonitrile butadiene rubber (hereinafter referred to as NBR), polyester resin, acrylic resin. It is manufactured by applying a thermosetting adhesive mixed with a thermoplastic resin that has been chemically modified with a thermosetting resin to make it semi-cured, and then laminating a release film. ing. In particular, epoxy resin and NB
A coverlay film using an R-based adhesive is most often used because it has a relatively excellent balance of the above-mentioned properties. (Japanese Patent Publication 3-28285, Japanese Patent Publication 4-32818)
3 gazette etc.). However, the moisture resistance and heat resistance, solder heat resistance, and adhesiveness of conventional adhesives are not always satisfactory.

In use, a copper-clad substrate on which a cover lay film having a necessary portion punched out in advance with a mold is patterned is placed at 160 to 180 ° C. and 20 to 40 kg / cm.
^It is common to bond by heating and pressure treatment for ² to 30 to 90 minutes.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a novel coverlay film which is excellent in moisture and heat resistance, solder heat resistance and adhesiveness.

[0005]

Means for Solving the Problems The present inventors have achieved the present invention as a result of earnestly examining the adhesive composition of the coverlay film and the modification of the resin in order to achieve the above object. is there.

That is, the present invention is a cover characterized by comprising an insulating plastic film, a thermosetting adhesive containing the following (A) to (D) as essential components, and a release film laminate. Regarding ray film.

(A) Epoxy resin 100 parts by weight (B) Carboxyl group-containing acrylonitrile butadiene rubber 20 to 100 parts by weight (C) Curing agent 0.01 to 50 parts by weight (D) One or both of epoxy group and carboxyl group 2 to 60 parts by weight of a block or graft copolymer having a functional group capable of chemically bonding.

The epoxy resin used in (A) of the present invention is not particularly limited as long as it contains at least two epoxy groups in the molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, or Examples thereof include biphenol type epoxy resin and novolac type epoxy resin. Further, in order to impart flame retardancy, it is effective to use a halogenated epoxy resin, particularly a brominated epoxy resin. At this time, although flame retardancy can be imparted only by the brominated epoxy resin, the heat resistance of the adhesive is greatly reduced, so that it is more effective to use a mixed system with a non-brominated epoxy resin. Examples of brominated epoxy resins include "Epicoat" 5045,5
046, 5048, 5050, 5051 (all manufactured by Yuka Shell Epoxy Co., Ltd.), "DER" -542 (manufactured by Dow Chemical Co., Ltd.), "BREN-S" (manufactured by Nippon Kayaku Co., Ltd.), etc., and bromine. 2 considering the content and epoxy equivalent
You may use it in mixture of 2 or more types.

The carboxyl group-containing acrylonitrile-butadiene rubber (hereinafter referred to as NBR-C) used in (B) is, for example, a copolymer obtained by copolymerizing acrylonitrile and butadiene at a weight ratio of about 10/90 to 50/50. Examples thereof include those obtained by carboxylating the terminal group of rubber, or terpolymer rubbers of acrylonitrile, butadiene and a polymerizable monomer containing a carboxyl group such as acrylic acid and maleic acid. Carboxyl group content is 0.2 ~
3 mmol / g is desirable. If it is less than 0.2 mmol / g, there are few reaction points with the epoxy resin, and the heat resistance of the finally obtained cured product is poor. On the other hand, if it exceeds 3 mmol / g, the viscosity and the stability of the adhesive solution when applied are increased during coating. Acrylonitrile amount is 10-50
wt% is required, and if it is less than 10%, the chemical resistance of the cured product becomes poor. On the other hand, if it exceeds 50 wt%, it becomes difficult to dissolve in a normal solvent, which leads to a decrease in workability. As specific NBR-C, PNR-1H (manufactured by Japan Synthetic Rubber Co., Ltd.), "Nipol" 1072J, "Nipol" D
Examples include N612, "Nipol" DN631 (all manufactured by Nippon Zeon Co., Ltd.), "Hiker" CTBN (manufactured by BF Goodrich).

The blending ratio of the above epoxy resin and NBR-C is NBR-based on 100 parts by weight of the epoxy resin.
C is 20 to 100 parts by weight, preferably 40 to 80 parts by weight. If it is less than 20 parts by weight, the adhesiveness will be deteriorated. Further, if it exceeds 100 parts by weight, the solder heat resistance is deteriorated, which is not preferable.

If the curing agent used in (C) is used as a curing agent for ordinary epoxy resins,
There is no particular limitation, and diaminodiphenylmethane,
Amine-based compounds such as diaminodiphenyl sulfide, diaminobenzophenone, diaminodiphenylsulfone, and diethyltriamine, imidazole derivatives such as 2-alkyl-4-methylimidazole, 2-phenyl-4-alkylimidazole, phthalic anhydride, trimellitic anhydride, etc. Examples of the organic acid, an amine complex of boron trifluoride such as boron trifluoride triethylamine complex, and dicyandiamide may be used, and these may be used alone or in combination of two or more.

The mixing ratio of the NBR-C and the epoxy resin to the curing agent is not particularly limited as long as the carboxyl group of the NBR-C and the epoxy resin can be cured, but the addition amount is 100 parts by weight of the epoxy resin. To 0.0
1 to 50 parts by weight is suitable. In the present invention,
It is important to use (D). (D) is a block or graft copolymer having a functional group capable of chemically bonding to one or both of an epoxy group and a carboxyl group. The co-polymer used in (D) has a basic structure composed of a soft segment and a hard segment,
It is not particularly limited as long as it has a functional group capable of chemically bonding to one or both of the epoxy resin and NBR-C, for example, a functional group such as a carboxyl group, an epoxy group and an amino group.

The copolymer comprises a conjugated diene homopolymer block and a vinyl aromatic hydrocarbon homopolymer block,
The double bond part of the conjugated diene is preferably hydrogenated, and the hydrogenation rate is preferably 90 mol% or more. If it is less than 90 mol%, the wet heat resistance tends to decrease.

The copolymer has a functional group capable of chemically bonding to one or both of an epoxy group and a carboxyl group of 0.01 to
It is preferable to contain 3 mmol / g. 0.01 mmol
If it is less than / g, it cannot be sufficiently crosslinked with the epoxy resin or NBR-C, and the solder heat resistance tends to decrease. On the other hand, if it exceeds 3 mmol / g, the dissolution stability in the solvent is lowered, and the workability is apt to be lowered.

The conjugated diene is not particularly limited, but butadiene, isoprene and the like are common. These may be one kind or a mixture of two or more kinds. The conjugated diene in the copolymer is preferably contained in an amount of 50 to 90 wt%. The conjugated diene referred to here may be hydrogenated, or part or all may be ethylene blocks. If the content is less than 50%, the adhesive strength will decrease due to the decrease in elasticity, and if it exceeds 90%, the solder resistance will decrease due to the decrease in toughness.

The vinyl aromatic hydrocarbon polymer is not limited as long as it can serve as a hard segment, and examples thereof include alkyl substitution products of styrene such as styrene, p-methylstyrene and o-methylstyrene, vinylnaphthalene, vinylanthracene and the like. These may be one kind or a mixture of two or more kinds, but styrene is particularly preferable because it is excellent in water resistance and insulating property.

An example of a copolymer satisfying the above characteristics is an acrylonitrile-butadienestyrene copolymer,
Examples thereof include a styrene-butadiene-styrene block copolymer and a modified copolymer having a styrene-isoprene block copolymer as a basic structure. The amount of copolymer added is
The amount is preferably 2 to 60 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the epoxy resin. If it is less than 2 parts by weight, the moisture and heat resistance tends to be lowered. This can be confirmed by, for example, increasing the rate of discoloration (discoloration rate) of the copper foil when the substrate to which the coverlay is pressure-bonded is immersed in boiling water. Further, if it is less than 2 parts by weight, the solder heat resistance is lowered, which is not preferable. Also, 6
If it exceeds 0 parts by weight, the adhesive strength tends to decrease.

In addition to the above-mentioned essential components, fine particles of inorganic flame retardant can be added if necessary. Examples of the finely divided inorganic flame retardant include metal hydroxides such as aluminum hydroxide, magnesium hydroxide and calcium aluminate hydrate, and metal oxides such as zinc oxide, antimony trioxide, antimony pentoxide and magnesium oxide. These may be used alone or in combination of two or more. Considering transparency and dispersion stability, the average particle size of the finely divided inorganic flame retardant is 0.2.
˜5.0 μ is preferable. Further, the addition amount is appropriately 20 to 100 parts by weight with respect to the epoxy resin.

In addition to the above components, addition of organic or inorganic components such as antioxidants and ion scavengers is not limited to the extent that the characteristics of the adhesive are not impaired.

The insulating plastic film in the present invention means polyimide, polyester, polyphenylene sulfide, polyether sulfone, polyether ether ketone, aramid, polycarbonate, polyarylate,
A film having a thickness of 10 to 200 μ and made of a plastic such as the above, and a plurality of films selected from these may be laminated and used. If necessary, surface treatment such as hydrolysis, corona discharge, low temperature plasma, physical surface roughening, and easy adhesion coating treatment can be applied.

The release film referred to in the present invention is not particularly limited as long as it can be peeled from the adhesive surface without impairing the form of the coverlay. For example, a polyester film, a polyolefin film, and a film obtained by coating silicone or a fluorine compound. The paper laminated with is mentioned.

In this way, the insulating plastic film and the release film form a laminate with an adhesive, and a coverlay film is obtained.

[0023]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. The evaluation method will be described before the description of the examples.

Evaluation Method (1) Evaluation Sample Preparation Method A coverlay film was coated on a glossy surface of a 35 μ electrolytic copper foil (JTC foil manufactured by Nikko Gould Foil Co., Ltd.)
Samples for evaluation were prepared by laminating under press conditions of 30 ° C., 30 kg / cm ² , and 30 minutes.

(2) Peel strength The normal peel strength was measured according to JIS-C6481 using a sample pressed on an electrolytic copper foil by the method of (1) above. The peel strength after moisture absorption was measured by treating the sample in boiling water of 95 ° C. for 24 hours, conditioning the humidity in an atmosphere of 22 ° C. and 55% RH for 24 hours, and measuring the same as in the normal state.

(3) Moisture and heat resistance reliability (discoloration rate due to boiling water) 9 samples of electrolytic copper foils pressed by the above method (1) were used.
The degree of discoloration after standing in boiling water at 5 ° C. for 240 hours was checked.

(4) Soldering heat resistance It was carried out by a method according to JIS-C6481. A 25 mm square sample pressed on an electrolytic copper foil by the above method (1) was conditioned under an atmosphere of 22 ° C. and 90% RH for 24 hours, and then immediately floated on a solder bath for 30 seconds to prevent swelling and peeling. Not the highest temperature measured.

(5) Solubility Stability A substance which is soluble in a coating solvent of toluene / methyl ethyl ketone (1: 1) and is compatible with NBR-C and an epoxy resin is marked with ◯, and any one of them is not satisfied, Those that were separated were designated as x. It is desirable that the adhesive does not phase separate.

It is desirable that the characteristics of the coverlay satisfy the following values. Adhesive strength (normal state): 0.8 kg / cm or more Adhesive strength (moisture absorption): 0.7 kg / cm or more Color change rate due to boiling water: less than 10% Solder heat resistance: 250 ° C or more

Example 1 Aluminum hydroxide (H-43, manufactured by Showa Denko KK) was used as a toluene solution and then subjected to a sand mill to prepare an aluminum hydroxide dispersion liquid. To this dispersion, NBR-C
(PNR-1H, manufactured by Japan Synthetic Rubber Co., Ltd.), brominated epoxy resin ("Epicote" 505, manufactured by Yuka Shell Co., Ltd.)
0, bromine content 49%), non-brominated epoxy resin (Yukaka Shell Co., Ltd., "Epicoat" 828, and "Epicoat" 1001), hydrogenation of maleic acid-modified styrene-ethylene-styrene block copolymer Thing (manufactured by Asahi Kasei Corp., "Tuftec" MX-073), 4, 4 '
-Diaminodiphenyl sulfone, boron trifluoride monoethylamine complex, and the same weight of toluene / methyl ethyl ketone (1: 1) as the dispersion are added so as to have the composition ratios shown in Table 1, and the mixture is stirred and mixed at 30 ° C to obtain an adhesive. A solution was made. A 25 μm thick polyimide film (“Kapton” manufactured by Toray DuPont Co., Ltd.)
00H) to a dry thickness of about 35μ.
Dry for 5 minutes at 50 ° C, thickness 2 with silicone release agent
A 5μ polyester film was laminated to obtain a coverlay film. The characteristics are shown in Table 2.

[0031]

[Table 1]

[0032]

[Table 2]

Examples 2 to 7 and Comparative Examples 1 to 8 When a copolymer different from that of Example 1 is used, the copolymer is synthesized by the anionic polymerization method, and otherwise the same as in Example 1, Coverlays were obtained using the adhesives prepared with the raw materials and the composition ratios shown in Table 1, respectively. The characteristics are shown in Table 2.

From the examples and comparative examples in Tables 1 and 2, it can be seen that the coverlay films obtained by the present invention are excellent in wet heat resistance, solder heat resistance and adhesiveness.

[0035]

INDUSTRIAL APPLICABILITY The present invention industrially provides a novel coverlay film having excellent resistance to moisture and heat, soldering heat resistance, and adhesiveness. The coverlay film of the present invention ensures reliability of a flexible printed circuit board. And economic efficiency can be improved.

Claims (4)

[Claims] 1. An insulating plastic film, the following (A):
A coverlay film comprising a laminate of a thermosetting adhesive containing (E) as an essential component and a release film. (A) Epoxy resin 100 parts by weight (B) Carboxyl group-containing acrylonitrile butadiene rubber 20 to 100 parts by weight (C) Curing agent 0.01 to 50 parts by weight (D) Chemically bonded to one or both of epoxy group and carboxyl group Block or graft copolymer having functional group 2 to 60 parts by weight 2. The coverlay film according to claim 1, wherein the copolymer of the component (D) contains 50 to 90 wt% of a hydrogenated conjugated diene polymer block. 3. The coverlay according to claim 2, wherein the copolymer of the component (D) contains 0.01 to 3 mmol / g of a functional group capable of chemically bonding to one or both of an epoxy group and a carboxyl group. the film. 4. The coverlay film according to claim 3, wherein the copolymer of the component (D) is a copolymer containing styrene and butadiene containing a carboxyl group or a carboxylic acid anhydride as a block component. .