JP2000273430A - Adhesive composition for flexible printed circuit board, and cover lay film and flex printed circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new adhesive composition for a flexible printed circuit board having excellent preservation stability, solder heat resistance and adhesiveness, capable of providing a cover lay film and a flexible printed circuit board. SOLUTION: This adhesive composition for a flexible printed circuit board comprises (A) 100 pts.wt. of an epoxy resin, (B) 20-100 pts.wt. of a carboxyl group-containing acrylonitrile butadiene rubber, (C) 2-19 pts.wt. of a thermoplastic saturated copolymer ester, (D) 0.01-50 pts.wt. of a curing agent and (E) 2-50 pts.wt. of an inorganic particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel adhesive composition for a flexible printed circuit board having excellent storage stability, solder heat resistance and adhesiveness, and a coverlay film and a flexible printed circuit board using the same.

[0002]

2. Description of the Related Art In recent years, electronic devices have been increasingly reduced in size and density, and the role of flexible printed circuit boards has become important for mounting components in narrow spaces. Also,
In recent years, fine patterning of flexible printed circuit boards,
Demands for higher performance are increasing, especially for electrical insulation,
Further improvement in adhesion is required.

Conventionally, a flexible printed circuit board has been coated with an adhesive solution on at least one of an insulating plastic film and a copper foil, dried and then heated and pressed using a heating press or a heating roll device. It is manufactured by laminating and further heating and curing. The cover lay film is manufactured by applying an adhesive to one surface of an insulating plastic film such as polyimide or polyester to make it semi-cured, and then bonding a release film layer. As the adhesive, a thermosetting type in which a thermosetting resin such as an epoxy resin and / or a phenol resin is mixed with a thermoplastic resin which can be chemically bonded to the thermosetting resin by modification is generally used. Is used regularly.

As the thermoplastic resin for the adhesive, many types such as acrylonitrile butadiene rubber (hereinafter referred to as NBR), polyamide, polyester and polyacryl have been proposed. However, these adhesives have advantages and disadvantages. For example, polyamides have slightly more moisture absorption,
The polyester type has a disadvantage that the adhesive strength to the polyimide film is weak. Polyacrylic resins require a high temperature and a long time for heat molding, and have a drawback that when the molding temperature is lowered and the time is shortened, the moisture resistance is poor. Epoxy resin and NBR
A system adhesive is most often used because of its relatively good balance of the above-mentioned properties. However, when a carboxyl group-containing NBR was used for the purpose of improving adhesiveness, the reactivity between the carboxyl group and the epoxy resin was high, and the storage stability was insufficient. There is also a method of adding a copolyester resin to these adhesives (JP-A-6-330014), but the solder heat resistance is insufficient.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a novel adhesive composition for a flexible printed circuit board having excellent storage stability, solder heat resistance and adhesiveness. It is an object of the present invention to provide a coverlay film and a flexible printed circuit board.

[0006]

That is, the present invention relates to an adhesive composition for a flexible printed circuit board, comprising the following components (A) to (E) as essential components. A coverlay film and a flexible printed circuit board. (A) 100 parts by weight of epoxy resin, (B) 20 to 100 parts by weight of acrylonitrile butadiene rubber containing carboxyl group, (C) thermoplastic saturated copolymerized polyester 2-1
9 parts by weight, (D) 0.01-50 parts by weight of a curing agent,
(E) 2 to 50 parts by weight of inorganic particles.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The epoxy resin used in (A) is not particularly limited as long as it contains at least two or more epoxy groups in a molecule. For example, bisphenol A type epoxy resin,
Bisphenol F-type epoxy resin or biphenol
And a novolak type epoxy resin. It is effective to use a halogenated epoxy resin, particularly a brominated epoxy resin, for imparting flame retardancy. At this time, although the use of only the brominated epoxy resin can impart flame retardancy, 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. Two or more kinds may be mixed and used in consideration of the bromine content and the epoxy equivalent.

[0008] The epoxy equivalent is determined by perchloric acid potentiometric titration. Perchloric acid is reacted with cetyltrimethylammonium, and the HBr generated thereby reacts by the amount of epoxy groups. The epoxy equivalent is determined from the change from the amount of perchloric acid used.

Preferably, in order to improve solder heat resistance, a low molecular weight epoxy resin having an epoxy equivalent of 300 g / eq or less is used in an amount of 20 wt% or more. If the low molecular weight epoxy resin of 300 g / eq or less is less than 20 wt%, the crosslink density becomes insufficient and the solder heat resistance decreases.

The carboxyl group-containing acrylonitrile-butadiene rubber (hereinafter referred to as NBR-) used in (B) of the present invention.
C), for example, acrylonitrile and butadiene are copolymerized in a molar ratio of about 10/90 to 50/50, and the end group of the copolymer rubber is carboxylated, or acrylonitrile, butadiene and acrylic acid, maleic acid And a terpolymer rubber of a carboxyl group-containing polymerizable monomer. Acrylonitrile content is 1
0 to 50 mol% is required, and if it is less than 10 mol%, the cured product has poor chemical resistance. On the other hand, if it exceeds 50 mol%, it becomes difficult to dissolve in a usual solvent, which leads to a decrease in workability.

The carboxyl group content is 0.01 to 0.1
5 ephr is preferred. Where ephr is equivalent par
It is an abbreviation of ts per hundred rubber and means an equivalent of a carboxyl group per 100 parts by weight of NBR-C. 0.0
If it is less than 1 ephr, the number of reaction points with the epoxy resin is small,
The cured product obtained finally has poor heat resistance. On the other hand, 0.1
If it exceeds 5 ephr, an increase in viscosity and a decrease in stability when an adhesive solution is used for application are caused. Furthermore, 0.
Those having a concentration of 03 to 0.1 ephr are preferred.

The above (A) epoxy resin and (B) NBR
The proportion of NBR-C is 20 to 100 parts by weight, preferably 30 parts by weight, based on 100 parts by weight of the epoxy resin.
８０80 parts by weight. If the amount is less than 20 parts by weight, the adhesiveness is reduced. On the other hand, if it exceeds 100 parts by weight, the solder heat resistance is lowered, which is not preferable.
_e) and (B) a ratio (n _e / n _c of NBR-C number of carboxyl groups (n _c)), it is effective to consider, for the 7-20 and n _e / n _c is specifically Is good. n The _e / n _c less than 7 storage stability the greater the impact of the reaction of the carboxyl groups of the NBR-C is reduced. n _e / n _c is lowered adhesiveness exceeds 20.

The thermoplastic saturated copolyester used in (C) of the present invention refers to a polybasic acid, particularly a dibasic acid and a polyhydric alcohol, particularly a diol, having an ester bond in the polymer main chain. Resins having a high molecular weight and not containing carbon-carbon unsaturated bonds. The addition amount of the polyester of the present invention is 2 to 1
9 parts by weight are preferred. If the amount is less than 2 parts by weight, the effect of improving the storage stability is not sufficient, and if it exceeds 19 parts by weight, the solder heat resistance decreases.

Representative acid components are aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and biphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid and sebacic acid; and ethylene as a diol component. Glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and the like can be mentioned, and these may be used alone or as a mixture of two or more. The molecular weight of the polyester of the present invention is not particularly limited, but those having a molecular weight of about 10,000 to 25,000 are particularly preferably used.

In the present invention, the content of the aromatic dicarboxylic acid such as terephthalic acid and isophthalic acid as the acid component is preferably 100 mol% or less, particularly preferably 40 to 80 mol%. If the amount of the aromatic dicarboxylic acid is less than 40 mol%, the solubility in a normal solvent such as toluene / methyl ethyl ketone will be low, and if it exceeds 80 mol%, the softening point will be high and the adhesiveness will be low. A diol component having a neopentyl glycol content of 30 to 70 mol% is particularly preferably used. When the content of neopentyl glycol in the diol component is less than 30 mol%, the solubility in a normal solvent is reduced, and when it exceeds 80 mol%, the heat resistance is reduced.

The polyester of the present invention has a glass transition point of 5
It is particularly preferable that the temperature is 40 to 40 ° C. Glass transition point is 5
If the temperature is lower than 40 ° C., the heat resistance decreases. If the temperature exceeds 40 ° C., the adhesive film becomes hard and the adhesiveness is lowered.

Examples of the curing agent used in (D) of the present invention include amine compounds such as diaminodiphenylmethane, diaminodiphenylsulfide, diaminobenzophenone, diaminodiphenylsulfone, and diethyltriamine; 2-alkyl-4-methylimidazole; Imidazole derivatives such as phenyl-4-alkylimidazole, phthalic anhydride, and organic acids such as trimellitic anhydride;
Examples include boron trifluoride amine complexes such as boron trifluoride triethylamine complex and dicyandiamide. These may be used alone or in combination of two or more.

A phenol resin such as a resol type or novolak type phenol resin may be used as a curing agent. Examples of phenolic resins include phenol, cresol,
Alkyl-substituted phenols such as pt-butylphenol, cyclic alkyl-modified phenols such as terpenes and dicyclopentadiene, nitro groups, halogen groups, amino groups, cyano groups and other functional groups containing heteroatoms, and skeletons such as naphthalene and anthracene And the like.

The inorganic particles used in (E) of the present invention include metal hydroxides such as aluminum hydroxide, magnesium hydroxide and calcium aluminate hydrate, silica, alumina, zinc oxide and antimony trioxide. ,
Examples thereof include metal oxides such as antimony pentoxide, magnesium oxide, and titanium oxide; inorganic salts such as calcium carbonate; and carbon black. These may be used alone or in combination of two or more. The inorganic particles are more preferably subjected to a hydrophobic treatment in order to improve adhesion to a resin, water resistance, and the like. Examples of the treating agent for hydrophobic treatment include silane coupling agents such as 3-aminopropyltriethoxysilane and 3-glycidoxypropyltrimethoxysilane, and silane compounds such as hexamethyldisilazane and chlorosilane. .

An appropriate amount of the inorganic particles to be added is 2 to 50 parts by weight based on 100 parts by weight of the epoxy resin. If the amount is less than 2 parts by weight, the solder heat resistance decreases, and if it exceeds 50 parts by weight, the adhesiveness decreases. In recent years, since flexible printed circuits have become finer and patterns of several tens of micrometers have been put to practical use, the particle size of the inorganic particles is preferably 10 μm or less, preferably 5 μm or less, and more preferably 2 μm or less.
Aluminum hydroxide is particularly preferably used among the above-mentioned inorganic particles for imparting flame retardancy.

In addition to the above components, addition of organic and inorganic components such as an antioxidant and an ion scavenger is not limited as long as the properties of the adhesive are not impaired.

The insulating plastic film referred to in the present invention is a film having a thickness of 10 to 200 μm made of a plastic such as polyimide, polyester, polyphenylene sulfide, polyether sulfone, polyether ether ketone, aramid, polycarbonate, polyarylate and the like. Yes, a plurality of films selected from these may be laminated and used. Also, if necessary, hydrolysis,
Surface treatments such as corona discharge, low-temperature plasma, physical roughening, and easy adhesion coating can be performed.

The release film layer referred to in the present invention is not particularly limited as long as it can be peeled off without impairing the form of the adhesive layer. Examples of the release film layer include polyester, polyolefin, polyvinyl chloride, coated with silicone or a fluorine compound, or the like. Examples include plastic films such as polyvinylidene fluoride and polyphenylene sulfide, paper laminated with these, and paper impregnated or coated with a resin having releasability.

In the adhesive composition of the present invention, as a solvent for dissolving or dispersing these components into a uniform adhesive solution, an organic solvent such as toluene, xylene, monochlorobenzene, methyl ethyl ketone (MEK), dimethylformamide, etc. Are preferred, and one or a mixture thereof is used.

The cover lay film is manufactured by applying an adhesive to one surface of an insulating plastic film such as polyimide or polyester, making it semi-cured, and then bonding a release film layer.

The flexible printed circuit board is formed by applying an adhesive solution to at least one of an insulating film and a metal foil and drying the applied adhesive solution, and then heating or pressing a heating roll.
It can be manufactured by laminating both using a screw device and further heating and curing.

[0027]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited to these examples. Before starting the description of the embodiments, an evaluation method will be described.

Evaluation method (1) Method for preparing sample for evaluation A coverlay film was coated on a glossy surface of a 35 μm electrolytic copper foil (JTC foil, manufactured by Nikko Gould Foil Co., Ltd.) to a thickness of 160 μm.
C., 30 kg / cm ² , laminated under pressing conditions for 30 minutes,
An evaluation sample was prepared. The cover lay film used had an adhesive thickness of 30 to 35 μm, and the insulating plastic film layer had a thickness of 25 μm.

(2) Exudation half-life The method was carried out in accordance with JPCA-BM02. The half-life of the exuding amount according to the present invention is defined as the time when the exuding amount after leaving the cover-lay film having an extruding amount of 200 μm at room temperature of 23 ° C. becomes half the initial value. The amount of bleeding was determined by making a 6mmφ hole in the coverlay film and pressing it onto the electrolytic copper foil by the method (1) above.
-16 type (Nippon Kogaku Co., Ltd.) and Linear Scale A
It measured using T-11-FN200 type (made by Mitutoyo Corporation). Next, the coverlay having an exudation amount of 200 μm was left at room temperature of 23 ° C., and the time when the exudation amount was half of the initial value was defined as the exudation amount half-life.

(3) Solder heat resistance The solder heat resistance was measured in accordance with JIS-C6481. The sample of 25 mm square pressed on the electrolytic copper foil by the method of the above (1) was conditioned for 24 hours in an atmosphere of 22 ° C. and 90% RH, and then immediately floated on a solder bath for 30 seconds to prevent swelling and peeling. (4) Peeling strength The peeling strength was measured in accordance with JIS-C6481 using a sample pressed on an electrolytic copper foil by the method (1).

Example 1 Aluminum hydroxide (H-42M, manufactured by Showa Denko KK)
Average particle size 1.0μm) dissolved in MEK / toluene (1: 1)
Liquid and then sand-milled to remove aluminum hydroxide
Make a sprinkle. NBR-C (Zeo Japan)
"Nipol" 1072 carboxyl group content
0.075 ephr), brominated epoxy resin (oiled shell)
"Epicoat" 5050 Epoxy equivalent 39
5), non-brominated epoxy resin (manufactured by Yuka Shell Co., Ltd.)
Epicoat "834 epoxy equivalent 250), thermoplastic
Saturated copolymerized polyester (manufactured by Toyobo Co., Ltd.)
300), 3,3'-diaminodiphenylsulfo
And boron trifluoride monoethylamine complex respectively in Table 1
And the solid content concentration becomes 35 wt%.
Add EK, stir and mix at 30 ℃ to make adhesive solution
did. In this composition, n _e/ N_cIs 12.

This adhesive was applied with a bar coater to a thickness of 25 μm.
Is coated on a polyimide film ("Kapton" 100H, manufactured by Toray Dupont Co., Ltd.) so as to have a dry thickness of about 30 μm, dried at 150 ° C. for 5 minutes, and laminated with a release paper with a silicone release agent. I got

Examples 2 to 6 and Comparative Examples 1 to 4 A coverlay film was obtained in the same manner as in Example 1 by using the raw materials and the adhesives prepared according to the composition ratios shown in Table 1.

Example 7 In the same manner as in Example 1, a polyimide film having a thickness of 25 μm (“Kapton” 1 manufactured by Toray Dupont Co., Ltd.) was applied using a bar coater.
00H), the adhesive solution of the present invention is applied to a dry thickness of about 18 μm, dried at 120 ° C. for 10 minutes, and then heated at 130 ° C. on a 35 μm thick electrolytic copper foil mat surface. And laminated. Then, the resultant was cured by heating at 150 ° C. for 4 hours to obtain a flexible printed circuit board.

Comparative Example 5 A flexible printed circuit board was prepared in the same manner as in Example 7 except that the adhesive having the composition of Comparative Example 4 was used, but the solder heat resistance was reduced. From the examples and comparative examples in Table 1, it can be seen that the coverlay film obtained by the present invention is excellent in storage stability, adhesiveness, and solder heat resistance.

[0036]

[Table 1]

In the table, Ep828 is “Epicoat” 828
(Yuika Shell Co., Ltd., Ep834 is "Epicoat 8"
34), Ep1001 is "Epicoat" 1001 (manufactured by Yuka Shell Co., Ltd.), and Ep5050 is "Epicoat" 50.
50 (manufactured by Yuka Shell Co., Ltd.), 3,3′-DDS is 3,
3′-Diaminodiphenyl sulfone is shown.

The content of aromatic dicarboxylic acid in the acid component of "Vylon" 300 is 65 mol%, and the content of neopentyl glycol in the diol component is 45 mol%. The content of the aromatic dicarboxylic acid in the acid component of "Erytel" UE3220 is 65 mol%, and the content of neopentyl glycol in the diol component is 45 mol%. The content of the aromatic dicarboxylic acid in the acid component of "Vylon" 200 is 100 mol%,
The neopentylglycol content in the toluene component was 53 mol%.

[0039]

According to the present invention, a novel adhesive composition for a flexible printed circuit board excellent in storage stability while maintaining good solder heat resistance and adhesiveness, and a coverlay film using the same. And a flexible printed circuit board.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H05K 3/38 H05K 3/38 EF term (reference) 4J040 CA071 CA072 EC001 ED022 ED042 GA07 KA03 KA16 KA42 LA02 LA05 LA06 LA08 LA09 MA02 MA10 MB03 NA20 5E314 AA32 AA33 AA37 CC15 FF06 FF19 GG10 GG11 5E343 AA16 AA18 BB24 BB67 CC03 CC07 DD53 DD54 GG16

Claims (7)

[Claims] 1. An adhesive composition for a flexible printed circuit board, comprising the following components (A) to (E) as essential components: (A) 100 parts by weight of epoxy resin, (B) 20 to 100 parts by weight of acrylonitrile butadiene rubber containing carboxyl group, (C) thermoplastic saturated copolymerized polyester 2-1
9 parts by weight, (D) 0.01-50 parts by weight of a curing agent,
(E) 2 to 50 parts by weight of inorganic particles. 2. The adhesive composition according to claim 1, wherein the copolymer component (C) has the following composition. (A) The content of aromatic dicarboxylic acid as the acid component is 40 to 80 mol%. (B) The content of neopentyl glycol as the diol component is 30 to 70 mol%. 3. The adhesive composition according to claim 1, wherein the glass transition point of (C) is 5 to 40 ° C. 4. The adhesive composition according to claim 1, wherein (A) contains 20 wt% or more of an epoxy resin having an epoxy equivalent of 300 g / eq or less. 5. A with an epoxy group the total number of _{(A) (n e) (} B)
The ratio of carboxyl groups _{(n c) (n e /} n c) is 7-2
The adhesive composition according to claim 1, wherein 0. 6. A coverlay film comprising a laminate of an insulating plastic film layer coated with the adhesive layer according to claim 1 and a release film layer. 7. A flexible printed circuit board obtained by bonding an insulating plastic film and a copper foil using the adhesive composition according to any one of claims 1 to 5.