JPH06330014A - Adhesive composition for flexible printing wiring board - Google Patents

Abstract

PURPOSE:To obtain an adhesive composition for flexible printing wiring board having excellent flexural resistance (flexibility), copper foil peel strength (adhesiveness to copper foil), electrically insulating properties (electrolytic corrosion resistance) and improved workability. CONSTITUTION:An adhesive composition for flexible printing wiring board comprises (A) a saturated copolyester resin, (B) a carboxy-modified (meth) acrylonitrile-butadiene rubber, (C) an epoxy resin and (D) an epoxy resin curing agent in the amounts of the components A and B based on the 100 pts.wt. of the component C of 20 pts.wt <= the amount of the component A<=70 pts.wt., 20 pts.wt. <= the amount of the component B<=50 pts.wt. and the amount of the component A<=130-2 X the amount of the component B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive composition for a flexible printed wiring board, which is excellent in folding resistance (flexibility), electrical insulation, copper foil peeling strength and workability.

[0002]

2. Description of the Related Art Conventionally, as a flexible adhesive sheet to be arranged between circuit boards when manufacturing a multilayer flexible printed wiring board, for example, an epoxy resin and acrylonitrile butadiene rubber (NBR) for imparting flexibility are used.
Alternatively, carboxy-modified NBR (C-NBR) as a main component, or acrylonitrile-acrylic acid n-
Those containing a butyl copolymer as a main component are commercially available.

However, this flexible adhesive sheet has an elastomer component in order to improve folding endurance.
Excessive (NBR) content causes coarse system cross-linking (long inter-crosslinking distance) and high nitrile group content results in long-term wet heat electrical insulation (electrolytic corrosion resistance)
There was a problem that was inferior. Also, epoxy resin / NB
The R or C-NBR system has surface tack, which makes workability difficult when used as an adhesive sheet.

[0004]

The present invention is excellent in folding resistance (flexibility), copper foil peeling strength (adhesion with copper foil), electrical insulation (electrolytic corrosion resistance), and workability. An object is to provide a good adhesive composition for flexible printed wiring boards.

[0005]

The adhesive composition for a flexible printed wiring board of the present invention comprises a saturated copolyester resin (A), a carboxy-modified (meth) acrylonitrile butadiene rubber (B), an epoxy resin (C), and The epoxy resin curing agent (D) is used, and the blending amount of each of (A) and (B) with respect to 100 parts by weight of (C) is 20.
It is characterized by being in the range of parts by weight ≦ (A) ≦ 70 parts by weight, 20 parts by weight ≦ (B) ≦ 50 parts by weight, and (A) ≦ 130−2 × (B). Here, the carboxy-modified (meth) acrylonitrile-butadiene rubber means carboxy-modified acrylonitrile-butadiene rubber (C-NBR) or carboxy-modified methacrylonitrile-butadiene rubber (C-MN).
BR).

As described above, in the present invention, since the epoxy resin is blended with the specific amount of the saturated copolymerized polyester resin and the carboxy-modified (meth) acrylonitrile-butadiene rubber, the above object can be achieved.
Hereinafter, the configuration of the present invention will be described in detail. Saturated copolyester resin (A) Ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol and other diol components and terephthalic acid, isophthalic acid and other aromatic dicarboxylic acids, adipic acid, sebacic acid and other aliphatic compounds It is obtained by polymerizing with a dicarboxylic acid. As the polyester resin preferably used in the present invention, those having an acid component of terephthalic acid or isophthalic acid, a part of the polyol component of which is an ethylene oxide adduct of bisphenol A and / or a propylene oxide adduct of bisphenol A, and the like can be used. It is illustrated.

The saturated copolyester resin is not particularly limited as long as it has a carboxyl group and a hydroxyl group at the terminal of the molecular chain. Specifically, Elitel UE-3500 and Elitel UE-3 manufactured by Unitika Ltd.
220, Toyron Byron 300, etc. Use of this resin not only imparts toughness to the resulting adhesive composition, but also has an effect on workability. The glass transition point (Tg) of this resin is preferably in the range of 5 to 40 ° C.
(40 ℃ ≧ Tg ≧ 5 ℃). If the temperature is lower than 5 ° C, the adhesive composition in the form of a sheet will have tackiness on the surface of the adhesive sheet, resulting in poor workability. On the other hand, if the temperature is higher than 40 ° C, the adhesive sheet will be hard, and the adhesive sheet will be flexible after curing. To lower the sex.

Carboxy-modified (meth) acrylonitrile-tolyl-butadiene rubber (B) Carboxy-modified (meth) acrylonitrile-butadiene rubber is a three-dimensional copolymer of methyl acrylate or methyl methacrylate with acrylonitrile and butadiene. It refers to the one in the side chain.

This makes it possible to enhance the crosslinkability with the epoxy resin as compared with NBR having no functional group. In addition, flexibility is imparted to the resulting adhesive composition, which is effective in folding endurance. Desirably, a Mooney viscosity of 20 to 80 is effective for imparting flexibility. Carboxyl content is 1.3 to 4.
0 mol% is preferable. If it is less than 1.3 mol%, the electrolytic corrosion resistance is deteriorated, and if it exceeds 4.0 mol%, the folding resistance is deteriorated. Specific examples thereof include Nippon Pol 1072J manufactured by Nippon Zeon Co., Ltd. and PNR-1H manufactured by Nippon Synthetic Rubber Co., Ltd. The nitrile group content is not particularly limited, but is preferably 25 to 40% by weight.

Epoxy resin (C) Among glycidyl ether type epoxy resins, epoxy resins having two or more epoxy groups in one molecule such as bisphenol A epichlorohydrin type are preferable.
Representative examples include Epicron 1050 (epoxy equivalent 500 g / eq) manufactured by Dainippon Ink and Chemicals, Inc.
There is no problem even if other commercially available products or CTBN-modified epoxy resin is used. The preferred range of epoxy equivalent is 4
It is from 00 to 2000 (g / eq). If it is less than 400 (g / eq), the cured film becomes hard and poor in flexibility, and if it exceeds 2000 (g / eq), the distance between the cross-links of the epoxy groups becomes long, and the electrical insulation becomes poor.

Further, hydrogen bonds between the hydroxyl groups in the resin and the curing agent cause poor dispersion of the curing agent. Further, for electronic materials, those having a chlorine ion content of 10 ppm or less and a hydrolyzable chlorine content of 0.1% or less are preferable. Epoxy resin curing agent (D) As the epoxy resin curing agent, a latent agent such as a guanidine compound represented by dicyanamide or an imidazole compound is preferable. For example, 2-phenylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-benzyl-5.
A one-liquid type such as -hydroxymethylimidazole is preferable. In addition, Lewis acid salts represented by boron trifluoride ethylamine complex, organic acid hydrazides such as adipic acid hydrazide, diaminomaleonitrile and its derivatives, melamine and its derivatives, thermally decomposable amine imide, and further curing A substance obtained by adsorbing the agent on a porous body such as a molecular sieve, or a body encapsulating a curing agent in microcapsules may be used. These curing agents can be added in the range of 0.5 to 60 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. .

Further, if a filler is used, inorganic ones such as calcined clay, calcium carbonate, silica, mica and calcium hydroxide are preferable. In addition, inorganic flame retardants such as tin oxide, molybdenum oxide, zirconium oxide and magnesium hydroxide may be added. In the present invention, the respective physical properties such as flexibility, copper foil peeling strength, electrical insulation, workability, etc. can be obtained by blending the components (A) to (D) within a predetermined composition range. Can be achieved. That is, the saturated copolymerized polyester resin (A) is blended in an amount of 20 to 70 parts by weight with respect to 100 parts by weight of the epoxy resin (C) (20 parts by weight ≤ (A) ≤ 70 parts by weight).
. If it is less than 20 parts by weight, non-tackiness cannot be imparted to the surface of the adhesive sheet (tack occurs). If it exceeds 70 parts by weight, the peeling strength from the copper foil deteriorates. Further, the compounding amount of the carboxy-modified (meth) acrylonitrile butadiene rubber of (B) with respect to 100 parts by weight of the epoxy resin of (C) is 20 parts by weight to 50 parts by weight (20 parts by weight ≤ (B) ≤ 50 parts by weight). )
. If it is less than 20 parts by weight, the folding endurance is not so effective, and if it exceeds 50 parts by weight, the electrical insulating property is lowered because the adhesive composition as a whole has low crosslinkability.

Furthermore, the relationship between (A) and (B) is (A)
≦ 130−2 × (B). Outside this range, epoxy resin and saturated copolyester resin, and C-NBR
The compatibility between (or C-MNBR) is poor, curing failure occurs, and a good adhesive sheet cannot be obtained.

[0014]

【Example】

Examples 1-9, Comparative Examples 1-8 Bisphenol A type epoxy resin (Epiclon 1050, Dainippon Ink and Chemicals, Inc., epoxy equivalent 500) 50 parts by weight and CTBN-modified epoxy resin (ESAB-500, Sumitomo Chemical Co., Ltd.) Co., Ltd., epoxy equivalent 550) 50 parts by weight, carboxy group-containing NBR 30 parts by weight dissolved with methyl ethyl ketone (MEK), saturated copolymerized polyester 30 parts by weight, curing agent (2PZ, Shikoku Chemicals ( stock)
4 parts by weight) was dissolved in MEK while stirring at room temperature, and then uniformly dispersed by a sand mill to obtain a varnish. This varnish is coated on a release-treated 40 μm thick polyethylene terephthalate film,
It was dried at 30 ° C. for 30 minutes to obtain a resin film having a thickness of about 50 μm (Example 1). Further, a resin film was obtained in the same manner with the content of formulation (parts by weight) shown in Table 1 and Table 2.
(Examples 2-9, Comparative Examples 1-8).

Copper foil coating using these resin films
Peel strength, electrical insulation (electrolytic corrosion resistance), flexibility, and workability
The workability was measured by the following method. The results are shown in Table 1 and Table
2 shows.Copper foil peeling strength (kgf / cm) : With one side oxidation copper foil 1.
The above resin film is ranate (article) on 6mm FR-4 substrate.
(Roll temperature: 120 ° C), and then laminating 18 μm copper foil
And cured with a press (conditions: press pressure;
20 kg / cm², Press temperature; 170 ℃, press time: 1:00
while) . The evaluation was performed according to JIS-C6481. That is,
Cut the copper foil with a width of 10 mm and peel it off in the 90 ° direction to find its strength
Was measured.Electrical insulation : Comb-shaped circuit (line / space = 0.2 mm / 0.
Vacuum laminating resin film on a laminated board designed for 2 mm)
Nate (condition; laminating temperature 120 ° C, vacuum degree 40 toe)
(Speed, 2 m / min) and cured at 170 ° C for 1 hour.
Let After that, 500 hours environmental test (85 ℃ / 85% RH, printing
After applying a voltage of 50 V (DC) to the electrode, apply a voltage of 500 V for 60 seconds.
The line insulation resistance value after the application was measured. As a result, 1
× 10¹¹It was judged as “OK” when the value was maintained above [Ω]. "↓"
The mark indicates a circuit short. The subscript is time.Flexibility : Performed with a MIT type folding endurance measuring instrument. condition is
Curvature radius R = 2.0mm, gap T = 0.35mm, rotation angle 1
It is 35 ° and the load is 500gf. Pass level is 1000 times or more
It Workability : With or without film tack
The performance was judged. The absence of tack was rated as "good".
“X” indicates tack (defective).

[0016]

[Table 1] Note) * 1 Saturated copolyester resin, Tg 5 ° C, Elitel UE-3220, manufactured by Unitika Ltd. * 2 Saturated copolyester resin, Tg 35 ° C, Elitel UE-3500, manufactured by Unitika Ltd.

* 3 Carboxyl-modified NBR, COOH 1.
3 mol%, manufactured by Nippon Zeon Co., Ltd. * 4 Carboxy modified NBR, COOH 4 mol%, JS
Made by R. * 5 Bisphenol A epoxy resin, epoxy equivalent of about 2000 g / eq, Epicron 7050, Dainippon Ink and Chemicals
Made by Co., Ltd. * 6 Bisphenol A type epoxy resin, epoxy equivalent of about 500 g / eq, Epicron 1050, Dainippon Ink and Chemicals
Made by Co., Ltd.

* 7 Epoxy equivalent 550g / eq, ESAB-500,
Made by Sumitomo Chemical Co., Ltd. * 8 Imidazole compound (2-phenylimidazole: 2PZ), manufactured by Shikoku Chemicals Co., Ltd. * 9 Dicyandiamide (DICY-15), mp207 ℃, manufactured by Yuka Shell Epoxy Co., Ltd. * 10 Diaminodiphenylmethane (DDM), mp89 ° C, active hydrogen equivalent 49.6, manufactured by Sumitomo Chemical Co., Ltd.

[0019]

[Table 2] Note) * 11 Saturated copolyester resin, Tg -20 ℃,
Elitel UE-3400, manufactured by Unitika Ltd. * 12 Saturated copolyester resin, Tg 67 ℃, Elitel UE-3200, manufactured by Unitika Ltd. From Table 1 and Table 2, the adhesive composition of the present invention shows copper foil peeling strength, electrical insulation (electrolytic corrosion resistance), flexibility (folding resistance).
, And workability are excellent (Examples 1 to 9). On the other hand, in Comparative Example 1, C-NBR
Is less than the specified range, the flexibility is low, and the Tg of the saturated copolyester resin is low, resulting in tack. Comparative Example 2 lacks C-NBR and therefore has poor flexibility as in Comparative Example 1. In Comparative Examples 3, 5, and 6, since only C-NBR was used, there was no tack suppressing effect by the saturated copolyester resin. In Comparative Example 4, NBR is used and the nitrile content is high, so that the electrical insulation is poor. In Comparative Example 7, since the Tg of the polyester resin is high, the sheet is hard, the flexibility is low, and the peeling strength of the copper foil is low. In Comparative Example 8, since the saturated copolyester resin was mixed in a larger amount than the specified range, the varnish was separated, and there was no film forming property, and the sheet could not be formed.

FIG. 1 shows the relationship between the blended amount of the saturated copolyester resin and the blended amount of the carboxy-modified NBR in these Examples and Comparative Examples. In Figure 1,
“Actual” represents the example and “ratio” represents the comparative example. Also, 4
The two characteristics (copper foil peeling strength, electrical insulation, flexibility, workability) were comprehensively evaluated, and "Good" was given as "Good" and "▲" as bad. As can be seen from FIG. 1, the scope of the present invention is a portion surrounded by a dotted line (20 parts by weight ≤ (B) ≤ 50 parts by weight, 20 parts by weight ≤ (A) ≤ 70 parts by weight, (A) ≤ 130 parts by weight. -2 x (B).

[0021]

As described above, the adhesive composition for a flexible printed wiring board of the present invention comprises a saturated copolymer polyester resin (A), a carboxy-modified (meth) acrylonitrile butadiene rubber (B) and an epoxy resin (C). , And a specific amount of epoxy resin curing agent (D), it has a good balance of peeling strength from copper foil, folding endurance, and workability. Moreover, conventional adhesives for flexible printed wiring boards cannot be used. Regarding the electrical insulation and migration resistance, which were not available, the physical properties can be maintained for a long period of time. Therefore, it is most suitable as an adhesive for flexible printed wiring boards.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the blended amount of a saturated copolyester resin and the blended amount of carboxy-modified NBR.

Claims (1)

[Claims] 1. A saturated copolymer polyester resin (A) and a carboxy-modified (meth) acrylonitrile butadiene rubber
(B), epoxy resin (C), and epoxy resin curing agent (D). (A) per 100 parts by weight of (C)
And (B) are mixed in an amount of 20 parts by weight ≦ (A)
≤70 parts by weight, 20 parts by weight ≤ (B) ≤50 parts by weight, (A) ≤13
An adhesive composition for a flexible printed wiring board in the range of 0-2 × (B).