JP2001164226A - Adhesive for flexible printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject adhesive capable of satisfying all of the requirements including adhesiveness, soldering heat resistance, resistance to copper migration and preservation stability when used as a cover lay adhesive. SOLUTION: This adhesive for flexible printed wiring boards essentially comprises 100 pts.wt. of an epoxy resin, 20-110 pts.wt. of a carboxyl-modified synthetic rubber, 1-50 pt(s).wt. of a resol-modified phenolic resin, 2-20 pts.wt. of an aromatic diamine and 0.02-2.5 pt(s).wt. of a boron trifluoride complex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adhesive for flexible printed wiring boards. More specifically, the present invention relates to an adhesive for a flexible printed wiring board which is effectively used as an adhesive for a coverlay or the like.

[0002]

2. Description of the Related Art With the recent increase in density and diversification of electronic devices, flexible printed circuits, which are very advantageous in terms of weight reduction, size reduction and thickness reduction, are mounted on circuit boards mounted thereon. As they are increasingly used, their circuits are becoming denser and more complex. This densification,
The complication promotes a reduction in the line width and line interval of the circuit pattern and a reduction in the land.

[0003] Coverlays are used for the purpose of protecting metal conductors of flexible printed circuits from corrosion and contamination, ensuring insulation between circuits, improving bendability and flexibility, and the like. What has formed the adhesive layer on the heat-resistant film, such as this, is used. The coverlay having such an adhesive layer formed thereon is used in a state where the adhesive layer is in contact with the copper circuit of the flexible copper-clad board to form a flexible printed wiring board.

[0004] The coverlay used for such a purpose has not only excellent electrical properties such as excellent adhesiveness and copper migration resistance, but also a small amount of flowout to the land portion and an embedding property in the pattern. There is an increasing demand for storage stability that can control a constant flow rate over a long period of time without lowering.

[0005] In addition, since soldering is performed at high temperature and high speed in order to improve the productivity of the process of mounting components on a circuit,
Excellent solder heat resistance is also required. Particularly, in recent years, since components to be mounted have become expensive, a reduction in the defective rate at the time of soldering has been strongly demanded.

In general, as an adhesive for flexible printed wiring, an epoxy resin excellent in heat resistance and electrical insulation is often used, but it is not used alone, and polyester, polyvinyl butyral, polyamide, High molecular substances such as polyimide, acrylic rubber, and NBR are used in order to impart flexibility to the adhesive layer. However, polymer materials other than synthetic rubbers have low solder heat resistance due to the water absorption of the resin, and tend to cause problems such as blistering and peeling. Such a problem is likely to occur particularly in soldering at high temperature and high speed.

On the other hand, as synthetic rubber-based polymer substances,
Generally, carboxyl-modified synthetic rubbers having excellent adhesiveness are used, but since these lack storage stability, in order to maintain their performance over a long period of time, B-
Expensive equipment such as a low-temperature device is required for transportation and storage at the stage, or a step of returning to room temperature before work is required due to low-temperature storage.

Japanese Patent Application Laid-Open No. 2-187485 discloses a flexible printed wiring comprising a synthetic rubber, an epoxy resin, a phenol-modified xylene resin having at least two phenolic hydroxyl groups in a molecule, and a curing accelerator as essential components. Board adhesives (coverlay adhesives) are described. Although there is a specific description of the adhesiveness, tackiness and insulation resistance between wires, the solder heat resistance and B-
There is no specific description of the storage stability at the stage.

Further, it is described that by using a cured phenol-modified xylene resin, an adhesive for a flexible printed wiring board with low stickiness in the B-stage and good workability can be obtained. From the point of view, it is stated that a novolak type having a linear structure instead of a three-dimensional structure is preferable, but the novolak type does not improve the storage stability in the B-stage.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a flexible adhesive which, when used as an adhesive for coverlay, satisfies all of adhesiveness, solder heat resistance, copper migration resistance and storage stability. An object of the present invention is to provide an adhesive for a printed wiring board.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
100 parts by weight of epoxy resin, carboxyl-modified synthetic rubber 20
~ 110 parts by weight, 1-50 parts by weight of resole-modified phenolic resin, 2-20 parts by weight of aromatic diamine and 0.02-2.5 parts by weight of boron trifluoride complex by an adhesive for flexible printed wiring boards containing as essential components Achieved.

[0012]

DETAILED DESCRIPTION OF THE INVENTION As the epoxy resin, any resin having two or more epoxy groups in one molecule can be used. For example, bisphenol A type, low or high brominated bisphenol A type can be used. , Bisphenol F
Phenol novolak type, brominated phenol novolak type, cresol novolak type, etc. glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, etc. One type is used.

As a carboxyl-modified synthetic rubber, SBR
Or carboxylated SBR or NBR in which a small amount of (meth) acrylic acid (ester) monomer is copolymerized in NBR, ethylene-methyl acrylate- (meth) acrylic acid terpolymer rubber, maleic anhydride-added rubber At least one kind is used, and it is actually a commercial product, for example, Nipol 10
72, Japanese synthetic rubber products PNR-1H, N-632S, DuPont products
Vamac G or the like can be used as it is.

These carboxyl-modified synthetic rubbers are used in an amount of about 20 to 110 parts by weight, preferably about 25 to 100 parts by weight, per 100 parts by weight of the epoxy resin. If the use ratio is lower than this, sufficient adhesiveness cannot be imparted, while if used at a higher ratio, the copper migration resistance decreases.

As the resol-modified phenol resin, 1
Resins having a methylol group directly bonded to at least two aromatic rings in the molecule, for example, an alkylphenol resin prepared from a phenol alkylated at the p-position in the presence of a basic catalyst, toluene, xylene, mesitylene and the like. An aromatic hydrocarbon resin obtained by reacting with formaldehyde, a modified aromatic hydrocarbon resin obtained by modifying it with phenol or alkylphenol, and the like are used. In practice, commercial products such as Sumitomo Durres products PR-22193, PR-507
02, PR-50530, Mitsubishi Gas Chemical Products PR-1440M, PR-1440, P
R-1540, PR-GR-L, Hitachi Chemical's Hitachil 643KN, 218
0, 2400, 2410 and the like can be used as they are.

These resol-modified phenolic resins are:
It is used in an amount of about 1 to 50 parts by weight, preferably about 2 to 30 parts by weight, per 100 parts by weight of the epoxy resin. At lower usage rates, the storage stability will be reduced, whereas at higher usage rates, the adhesion will be reduced.

Examples of the aromatic diamine include 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, and 4,4'-diamino-3,3'-diethyl-5. At least one kind of such as 5,5'-diphenylmethane is used.
4'-Diaminodiphenyl sulfone is used. These aromatic diamines are used in an amount of about 2 to about 100 parts by weight of the epoxy resin.
It is used in a proportion of 20 parts by weight, preferably about 5 to 20 parts by weight. Outside of this range, both the solder heat resistance and the adhesiveness are reduced.

As the boron trifluoride complex, a complex with piperidine, monoethanolamine, triethanolamine or the like is used, and a complex with piperidine is preferably used from the viewpoint of storage stability. These boron trifluoride complexes are used in an amount of about 0.02 to 2.5 parts by weight, preferably about 0.1 to 1.5 parts by weight, per 100 parts by weight of epoxy.
At lower usage rates, copper migration resistance decreases, while at higher usage rates,
The storage stability is reduced.

The adhesive for a flexible printed wiring board containing the above components as essential components may contain, if necessary, imidazole, dicyandiamide, and quaternary ammonium salt as long as the storage stability and other properties are not impaired. Curing accelerators, such as plasticizers, antioxidants, fillers such as silica, alumina, and titanium oxide; flame retardants such as aluminum hydroxide and antimony trioxide; dispersants that are various surfactants; silane-based cups An adhesion promoter such as a ring agent, a viscosity modifier such as organic bentonite, a leveling agent, and the like are appropriately added and used.

The adhesive for flexible printed wiring boards is diluted with an organic solvent such as ketones such as acetone and methyl ethyl ketone, alcohols such as isopropanol, and aromatic hydrocarbons such as toluene and xylene. It is used after adjusting to 20 to 40% by weight. Application of such an adhesive solution to an adherend is performed by applying the adhesive solution onto a heat-resistant plastic film, for example, a polyimide film, and drying to form a film having an adhesive layer. Stored with film attached.

Before use, peel off the protective film,
Adhesion is performed by placing the adhesive layer surface side of the film having the adhesive layer on a flexible printed wiring board and pressing the film by a roll-type or batch-type press. This pressure bonding is performed under the conditions of about 100 to 190 ° C., about 0.5 to 5 MPa and about 1 to 50 minutes, and generally post-cured at about 120 to 200 ° C. to further improve the properties.

[0022]

The adhesive for a flexible printed wiring board according to the present invention, when used as an adhesive for a coverlay, has a small hygroscopic property and has excellent electrical properties and adhesiveness of a cured product.
Since a material that suppresses the curing reaction of the B-stage is used, it is excellent in adhesiveness, solder heat resistance, copper migration resistance, etc., and particularly excellent in storage stability in the B-stage. It is also used for copper-clad boards (circuits).

Furthermore, in transportation and storage, there is no need for low-temperature storage equipment, so that it is economically excellent, and furthermore, there is no need for a step of returning to room temperature. it can.

[0024]

Next, the present invention will be described with reference to examples.

Example 1 41 g of bisphenol A type epoxy resin (oiled shell epoxy product EP 1004AF) 38 g of brominated bisphenol A type epoxy resin (EP5051 product of the company) 21 g of brominated phenol novolak type epoxy resin (Nippon Kayaku product BREN-S ) carboxyl-modified NBR 39g (Japan Synthetic Rubber product PNR-IH) resol type modified phenolic resin 5 g (Hitachi Chemical products HN-643KN) 4,4'- diaminodiphenyl sulfone _{[4,4'-DDS] 6g BF 3} · piperidine complex (Hashimoto Chemical Co., Ltd.) 0.6 g Methyl ethyl ketone An adhesive solution with a solid content of about 35% by weight, prepared by uniformly dissolving 280 g or more of each component using a ball mill, is coated on a polyimide film to a dry film thickness of 35 μm. (Dupont product Kapton 100H, thickness 25μm), dried at room temperature for 10 minutes, and then at 120 ° C for 2 minutes to form a film having an adhesive layer. A protective film was adhered.

The film having the adhesive layer and the flexible copper-clad laminate on which the test pattern is formed by the subtract method are heated and pressed at 165 ° C., 1 MPa for 5 minutes, and then heated at 140 ° C. After 2 hours of post cure,
A flexible laminated film was made.

With respect to the obtained laminated film, the following items were measured to evaluate the coverlay adhesive for flexible printed wiring. Peel strength: 90 mm for a 10 mm wide measurement sample in accordance with JIS C-5016
Measure the strength when the copper foil is peeled off at a speed of 50 mm / min in the direction of °. Solder heat resistance: Laminated film (25 × 25 mm) at 40 ° C, 90% RH, 2
After leaving it for 4 hours, immerse it in a solder bath for 10 seconds and measure the temperature at which blistering and peeling do not occur. Copper migration: 0.1 mm between wires under a constant temperature and humidity environment of 85 ° C and 85% RH. , 0.1mm line width comb test pattern,
Visual observation of the occurrence of dendrites when a voltage of 50 V is applied for 500 hours. Storage stability: A film with an adhesive layer with a protective film (B-stage coverlay) at 40 ° C and 90% RH. And measure the number of days before embedding in a circuit with a line gap of 0.1 mm, a line width of 1.0 mm and a line thickness of 35 μm becomes impossible

Examples 2 to 3 and Comparative Examples 1 to 9 In Example 1, the amounts of the components (excluding the bisphenol A type epoxy resin, the brominated bisphenol A type epoxy resin and the brominated phenol novolak type epoxy resin (100 g in total)) The unit: g) was changed as shown in Table 1 below.

Vamac G is an ethylene-unsaturated carboxylic acid copolymer manufactured by DuPont, and GHP-160 is a novolak-type modified xylene resin manufactured by Mitsubishi Gas Chemical. Table 1 Example PNR-1H Vamac G HN-643KN 4,4'-DDS BF ₃ Complex GHP-160 Example 2 21-11 14 0.4-〃 3 34 22 37 3 0.5-Comparative Example 1 96 24 7 7 1.2-〃 2 7 8 7 6 0.4-〃 3 21 30 0.5 5 0.6-〃 4 27 20 65 6 0.5-〃 5-43 8 1 0.7-〃 6 24 15 10 22 0.1-〃 7 33 5-8 0.3 11 〃 8 7 30 5 6 0.01-〃 9 39-10 5 3-

Table 2 below shows the measurement results in the above Examples and Comparative Examples. Table 2 peel strength Solder heat resistance copper migration storage stability Example (N / cm) (° C.) Deployment of (day) Example 1 10.20 270 None 28 〃 2 9.61 270 〃 28 〃 3 10.88 270 〃 26 Comparative Example 1 12.55 260 With 26 〃 2 5.49 260 Without 28 〃 3 9.02 260 〃 10 〃 4 5.00 270 〃 30 〃 5 5.00 220 〃 28 〃 6 5.20 230 〃 28 〃 7 7.94 260 〃 10 〃 8 9.32 260 With 28 〃 9 8.14 270 Without 12

From the above results, the following can be said. (1) The adhesive for a flexible printed wiring board according to the present invention has good adhesiveness, solder heat resistance and storage stability, and shows no copper migration. (2) In Comparative Example 1 in which the amount of the carboxyl-modified rubber was too large, copper migration occurred, while in Comparative Example 2 in which the amount was too small, the peel strength (adhesiveness) was reduced. (3) In Comparative Example 3 in which the amount of the resol-modified phenolic resin was too small, the storage stability was lowered, while in Comparative Example 4 in which the amount was too large, the peel strength (adhesion) was lowered. (4) In Comparative Example 5 and Comparative Example 6 in which the amount of aromatic diamine is too small, both the solder heat resistance and the peel strength (adhesion) are reduced. (5) In Comparative Example 8 in which the amount of the boron trifluoride complex was too small, copper migration occurred, and in Comparative Example 9 in which the amount was too large, the storage stability was reduced. (6) In Comparative Example 7, in which a novolak-type modified xylene resin was used instead of the resol-type modified phenol resin, storage stability was reduced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09J 161: 06) C09J 161: 06) F-term (Reference) 4J040 CA071 CA081 DA061 DA071 DB051 DF011 DF041 DF081 EB052 EB072 EC061 EC071 EC091 EC121 EC151 EC261 GA07 HB03 HB09 HB19 HC08 HD16 HD39 JA02 JB02 KA16 KA23 LA05 LA06 LA08 NA20 5E343 AA33 CC03 GG01 GG16

Claims (3)

[Claims] 1. 100 parts by weight of an epoxy resin, 20 to 110 parts by weight of a carboxyl-modified synthetic rubber, 1 to 50 parts by weight of a resol-modified phenolic resin, 2 to 20 parts by weight of an aromatic diamine, and 0.02 to 2.5 parts by weight of a boron trifluoride complex. An adhesive for a flexible printed wiring board, comprising as an essential component. 2. The method according to claim 1, which is prepared as an organic solvent solution.
The adhesive for a flexible printed wiring board according to the above. 3. The adhesive for a flexible printed wiring board according to claim 1, which is used as an adhesive for a coverlay.