JPH0793497B2 - 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 flexible printed circuit boards.

[0002]

2. Description of the Related Art In recent years, the demand for printed circuit boards has increased along with the trend toward lighter, thinner, smaller, and more sophisticated electric appliances, and the range of use of flexible boards has expanded. In particular, with the progress of high-density mounting and the increasing demand for multi-layer flexible printed circuit boards, the bonding sheets used for laminating each layer are expected to have improved adhesiveness, heat resistance, processability, and other performance. It is rare.

[0003]

The conventional products have poor adhesion due to insufficient adhesiveness, and have poor heat resistance, resulting in blistering or the like during soldering, and poor workability, requiring high-temperature long-time processing. There was a difficulty such as becoming. It is believed that most of these problems are caused by adhesives. So far, adhesives for bonding sheets have been NBR / phenol resin, epoxy / phenol / NBR, NBR / epoxy resin, epoxy / polyester, epoxy. / Acrylic resin, acrylic resin, etc. have been used, but these adhesives have advantages and disadvantages. For example, NBR type has large thermal deterioration, epoxy type has low adhesiveness, and acrylic type has high temperature and long time. In the present situation, it is not possible to find a sufficiently satisfactory one in that it requires heating and pressure bonding and is inferior in workability.
The present invention is intended to solve the above-mentioned various drawbacks and to provide a bonding sheet excellent in adhesiveness, heat resistance and workability.

[0004]

Means for Solving the Problems The present inventors have completed the present invention as a result of earnestly researching the adhesive composition in order to achieve the above object. That is, the present invention is
A bonding sheet comprising a heat-resistant adhesive layer in a semi-cured state and a release film laminated together, wherein the adhesive has the following composition. I)
Epoxy resin 100 parts by weight, b) Carboxyl group-containing nitrile rubber 40 to 150 parts by weight, c) Curing agent 1 to 50 parts by weight, d) One or more curing accelerators selected from zinc, tin and nickel fluorides. 0.1-5 parts by weight. Is the gist.

The present invention will be described in detail below.
First, the adhesive composition for a bonding sheet of the present invention will be described. A) Any epoxy resin may be used as long as it has two or more epoxy groups in one molecule. For example, bisphenol type epoxy resin, novolac resin and other glycidyl ether type, cycloaliphatic epoxy resin, aromatic type epoxy resin. The halogenated epoxy resin and the like can be used alone or in combination of two or more. Further, among the epoxy resins exemplified above, by using a halogenated epoxy resin, preferably 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, and examples thereof include bisphenol type brominated epoxy resin and novolac type brominated epoxy resin. .
Specifically, Epicoat manufactured by Yuka Shell Epoxy Co., Ltd.
5045 (Br%: 19% by weight (hereinafter% represents% by weight)), 50
46 (Br%: 21%), 5048 (Br%: 25%), 5049 (Br%:
26%), 5050 (Br%: 49%), BREN manufactured by Nippon Kayaku Co., Ltd.
-S (Br%: 35%) etc. These brominated epoxy resins having different Br contents can be used alone or in combination of two or more. Brominated epoxy resins having a Br content of 21% to 51% are preferable from the viewpoint of flame retardancy.

Examples of the carboxyl group-containing nitrile rubber of the component (b) include those obtained by carboxylating an acrylonitrile-butadiene copolymer rubber in which acrylonitrile and butadiene are copolymerized. Specifically, Goodrich Hiker CTBN, Hiker CTBNX, Hiker 1072, Nippon Zeon Co., Ltd. Nipol 1072J, Nipol 1072, Nipol DN612, Nipol DN631, Nipol
There is DN601 etc. These carboxyl group-containing nitrile rubbers may 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 curing agent for ordinary epoxy resins, and 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 compounds. These may be used alone or in combination of two or more. These curing agents are usually
The component (a) can be added in a wide range of 1 to 50 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.

Examples of the curing accelerator (d) include zinc borofluoride, tin borofluoride, and nickel borofluoride, which may be used alone or in combination of two or more. The addition amount of these is appropriately 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight.

If desired, fine particle inorganic powder can be added to the adhesive. As fine particle 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, etc. Silicates, silicic acids, and boron nitrides. These may be used alone or in combination of two or more.

Since flexible printed circuits have become finer and patterns of several tens of μm have been put into practical use recently, the particles of the inorganic powder have a particle size of 10 μm or less, preferably 5 μm.
The following are appropriate: In order to improve the fixability and water resistance of these finely divided inorganic powders to the resin matrix, hydrophobizing treatment is desirable. Chlorosilane such as dimethyldichlorosilane, silicone oil, silane cup such as alkyltriethoxysilane, and methyltriethoxysilane. A treating agent such as a ring agent is used.

The present invention is based on the above a), b), c) and d).
The intended effect is achieved by the adhesive having the composition of each of the above components, and the following inconvenience occurs when the composition is out of the above range. That is, component a) epoxy resin 1
When the amount of the nitrile rubber containing the carboxyl group of component (b) is less than 40 parts by weight with respect to 00 parts by weight, the peel strength is reduced,
If it exceeds 150 parts by weight, the heat resistance of the solder will deteriorate. If the amount of the (c) component curing agent is less than 1 part by weight, the curing will be insufficient and the solder heat resistance will decrease, and if it exceeds 50 parts by weight, the life of the adhesive will be short, and in addition, the solder heat resistance and peel strength will decrease. descend. If the amount of the curing accelerator as the component (d) is less than 0.1 part by weight, the solder heat resistance will be lowered, the flow of the adhesive will be too large, and processing at a high temperature for a long time is required. The life is shortened and the peel strength is reduced.

The release film used in the present invention includes:
PE film, PP film, TPX film, plastic film such as PET film with silicone release agent, and polyolefin film such as PE and PP, vinylidene chloride film, TPX film, etc. coated on one or both sides of the base paper. Examples of the release paper include paper.

Next, a method for manufacturing the bonding sheet of the present invention will be described. The release film is coated with the adhesive so as to have a thickness of 20 to 60 μm and dried to remove the solvent, so that the adhesive is semi-cured. In this case, if necessary, it can be heated to about 100 ° C for a short time. Furthermore, using a roll laminator for the release film
30-100 ℃, linear pressure 2-10kg / cm, line speed 2m / m
It is manufactured by laminating under pressure with in and winding up in a roll.

[0015]

EXAMPLES Next, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these. The parts and percentages in the specific examples are all based on the weight of the solid content. (Examples 1 to 3 and Comparative Examples 1 to 10 ) Using the adhesive composition shown in Table 1, a 30% MEK solution was prepared and uniformly dispersed by a ball mill to obtain an adhesive solution. Next, 25 μm PET with silicone release treatment on one side so that the coating thickness of these adhesive solutions after drying is 30 μm.
It was applied to a film and heated and dried at 80 ° C. for 2 minutes and 120 ° C. for 5 minutes to remove the solvent, and the adhesive was semi-cured. Then, release paper coated with TPX film on both sides was heated by a roll laminator at a temperature of 50 ° C, linear pressure of 5 kg / cm, speed of 2 m / min.
Was pressure-bonded and laminated to produce a bonding sheet. next,
In order to measure the physical properties of this bonding sheet, release
25μ adhesive sheet without PET film and release paper
Set on m polyimide film, electrolytic copper foil 35μm
It was laminated on the glossy surface of No. 1 and pressed at 160 ° C. under 50 kg / cm ² for 15 minutes to prepare a laminated film. The characteristics of the flexible laminated film thus obtained are also shown in Table 1.

The methods for measuring the physical properties of the flexible laminated film shown in Table 1 are as follows. (Method for measuring physical properties of flexible laminated film) 1) Peel strength: Performed according to JIS C6481. A copper foil is peeled off at a speed of 50 mm / min in the 90 ° direction of a 10 mm wide sample. 2) Solder heat resistance: After the sample is floated in a solder bath for 30 seconds, the temperature at which blistering does not occur is measured. Moisture absorbing solder absorbs moisture under the condition of 40 ℃ × 90% RH × 1hr, and then floats the sample in the solder bath for 30 seconds.
Check the appearance and blisters.

[0017]

[Table 1]

[0018]

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

Claims (1)

[Claims] 1. A bonding sheet obtained by laminating a semi-cured heat-resistant adhesive layer and a release film, wherein the adhesive has the following composition. A) Epoxy resin 100 parts by weight, b) Carboxyl group-containing nitrile rubber 40 to 150 parts by weight, c) Curing agent 1 to 50 parts by weight, d) One or more types of curing selected from zinc, tin and nickel fluorides. Accelerator 0.1-5 parts by weight.