JPH04154884A - Flexible adhesive - Google Patents

Abstract

PURPOSE:To obtain the title adhesive useful especially between flex-rigid wiring board layers, having excellent flexural characteristics and flame retardance, comprising a bisphenol type epoxy resin, a bromine group-containing epoxy resin and a liquid epoxy resin as essential components. CONSTITUTION:The objective adhesive comprising (A) preferably 40-80wt.% bisphenol type epoxy resin having >=1,300 molecular weight, (B) preferably 15-40wt.% bromine group-containing epoxy resin having >=1,300 molecular weight and (C) 5-30wt.% epoxy resin liquid in a normal state having <=1,300 molecular weight as essential components and having >=80 deg.C glass transition temperature after curing and further preferably 10-20wt.% bromine content.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a flexible epoxy adhesive composition.

[Conventional technology]

Conventional flexible adhesives have generally been NBR adhesives, acrylic elastomer adhesives, or compositions in which these are combined with epoxy resins.

For example, in the case of a system consisting of an epoxy resin and an elastomer, a composition consisting of an epoxy resin and a chloroprene polymer is disclosed in Japanese Patent Publication No. 42-22160,
The reaction product of an epoxy resin and a carboxyl group-containing NBR as disclosed in JP-A-5056 or JP-A-47-43100, etc., is mixed with other epoxy resin and NBR.
Compositions in combination with BR, compositions consisting of epoxy and acrylate as disclosed in Japanese Patent Publication No. 1-30320, and NBR containing epoxy and carboxyl groups as disclosed in Japanese Patent Publication No. 1-30320. The composition is used for flexible wiring boards. However, in either case, it is insufficient for advanced applications that require flexibility, flame retardance, heat deterioration resistance, and electrolytic corrosion resistance at the same time.

In addition, in the system mainly composed of epoxy,
Compositions in which a reaction product of epoxy and terminal carboxypolyester is combined with polyhydroxy ether (phenoxy resin) as disclosed in Japanese Patent Publication No. 7937, and high Compositions consisting of high-purity epoxy and flame retardants have been used, but both are insufficient in terms of bending properties and are also insufficient as interlayer adhesives for smoothing the surface of multilayer wiring boards. be.

[Problem to be solved by the invention]

Conventional flexible adhesives are insufficient in terms of bending properties, resin flow, etc., and have had the problem of not being able to simultaneously satisfy highly required properties as interlayer adhesives for flexible wiring boards and multilayer wiring boards.

The present invention has been made in view of the above circumstances, and its purpose is to provide a flame-retardant flexible adhesive composition with poor bending properties. The flexible adhesive of the present invention is useful as an interlayer adhesive for flexible wiring boards or multilayer wiring boards that have excellent bending properties, and is particularly useful as an interlayer adhesive for so-called flex-rigid wiring boards that combine flexible wiring boards and rigid wiring boards. It is.

[Means to solve the problem]

The present invention is directed to claim 1 to achieve the above objects.
As described in , (A) a bisphenol-type epoxy resin with a molecular weight of 13 () 0 or more, (I3) a bromine group-containing epoxy resin, and ([;) an epoxy resin with a molecular weight of 1300 or less and which is liquid in a normal state are essential. The object of the present invention is to provide a flexible adhesive composition which contains the compound as a component and has an 'I''g of 80°C or more after curing.

In addition, as described in claim 2, in order to exhibit coating film forming properties and appropriate flow properties during curing, (A):
The ratio of (B): (C) is 40 to 80:15 by weight
The range of 40:5 to 30 is preferable.

Flame retardancy can be imparted to the adhesive composition of the present invention by using the brominated epoxy (B), in which case the bromine content in the adhesive composition is 8.0% or more. This is desirable.

As the bisphenol type epoxy resin used as the component (A) in the present invention, for example, Epicoat 100 manufactured by Yuka Shell ■ is used.
4.1007.1009.101O101,-53,0
1-55, J Potoichi Y D-7017, manufactured by Monkyou Kasei ■
70I9.7 (120, Phenoi・-toYP-4
0, YP-50, Yl'-60, ESA- manufactured by Juman Kagaku ■
012, 014, 017, 019, 020, etc.

([3) The bromine group-containing epoxy resin with the component number is, for example, DER-511,5 manufactured by Dow Chemical Co., Ltd.
21,542,1 Co. BREN manufactured by Hon Kayaku ■, YDB-34 manufactured by Tobu Kasei ■ (1,400,700, Denacol EX-147, 221 manufactured by Nagase Kasei etc.) Liquid epoxy resin used for component (C) For example, Epicoat 828 manufactured by Yuka Shell ■, YD-127 manufactured by Tobu Kasei ■,
Examples include ELA-115, 127, and 128 manufactured by Susumu Chemical ■, and DER-330, 331, and DEN-438 manufactured by Dow Chemical ■.

Further: The crosslinking agent for these epoxy resins is not particularly limited, and commonly used epoxy curing agents can be used as appropriate. For example, aliphatic or aromatic amines, imidazoles, acid anhydrides, etc. can be used.

The glass transition temperature of the coating film after curing is ta determined by a viscoelasticity measuring device, such as a wide-range viscoelasticity measuring device manufactured by Rheology.
It can be achieved at a temperature of r1δ peak value.

The ratio of (A): (B): (C) is (A) by weight.
) 40-80: (B) 15-40: (C) 5-20.

The preferred range of component (A) varies depending on the epoxy equivalent and number of functional groups of components (B) and (C), but if it is less than 40%, the flexibility of the cured coating will be small, and if it is more than 80%, the Tg will be 80°. C or lower, and the bending properties and soldering heat resistance deteriorate. Furthermore, if the content of component (B) is below this range, the flame retardance will be insufficient, and if it is above this range, problems will arise in the adhesive properties and flexibility of the cured coating film. If component (C) is below this range, the flexibility of the dried coating film will be small, and if it is above this range, the coating film will become sticky when drying, causing problems in workability and resin flow during heat-pressing. This is because it becomes excessive.

In the adhesive composition of the present invention, the solvent E for dissolving these components to form an adhesive solution is preferably an organic solvent such as methylethylene, toluene, xylene, secosolve, or trimethylformamide. , one type or a mixture of these may be used.

(Function) When the adhesive composition according to claim 1 is applied, both the dried coating film and the heat-cured coating film have flexibility and the IQ5 glass transition temperature is 80°C. The bending properties will be good when it is applied to

In addition, if it is used as an interlayer adhesive in a multilayer wiring board consisting of the above flexible wiring board using polyimide film and a rigid wiring board using a glass ubiquitous board, there will be less smearing during hole drilling, and through-hole plating will be less likely. The connection reliability is high, and deterioration of the adhesive layer is suppressed in thermal cycle tests. The effect of the present invention is based on the synergistic effect of each component in the adhesive composition, and in particular (A) and (B).
(C) A flexible coating film that cannot be obtained with each individual component is due to the mutual interpenetration effect between the high molecular weight epoxy resin and the liquid epoxy resin at the molecular level.

Furthermore, the cured coating film in which the adhesive composition of the present invention has a glass transition temperature of 80° C. or higher can be used as a special flexible adhesive composition.
This seems to be because fatigue failure due to stress concentration at the adhesive interface during bending is less likely to occur when the bending properties of n are good, but the Tg is higher than that under continuous use conditions of electronic equipment.

(Examples) Hereinafter, the invention according to claims 1 and 2 will be described in detail based on examples. However, each invention is not limited only to this example.

Examples 1 to 7 Adhesive compositions were prepared at the ratios shown in Table 1, and applied to copper foil at a dry film thickness of approximately 25 mm.
Dry for 0 minutes. Next, using a hot roll at 150° C., a polyimide film with a thickness of 25 μI and a laminated sheet were further heated and cured at 150° C. for 2 hours to prepare a flexible base material for rice grains. was applied to a polyimide film so that the dry film had a thickness of 35 μm,
] After drying at 20'C for 10 minutes, dry at I50'C for 2 minutes.
It was dried for an additional minute to form a coverlay film.

A circuit was formed on the above-mentioned copper-clad base material by etching, and a flexible wiring board including a bending test pattern with an interval of 0.2 mm in the circuit conductor was produced. Next, after laminating the coverlay film, it was heated at 160° using a hot press.
c. Coverlay coating was performed by hot pressing for 60 minutes under the conditions of 30 kg/c-.

Table 1 shows the test results of the characteristics of these flexible wiring boards, coverlays, and copper-clad substrates.

Among the test items, the bending characteristics were tested at room temperature or in an atmosphere of 40'C under the test conditions of a bending radius of 4.51, a stroke of 30 mm, and a bending frequency of 1500 times/min, and the number of bends was defined as the time for a resistance increase of 2%. . Soldering heat resistance is 280°C
The time required for blistering and peeling to occur was measured. Flame retardancy (combustibility) was determined based on the UL-94 test method. In addition, as an electrolytic corrosion test method, a comb-shaped pattern for evaluating electrolytic corrosion in the circuit conductor and where i is both 0.2,
65°C/95% heating and humidification F'? 'DC 50 between conductors
Although V was applied and current was continuously applied, no decrease in insulation resistance or generation of dendrites was observed in both Examples and Comparative Examples after 300 hours.

In addition, the dry film thickness of the above adhesive on a release film was approximately 65 mm.
After drying at 120°C for 10 minutes and then at 150°C for 5 minutes, the adhesive surface was
Laminated using a heated roll at ℃, film thickness is approximately 125μ
An adhesive sheet of m was prepared. Next, a circuit is fabricated by etching from the glass epoxy base copper-clad laminate, the circuit surface is oxidized (blackened) to form an inner layer circuit board, and this and the flexible wiring board are interposed with the adhesive sheet. A rigid-flex multilayer wiring board having six layers of rigid parts and two layers of flex parts as shown in FIG. 1 was prepared by a conventional method. Table 1 summarizes the characteristics test results of the interlayer adhesive and multilayer wiring board.

Note that connection reliability was tested based on MIL-107.

〔Effect of the invention〕

As explained above, according to the invention according to claims 1 and 2, the dry adhesive coating film and the coating film after curing have 6J flexibility, and a flexible wiring board or A flexible adhesive composition that can provide a multilayer wiring board with excellent connection reliability is obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a flex-rigid wiring board made of a flexible wiring board and a rigid wiring board using an adhesive according to an embodiment of the present invention. 1 Interlayer adhesive 2 Conductor 3 Glass epoxy base rigid wiring board 4 Single-sided flexible wiring board 5 Double-sided flexible wiring board 6 Through hole

Claims (1)

[Claims] 1. (A) a bisphenol-type epoxy resin with a molecular weight of 1300 or more, (B) a bromine group-containing epoxy resin, and (C)
It has a molecular weight of 1300 or less, contains an epoxy resin that is normally liquid as an essential component, and has a glass transition temperature (
A flexible adhesive having a Tg) of 80°C or higher. 2. The ratio of (A):(B):(C) is 40 to 8 by weight
0:15 to 40:5 to 3, and the bromine content in the adhesive is in the range of 10 to 20%.