Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-08-13
2001-02-13
Woodward, Ana (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S421000, C525S432000, C525S436000
Reexamination Certificate
active
06187874
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to adhesives for electronic parts and adhesive tapes using them, which are suitable for use in production of tape carrier packages (TCP), tape BGA (ball grid arrays), CSP (chip size packages), etc. which are suitable for the inclusion of many pins, miniaturization and high density assembly in a fabrication process of semiconductor devices, and particularly are most suitable for use in bonding of semiconductor chips, radiation plates and circuit boards making good used of TAB (tape automated bonding) techniques, which are all used in these packages.
2. Description of the Related Art
In the conventional adhesive tapes for electronic parts, an adhesive layer composed of an aliphatic polyamide resin and an epoxy resin, a polyamide resin, an epoxy resin and a phenol resin, or the like is formed on at least one side of a heat-resistant film as represented by TAB tapes. As the polyamide resin in the adhesive layer, is used nylon, dimeric acid polyamide or the like.
Film carrier tapes represented by the TAB system have been recently required to make fine by narrowing their conductor width and conductor spacing. Therefore, such a conventional adhesive as described above has become insufficient in insulating property and heat resistance. In wire bonding, copper forming a circuit requires to be plated with nickel or gold. Electro-plating has heretofore been used. However, electroless plating is suitable for thin film plating attendant upon the fining. By the way, the above-described adhesives heretofore used in TAB tapes have encountered problems such as lowering of electrical reliability due to lowering of their adhesive strength by a high temperature upon electroless plating and wire bonding failure by adsorption of impurity components such as sulfur in a plating solution.
In recent years, circuit board materials of the additive type, in which a copper layer is formed directly on a polyimide film or the like, have begun to be marketed. Since perforating in the fabrication of a semiconductor device comes to depend on laser and etching, however, they have a demerit that the productivity of semiconductor devices is low. The additive type circuit board material itself also involves a problem of poor productivity, since plating forms its conductor layer.
With such circumstances in view, various kinds of polyimide adhesives have been developed to date. For example, Japanese Patent Application Laid-Open No. 25453/1993 discloses a heat-resistant resin adhesive comprising soluble polyimide siloxanes consisting of an aromatic tetracarboxylic acid component composed mainly of a biphenyltetracarboxylic acid, a diaminopolysiloxane component and an aromatic diamine component, an epoxy compound and an epoxy hardener, and Japanese Patent Application Laid-Open No. 25452/1993 discloses a heat-resistant adhesive in which a bismaleimide resin is additionally added to the above described adhesive. Furthermore, Japanese Patent Application Laid-Open No. 200216/1994 discloses an adhesive film comprising a polyimide resin having silicon units, and an epoxy resin, and describes the polyimide resin to the effect that at least 1 mol % of a divalent aromatic group having a functional group is preferably contained as a component thereof.
SUMMARY OF THE INVENTION
However, the polyimide resins containing silicon units disclosed in these publications do not satisfy both of heat resistance and formability of the layer, and of low-temperature adhesive property. More specifically, when they have high heat resistance, adhesion must be conducted at a temperature higher than the conventional adhesives used in TAB tapes. In such a case, problems such as deterioration of dimensional stability to heat history, curing of a tape for TAB, strength reduction of a copper foil and reduction in the productivity of TAB tapes have arisen. On the other hand, the preparation for use of a polyimide resin which permits adhesion at a low temperature has involved such problems that the heat resistance is insufficient, its properties upon melting become unsuitable for the formation of an adhesive layer, it exhibits uneven adhesive property to become unsuitable for fining, and reduction in the productivity of TAB tapes is caused.
It is therefore an object of the present invention to provide an adhesive for electronic parts, which satisfies both of heat resistance and formability of the adhesive layer, and of low-temperature adhesive property, and an adhesive tape for electronic parts making use of such an adhesive.
In view of the above-described problems, the present inventors have carried out repeated investigations as to adhesives which are improved in low-temperature adhesive property and can solve the above-described problems such as dimensional stability while possessing properties suitable for the fining, such as good heat resistance and stable adhesive property. As a result, it has been found that when at least two specific polyimide resins different in glass transition temperature (Tg) from each other and an epoxy resin are used, an adhesive which can achieve the above object can be provided, thus leading to completion of the present invention.
According to the present invention, there is thus provided an adhesive for electronic parts, comprising, as a resin component, two polyimide resins different in Tg by at least 20° C. from each other, and an epoxy resin, wherein at least one of the two polyimide resins is a reactive polyimide having structural units represented by the following formula (I), structural units represented by the following formula (II) and structural units represented by the following formula (III), and the other is a polyimide having structural units represented by the following formula (I) and structural units represented by the following formula (II), and the reactive polyimide and the epoxy resin are contained in ranges of at least 25 parts by weight and 10 to 100 parts by weight, respectively, per 100 parts by weight of the whole polyimide resin,
wherein W means a single bond, an alkylene group having 1 to 4 carbon atoms, —O—, —SO
2
— or —CO—, Ar
1
denotes a divalent aromatic group represented by the following formula (1) or (2):
in which X is a single bond, an alkylene group having 1 to 4 carbon atoms, —O—, —SO
2
— or —CO—, Y is an alkylene group having 1 to 4 carbon atoms, and Z
1
and Z
2
are each a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, Ar
2
represents a divalent aromatic group having one or two hydroxyl groups or carboxyl groups, preferably, a divalent aromatic group represented by the following formula (4) or (5):
in which X and Y have the same meanings as defined above, and Z
3
and Z
4
are both hydroxyl groups or carboxyl groups, or one of them is a hydroxyl group or carboxyl group and the other is a hydrogen atom, R
1
and R
6
individually mean an alkylene group having 1 to 4 carbon atoms or a group represented by the following formula (3):
in which Alk is an alkylene group bonded to a silicon atom and having 1 to 4 carbon atoms, R
2
and R
5
individually denote an alkylene group having 1 to 4 carbon atoms, and n stands for an integer of 1 to 32.
In the adhesive for electronic parts according to the present invention, the epoxy resin may preferably be a trihydroxyphenylmethane type epoxy resin. The adhesive for electronic parts according to the present invention may further comprise a novolak type phenol resin or a bismaleimide resin.
According to the present invention, there is also provided an adhesive tape for electronic parts, comprising a substrate and an adhesive layer formed on at least one side of the substrate using the adhesive for electronic parts described above.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The polyimide resins used in the adhesives for electronic parts according to the present invention will be first described. At least one of the two polyimide resins is a reactive polyimide having a functional group
Narushima Hitoshi
Oka Osamu
Yoshioka Ken
McDermott & Will & Emery
Tomoegawa Paper Co. Ltd.
Woodward Ana
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