Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-03-08
2001-09-04
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S460000
Reexamination Certificate
active
06284818
ABSTRACT:
This application is based on Japanese Patent Applications No. Hei 11-061514, No. 2000-021785 and No. 2000-030636 filed in Japan, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an encapsulant composition having a superior moisture resistance and also having good continuous operability and reflow resistance, and an electronic device having device components encapsulated with this composition.
2. Description of the Related Art
In recent years, with an improvement in integration of semiconductor device components such as ICs (integrated circuits) and LSIs (large-scale integrated circuits), device components are being made larger in scale and semiconductor devices are being made smaller and thinner. In thin-type semiconductor devices, however, the occurrence of blistering or cracking in their production steps has come into question. This is because, when semiconductor devices are mounted to a substrate, they are exposed to a high temperature of 200° C. or above in a short time as a result of their immersion in a soldering bath, so that the moisture contained in an encapsulant vaporizes and the vapor pressure thereby produced acts as a peel stress at the interface between the encapsulant and a insert such as the device component or a lead frame to cause separation of the encapsulant from the insert at their interface.
As measures for preventing the blistering or cracking caused by such separation, used are a method in which a coat material is used on the device surface or the back of islands of a lead frame so as to improve its adhesion to the encapsulant, a method in which dimples or slits are formed on the back of islands of a lead frame, and a method in which an LOC (lead on chip) structure is employed so as to improve the adhesion to the encapsulant. These methods, however, have the problems that a high cost may result or no satisfactory effect can be attained. Accordingly, it is sought to improve the encapsulant itself.
Under such circumstances, as a measure for improving the adhesion between the encapsulant and the insert, the manner of addition of and treatment with various coupling agents has been studied on, e.g., making epoxy resins and curing agents have lower viscosity (lower molecular weight), using epoxysilane and mercaptosilane in combination, and using ureidosilane and mercaptosilane in combination. These conventional methods, however, can not be said that they provide sufficient adhesion between the encapsulant and the insert. Moisture may enter from slightly separated portions to cause the problem of a low moisture resistance.
SUMMARY OF THE INVENTION
The present invention was made taking account of such existing circumstances. Thus, an object of the present invention is to provide an encapsulant composition having a superior moisture resistance and also having good continuous operability and reflow resistance, and an electronic device making use of such a composition.
As a result of extensive studies made in order to solve the above problem, the present inventors have discovered that the above object can be achieved by mixing in an encapsulant composition an adduct of triphenylphosphine with benzoquinone, a specific amount of hydrous bismuth nitrate oxide and a specific amount of an inorganic filler. Thus, they have accomplished the present invention.
The present invention provides an encapsulant composition comprising as essential constituents an epoxy resin, a curing agent, an inorganic filler, an adduct of triphenylphosphine with benzoquinone, and a hydrous bismuth nitrate oxide; the inorganic filler being mixed in an amount of from 70% by volume to 85% by volume based on the volume of the encapsulant composition, and the hydrous bismuth nitrate oxide being mixed in an amount of from 2.5 parts by weight to 20 parts by weight based on 100 parts by weight of the epoxy resin. It also provides an electronic device having an encapsulating member comprising a cured product of this encapsulant composition. In the encapsulant composition of the present invention, at least 50% by weight of the inorganic filler may preferably comprise spherical particles. Also, the epoxy resin may preferably comprise a biphenyl type epoxy resin, and the curing agent may preferably comprise an aralkyl type phenolic resin.
REFERENCES:
patent: 6194491 (2001-02-01), Fujii
patent: 6211277 (2001-04-01), Kawata
Kawata Tatsuo
Sakai Hiroyuki
Tsukahara Terumi
Antonelli Terry Stout & Kraus LLP
Hitachi Chemical Company Ltd.
Michl Paul R.
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