Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-27
2001-07-03
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S466000, C528S089000, C528S094000, C528S103000, C528S104000
Reexamination Certificate
active
06255365
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an epoxy resin composition for semiconductor encapsulation, which cures rapidly, has excellent molding fluidity, and results in a cured product exhibiting minimal moisture absorption and excellent solder crack resistance.
BACKGROUND OF THE INVENTION
Epoxy resin compositions are used in a wide variety of fields, such as adhesion, casting, encapsulation, lamination, molding and coating, due to their excellent cured properties and ease of handling. There are a large variety of epoxy resins with greatly varying cured properties. Therefore, epoxy resins should be chosen according to their intended purpose.
In recent years, the requirements for various characteristics of polymeric materials have become more stringent as conditions under which the polymeric materials are used have become more severe. Many commonly used epoxy resins have been unable to accommodate these increased demands.
For example, epoxy resin compositions are used for semiconductor encapsulation. However, the required performance level has increased in this field. As high integration of semiconductor devices has increased, the resulting enlargement of semiconductor elements has been remarkable, creating a need for miniaturized and thinned packages. In addition, mounting of semiconductor devices has shifted to surface mounting. In surface mounting, the semiconductor devices are directly dipped into a solder bath, thus being suddenly exposed to high temperature. Due to rapid expansion of absorbed water, high stress is applied to the whole package, generating cracks in the encapsulating material. For this reason, epoxy resin compositions for encapsulation having good solder crack resistance require high heat resistance (high glass transition temperature), low moisture absorption and low stress property (a small thermal expansion coefficient).
To reduce moisture absorption and improve resistance to thermal stress, a large amount of an inorganic filler such as fused silica powder is commonly used. This significantly improves solder crack resistance. However, if an excessive amount of the inorganic filler is used, fluidity at molding is impaired. For this reason, an epoxy resin for semiconductor encapsulation is required to have a low melt viscosity.
In addition, for use with thinned and miniaturized packages, the epoxy resin for semiconductor encapsulation is also required to have high fluidity, thus the demand for low melt viscosity of the epoxy resin is even greater.
Further, rapid curability is required in order to increase molding speed, and it is the recent trend that materials not having rapid curability are not used even if other characteristics are good.
Novolak type epoxy resins (particularly cresol novolak type epoxy resin) currently in common use have excellent heat resistance and rapid curability, but have been unable to sufficiently meet low moisture absorption and low melt viscosity requirements.
Further, phenol novolak resin currently in common use as an epoxy resin hardener is also insufficient with respect to low moisture absorption and low melt viscosity, although heat resistance and curability properties are excellent.
The use of biphenyl type epoxy resins having a low melt viscosity has been widely investigated. Japanese Patent Application No. Sho 61-47725, for example, describes mixing 20-400 parts by weight of a novolak type epoxy resin per 100 parts by weight of a biphenyl type epoxy resin, and using phenol novolak resin as a hardener, to take up the balance. However, because the heat resistance of these compounds is poor, they are not sufficiently solder crack resistant. Curability and moisture absorption properties of these resins are also insufficient.
Japanese Patent Application No. Hei 7-118366 and Japanese Patent Application No. Hei 7-216054 describe improved solder crack resistance by mixing a novolak type epoxy resin and 50 wt % or more of a tetramethyl biphenyl type epoxy resin in addition to an aralkyl phenol resin which achieves low moisture absorption, as a hardener. However, if tetramethyl biphenyl type epoxy resin, which has poor curability, is added in a large amount, curability is insufficient.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a novel epoxy resin composition for semiconductor encapsulation, having rapid curability and excellent fluidity, resulting in a cured product having low moisture absorption and excellent solder crack resistance.
As a result of various investigations to solve the above-mentioned problems, inventors of the present invention have been able to achieve the object by adding the same amount or less of a 4,4′-biphenol type epoxy resin to a novolak type epoxy resin as an epoxy resin, combining a phenolic resin which achieves low moisture absorption as an epoxy resin hardener, and also adding large quantities of an inorganic filler.
That is, the epoxy resin composition of the present invention comprises:
1. An epoxy resin composition comprising a blend of
(a) an epoxy resin comprising a mixture of the following components:
(1) 50-95 parts by weight of a novolak type epoxy resin, and
(2) 5-50 parts by weight of 4,4′-biphenol type epoxy resin represented by the general formula (I)
(where the average value of m is a number of about 0-0.5), and
(b) a phenolic resin as an epoxy resin hardener represented by the general formula (II)
wherein R, which may be the same or different, represents an alkyl group having 1-10 carbon atoms, a substituted or unsubstituted phenyl group, a substituted or unsubstituted aralkyl group, an alkoxyl group or a halogen atom; Z, which may be the same or different, represents a divalent hydrocarbon group having 1-15 carbon atoms, provided that at least one Z is a divalent hydrocarbon group having 5-15 carbon atoms; n is a number of 0-8 on the average value; and i, which may be the same or different, is an integer of 0-3
(c) 80-95% by weight of an inorganic filler of the whole composition, and
(d) a curing accelerator, as the essential components.
2. The epoxy resin composition as described in item 1, characterized by using, as the novolak type epoxy resin (1), at least one epoxy resin selected from phenol novolak type epoxy resins, cresol novolak type epoxy resins, and bisphenol A novolak type epoxy resins.
3. The epoxy resin composition as described in item 1 or 2, characterized by using an epoxy resin mixture obtained by reacting a mixture of the novolak type phenolic resin and the 4,4′-biphenol with 3-20 moles, per one mole of phenolic hydroxyl group of the mixture of the phenol compounds, of an epihalohydrin in the presence of an alkali metal hydroxide as a total amount or a part of the epoxy resin in component (a).
4. The epoxy resin composition as described in any one of items 1-3, wherein an epoxy resin other than and in addition to the novolak type epoxy resin and the 4,4′-biphenol type epoxy resin of component (a) is added in an amount of 100 parts by weight or less per 100 parts by weight of the sum of both epoxy resins.
5. The epoxy resin composition as described in any one of items 1-4, characterized by using, as the epoxy resin hardener (b), at least one epoxy resin hardener selected from phenol aralkyl resin, terpene phenolic resin, and dicyclopentadiene phenolic resin.
6. The epoxy resin composition as described in any one of items 1-5, wherein in addition to the phenolic resin represented by the general formula (II), one of another hardener such as polyhydric phenols, polyhydric phenolic resins, acid anhydrides or amines is compounded in an amount of 50% by weight or less to the total amount of the epoxy resin hardeners.
7. The epoxy resin composition as described in any one of items 1-6, wherein the epoxy resin hardener (b) is used in an amount such that the sum of groups reacting with epoxy groups in all epoxy resin hardener components is 0.5-2.0 moles per one mole of epoxy group in all epoxy resin components.
8. The epoxy resin composition as described in any one of items 1-7, characterized by containin
Hayakawa Atsuhito
Murata Yasuyuki
Aylward D.
Dawson Robert
Shell Oil Company
Tsang Y. Grace
LandOfFree
Epoxy resin composition for semiconductor encapsulation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Epoxy resin composition for semiconductor encapsulation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Epoxy resin composition for semiconductor encapsulation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2477279