Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2002-02-22
2004-03-23
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S413000, C438S780000, C525S474000, C525S476000, C525S477000, C525S478000, C525S523000, C525S524000, C525S525000, C525S534000
Reexamination Certificate
active
06709753
ABSTRACT:
This invention relates to silicone-modified epoxy or phenolic resin compositions which cure into products having both the flexible and impact resistant properties of silicone resins and the adherent, heat resistant and humidity resistant properties of epoxy or phenolic resins. It also relates to semiconductor devices coated or sealed with the cured product of the resin compositions.
BACKGROUND OF THE INVENTION
Epoxy resins and phenolic resins have good adhesion, heat resistance and humidity resistance and find use in a wide variety of applications including adhesives and paints, and recently in advanced applications such as encapsulants for semiconductor devices. However, these resins have the drawbacks of being rigid and brittle and cannot be used in hostile environments as encountered in automobiles and aircraft.
To date, extensive efforts have been made to make flexible cured products of epoxy resins and phenolic resins. For example, the inventors proposed the use of modified epoxy or phenolic resins which have been reacted with silicone (see JP-B 61-48544, JP-B 62-36050, JP-B 63-63807). This approach is to control the compatibility between an epoxy or phenolic resin as the main component and a silicon as the modifying component so as to form a phase separation structure. If the phase separation structure is an adequate microstructure, it serves to absorb impacts, contributing to improvements in the flexibility and strength of cured resin. However, this approach is among the concept of stress reduction and does not reach the flexibility level of silicone resins.
On the other hand, silicone resins achieve levels of adhesion, heat resistance and humidity resistance which are far below those of epoxy and phenolic resins.
SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide a resin composition comprising a silicone-modified epoxy or phenolic resin which cures into a product having both the adherence, heat resistance and humidity resistance characteristic of epoxy resins or phenolic resins and the flexibility and impact resistance characteristic of silicone resins. Another object is to provide a semiconductor device coated or sealed with the cured product of the resin composition.
We have found that a satisfactory silicone-modified epoxy resin or silicone-modified phenolic resin is obtained by reacting an epoxy resin or phenolic resin having in a molecule at least two structural units of the following formula (1) with an organopolysiloxane having the following average compositional formula (2). The modified epoxy or phenolic resin is such that after the modified epoxy or phenolic resin is cured alone to form a cured product or after the modified epoxy or phenolic resin is added to another epoxy resin and/or phenolic resin and cured together to form a cured product, the organopolysiloxane component does not form a phase separation structure in the cured product. This modified epoxy or phenolic resin cures into a product having both the adherence, heat resistance and humidity resistance characteristic of epoxy resins or phenolic resins and the flexibility and impact resistance characteristic of silicone resins.
Specifically, the invention provides a resin composition comprising a silicone-modified epoxy resin or silicone-modified phenolic resin obtained by reacting an epoxy resin or phenolic resin having in a molecule at least two structural units of the following formula (1) with an organopolysiloxane having the following average compositional formula (2), the modified epoxy or phenolic resin being such that after the modified epoxy or phenolic resin is cured alone to form a cured product or after the modified epoxy or phenolic resin is added to another epoxy resin and/or phenolic resin and cured together to form a cured product, the organopolysiloxane component does not form a phase separation structure in the cured product.
Herein R
3
is hydrogen or glycidyl and R
4
is hydrogen or a monovalent hydrocarbon group having 1 to 6 carbon atoms.
(R
1
)
a
(R
2
)
b
SiO
(4−a−b)/2
(2)
Herein R
1
is selected from the class consisting of a hydrogen atom, a hydroxyl group, an alkoxy group, an alkenyloxy group, and a monovalent organic group containing an amino, epoxy, hydroxyl or carboxyl group, R
2
is a substituted or unsubstituted monovalent hydrocarbon group, letters a and b are positive numbers satisfying 0.001≦a≦1, 1≦b≦2.5 and 1≦a+b≦3, the number of silicon atoms in a molecule is an integer of 2 to 1,000, and the number of functional groups R
1
directly attached to silicon atoms in a molecule is an integer of at least 1.
The invention also provides a semiconductor device comprising a semiconductor chip whose surface is coated or sealed with the resin composition in the cured state.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The silicone-modified epoxy resin or silicone-modified phenolic resin used herein is obtained by reacting an epoxy resin or phenolic resin having in a molecule at least two, preferably 2 to 10, and more preferably 2 to 5, structural units of the formula (1) with an organopolysiloxane having the average compositional formula (2).
The epoxy resin or phenolic resin serving as a raw material for the silicone-modified resin should have at least two structural units of the following formula (1) in a molecule.
Herein R
3
is hydrogen or a glycidyl group represented by
and R
4
is hydrogen or a monovalent hydrocarbon group having 1 to 6 carbon atoms.
The monovalent hydrocarbon groups represented by R
4
are those of 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, for example, alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl and cyclohexyl, alkenyl groups such as vinyl, allyl, propenyl and butenyl, aryl groups such as phenyl. Also included are halo-substituted monovalent hydrocarbon groups in which some or all of the hydrogen atoms on the foregoing hydrocarbon groups are substituted with halogen atoms.
At least two structural units of formula (1) should be included for the following reason. When the epoxy or phenolic resin is reacted with an organopolysiloxane, either one of R
3
and R
4
in formula (1) reacts with functional groups R
1
in formula (2). If only one structural unit of formula (1) is included and R
3
reacts with the functional group R
1
, then the epoxy group or phenolic hydroxyl group is eliminated from the site of formula (1), and so the resin loses the function of epoxy or phenolic resin. If only one structural unit of formula (1) is included and R
4
reacts with the functional group R
1
, the resulting reaction product has both an epoxy or phenolic hydroxyl group and an organopolysiloxane attached to a common benzene ring so that reactivity lowers due to the steric factor. In contrast, in the event where two or more structural units of formula (1) are included, if the ratio of the epoxy or phenolic resin and the organopolysiloxane blended is controlled, there is a possibility that either one of the epoxy or phenolic hydroxyl group and the organopolysiloxane be present on some benzene rings, that is, a possibility to maintain reactivity. As compared with the inclusion of one structural unit of formula (1), the inclusion of two or more structural units of formula (1) leads to a silicone-modified resin having an increased number of functional groups, resulting in a cured product having an increased crosslinking density and hence, improved mechanical strength, heat resistance and humidity resistance.
Of the epoxy resins and phenolic resins described above, those of the following formulae (3), (4) and (5) are desirable.
Herein R
3
is hydrogen or glycidyl:
R
4
is hydrogen or a monovalent hydrocarbon group having 1 to 6 carbon atoms,
R
5
is —CH
2
— or
R
6
is
letters n and m are integers of at least 0.
Illustrative examples of the epoxy resins and phenolic resins of the formulae (3), (4) and (5) are compounds of the following structures.
Herein R
3
is hydrogen or glycidyl:
R
7
, which may be the same or diffe
Honda Tsuyoshi
Kanamaru Tatsuya
Shiobara Toshio
Birch & Stewart Kolasch & Birch, LLP
Dawson Robert
Feely Michael J
Shin-Etsu Chemical Co. , Ltd.
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