Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2001-04-06
2002-05-07
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C257S789000, C257S794000, C257S795000, C523S443000, C523S444000
Reexamination Certificate
active
06383660
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a low-dielectric constant epoxy resin composition for encapsulating a semiconductor, the epoxy resin composition having a remarkably reduced specific dielectric constant, and a semiconductor device in which a semiconductor element is resin-encapsulated by using the epoxy resin composition.
2. Discussion of the Related Art
Conventionally, a resin-encapsulating type semiconductor device, comprising a semiconductor element such as a transistor, IC or LSI and an encapsulating material such as an epoxy resin composition, wherein the semiconductor element is encapsulated by molding the encapsulating material by transfer molding, has been widely used along with ceramic-encapsulating type semiconductor devices, because of reliability, mass-productivity and low costs of the resin-encapsulating type semiconductor device.
However, recently, high-functionalizing and high-performance of the semiconductor element of a microprocessor or the like have been contrived. With such contrivances, operating frequency tends to be markedly increased. In addition, in the fields associated with information communication, the frequency band in miniaturized electronic devices such as cellular phones and PHS near giga-Hertz has been used, and the development of the communication using a two-digit giga-Hertz band has been currently progressed.
With the trend of high-frequency development in the semiconductor devices, ceramic-encapsulating type semiconductor devices having excellent high-frequency characteristics have been presently employed in a large number for semiconductor devices requiring high reliabilities. On the other hand, however, a current project is to employ a low cost resin-encapsulating type semiconductor device which is excellent in mass-productivity and various reliabilities mentioned above. Therefore, the development of an epoxy resin composition with a low dielectric constant for a low-pressure transfer molding has been in demand to be used in the resin-encapsulating type semiconductor device.
In addition, there have been proposed a process of resin-encapsulating a semiconductor by using a silicone resin having a low dielectric constant; a process utilizing a double molding technique, in which a semiconductor element is molded with a low-dielectric constant resin in the inner layer, and with a conventional epoxy resin in the outer layer (Japanese Patent Laid-Open No. Sho 61-237455); a process utilizing a hollow inorganic filler such as glass hollow spheres (Japanese Patent Laid-Open No. Hei 5-283561); and the like. However, there is a limitation in the lowering of the dielectric constant of the encapsulating resin. With the present ever increasing progress in the trend of high-frequency development of the semiconductor element, the desired lowering of the dielectric constant cannot yet be accomplished.
In addition, as the epoxy resin composition using a hollow inorganic filler for low-pressure transfer molding, which is used for resin-encapsulating the semiconductor element, Japanese Patent Laid-Open No. Sho 62-161851 discloses an epoxy resin composition for encapsulating a semiconductor wherein a silica having a void in its inner part is used as all or a part of the inorganic filler. However, this publication is completely silent on the dielectric properties of the cured product. On the other hand, Japanese Patent Laid-Open No. Hei 5-9270 discloses an epoxy resin composition for encapsulating a semiconductor in which the composition has a lowered dielectric constant, wherein the hollow inorganic filler constitutes 30 to 100% by weight of the inorganic filler. However, since the hollow structure is broken down by applying a shearing force during kneading or melt-dispersion of various added components, there is a disadvantage from the viewpoint of the productivity that not all of the raw materials can be kneaded at once. In addition, Japanese Patent Laid-Open No. Hei 5-206325 discloses a resin composition for encapsulating a semiconductor using a gas-containing filler, wherein the dielectric constant of the cured product of the resin composition is 3.5 or less at 50° C. in a frequency band of 1 MHz to 50 GHz. However, the resin composition disclosed in this publication can be hardly said to be a filler-containing resin composition favorably encapsulating a semiconductor having a narrow-pitched wiring structure of the recent development.
Accordingly, in view of the advancement in the development of a high-frequency semiconductor element, an object of the present invention is to provide an epoxy resin composition for encapsulating a semiconductor which has a further reduced specific dielectric constant matching the demands of the trend of high-frequency development, is favorable in the assembly of the semiconductor having a narrow-pitched wiring structure, and has excellent productivity.
Another object of the present invention is to provide a semiconductor device which is resin-encapsulated by using the epoxy resin composition.
These and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
A first embodiment of the present invention pertains to an epoxy resin composition for encapsulating a semiconductor device comprising as essential components:
(A) an epoxy resin;
(B) a phenolic resin;
(C) a curing accelerator; and
(D) a hollow inorganic filler having an average particle size of 4 to 100 &mgr;m and an average shell thickness of 1.5 &mgr;m or more,
wherein the amounts of the component (A) and the component (B) are adjusted such that a total amount of X and Y (X+Y) is 350 or more, wherein X is an epoxy equivalent of the epoxy resin (A), and Y is a hydroxyl group equivalent of the phenolic resin (B).
A second embodiment of the present invention pertains to a semiconductor device comprising a semiconductor element encapsulated by the epoxy resin composition described above.
As a result of intensive studies in view of accomplishing the above objects, the present inventor has remarked on the epoxy resin and the phenolic resin, which are organic components of the epoxy resin composition for encapsulating a semiconductor, and found that the reduction of a concentration of secondary hydroxyl group of the product formed after the reaction of these components is effective in lowering the dielectric constant, i.e., adjustment of a total amount of the epoxy equivalent of the epoxy resin and the hydroxyl equivalent of the phenolic resin to a specified value or higher. Also, the present inventor has found that in addition to the above adjustment in the organic components, since a hollow inorganic filler is used as an inorganic filler together with the organic components of the above-mentioned epoxy resin composition, there can be obtained an epoxy resin composition of which specific dielectric constant is further reduced. This specific dielectric constant matches the development of the high-frequency trend of the semiconductor element.
In addition, when, for instance, a hollow silica balloon, a hollow Shirasu balloon, a hollow glass balloon, or a hollow sphere comprising a silicon oxide and aluminum oxide, and a hollow material comprising various other ceramics is supplied to a conventional process for preparing a conventional epoxy resin composition as a gas (air)-containing hollow inorganic filler, the hollow material is liable to be broken down in the heating and kneading-dispersion process in which a strong shearing force is applied by a kneader, a heat roller or the like. Therefore, it has been necessary to use a hollow inorganic filler having a shell strength strong enough to withstand the above-mentioned heating and kneading-dispersion process.
Further, the semiconductor element is provided with a narrow-pitched wiring of 80 to 100 &mgr;m according to the wire bonding method, which is a representative example of the electrical wiring of the semiconductor element of the recent trend. Therefore, the present inventor has found that a particle size of
Aylward D.
Dawson Robert
Nitto Denko Corporation
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