Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1999-02-26
2001-02-20
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C523S210000, C523S216000, C523S458000, C523S459000
Reexamination Certificate
active
06190787
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an epoxy resin composition for sealing semiconductors and a semiconductor device. More particularly, the present invention relates to an epoxy resin composition for sealing semiconductors which does not contain any halogen fire retardants or antimony fire retardants and shows excellent high temperatures storage life, flame retarding property and reliability in a humid condition, and to a semiconductor device using this epoxy resin composition.
BACKGROUND ART
Heretofore, electronic parts such as diodes, transistors and integrated circuits are sealed mainly with epoxy resin compositions. The epoxy resin compositions contain fire retardants containing a halogen and an antimony compound to provide the composition with the flame retarding property. The flame retarding property of the composition is exhibited by generation of a gas of a halogen or an antimony halide at high temperatures.
However, in accordance with the above method for exhibiting the flame retarding property, a gas of a halogen or an antimony halide is generated when an electronic part is exposed to a high temperature and this causes a big problem in that corrosion of aluminum circuits and fracture of connecting portions between aluminum pads and gold wires in chips take place. Moreover, it is required for protection of the environment and the health that an epoxy resin composition which does not use any fire retardants containing a halogen or an antimony compound and exhibits an excellent flame retarding property be developed.
To overcome the above problems, a resin composition having a glass transition temperature higher than the temperature of the environment which is obtained by a combination of an epoxy resin and a phenol resin curing agent is used to decrease diffusion of a gas of a halogen or an antimony halide during storage at high temperatures and high temperatures storage life can be improved. Alternatively, an ion scavenger may be added to scavenge gases of a halogen or an antimony halide generated during storage at high temperatures. A combination of these methods may also be used.
On the other hand, recently, electronic parts are often disposed at the surface of substrates of circuits. The size of electronic parts are becoming smaller and thinner. Therefore, improvement in crack resistance is required in soldering for attachment of electronic parts to substrates of circuits. Thus, an epoxy resin composition exhibiting both of excellent crack resistance in soldering and excellent high temperatures storage life has been desired. However, even when an epoxy resin composition which contains a fire retardant of a halogen compound or a combination of a halogen compound and an antimony compound and exhibits excellent crack resistance in soldering is used, addition of an ion scavenger cannot provide sufficient high temperatures storage life when the epoxy resin composition has a low glass transition temperature. On the other hand, an epoxy resin composition shows insufficient crack resistance in soldering when the epoxy composition has a high glass transition temperature. No epoxy resin compositions which have a low glass transition temperature and exhibit excellent high temperatures storage life have been provided.
Various fire retardants other than fire retardants containing a halogen and antimony compounds have been studied. For example, metal hydroxides such as aluminum hydroxide and magnesium hydroxide and boron compounds have been studied. However, these compounds do not effectively exhibit the flame retarding property unless they are used in a large amount. Moreover, these compounds contain large amounts of impurities and reliability in a humid condition is not satisfactory. Therefore, these compounds are not practically used. Fire retardants containing red phosphorus are effective even when these fire retardants are used in small amounts and are useful for fire retardation of epoxy resin compositions. However, red phosphorus has a problem in reliability in a humid condition because red phosphorus reacts with a minute amount of water to form phosphines and corrosive phosphoric acid. An epoxy resin composition which exhibits both of the flame retarding property and the reliability in a humid condition without using a fire retardant containing a halogen or an antimony compound has been desired.
The present invention has an object to provide an epoxy resin composition for sealing semiconductors which does not contain any halogen compounds or antimony compounds, has an excellent flame retarding property and exhibits excellent high temperatures storage life and reliability in a humid condition, and to provide a semiconductor device using this epoxy resin composition.
DISCLOSURE OF THE INVENTION
As the result of extensive studies by the present inventors to achieve the above object, it was found that the long term reliability of an epoxy resin composition in a humid condition can be remarkably improved by using zinc molybdate without deterioration in the flame retarding property. The present invention has been completed on the basis of this knowledge.
Accordingly, the present invention provides:
(1) An epoxy resin composition for sealing semiconductors which comprises (A) an epoxy resin, (B) a phenol resin curing agent, (C) a curing accelerator, (D) an inorganic filler and (E) zinc molybdate as essential components;
(2) An epoxy resin composition for sealing semiconductors described in (1), wherein zinc molybdate coats an inorganic substance;
(3) An epoxy resin composition for sealing semiconductors described in (2), wherein the inorganic substance is fused spherical silica;
(4) An epoxy resin composition for sealing semiconductors described in any of (1), (2) and (3), wherein the epoxy resin is a crystalline epoxy resin represented by one of the following formulae [1], [2] and [3]:
wherein R represents hydrogen atom, a halogen atom or an alkyl group having 1 to 12 carbon atoms and the plurality of R may be the same with or different from each other;
(5) An epoxy resin composition for sealing semiconductors described in any of (1), (2), (3) and (4), which further comprises an ion scavenger represented by one of the following formulae [4], [5] and [6]:
BiO
a
(OH)
b
(NO
3
)
c
[4]
wherein a=0.9 to 1.1, b=0.6 to 0.8 and c=0 to 0.4
BiO
d
(OH)
e
(NO
3
)
f
(HSiO
3
)
g
[5]
wherein d=0.9 to 1.1, e=0.6 to 0.8 and f+g=0.2 to 0.4
Mg
h
Al
i
(OH)
2h+3i−2k
(CO
3
)
k
·mH
2
O [6]
wherein 0<j/h≦1, 0≦k/j<1.5 and m represents a positive number; and
(6) A semiconductor device sealed with an epoxy resin composition for sealing semiconductors described in any of (1), (2), (3), (4) and (5).
THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION
The epoxy resin composition for sealing semiconductors of the present invention comprises (A) an epoxy resin, (B) a phenol resin curing agents, (C) a curing accelerator, (D) an inorganic filler and (E) zinc molybdate as the essential components.
The epoxy resin of component (A) used in the composition of the present invention is not particularly limited and a monomer, an oligomer or a polymer having two or more epoxy groups in one molecule can be used. Examples of the epoxy resin include epoxy resins derived from bisphenol A, epoxy resins containing bromine, epoxy resins derived from bisphenol F, epoxy resins derived from bisphenol AD, epoxy resins derived from biphenyl, epoxy resins derived from hydroquinone, epoxy resins derived from stilbene, epoxy resins derived from phenol novolaks, epoxy resins derived from cresol novolaks, epoxy resins derived from triphenolmethane, epoxy resins derived from triphenolmethane and modified with alkyl groups, epoxy resins containing triazine cores, epoxy resins derived from phenol and modified with dicyclopentadiene, cyclic aliphatic epoxy resins, epoxy resins derived from glycidyl esters, epoxy resins der
Iwasaki Shinichi
Maeda Masakatu
Aylward D.
Dawson Robert
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Sumitomo Bakelite Company Ltd.
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