Adhesives and electric devices

Details Adhesives and electric devices Adhesives and electric devices

2001-10-05

2003-11-04

Dawson, Robert (Department: 1712)

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

C428S620000, C523S457000, C523S458000, C523S459000

Reexamination Certificate

active

06641928

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to adhesives, and particularly adhesives for connecting a semiconductor chip to a wiring board.
PRIOR ART
Adhesives based on a thermosetting or thermoplastic resin have been used to bond a semiconductor element onto a wiring board.
FIG. 4
shows that a semiconductor chip
111
is applied on a wiring board
113
via an adhesive
112
, and bump-like terminals
121
on the semiconductor chip
111
are in contact with terminals
122
formed of parts of the wiring pattern on the wiring board
113
. In this state, electric components in the semiconductor chip
111
are electrically connected to the wiring pattern on the wiring board
113
via the terminals
121
,
122
.
However, the adhesive
112
has a linear expansion coefficient of 25-60 ppm/° C., which is higher than that of the semiconductor chip of about 3 ppm/° C., leading to residual stress at the bonding interface due to the difference of the linear expansion coefficient. Especially, the residual stress increases with the chip size at the periphery of the semiconductor chip, which causes the problem that semiconductor chip
111
may be separated during temperature cycle tests or pressure cooker tests after the thermosetting adhesive
112
is cured.
Moreover, adhesives of the prior art show a marked deterioration of reliability under some moisture adsorption conditions after the semiconductor chip
111
has been bonded, which required a dehydration process by preheating to about 100° C. before the assembly is passed through a reflow furnace to cure the adhesive
112
after the semiconductor chip
111
is applied.
The present invention was made to overcome the disadvantages of the prior art described above with the purpose of providing a highly reliable adhesive.
SUMMARY OF THE INVENTION
The present invention provides an adhesive for connecting a semiconductor chip and a wiring board, comprising a first resin component which is polymerizable, a first hardener for inducing a self-polymerization reaction of the first resin component, and a second hardener which is addition-polymerized with the first resin component.
The present invention provides the adhesive having an elastic modulus decreasing with a temperature increase after curing, wherein the elastic modulus loss sharply increases at both of a first temperature higher than 30° C. and lower than 150° C. and a second temperature within a range of 130° C. or more and 250° C. or less and higher than the first temperature. The difference between the first temperature and the second temperature is preferably 40° C. or more.
The present invention provide the adhesive wherein a ratio of an elastic modulus at the first temperature to an elastic modulus at the second temperature is 2.8 or more. The present invention provides the adhesive wherein the first resin component is an epoxy resin. The adhesive may also contain (1) conductive particles, (2) filler and/or (3) a second resin component which is polymerized separately from the first resin component.
The present invention further provides the adhesive wherein the first hardener is one or more of an imidazole, a tertiary amine or a Lewis acid catalyst and the second hardener is one or more of an active hydrogen-containing amine, a phenol, a hydrazide, a mercapto or a dicyandiamide hardener. The present invention provides the adhesive wherein the adhesive further contains a filler of silica, alumina or titanium oxide.
The adhesive may be preliminarily semicured and formed in the form of a sheet.
The present invention provide an electric device comprising a semiconductor chip and a wiring board, wherein the semiconductor chip is adhesively bonded to the wiring board with the adhesive.
The present invention provides the electric device wherein the semiconductor chip includes connection terminals that contact connection terminals of a wiring pattern on the wiring board.


REFERENCES:
patent: 5278259 (1994-01-01), Futakuchi
patent: 6475641 (2002-11-01), Shinozaki
Japanese Industrial Standard, JIS K 7244-4: 1999, “Plastics—Determination of dynamic mechanical properties—Part 4: Tensile vibration—Non-resonance method”.
International Standard ISO 6721-4, Nov. 1, 1994, “Plastics—Determination of dynamic mechanical properties—Part 4: Tensile vibration—Non-resonance method”.

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