Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-06-21
2001-04-10
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C029S832000
Reexamination Certificate
active
06214156
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a semiconductor device mounted on a board by flip-chip and a method for mounting the same.
Conventionally, a semiconductor device mounted on a board by flip-chip is mounted by inserting solder bumps
13
between pad portions of a semiconductor chip
11
and a board
12
as shown in FIG.
1
and reflowing and melting the solder bumps
13
to electrically connect the pad portions of the semiconductor chip
11
to the board
12
.
However, in the above flip-chip type semiconductor device and the mounting method thereof, since the thermal expansion coefficients of the semiconductor chip
11
and the board
12
are different from each other, the solder bump
13
is liable to be destroyed after the surface mounting because of the difference in the thermal expansion between the semiconductor chip
11
and the board
12
, thereby causing poor electrical connection. For example, the thermal expansion coefficient of silicon used for the semiconductor chip
11
is approximately 5 [×10
−6
/° C.] and the thermal expansion coefficient of glass epoxy used for the board
12
is 11 to 12 [×10
−6
/° C.].
BRIEF SUMMARY OF THE INVENTION
Accordingly, a first object of this invention is to provide a semiconductor device capable of suppressing occurrence of poor connection after the surface mounting due to a difference in the thermal expansion between the semiconductor chip and the board.
A second object of this invention is to provide a method for mounting a semiconductor device which can suppress occurrence of poor connection after the surface mounting due to a difference in the thermal expansion between the semiconductor chip and the board.
The above first object of this invention can be attained by a semiconductor device comprising a semiconductor chip having a plurality of pads formed thereon; and a plurality of fine metal wires (bonding wires) connected at one end onto the pads of the semiconductor chip by wire bonding, wherein the other ends of the plurality of fine metal wires are mounted on a board by flip-chip.
With the above structure, since stress caused by a difference in the thermal expansion between the semiconductor chip and the board can be absorbed by utilizing the flexible bending action of the fine metal wires, occurrence of poor connection after the surface mounting due to a difference in the thermal expansion can be suppressed.
Further, the above first object of this invention can be attained by a semiconductor device comprising a semiconductor chip having a plurality of pads formed thereon; and a plurality of fine metal wires (bonding wires) connected at one end onto the pads of the semiconductor chip by wire bonding and each: having a bent portion, wherein the bent portions of the plurality of fine metal wires are mounted on a board by flip-chip.
With the above structure, since stress caused by a difference in the thermal expansion between the semiconductor chip and the board can be absorbed by utilizing the flexible bending action of the fine metal wires, occurrence of poor connection after the surface mounting due to a difference in the thermal expansion can be suppressed. In addition, since the fine metal wire is bent and the bent portion is mounted on the board, the mechanical strength of the connecting portion can be enhanced and the mounting strength can be enhanced. Further, it is possible to use fine metal wires.
The above second object of this invention can be attained by a method for mounting a semiconductor device, comprising the steps of bonding one-side ends of fine metal wires (bonding wires) on pads of a semiconductor chip by a wire bonding method; pulling up the fine metal wires and cutting apart the fine metal wires when the fine metal wires are pulled up by a preset length; and mounting the other ends of the fine metal wires formed on the semiconductor chip onto a board.
With the above mounting method, since stress caused by a difference in the thermal expansion between the semiconductor chip and the board can be absorbed by utilizing the flexible bending action of the fine metal wires, occurrence of poor connection after the surface mounting due to a difference in the thermal expansion can be suppressed. In addition, since connecting portions used in place of solder bumps are formed by use of the conventional wire bonding technique, the manufacturing process can be simplified and the manufacturing cost can be lowered in comparison with a case wherein the solder bumps are used.
Further, the above second object of this invention can be attained by a method for mounting a semiconductor device, comprising the steps of first-bonding one-side ends of fine metal wires (bonding wires) on pads of a semiconductor chip by a wire bonding method; pulling up the fine metal wires and pulling down and bending the fine metal wires when the fine metal wires are pulled up by a preset length; second-bonding the fine metal wires on the semiconductor chip and then cutting apart the fine metal wires; and mounting the bent portions of the fine metal wires on a board.
With the above mounting method, since stress caused by a difference in the thermal expansion between the semiconductor chip and the board can be absorbed by utilizing the flexible bending action of the fine metal wires, occurrence of poor connection after the surface mounting due to a difference in the thermal expansion can be prevented. Further, since connecting portions used in place of solder bumps are formed by use of the conventional wire bonding technique, the manufacturing process can be simplified and the manufacturing cost can be lowered in comparison with a case wherein the solder bumps are used. In addition, since the fine metal wires are bent and the bent portions are mounted on the board, the mechanical strength of the connecting portion can be enhanced and the mounting strength can be enhanced.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 5189507 (1993-02-01), Carlomagno et al.
patent: 5719440 (1998-02-01), Moden
patent: 5742100 (1998-04-01), Schroeder et al.
patent: 5813115 (1998-09-01), Misawa et al.
patent: 5889326 (1999-03-01), Tanaka
patent: 5917707 (1999-06-01), Khandros et al.
Shimizu Shinya
Takano Eiji
Ball Michael W.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Haran John T.
Kabushiki Kaisha Toshiba
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