Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Die bond
Reexamination Certificate
2000-07-26
2002-07-02
Clark, Jasmine J B (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Die bond
C257S793000, C257S795000, C257S789000, C438S124000, C438S126000, C438S127000
Reexamination Certificate
active
06414397
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to anisotropic conductive films, methods of mounting semiconductor chips, and semiconductor devices, and more particularly, the invention relates to an anisotropic conductive film which is suitable for mounting a semiconductor chip so that an active element-formed surface thereof faces the substrate side, a method of mounting a semiconductor chip, and a semiconductor device.
2. Description of Related Art
In a method of mounting a semiconductor chip so that a surface thereof provided with an active element faces downward, i.e., in so-called “flip chip mounting”, anisotropic conductive films are often used. The anisotropic conductive film exhibits adhesive ability and also acts as a conductive medium between the semiconductor chip and the substrate. The anisotropic conductive film is a thin film and is formed as a long tape. In general, the anisotropic conductive film is composed of a binder, which is composed of a solid epoxy resin and a liquid epoxy resin, and conductive particles composed of metal-clad resin particles. The conductive particles are blended so that the volumetric ratio thereof is uniform over the binder. Additionally, metal particles may be used as the conductive particles. Conductive particles having a diameter of approximately 2 to 10 &mgr;m, and mostly approximately 5 &mgr;m, are predominantly used.
Herein, an example of a method of mounting a chip using a conventional anisotropic conductive film is shown in FIG.
5
. First, an anisotropic conductive film
3
is attached to a substrate
2
provided with wiring
21
, and then a semiconductor chip
1
is placed on the anisotropic conductive film
3
in such a manner that electrode pads
11
and the wiring
21
are opposed to each other. Next, the semiconductor chip
1
is pressed while being heated by a hot pressing tool
71
from a surface opposite to the surface provided with the electrode pads
11
.
Because of an increase in fluidity by heating, the anisotropic conductive film
3
fills the space around the electrode pads
11
and the wiring
21
, and further flows out of the bond area between the semiconductor chip
1
and the substrate
2
to adhere to the sides of the semiconductor chip
1
. Some conductive particles
61
are sandwiched between the electrode pads
11
and the wiring
21
.
When the anisotropic conductive film
3
is cured after thermocompression, the semiconductor chip
1
and the substrate
2
are bonded together by the anisotropic conductive film
3
. In particular, the anisotropic conductive film
3
adhered to the sides of the semiconductor chip
1
forms fillets
34
and strengthens mechanical connection between the semiconductor chip
1
and the substrate
2
. The conductive particles
61
sandwiched between the electrode pads
11
and the wiring
21
act as conducting media between the semiconductor chip
1
and the substrate
2
.
However, the conventional technique described above gives rise to the following problems.
SUMMARY OF THE INVENTION
In the case of a low-profile semiconductor chip
1
, when the semiconductor chip
1
is heated and pressed by the hot pressing tool
71
, the anisotropic conductive film
3
adheres not only to the sides of the semiconductor chip
1
, but also to the hot pressing tool
71
, as shown in
FIG. 5
, by an adhered portion
35
. If a portion of the anisotropic conductive film
3
frequently adheres to the hot pressing tool
71
, the hot pressing tool
71
must be frequently cleaned accordingly, resulting in an increase in controlling workload in the thermocompression process for the semiconductor chip. Additionally, the appearance of the semiconductor chip in such a state is unfavorable.
However, in order to avoid the problems described above, if the area of the anisotropic conductive film
3
to be provided on the substrate
2
is set smaller than the area of the semiconductor chip
1
provided with the electrode pads
11
, or if the heating temperature of the hot pressing tool
71
is set lower than that in the conventional technique, the strength of mechanical connection between the semiconductor chip and the substrate may become sufficient.
DISCLOSURE OF INVENTION
In order to overcome the drawbacks in the conventional technique described above, it is an object of the present invention to provide an anisotropic conductive film in which satisfactory strength of mechanical connection between a substrate and a semiconductor chip can be obtained, and also, in which the process for connecting the semiconductor chip and the substrate can be easily controlled by preventing the anisotropic conductive film from adhering to a hot pressing tool. It is another object of the present invention to provide a circuit substrate provided with the anisotropic conductive film. It is another object of the present invention to provide an electronic apparatus provided with the circuit substrate.
It is another object of the present invention to provide a semiconductor device in which a semiconductor chip is mounted by means of an anisotropic conductive film, in which satisfactory strength of mechanical connection between a substrate and the semiconductor chip can be obtained, and which can be prevented from adhering to a hot pressing tool.
It is another object of the present invention to provide a method of mounting a semiconductor chip using the anisotropic conductive film. It is another object of the present invention to provide a semiconductor device which is fabricated by the method of mounting the semiconductor chip. It is another object of the present invention to provide an electronic apparatus provided with the semiconductor device.
In order to achieve the objects described above, an anisotropic conductive film according to an exemplary embodiment of the present invention for bonding a semiconductor chip and a substrate to each other and for acting as an electrically conductive medium between the semiconductor chip and the substrate includes a first member and a second member disposed adjacent to the first member. The first member is composed of a material having characteristics with lower fluidity than that of the second member.
In the anisotropic conductive film according to the exemplary embodiment constructed as described above, when the semiconductor chip is connected to the substrate by thermocompression bonding of the semiconductor chip to the anisotropic conductive film attached to the substrate with a hot pressing tool, the first member inhibits the second member from flowing toward the sides of the semiconductor chip. Thereby, it is possible to prevent the second member from adhering excessively to the sides of the semiconductor chip in such a manner that the adhesion reaches the hot pressing tool. Consequently, the process for connecting the semiconductor chip and the substrate can be easily controlled.
An anisotropic conductive film according to another exemplary embodiment of the present invention for bonding a semiconductor chip and a substrate to each other and for acting as an electrically conductive medium between the semiconductor chip and the substrate includes a first member and a second member disposed adjacent to the first member. The first member is composed of a material which exhibits characteristics with lower fluidity than that of the second member when the semiconductor chip and the substrate are bonded together.
In the anisotropic conductive film according to the exemplary embodiment constructed as described above, since the first member has lower fluidity than that of the second member at the point where the semiconductor chip is connected to the substrate by thermocompression bonding of the semiconductor chip to the anisotropic conductive film attached to the substrate with a hot pressing tool, the first member can inhibit the second member from flowing toward the sides of the semiconductor chip. Thereby, it is possible to prevent a material used for the second member from excessively adhering to the sides of the semiconductor chip in such a manner
Clark Jasmine J B
Oliff & Berridg,e PLC
Seiko Epson Corporation
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