Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-09-25
2002-12-24
Pham, Long (Department: 2823)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
C438S121000, C438S122000, C438S123000, C438S124000, C438S125000, C257S704000
Reexamination Certificate
active
06498051
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of mounting a semiconductor device whereby the semiconductor device is connected with, and fixed to the surface of a circuit board with the use of an anisotropic conductive adhesive.
BACKGROUND TECHNOLOGY
A method of mounting a semiconductor device whereby the semiconductor device is connected with, and fixed to the surface of a circuit board with the use of an anisotropic conductive adhesive has been put to practical use. The conventional method of mounting a semiconductor device is described hereinafter with reference to
FIGS. 11
to
16
.
FIGS. 11
to
14
are sectional views showing respective steps of the conventional method of mounting the semiconductor device. As shown in these figures, with the conventional method of mounting the semiconductor device, wiring patterns
15
provided on a circuit board
17
are connected with bumps
14
formed on a semiconductor device
16
, respectively. When making such a connection, conductive particles
12
having electric conductivity, contained in an anisotropic conductive adhesive
13
, are sandwiched between the respective wiring patterns
15
and the respective bumps
14
, thereby effecting electric conduction therebetween by the agency of the conductive particles
12
.
The anisotropic conductive adhesive
13
is composed of the conductive particles
12
which are mixed in an adhesive resin
11
of a thermosetting type, made of an epoxy based adhesive, so as to have electric conductivity, and is formed in a film-like shape on a base film while being protected by a cover film. The conductive particles
12
are metallic particles made of silver, solder, or so forth, 5 to 10 &mgr;m in diameter, or composed of resin particles made of a plastic, with gold (Au) plating applied on the surface thereof.
The circuit board
17
is provided with the wiring patterns
15
formed on a substrate thereof, made of glass epoxy resin, ceramic, or glass. The wiring patterns
15
are formed of copper or gold, or composed of an indium tin oxide (ITO) film, or so forth for use in a liquid crystal display panel, and the like.
An operation of mounting a semiconductor device comprises the following steps.
First, as shown in
FIG. 11
, the anisotropic conductive adhesive
13
is transferred onto a part of the circuit board
17
where the semiconductor device
16
is to be connected.
In a next step, as shown in
FIG. 12
, the semiconductor device
16
is placed on the circuit board
17
disposed opposite thereto, after aligning the respective wiring patterns
15
provided on the circuit board
17
with the respective bumps
14
formed on the semiconductor device
16
.
Subsequently, the semiconductor device
16
is thermally press-bonded to the circuit board
17
by heating the semiconductor device
16
while applying a pressure P thereto by use of a heating and pressurizing tool
18
provided with a built-in heater as shown in
FIG. 13
, thereby curing the adhesive resin
11
contained in the anisotropic conductive adhesive
13
.
Then, as shown in
FIG. 14
, upon curing of the adhesive resin
11
, the semiconductor device
16
is bonded to, and fixed to the surface of the circuit board
17
, so that electric conduction is maintained between the respective bumps
14
of the semiconductor device
16
, and the respective wiring patterns
15
through the intermediary of the conductive particles
12
contained in the anisotropic conductive adhesive
13
.
With this method of mounting the semiconductor device, a thermal press-bonding process proceeds from the outset at a temperature required for curing the adhesive resin
11
by use of the heating and pressurizing tool
18
, however, the adhesive resin
11
of the thermosetting type, such as an epoxy based adhesive, and so forth, softens up rapidly when heated to more than a certain temperature, and is turned into a half-fusion state. Thereafter, a curing reaction proceeds, thereby curing the adhesive resin
11
.
FIGS. 15 and 16
are enlarged views showing conditions of a structure for mounting the semiconductor device before, and after the thermal press-bonding process, respectively.
FIG. 15
shows the condition when the semiconductor device
16
is placed on the circuit board
17
, that is, the condition before heating and pressurizing are carried out by use of the heating and pressurizing tool
18
as shown in
FIG. 13
, showing an enlarged view of a part of the semiconductor device
16
, and the circuit board
17
, respectively, so as to illustrate with clarity the state of the conductive. particles
12
existing between the bumps
14
and the wiring patterns
15
. At this point in time, preceding the heating and pressurizing, the adhesive resin
11
remains in the film-like shape as transferred.
Subsequently, as shown in
FIG. 16
, when a pressure P is applied to the semiconductor device
16
while applying heat thereto a temperature at which curing reaction occurs to the adhesive resin
11
by use of the heating and pressurizing tool
18
in order to cause the adhesive resin
11
to be cured, the adhesive resin
11
is cured rapidly, and at the same time, is crushed and fluidized, thereby being forced out of under the semiconductor device
16
. Since a spacing between the respective bumps
14
and the respective wiring patterns
15
is narrowed down to a minimum, portions of the adhesive resin
11
, in the vicinity of the respective bumps
14
, is forcefully pushed out by the respective bumps
14
, and are fluidized at the maximum.
Along with the adhesive resin
11
, which has been fluidized, the conductive particles
12
are also pushed out outside under the respective bumps
14
, and consequently, when the thermal press-bonding process is completed upon curing of the adhesive resin
11
later on, many of the conductive particles
12
will be found to be present in regions lying off the bottom face of the respective bumps
14
. Accordingly, there will remain only a few of the conductive particles
12
between the respective bumps
14
and the respective wiring patterns
15
.
Thus, a problem has been encountered with the conventional method of mounting the semiconductor device in that connecting resistance between the respective bumps
14
and the respective wiring patterns
15
became high because of a temporary softening phenomenon occurring to the adhesive resin
11
of the anisotropic conductive adhesive
13
prior to curing thereof caused by heating during the thermal press-bonding process, and pushing out of the conductive particles
12
and a decrease in the number of the conductive particles
12
left out between the respective bumps
14
and the respective wiring patterns
15
caused by pressurizing force applied to the semiconductor device.
In order to hold down the connecting resistance at a low level, it is required that as many as possible of the conductive particles
12
are left out between the respective bumps
14
and the respective wiring patterns
15
. To this end, it is necessary to expand an area of a connecting region where both the parts described are to be connected with each other so that many of the conductive particles
12
can be arrested therebetween.
However, in order to implement high-density mounting, it is necessary to reduce an area of the connecting region, thereby rendering it difficult to arrest many of the conductive particles
12
between the respective bumps
14
and the respective wiring patterns
15
. Consequently, the number of the conductive particles
12
left out in the connecting region will become fewer. Accordingly, the conventional method of mounting the semiconductor device described in the foregoing is unsuitable for high-density mounting because a connecting resistance value becomes high, and connection tends to become unstable.
The invention has been developed to solve such a problem as described above with the conventional method of mounting the semiconductor device using the anisotropic conductive adhesive, and it is therefore an object of the invention to enable stable connection to be effecte
Armstrong Westerman & Hattori, LLP
Citizen Watch Co. Ltd.
Nguyen Khiem
Pham Long
LandOfFree
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