Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor
Reexamination Certificate
2000-06-13
2002-04-30
Lebentritt, Michael (Department: 2824)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
C257S668000, C257S690000, C257S696000, C257S737000, C257S796000, C361S715000, C361S745000, C361S773000, C029S810000, C029S840000
Reexamination Certificate
active
06379997
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to semiconductor devices and methods of producing the same, and to semiconductor device units and methods of producing the same. More particularly, the present invention relates to a semiconductor device which encapsulates a semiconductor element by a resin and to a method of producing such a semiconductor device, and to a semiconductor device unit and a method of producing the semiconductor device unit.
Recently, there are demands to further reduce the size of electronic equipments such as personal computers, and as a result, there are increased demands to realize smaller semiconductor devices which are used in such electronic equipments.
In semiconductor devices, a substrate which holds a semiconductor element or the volume of an encapsulating resin is large compared to the size of the semiconductor element. For this reason, in order to reduce the size of the semiconductor device, it is necessary to appropriately reduce the size of the substrate or the encapsulating resin.
On the other hand, when the size of the semiconductor device is reduced, the heat radiation characteristic of the semiconductor device deteriorates. As a result, it is necessary to provide an efficient heat radiation means.
Therefore, there are demands to realize a semiconductor device which has a reduced size but can be formed with ease and has a satisfactory heat radiation characteristic.
A description will be given of an example of a conventional semiconductor device and a method of producing the same, by referring to
FIGS. 1A through 1C
.
FIGS. 1A through 1C
respectively show cross sections of the conventional semiconductor device at various stages of the production process.
As shown in
FIG. 1C
, a conventional semiconductor device
60
includes a semiconductor element
1
, a mold resin
3
, a lead frame
46
and the like. The semiconductor element
1
is die-bonded on a die-pad portion
39
which is formed on the lead frame
46
. In addition, wires
10
are provided between electrode pad portions
40
on the top surface of the semiconductor element
1
and inner lead portions of the lead frame
46
. The electrode pad portions
40
are shown in FIG.
1
A. The mold resin
3
encapsulates the semiconductor element
1
, the wires
10
and the inner lead portions of the lead frame
46
, so as to protect the semiconductor element
1
and the wires
10
.
The mold resin
3
is formed as shown in FIG.
1
B. In
FIG. 1B
, an upper mold
20
a
and a lower mold
20
b
form a transfer mold. When the lead frame
46
mounted with the semiconductor element
1
and having the wires
10
bonded thereto as shown in
FIG. 1A
is loaded between the upper and lower molds
20
a
and
20
b.
A plunger
22
arranged on the upper mold
20
a
heats and presses a resin tablet (mold resin
3
) which is indicated by a dot-pattern, so that the melted resin tablet flows into a cavity part formed between the upper and lower molds
20
a
and
20
b
via a cull part
43
, a runner part
44
and a gate part
45
. The cavity formed between the upper and lower molds
20
a
and
20
b
has a shape corresponding to the outer shape of the semiconductor device
60
. Hence, by filling the rein into this cavity part, the mold resin
3
is formed into a package having a predetermined shape.
According to the conventional resin filling method, the mold resin
3
remains at the cull part
43
, the runner part
44
and the gate part
45
, integrally to the package part of the semiconductor device
60
. Accordingly, when the semiconductor device
60
is removed from the upper and lower molds
20
a
and
20
b
, the remaining resin is broken at the gate part
45
and the broken off resin is thrown away.
On the other hand, as is well known, the semiconductor element
1
generates heat when driven. In the case of the semiconductor device
60
which is produced in the above described manner, the heat generated from the semiconductor element
1
thermally conducts via the mold resin
3
, and the heat radiation takes place particularly at the back surface of the package where the thickness of the mold resin
3
is thin. The back surface of the package is the bottom surface of the mold resin
3
in FIG.
1
C.
As described above, the main function of the mold resin
3
is to protect the semiconductor element
1
and the wires
10
. However, the mold resin
3
must also have a satisfactory adhesive strength. In other words, if the adhesive strength of the mold resin
3
with respect to the semiconductor element
1
and the wires
10
provided within the mold resin
3
is weak, the semiconductor element
1
and the wires
10
may move within the package. If the semiconductor element
1
and the wires
10
move within the package, it becomes impossible to positively protect the semiconductor element
1
and the wires
10
, and the reliability of the semiconductor device
60
will deteriorate.
But when carrying out the transfer molding, it is essential to separate the upper and lower molds
20
a
and
20
b
from the molded package, and the upper and lower molds
20
a
and
20
b
can be separated more satisfactorily if the above adhesive strength is not too strong. For this reason, a mold release agent which facilitates the separation of the upper and lower molds
20
a
and
20
b
is conventionally added to the mold resin
3
. The kind and quantity of this mold release agent that is to be added are selected to optimize the balance between the reliability of the semiconductor device
60
and the mold release (or parting) characteristic of the upper and lower molds
20
a
and
20
b
with respect to the molded package. More particularly, out of the cull part
43
, the runner part
44
and the gate part
45
, the mold release characteristic is poorest at the gate part
45
where the flow passage of the mold resin
3
is the narrowest. Hence, the kind and quantity of the mold release agent to be added are generally selected with reference to the mold release characteristic at the gate part
45
.
However, as the size of the semiconductor device
60
is further reduced and the package becomes smaller, the cull part
43
, the runner part
44
and the gate part
45
all become smaller, thereby deteriorating the mold release characteristic. For this reason, it is necessary to increase the amount of the mold release agent that facilitates the mold release as the package becomes smaller, but there was a problem in that the reliability of the semiconductor device
60
deteriorates if the amount of the mold release agent is increased for the reasons described above.
On the other hand, as for the heat radiation characteristic, the conventional semiconductor device
60
is designed to radiate heat via the back surface of the package. For this reason, there was a problem in that the heat generated from the semiconductor element
1
could not be released efficiently. In addition, there have been proposals to provide a plurality of radiator fins independently on the package, but the provision of the radiator fins increases the overall size of the semiconductor device
60
, and there was a problem in that the provision of the independent radiator fins cannot realize the size reduction of the semiconductor device
60
.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful semiconductor device and a method of producing the same, wherein the problems described above are eliminated.
Another and more specific object of the present invention is to provide a semiconductor device which can be made small while at the same time improving the mold release characteristic and the reliability of the semiconductor device, and to a method of producing such a semiconductor device.
It is also an object of the present invention is to provide a semiconductor device unit which can be made small while at the same time improving the mold release characteristic and the reliability of the semiconductor device unit, and to a method of producing such a semiconductor device unit.
Ishiquro Hiroyuki
Kasai Junichi
Katoh Yoshitugu
Kawahara Toshimi
Nakaseko Sinya
Arent Fox Kintner & Plotkin & Kahn, PLLC
Fujitsu Limited
Lebentritt Michael
Luu Pho M.
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