Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Assembly of plural semiconductive substrates each possessing...
Reexamination Certificate
2000-05-25
2002-02-26
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Assembly of plural semiconductive substrates each possessing...
C156S089210, C156S288000, C118S052000, C174S050510, C361S689000
Reexamination Certificate
active
06350631
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electronic device, a method of manufacturing the same, and an apparatus for manufacturing the same. The present invention relates to an electronic device of a semiconductor device such as, for example, a leadless small surface mount transistor or diode, a method of manufacturing the same, and an apparatus for manufacturing the same.
BACKGROUND OF THE INVENTION
FIGS. 9A
to
9
C show a structural example of a conventional leadless small surface mount transistor:
FIG. 9A
is its plan view;
FIG. 9B
is its sectional side view; and
FIG. 9C
is its bottom view.
As shown in
FIGS. 9A and 9B
, a leadless small surface mount electronic device
3
includes: a first upper electrode
11
provided with an element mount portion on an upper surface
321
of a ceramic substrate
32
; and a second upper electrode
12
and a third upper electrode
13
that are positioned so as to be separated from the first upper electrode
11
.
On the back surface of a semiconductor chip on which a transistor
14
is formed, for instance, a collector electrode is formed by metal deposition or the like. The collector electrode of the transistor
14
is fixed to the first upper electrode
11
by die bonding or the like and thus the first upper electrode
11
is electrically connected to the collector electrode of the transistor
14
.
The second upper electrode
12
and for example, a base electrode of the transistor
14
are connected with a metal wire
15
. Similarly, the third upper electrode
13
and for example, an emitter electrode of the transistor
14
are connected with a metal wire
16
. A pair of lower electrodes
21
and
22
electrically connected to the first upper electrode
11
are formed on a lower surface
322
of the ceramic substrate
32
. The first upper electrode
11
and the pair of lower electrodes
21
and
22
are electrically connected through conductive relay members going through the ceramic substrate
32
, i.e. via holes
17
and
18
.
Similarly, on the lower surface
322
of the ceramic substrate
32
, lower electrodes
23
and
24
are formed, which are electrically connected to the second upper electrode
12
and the third upper electrode
13
through via holes
19
and
20
going through the ceramic substrate
32
, respectively.
As shown in
FIG. 9C
, the lower electrodes
21
,
22
,
23
, and
24
are positioned at the four corners of the lower surface
322
of the ceramic substrate
32
.
These lower electrodes
21
to
24
are attached, for example, to a wiring pattern provided in a printed circuit board, which is not shown in the figure, with a conductive adhesive such as solder or the like.
FIGS. 10A and 10B
show a so-called master electronic device in which a plurality of individual electronic devices are formed, which is divided into individual electronic devices as shown in
FIGS. 9A
to
9
C later. In other words, as shown in
FIG. 10A
, m×n pieces of electronic devices
3
are formed on one common ceramic substrate
32
in a matrix form. In the respective electronic devices
3
, electronic elements such as a transistor, a diode, a resistor, and the like already have been mounted on a wiring pattern (electrode) formed on the ceramic substrate
32
. In addition, predetermined electrodes of the electronic elements, for example, a collector electrode, a base electrode, and an emitter electrode of the transistor are connected to the wiring pattern (electrode) provided on the ceramic substrate directly or via metal wires or the like.
After that, as shown in
FIG. 10B
, generally the upper surface of the electrode ceramic substrate
32
is coated with liquid resin
26
by a potting method, a dispenser method, a vacuum printing method, or the like. The liquid resin
26
is cured by heating, and thus the upper surface is sealed with the resin. Then, the master electronic device is divided into individual electronic devices along cutting plane lines
33
(
FIG. 10A
) by a dicing saw.
Generally, the conventional leadless small surface mount electronic device is obtained by allowing liquid resin to form a resin package by the potting method, the dispenser method, the vacuum printing method, or the like and then curing the resin in a curing oven or the like. However, the material obtained by curing the liquid resin has a glass transition point of about 100° C., which is low. Therefore, when solder reflow is carried out at 230° C., the resin that has been cured is resoftened and therefore the resin thus softened is peeled off from the ceramic substrate easily, which has been a problem.
Furthermore, in the potting method and the dispenser method, the liquid resin merely is dropped or poured onto the ceramic substrate and then is cured without being molded under pressure, thus forming a resin package. Therefore, there have been the following problems. As shown in
FIG. 9B
, not only unevenness d
1
in thickness of the resin that has been cured is caused but also it is difficult to increase the density of the resin. Thus, the strength of the resin is low, and when subjected to an external stress, the resin package is deformed easily.
Similarly, in the vacuum printing method, liquid resin simply is applied onto the ceramic substrate using a printing means and then is cured. Therefore, there has been a problem that an unevenness d
1
in thickness of about 5 to 15 &mgr;m occurs in the resin that has been cured.
As described above, in the conventional formation methods, not only has the difference in thickness of the resin in an electronic device been caused to increase an irregularity of its surface, but also between electronic devices the difference in thickness of the resin has been caused. Therefore, there has been a problem that after the formation by resin sealing, after-processing such as grinding of the resin surface using a grindstone or the like must be carried out.
As shown in
FIG. 10B
, when using the liquid resin, the thickness of the resin increases in the peripheral portion of the ceramic substrate and is uniform only in the vicinity of the center of the substrate. The difference d
2
in thickness of the resin between the vicinity of the center and the peripheral portion of the ceramic substrate reaches about 0.1 mm.
Furthermore, there have been the following problems. In a dicing step for forming individual packages, it is difficult to allow the resin surface of the electronic device to adhere to a fixing tape or the like due to the irregularities d
1
and d
2
on the surface of the electronic device after the resin is cured. In addition, the individual electronic devices cut in dicing come off from the fixing tape and thus are lost easily.
In the resin sealing by a transfer molding method using a mold, which has been known conventionally as a method of sealing a semiconductor, the ceramic substrate is not easily bent compared to other resin substrates or metal lead frames. Therefore, due to the distortion caused by pressure applied when the ceramic substrate is sandwiched between upper and lower molds, cracks or breakage occur easily in the ceramic substrate. Consequently, the resin sealing by the transfer molding method was not employed for the conventional leadless small surface mount transistor.
SUMMARY OF THE INVENTION
In order to solve the aforementioned conventional problems, the present invention is intended to provide an electronic device, a method of manufacturing the same, and an apparatus for manufacturing the same, wherein the occurrence of cracks or breakage in a ceramic substrate can be prevented by buffering the pressure applied to the ceramic substrate so as to prevent a distortion force from being caused even when the ceramic substrate is sandwiched and compressed between upper and lower molds.
In order to achieve the above-mentioned object, an electronic device of the present invention is obtained by mounting plural sets of electronic components on a ceramic substrate and sealing the electronic components with thermosetting resin by transfer molding. The electronic device is provided wi
Araki Takashi
Kobayashi Takeshi
Elms Richard
Luu Pho
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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