U.S. patent application number 09/845568 was filed with the patent office on 2002-02-14 for electronic device, method of manufacturing the same, and apparatus for manufacturing the same.
This patent application is currently assigned to Matsushita Electronics Corporation. Invention is credited to Araki, Takashi, Kobayashi, Takeshi.
Application Number | 20020019072 09/845568 |
Document ID | / |
Family ID | 27319450 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020019072 |
Kind Code |
A1 |
Kobayashi, Takeshi ; et
al. |
February 14, 2002 |
Electronic device, method of manufacturing the same, and apparatus
for manufacturing the same
Abstract
An electronic device such as a semiconductor device, a method of
manufacturing the same, and an apparatus for manufacturing the
same, wherein by placing a ceramic substrate provided with a
metallic thin film integrated into at least one selected from an
upper surface and a lower surface of the ceramic substrate in its
peripheral portion so as to extend both inside and outside a cavity
of a mold for transfer molding, and positioning the metallic thin
film in a position with which an upper mold and a lower mold of the
mold come into contact, occurrence of cracks or breakage in the
ceramic substrate is 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 the upper mold and the lower mold.
Inventors: |
Kobayashi, Takeshi;
(Tochigi, JP) ; Araki, Takashi; (Tochigi,
JP) |
Correspondence
Address: |
Attn: Douglas P. Mueller
MERCHANT & GOULD P.C.
P.O. Box 2903
Minneapolis
MN
55402-0903
US
|
Assignee: |
Matsushita Electronics
Corporation
1-1, Saiwai-cho, Takasuki-shi
Osaka
JP
569-1193
|
Family ID: |
27319450 |
Appl. No.: |
09/845568 |
Filed: |
April 30, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09845568 |
Apr 30, 2001 |
|
|
|
09578438 |
May 25, 2000 |
|
|
|
Current U.S.
Class: |
438/107 ;
257/E21.504; 257/E23.07; 257/E23.125; 425/125; 425/127; 438/124;
438/127 |
Current CPC
Class: |
H01L 24/48 20130101;
H01L 21/561 20130101; H01L 2924/15787 20130101; H01L 2924/14
20130101; H01L 24/45 20130101; H01L 2924/181 20130101; H01L
2924/01078 20130101; H01L 2924/01005 20130101; H01L 23/3121
20130101; H01L 2224/48091 20130101; H01L 2924/01087 20130101; H01L
2924/01082 20130101; H01L 24/97 20130101; H01L 23/49838 20130101;
H01L 21/565 20130101; H01L 2924/01006 20130101; H01L 2924/01033
20130101; H01L 2224/48227 20130101; H01L 2924/01009 20130101; H01L
2924/00014 20130101; H01L 2924/19043 20130101; H01L 2224/451
20130101; H01L 24/49 20130101; H01L 2224/97 20130101; H01L
2924/01074 20130101; H01L 2224/49171 20130101; H01L 2224/48465
20130101; H01L 2924/30105 20130101; H01L 2924/01079 20130101; H01L
2924/01004 20130101; H01L 2224/97 20130101; H01L 2224/85 20130101;
H01L 2224/48091 20130101; H01L 2924/00014 20130101; H01L 2224/48465
20130101; H01L 2224/48227 20130101; H01L 2224/49171 20130101; H01L
2224/48465 20130101; H01L 2924/00 20130101; H01L 2224/49171
20130101; H01L 2224/48227 20130101; H01L 2924/00 20130101; H01L
2224/48465 20130101; H01L 2224/48227 20130101; H01L 2924/00012
20130101; H01L 2224/48465 20130101; H01L 2224/48091 20130101; H01L
2924/00 20130101; H01L 2224/48465 20130101; H01L 2224/48227
20130101; H01L 2924/00 20130101; H01L 2224/451 20130101; H01L
2924/00014 20130101; H01L 2224/451 20130101; H01L 2924/00015
20130101; H01L 2924/00014 20130101; H01L 2224/05599 20130101; H01L
2924/181 20130101; H01L 2924/00012 20130101 |
Class at
Publication: |
438/107 ;
438/124; 438/127 |
International
Class: |
H01L 021/44; H01L
021/48; H01L 021/50 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 1999 |
JP |
11-147956 |
Sep 6, 1999 |
JP |
11-251149 |
May 11, 2000 |
JP |
2000-139072 |
Claims
What is claimed is:
1. An electronic device in which plural sets of electronic
components are mounted on a ceramic substrate and are sealed and
molded with thermosetting resin by transfer molding, wherein the
electronic device is provided with a metallic thin film integrated
into at least one selected from an upper surface and a lower
surface of the ceramic substrate at its peripheral portion.
2. The electronic device according to claim 1, wherein the metallic
thin film is present on each of the upper surface and the lower
surface of the ceramic substrate.
3. The electronic device according to claim 1, wherein the metallic
thin film is formed by printing a metal paste on a green sheet of a
material of the ceramic substrate and sintering it so as to
integrate it into the ceramic substrate when the green sheet is
sintered.
4. The electronic device according to claim 1, wherein the metallic
thin film is tungsten.
5. The electronic device according to claim 1, wherein the metallic
thin film has a thickness in a range of 10 to 50 .mu.m.
6. The electronic device according to claim 1, wherein the metallic
thin film has a width in a range of 1.0 to 2.5 mm.
7. The electronic device according to claim 1, wherein the
thermosetting resin is epoxy resin.
8. The electronic device according to claim 1, wherein the
thermosetting resin is coated to have a thickness in a range of
0.35 to 0.6 mm.
9. The electronic device according to claim 1, wherein the ceramic
substrate has a thickness in a range of 0.1 to 0.5 mm.
10. An electronic device obtained by dividing the electronic device
according to claim 1 into individual electronic devices by
dicing.
11. A method of manufacturing an electronic device, comprising
mounting plural sets of electronic components on a ceramic
substrate and sealing and molding the electronic components with
thermosetting resin by transfer molding, wherein the ceramic
substrate is provided with a metallic thin film integrated into at
least one selected from an upper surface and a lower surface of the
ceramic substrate in its peripheral portion, the ceramic substrate
is placed so as to extend both inside and outside a cavity of a
mold for transfer molding, and the metallic thin film is positioned
on a portion with which an upper mold and a lower mold of the mold
come into contact; and the thermosetting resin for transfer molding
is injected into the cavity, is molded, and is cured by
heating.
12. The method of manufacturing an electronic device according to
claim 11, wherein the metallic thin film is present on each of the
upper surface and the lower surface of the ceramic substrate.
13. The method of manufacturing an electronic device according to
claim 11, wherein the metallic thin film is formed by printing a
metal paste on a green sheet of a material of the ceramic substrate
and sintering it so as to integrate it into the ceramic substrate
when the green sheet is sintered.
14. The method of manufacturing an electronic device according to
claim 11, wherein the metallic thin film is tungsten.
15. The method of manufacturing an electronic device according to
claim 11, wherein the metallic thin film has a thickness in a range
of 10 to 50 .mu.m and a width in a range of 1.0 to 2.5 mm.
16. The method of manufacturing an electronic device according to
claim 11, wherein the thermosetting resin is epoxy resin.
17. The method of manufacturing an electronic device according to
claim 11, wherein conditions in molding the electronic components
include a temperature in a range between 140 and 190.degree. C. a
molding pressure of 10 to 50 kg/cm.sup.2, and a curing time of 60
to 100 sec.
18. The method of manufacturing an electronic device according to
claim 11, wherein a slide member is further provided in a portion,
where the ceramic substrate is placed, of at least one of the upper
mold and the lower mold, and the slide member is positioned so as
to press the ceramic substrate in its thickness direction.
19. The method of manufacturing an electronic device according to
claim 11, wherein a resin film is allowed to adhere to a surface
for molding the resin of at least one of the upper mold and the
lower mold.
20. The method of manufacturing an electronic device according to
claim 11, wherein the metallic thin film is formed integrally at
the same time an electrode on at least one surface of the ceramic
substrate is sintered.
21. The method of manufacturing an electronic device according to
claim 11, wherein pressure applied to at least one of the upper
mold and the lower mold is varied corresponding to pressure for
injecting the thermosetting resin for transfer molding.
22. The method of manufacturing an electronic device according to
claim 21, wherein the pressure applied to at least one of the upper
mold and the lower mold is controlled in two stages.
23. The method of manufacturing an electronic device according to
claim 22, wherein at least one of the two stages is used when the
resin for transfer molding is injected into the cavity, and the
other of the two stages is used after injection of the resin for
transfer molding is completed.
24. A method of manufacturing an electronic device, wherein a
master electronic device obtained by the method according to claim
11 is divided into individual electronic devices by dicing.
25. An apparatus for manufacturing an electronic device,
comprising: a plunger for pressurizing thermosetting resin for
transfer molding; a runner in which the thermosetting resin for
transfer molding flows; a cavity into which the thermosetting resin
for transfer molding flows, which communicates with the runner; and
a mold for transfer molding including an upper mold and a lower
mold that define the cavity, wherein a ceramic substrate provided
with a metallic thin film integrated into at least one selected
from an upper surface and a lower surface of the ceramic substrate
in its peripheral portion is placed so as to extend both inside and
outside the cavity of the mold for transfer molding, and the
metallic thin film is positioned in a portion with which the upper
mold and the lower mold of the mold come into contact; and the
thermosetting resin for transfer molding is injected into the
cavity, is molded, and is cured by heating.
26. The apparatus for manufacturing an electronic device according
to claim 25, wherein the apparatus further comprises a member for
varying pressure to be applied, the member varies pressure applied
between the upper mold and the lower mold, and the member for
varying pressure to be applied is operated corresponding to
pressurization by the plunger.
Description
FIELD OF THE INVENTION
[0001] 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
[0002] FIGS. 9A to 9C 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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 9C later. In other words, as shown in FIG. 10A,
m.times.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.
[0010] 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.
[0011] 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.degree.
C., which is low. Therefore, when solder reflow is carried out at
230.degree. 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.
[0012] 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 d1 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.
[0013] 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 d1 in thickness of about 5 to 15 .mu.m occurs in the
resin that has been cured.
[0014] 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.
[0015] 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 d2 in thickness of the resin
between the vicinity of the center and the peripheral portion of
the ceramic substrate reaches about 0.1 mm.
[0016] 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 d1 and d2 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.
[0017] 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
[0018] 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.
[0019] 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 with a metallic
thin film integrated into at least one selected from an upper
surface and a lower surface of the ceramic substrate at its
peripheral portion.
[0020] As the metallic thin film, upper electrodes provided on the
ceramic substrate also can be used. That is to say, the metallic
thin film includes one utilizing electrodes.
[0021] A method of manufacturing an electronic device according to
the present invention includes: mounting plural sets of electronic
components on a ceramic substrate; and sealing the electronic
components with thermosetting resin by transfer molding. In the
method, the ceramic substrate provided with a metallic thin film
integrated into at least one selected from an upper surface and a
lower surface of the ceramic substrate in its peripheral portion is
placed so as to extend both inside and outside a cavity of a mold
for transfer molding and the metallic thin film is positioned in a
portion with which an upper mold and a lower mold of the mold come
into contact, and the thermosetting resin for transfer molding is
injected into the cavity, is molded, and then is cured by
heating.
[0022] An apparatus for manufacturing an electronic device
according to the present invention includes: a plunger for
pressurizing thermosetting resin for transfer molding; a runner in
which the thermosetting resin for transfer molding flows; a cavity
into which the thermosetting resin for transfer molding flows,
which communicates with the runner; and a mold for transfer molding
including an upper mold and a lower mold that define the cavity. In
the apparatus, a ceramic substrate provided with a metallic thin
film integrated into at least one selected from an upper surface
and a lower surface of the ceramic substrate in its peripheral
portion is placed so as to extend both inside and outside the
cavity of the mold for transfer molding, and the metallic thin film
is positioned in a portion with which the upper mold and the lower
mold of the mold come into contact, and the thermosetting resin for
transfer molding is injected into the cavity, is molded, and then
is cured by heating.
[0023] According to the present invention, the ceramic substrate
provided with the metallic thin film integrated into at least one
selected from the upper surface and the lower surface of the
ceramic substrate in its peripheral portion is placed so as to
extend both inside and outside the cavity of the mold for transfer
molding, and the metallic thin film is positioned in a portion with
which the upper mold and the lower mold of the mold come into
contact. Therefore, even when the ceramic substrate is sandwiched
and compressed between the upper and lower molds, the pressure
applied to the ceramic substrate is buffered. Thus, no distortion
force is caused and the occurrence of cracks or breakage in the
ceramic substrate can be prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a sectional side view of an electronic device
according to a first embodiment of the present invention.
[0025] FIG. 2A is a plan view of an electronic device on which a
plurality of electronic elements are mounted, according to a second
embodiment of the present invention, FIG. 2B is its sectional side
view, and FIG. 2C is its bottom view.
[0026] FIG. 3A is a plan view of a master electronic device in
which a plurality of electronic devices according to the first and
second embodiments of the present invention are formed, and FIG. 3B
is its sectional side view.
[0027] FIG. 4 is a sectional view showing a manufacturing method
using a mold for transfer molding according to a third embodiment
of the present invention.
[0028] FIG. 5 is a schematic sectional view of a mold for transfer
molding using a resin film, which shows a further example according
to the third embodiment of the present invention.
[0029] FIG. 6 is a schematic sectional view of a mold for transfer
molding having a slide member in a lower mold, which shows another
example according to the third embodiment of the present
invention.
[0030] FIG. 7A shows a fourth embodiment of the present invention
and is a view illustrating a state in which an upper mold and a
lower mold of a mold for transfer molding are positioned apart, and
FIG. 7B is a view illustrating a state in which the upper mold and
the lower mold of the mold for transfer molding are in contact and
a pressure is applied to electronic devices.
[0031] FIG. 8 is a graph showing the relationship between time and
molding pressure in transfer molding carried out according to the
fourth embodiment of the present invention.
[0032] FIG. 9 shows a conventional electronic device; FIG. 9A is
its plan view, FIG. 9B is its sectional side view, and FIG. 9C is
its bottom view.
[0033] FIG. 10 shows a conventional master electronic device in
which a plurality of electronic devices are formed; FIG. 10A is its
plan view, and FIG. 10B is its sectional side view.
DETAILED DESCRIPTION OF THE INVENTION
[0034] In the electronic device of the present invention, it is
preferable that the metallic thin film is present on each of the
upper surface and the lower surface of the ceramic substrate, since
the pressure applied by both the upper and lower molds of the mold
can be buffered.
[0035] In the electronic device of the present invention, it is
preferable that the metallic thin film is formed by printing a
metal paste on a green sheet of a material of the ceramic substrate
and sintering it so as to integrate it into the ceramic substrate
when the green sheet is sintered, since cost reduction can be
achieved. In terms of cost, it is preferable that the same material
as that of the electrodes formed on the upper surface and/or the
lower surface of the ceramic substrate is used as the metal paste
and the metallic thin film is formed in the same step as that for
forming the electrodes. For the metallic thin film, for instance,
tungsten can be used.
[0036] It is preferable that the metallic thin film has a thickness
in a range of 10 to 50 .mu.m. In the case where the thickness is in
this range, the pressure applied by the mold can be buffered. It is
preferable that the metallic thin film has a width in a range of
1.0 to 2.5 mm. In the case where the width is in this range, when
the upper and lower molds are set, their peripheries can be brought
into contact with the metallic thin film accurately.
[0037] As the thermosetting resin, resins well known in the art can
be used. For instance, epoxy resin can be used. The epoxy resin is
obtained by using well-known bisphenol A or cresol-novolac glycidyl
ether resin as a base, mixing an aromatic amine hardener or an acid
anhydride hardener and a filler thereto, and allowing it to react
to some degree to provide suitable moldability. As the filler, a
filler such as silica powder, talc powder, or the like of about 85
wt. % can be added.
[0038] The coating thickness of the thermosetting resin varies
depending on a standard of a product, but is in a range of 0.35 to
0.6 mm as one example.
[0039] The thickness of the ceramic substrate varies depending on a
standard of a product, but is in a range of 0.1 to 0.5 mm as one
example.
[0040] The master electronic device obtained according to the
present invention is divided into individual electronic devices by
dicing.
[0041] In the method of the present invention, it is preferable
that conditions in the transfer molding include a temperature in a
range between 140 and 190.degree. C., a molding pressure of 10 to
50 kg/cm.sup.2, and a curing time of 60 to 100 sec.
[0042] It is preferable that a slide member is further provided in
a portion, where the ceramic substrate is placed, of at least one
of the upper mold and the lower mold, and the slide member is
positioned so as to press the ceramic substrate in its thickness
direction.
[0043] Further, it is preferred to allow a resin film to adhere to
a surface for molding resin of at least one of the upper mold and
the lower mold, since a buffer effect on the ceramic substrate
further increases.
[0044] An electronic device according to an example of the present
invention includes: an electronic element provided with at lest two
electrodes; a ceramic substrate; a first electrode that is provided
on one surface of the ceramic substrate and is electrically
connected to one of the electrodes of the electronic element; a
second electrode electrically connected to the other electrode of
the electronic element; a metal wire for connecting the second
electrode and the other electrode of the electronic element; a
third electrode and a fourth electrode that are provided on the
other surface of the ceramic substrate and are electrically
connected to the first and second electrodes, respectively; a
plurality of conductive relay members that are formed between the
one surface and the other surface of the ceramic substrate and
electrically connect the first electrode to the third electrode and
the second electrode to the fourth electrode; and coating resin for
coating the electronic element. The electronic device is coated and
sealed with the coating resin of thermosetting resin for transfer
molding except for the other surface of the ceramic substrate.
According to this configuration, the surface coated with the resin
can be improved in flatness and in glass transition point compared
to the case of using liquid resin. Consequently, the resin that has
been cured is not resoftened at high temperatures in solder reflow,
thus solving the problems of peeling off of the resin from the
ceramic substrate, deformation of a resin package due to an
external force, or the like by increasing the density of the
resin.
[0045] An electronic device according to another example of the
present invention includes: an electronic element provided with at
least two electrodes; a circuit unit including a plurality of the
electronic elements; a ceramic substrate; a first electrode that is
provided on one surface of the ceramic substrate and is connected
to a predetermined electrode of the circuit unit; a second
electrode connected to another predetermined electrode of the
circuit unit; a metal wire for connecting the second electrode and
the another predetermined electrode of the circuit unit; a third
electrode and a fourth electrode that are provided on the other
surface of the ceramic substrate and are connected to the first and
the second electrodes, respectively; a plurality of conductive
relay members that are formed between the one surface and the other
surface of the ceramic substrate and connect the first electrode to
the third electrode and the second electrode to the fourth
electrode; and coating resin for coating the circuit unit. The
electronic device is coated with the coating resin of thermosetting
resin for transfer molding except for the other surface of the
ceramic substrate. According to this example, the same effect as
that mentioned above can be obtained.
[0046] An electronic device according to still another example of
the present invention is obtained by: positioning circuit units
including at least one or a plurality of the electronic elements,
on one common ceramic substrate in a matrix form; coating the
electronic elements or the circuit units with coating resin, and
dividing it throughout from the coating resin to the ceramic
substrate so that the electronic elements or the circuit units are
separated from one another to have a substantially rectangular
solid shape. According to this example, the resin surface can be
fixed to a fixing tape securely in dicing and therefore individual
electronic devices do not come off from the fixing tape to be
lost.
[0047] Furthermore, in an electronic device of still another
example according to the present invention, an electronic element
having at least two electrodes is positioned on one surface of a
ceramic substrate, a first electrode to be electrically connected
to one of the two electrodes of the electronic element and a second
electrode to be electrically connected to the other of the two
electrodes of the electronic element are formed on the one surface
of the ceramic substrate, the other of the two electrodes of the
electronic element and the second electrode are connected with a
metal wire, a third electrode and a fourth electrode to be
electrically connected to the first and second electrodes
respectively are formed on the other surface of the ceramic
substrate, conductive relay members for electrically connecting the
first electrode to the third electrode and the second electrode to
the fourth electrode are formed between the one surface and the
other surface of the ceramic substrate, at least a part of the
peripheral portion of the ceramic substrate is positioned so as to
extend both inside and outside a cavity of a mold for transfer
molding, and resin for transfer molding is injected into the
cavity. According to this example, resin packages of a plurality of
electronic devices are formed uniformly on the ceramic substrate.
In addition, the unevenness in thickness of the resin among the
plurality of electronic devices formed on the ceramic substrate
also is reduced. Therefore, after the molding, not only the
after-processing such as grinding of the surface of the resin using
a grinder or the like is no longer necessary but also the surface
of the resin is allowed to adhere to a fixing tape easily, thus
solving the problem that the electronic devices come off from the
fixing tape and are lost in a dicing process. Furthermore, since
this example enables the thickness of the resin to be uniform,
electronic devices can be formed not only in the vicinity of the
center of the ceramic substrate but also in the vicinity of the
periphery of the ceramic substrate, thus increasing the number of
electronic devices that can be formed on the ceramic substrate.
[0048] In an electronic device of yet another example according to
the present invention, a ceramic substrate is positioned so as to
extend both inside and outside a cavity of a mold for transfer
molding, and a metallic thin film is present in a gap between the
mold for transfer molding and at least a part, which is positioned
outside the cavity, of the periphery of the ceramic substrate.
According to this example, the metallic thin film serves as a
buffer and thus the ceramic substrate is not damaged.
[0049] In another example of the present invention, a mold for
transfer molding is formed of an upper mold and a lower mold, and a
part, where the ceramic substrate is placed, of at least one of the
upper and lower molds has a slide member that slides in a direction
of pressing the ceramic substrate in its thickness direction.
According to this example, slight tilt or distortion of the upper
and lower molds heated to a high temperature can be compensated and
the pressure applied to the ceramic substrate can be adjusted to be
uniform, thus preventing cracks or breakage from occurring in the
ceramic substrate.
[0050] According to still another example of the present invention,
a resin film is allowed to adhere to a surface for molding resin of
at least one of an upper mold and a lower mold. Preferably, this
resin film is fluororesin and has a thickness of at least 50 .mu.m.
According to this example, a buffer effect of the resin film
relieves a stress applied to the ceramic substrate in clamping by
the mold, thus preventing cracks or breakage in the ceramic
substrate. Further, the pressure for supplying resin into the mold
can prevent thermosetting resin for transfer molding from entering
under the ceramic substrate. In addition, the film is allowed to
adhere to an inner face of a cavity, thus preventing the resin from
sticking to the mold. This example can ensure the thickness that
enables the pressure applied to the ceramic substrate to be
buffered sufficiently. Therefore, the resin can be injected without
breaking a portion of a film deformed and compressed by the mold
pressure, the pressure for injecting the resin, or the like. In
addition, the resin can be prevented from sticking to the mold. In
order to spread the film inside the mold to cover the inner face of
the cavity and to allow the film to adhere thereto and in order to
relieve the stress applied to the ceramic substrate, it is possible
to allow the film to have flexibility.
[0051] Another example of the present invention is directed to a
method of manufacturing an electronic device in which a metallic
thin film is formed at the same time at least one of an electrode
formed on one side of a ceramic substrate and an electrode formed
on the other side is formed. According to this configuration, the
metallic thin film is preformed on the ceramic substrate at the
same time at least any one of the first to fourth electrodes is
formed. Therefore, a step for preparing the metallic thin film can
be omitted.
[0052] Moreover, another example of the present invention is
directed to an apparatus for manufacturing an electronic device
that includes a ceramic substrate provided with electrodes,
electronic elements, and metal wires and is formed by placing the
ceramic substrate so as to extend both inside and outside a cavity
of a mold for transfer molding and injecting resin for transfer
molding into the cavity. In the apparatus, the mold for transfer
molding is formed of an upper mold and a lower mold, and the
pressure applied to at least one of the upper mold and the lower
mold is allowed to vary corresponding to the pressure for injecting
the resin for transfer molding. According to this example, the
pressure applied between the upper mold and the lower mold is set
to be slightly higher than the pressure for injecting the resin
when the injection pressure is low and is set to enable the mold to
resist the pressure for injecting the resin when the injection
pressure is relatively high. Therefore, the state in which high
pressure is applied to the ceramic substrate constantly can be
relieved, thus preventing the ceramic substrate from breaking.
[0053] In another example of the present invention, pressure
applied to at least one of an upper mold and a lower mold can be
controlled in two stages. According to this example, it is possible
to cope with two steps during and after resin injection. During the
resin injection, a relatively low pressure is required for
injecting the resin, and after the resin injection, a relatively
high pressure is required to be applied to the resin.
[0054] Further, in another example of the present invention, at
least one of the two stages of the pressure to be applied is
employed in injecting resin for transfer molding into a cavity and
the other is employed after the injection of the resin for transfer
molding. According to this example, it is possible to cope with two
steps: during the injection (filling) of the resin for transfer
molding requiring relatively low pressure for injecting the resin;
and after the resin injection requiring relatively high pressure
applied to the resin to eliminate bubbles inside the cavity.
[0055] The present invention is described with reference to the
drawings as follows.
[0056] First Embodiment
[0057] FIG. 1 shows a schematic configuration of an electronic
device according to a first embodiment of the present invention,
which is obtained by cutting a master electronic device shown in
FIGS. 3A and 3B by dicing. Specifically, FIG. 1 shows a sectional
side view of a three-terminal leadless small surface mount
transistor provided with three electrodes including a collector
electrode, a base electrode, and an emitter electrode.
[0058] As shown in the figure, an electronic device 1 according to
the first embodiment of the present invention includes a ceramic
substrate 32, upper electrodes 11 to 13, lower electrodes 21 to 24,
via holes 17 to 20 provided in the ceramic substrate 32, and metal
wires 15 and 16.
[0059] The thickness t of the ceramic substrate 32 was set to be
0.15 to 0.20 mm. The via holes 17 to 20 having a diameter of
approximately 0.10 mm were provided in predetermined places of the
ceramic substrate 32. Inside the via holes 17 to 20, for instance,
a conductive paste was injected to form conductors. The conductors
formed inside these via holes serve as conductive relay members for
electrically connecting the upper electrodes 11 to 13 and the lower
electrodes 21 to 24.
[0060] The first to third upper electrodes 11 to 13 and the lower
electrodes 21 to 24 on the ceramic substrate 32 were
gold-plated.
[0061] The collector electrode of the transistor 14 was die-bonded
directly to the first upper electrode 11. The second upper
electrode 12 and the third upper electrode 13, which were
positioned so as to be separated from the first upper electrode 11,
were electrically connected to the base electrode and the emitter
electrode of the transistor 14 with the first metal wire 15 and the
second metal wire 16, respectively.
[0062] Then, the transistor 14, the first metal wire 15, and the
second metal wire 16 were coated with thermosetting resin 25 (for
instance, epoxy resin using bisphenol A or cresol-novolac glycidyl
ether resin as a base) for transfer molding that generally had been
used conventionally. A coating method is described in detail in a
third embodiment later. The coating thickness of the resin for
transfer molding was set to be 0.35 to 0.39 mm. The electronic
device 1 divided by dicing had a dimension of 1 mm
(length).times.0.8 mm (width).times.0.6 mm (height).
[0063] In the above-mentioned embodiment, a transistor with three
electrodes was illustrated. However, the present embodiment is not
limited to this. Any electronic devices are acceptable as long as
they are provided with at least two electrodes such as, for
example, a diode, a resistor, or the like. In this case, an
electronic device can have a configuration using smaller numbers of
the upper electrodes 11 to 13, the lower electrodes 21 to 24, the
via holes 17 to 20, and the metal wires 15 and 16.
[0064] Second Embodiment
[0065] FIGS. 2A, 2B, and 2C show a surface view, a sectional side
view, and a bottom view of a six-terminal small surface mount
electronic device in which electronic elements including two
transistors 14b and 14c are mounted in one package. The electronic
device is obtained by cutting a master electronic device shown in
FIGS. 3A and 3B by dicing.
[0066] As in the first embodiment, the thickness t of a ceramic
substrate 32 is selected to be in a range of 0.15 to 0.2 mm. In the
ceramic substrate 32, six via holes 17a, 17b, 19a, 19b, 20a, and
20b having a diameter of approximately 0.1 mm are formed. Inside
these via holes, for instance, a conductive paste is injected to
form conductors.
[0067] On the ceramic substrate 32, first to sixth upper electrodes
11a, 11b, 12a, 12b, 13a and 13b, and lower electrodes 22a, 22b,
23a, 23b, 24a and 24b are formed by gold plating.
[0068] To the first upper electrode 11a, a collector electrode of
the transistor 14b is die-bonded. To the second upper electrode 11b
positioned so as to be separated from the first upper electrode
11a, a collector electrode of the transistor 14c is die-bonded. The
third upper electrodes 12a and 12b, which are positioned between
the first upper electrode 11a and the second upper electrode 11b,
are electrically connected to, for example, emitter electrodes of
the transistors 14b and 14c with metal wires 16a and 15b,
respectively.
[0069] The fifth upper electrode 13a positioned so as to be
separated from the first upper electrode 11a is electrically
connected to, for example, a base electrode of the transistor 14b
with a metal wire 16a. The sixth upper electrode 13b positioned so
as to be separated from the second upper electrode 11b is
electrically connected to, for example, a base electrode of the
transistor 14c with a metal wire 16b.
[0070] The upper electrodes 11a, 11b, 12a, 12b, 13a, and 13b on an
upper surface 321 of the ceramic substrate 32 are electrically
connected to the lower electrodes 22a, 22b, 24a, 24b, 23a, and 23b
on a lower surface 322 of the ceramic substrate 32 via the via
holes 17a, 17b, 19a, 19b, 20a, and 20b, respectively. The lower
electrodes are gold-plated.
[0071] The via holes 17a, 17b, and the like are conductive relay
members for electrically connecting the upper electrodes and the
lower electrodes formed on one surface and the other surface of the
ceramic substrate.
[0072] The upper surface of the ceramic substrate 32, the first to
sixth upper electrodes 11a, 11b, 12a, 12b, 13a, and 13b, the
transistors 14b and 14c, and the metal wires 15a, 15b, 16a, and 16b
were coated with thermosetting resin 25 for transfer molding.
[0073] The second embodiment was directed to a configuration with
six terminals in which two transistors provided with three
electrodes can be connected separately, but is not limited to this.
For example, an integrated circuit unit such as a comparator, an
operational amplifier, or the like is allowed to be built in and
its predetermined electrodes such as an input terminal, an output
terminal, a power terminal, or the like may be connected.
[0074] FIGS. 3A and 3B show a so-called master electronic device
obtained before individual electronic devices of the present
invention are formed. In this master electronic device, on one
common ceramic substrate 32 on which wires and electrodes already
have been formed, for example, m.times.n pieces of integrated
circuit units shown in FIG. 1 or FIG. 2, or those not shown in the
figures are arranged in a matrix form. This master electronic
device is coated and sealed with the resin 25 for transfer molding.
The master electronic device sealed with the resin is cut along
cutting plane lines 33, thus forming individual electronic devices
1. In a portion at the periphery of the ceramic substrate 32, a
metallic thin film 2 is formed, which is described later.
[0075] Third Embodiment
[0076] The following description is directed to an example of the
method for manufacturing an electronic device of the present
invention. Particularly, the present invention relates to a
manufacturing method until the master electronic device shown in
FIGS. 3A and 3B is completed.
[0077] As shown in FIG. 4, a ceramic substrate 32 is sandwiched
between an upper mold 30 and a lower mold 31 of a mold for transfer
molding. On the ceramic substrate 32, upper electrodes 11 to 13 and
lower electrodes 21 to 24 already have been formed. In addition,
predetermined electrodes of a transistor 14 and the upper
electrodes already have been connected electrically through wires
15 and 16.
[0078] Furthermore, via holes for electrically connecting the upper
electrodes 11 to 13 and the lower electrodes 21 to 24 also have
been formed, which are not shown in FIG. 4.
[0079] The ceramic substrate 32 is positioned so as to extend both
inside and outside a cavity 38 provided on the upper mold 30 side.
In other words, the peripheral portion of the ceramic substrate 32
is allowed to extend outwards from the cavity and the portion
extended outwards is positioned so as to come into contact with
both the upper mold 30 and the lower mold 31.
[0080] In the portion that comes into contact with the upper and
lower molds 30 and 31, a metallic thin film 2 was formed. The
metallic thin film 2 functions as a buffer when the ceramic
substrate 32 is sandwiched and compressed between the upper and
lower molds 30 and 31.
[0081] As shown in FIG. 3A, the metallic thin film 2 was formed in
the peripheral portion of the ceramic substrate 32 by being
sintered at the same time the upper electrodes and the lower
electrodes were printed to be formed with a conductive paste
material. The material of the metallic thin film was tungsten and
its thickness and width were set to be 20 .mu.m and 1.0 mm.
[0082] The metallic thin film 2 functioning as a buffer may be
formed only on one of the upper surface and the lower surface of
the ceramic substrate 32. As the metallic thin film2, the upper
electrodes 11 to 13 also can be used. That is to say, the metallic
thin film includes one utilizing electrodes. There is a difference
in thickness among the upper electrodes 11 to 13, but the
difference in thickness is approximately equivalent to an air vent
used in the mold. Therefore, the thicknesses of the electrodes
provide the same function as that of the air vent, thus enabling
molding. The region indicated by a broken-line circle in FIG. 4
indicates the electronic device 1 shown in FIG. 1.
[0083] As described above, the upper mold 30 and the lower mold 31
were allowed to maintain the ceramic substrate 32 in parallel
thereto, and the ceramic substrate 32 was pressurized with a
predetermined pressure. After that, molten thermosetting resin 25
for transfer molding was allowed to flow into the cavity 38 via a
runner 35 by a plunger 36. Thus, the ceramic substrate 32 was
coated with the resin 25 for transfer molding (FIG. 5).
[0084] The transfer molding was carried out at a temperature of
175.degree. C. with a molding pressure of 15 kg/cm.sup.2 for a
curing time of 90 sec.
[0085] FIG. 5 shows another example of the present invention in
which a resin film 34 is allowed to adhere to an inner face of the
lower mold 31 of the mold for transfer molding.
[0086] In FIG. 5, the resin film 34 is allowed to adhere uniformly
to the upper face of the lower mold 31 by, for example, an
evacuation method. As this resin film, a polytetrafluoroethylene
resin film having a thickness of about 100 .mu.m was used. However,
when the film has a thickness of at least 50 .mu.m, a sufficient
buffer effect can be obtained.
[0087] In FIG. 5, the resin film 34 was allowed to adhere to the
inner face of the lower mold 31, but the mold to which the resin
film 34 adheres is not limited to the lower mold. The resin film 34
may be allowed to adhere to the upper mold or to the entire inner
surfaces of the upper and lower molds. When a film of fluororesin
such as, for example, polytetrafluoroethylene or the like is
employed as the resin film 34, it is effective in terms of
flexibility and heat resistance.
[0088] In the present embodiment, a three terminal transistor was
used. However, the present embodiment also can be applied to
electronic devices other than that with three terminals.
[0089] FIG. 6 shows another example of the present invention in
which a slide member is provided in the lower mold 31 of the mold
for transfer molding.
[0090] In FIG. 6, a slide member 311 capable of pressing the
ceramic substrate 32 in its thickness direction is provided at
least in a portion, where the ceramic substrate 32 is placed, of
the lower mold 31 receiving the ceramic substrate 32. This slide
member 311 is supported by the lower mold 31 via, for example, a
coiled spring 37 in a predetermined space 312 provided in the lower
mold 31.
[0091] The slide member 311 is operated so that pressure is applied
to the ceramic substrate 32 in its thickness direction. In this
case, the slide member 311 was provided on the lower mold 31 side.
However, the slide member 311 may be provided on the upper mold
side.
[0092] Fourth Embodiment
[0093] FIGS. 7A and 7B show a manufacturing apparatus with a mold
for transfer molding according to the present invention. The
present embodiment is different from the third embodiment in that
the pressure applied between an upper mold 30 and a lower mold 31
varies corresponding to pressure for injecting resin for transfer
molding, i.e. the motion of a plunger 36 shown in FIGS. 5 and
6.
[0094] The upper mold 30 and the lower mold 31 are supported by a
stopper 42 for stroke adjustment and columns 43. On the upper mold
30 side, a runner 35 used in injecting thermosetting resin 25 for
transfer molding into a cavity 38, the plunger 36 for delivering
the thermosetting resin 25 into the cavity 38, and a plunger pot 40
for storing the thermosetting resin 25 are provided. In addition, a
servo motor 41 is provided on the upper mold 30 side.
[0095] The servo motor 41, which is not shown in detail in the
figures, is equipped so as to operate at least one of the upper
mold 30 and the lower mold 31 corresponding to the motion of the
plunger 36.
[0096] The thermosetting resin 25 for transfer molding melted
inside the plunger pot 40 flows through the runner 35 by the
plunger 36, thus filling the cavity 38. Inside the cavity 38,
electronic devices 1 to be sealed with the thermosetting resin 25
have been placed in advance.
[0097] In FIG. 7A, details of the electronic devices 1 are not
shown. However, before being coated with the thermosetting resin
25, the electronic devices 1 are in a state similar to that shown
in FIG. 4 used for explaining the third embodiment. After being
coated with the thermosetting resin 25, the electronic devices 1
are in approximately the same state as that shown in FIG. 3 used
for explaining the third embodiment.
[0098] The peripheral portion of the electronic devices 1 is
positioned so as to extend outwards from the ends of the cavity 38
for L1 and L2. In other words, the electronic devices 1 are
positioned so as to extend both inside and outside the cavity 38.
The peripheral portion of the electronic devices 1 extending for L1
and L2 comes into contact with both the upper mold 30 and the lower
mold 31 and are sandwiched between them. Therefore, when for
example, the ceramic substrate of the electronic devices 1 is
sandwiched between the upper and lower molds 30 and 31, the
peripheral portion of the electronic devices 1 are subjected to
pressure (indicated by an arrow X in FIG. 7B) from both the molds
30 and 31. When this pressure exceeds the critical pressure for the
ceramic substrate of the electronic devices 1, the electronic
devices 1 are deformed or broken.
[0099] Generally, the inlet velocity of the resin varies depending
on a resin material, a volume of the cavity, or the like. However,
once the resin material and the volume of the cavity are
determined, an approximately constant inlet velocity of the resin
can be obtained. Thus, the time required for the transfer molding
step can be determined.
[0100] FIG. 8 shows a molding pattern in a transfer molding method
of the present invention. The horizontal axis indicates time and
the vertical axis indicates pressure. A solid line S1 indicates
pressure when the plunger 36 delivers the thermosetting resin 25
into the cavity 38. A broken line S2 indicates pressure applied
between the upper mold 30 and the lower mold 31. In order to carry
out the transfer molding normally, the pressure indicated by the
broken line S2 applied between the molds 30 and 31 is set and
maintained so as to be higher than the delivery pressure of the
plunger 36, which is indicated by the solid line S1, constantly,
i.e. so as to have the relationship of S2>S1.
[0101] The solid line S1 shows that injection of the thermosetting
resin 25 for transfer molding is started at the time T1, the
filling of the resin is completed and simultaneously the
pressurization of the resin is started at the time T2, and
pressurization packing is completed at the time T3. The time
(T2-T1) for filling the resin is a few seconds, and the pressure P1
when the filling is completed is a few kilogram-weight.
Furthermore, immediately after the completion of the injection
(filling) of the resin (T2), in order to remove bubbles inside the
cavity 38, a further pressure of a few hundreds kilogram-weight is
applied to pressurize the resin (to carry out the pressurization
packing). The time (T3-T2) for the pressurization packing for
removing bubbles is set to be one second or shorter.
[0102] The time (T3-T2) for pressurizing the resin is set to be one
second or shorter and the pressure P3 when the pressurization
packing of the resin is completed is 150 to 300
kilogram-weight.
[0103] On the other hand, as shown with the broken line S2, a
slightly higher pressure P2 than the pressure P1 for injecting the
resin is applied between the upper mold 30 and the lower mold 31 at
a time (T0) prior to the time T1 when the injection of the resin is
started and is set so that the molds 30 and 31 can resist the
pressure P1. The pressure for injecting the resin corresponds to
the delivery pressure of the plunger 36. In addition, a slightly
higher pressure P4 than the pressure P3 required for pressurizing
the resin is applied between the upper mold 30 and the lower mold
31 at the same time the pressurization of the resin is started
(T2).
[0104] In this case, the pressure P4 is 200 to 400 kilogram-weight
and is set to maintain the relationship of P4>P3, thus excluding
the state in which excessive pressure is applied between the molds
30 and 31 constantly. In other words, conventionally, the pressure
applied between the upper and lower molds 30 and 31 must be fixed
to the highest pressure P4 constantly. In the present invention,
however, the pressure can be varied corresponding to the pressure
for injecting the resin for transfer molding, i.e. the delivery
pressure of the plunger 36. That is to say, the pressure applied
between the upper and lower molds 30 and 31 is controlled in the
two stages of P2 and P4. Of course, the control in three stages or
more also is possible.
[0105] By such control and change of the pressures, excessive
pressure applied to the ceramic substrate sandwiched between the
molds 30 and 31 can be reduced, thus preventing the ceramic
substrate from being deformed or broken.
[0106] The variability of the pressure applied between the upper
mold 30 and the lower mold 31 is controlled by a member for varying
pressure to be applied. A main component of the member for varying
pressure to be applied is a servo motor 41. This servo motor 41
operates the lower mold 31 together with a lower plate 44 to which
the lower mold 31 is attached, vertically as shown by the arrow A
and operates so that the peripheral portion of the electronic
devices 1 comes into contact with the upper mold 31. Numeral 45
indicates a plate guide for guiding a lower plate 44, and numeral
46 a base for supporting the upper mold 30 and the lower mold
31.
[0107] The time (T2-T1) for filling the resin is allowed to be
approximately constant as described above. Therefore, by measuring
this time and setting, for example, a timer or the like, the servo
motor 41 is controlled and the pressure applied between the molds
30 and 31 for transfer molding can be varied in two stages from the
primary pressure (P2) in filling the resin to the secondary
pressure (P4) in pressurization packing.
[0108] In other words, since the pressure applied between the molds
30 and 31 is allowed to correspond to the pressure for injecting
the resin for transfer molding or the motion of the plunger 36, it
is not always necessary to detect the pressure for injecting the
resin or the motion directly. Thus, the manufacturing apparatus can
be simplified by controlling the servo motor 41 using a timer as
described above.
[0109] In the fourth embodiment of the present invention, as
described in the third embodiment and as shown in FIG. 4, a
metallic thin film 2 may be provided in a portion with which the
upper mold 30 and the lower mold 31 come into contact, thus
providing a function of a buffer. In addition, as shown in FIG. 5,
a resin film 34 may be allowed to adhere to a surface for molding
the resin of at least one of the upper mold 30 and the lower mold
31. Moreover, as shown in FIG. 6, a slide member 311 may be
employed. Of course, they may be combined.
[0110] In the present embodiment, the explanation was given using a
three terminal transistor. However, the present embodiment also can
be applied to electronic devices other than that having three
terminals.
[0111] As described above, according to the present invention, the
ceramic substrate provided with the metallic thin film integrated
into at least one selected from the upper surface and the lower
surface of the ceramic substrate in its peripheral portion is
placed so as to extend both inside and outside the cavity of the
mold for transfer molding and the metallic thin film is positioned
in a portion with which the upper mold and the lower mold of the
mold come into contact. Therefore, even when the ceramic substrate
is sandwiched and compressed between the upper and lower molds, the
pressure applied to the ceramic substrate is buffered.
Consequently, no distortion force is caused, thus avoiding cracks
or breakage in the ceramic substrate.
[0112] According to an electronic device of the present invention,
the adhesion between a ceramic substrate and resin in reflow in
mounting a printed circuit board is improved and the strength of
the resin also increases. Furthermore, the use of a ceramic
substrate with a thickness of 0.2 mm or less enables via holes with
a diameter of 0.1 mm to be formed, thus reducing the weight of the
electronic device. Moreover, a suitable design of the configuration
of the mold for transfer molding enables the electronic device to
be coated with thermosetting resin for transfer molding.
[0113] Further, according to the method of manufacturing an
electronic device of the present invention, even when the ceramic
substrate has a thickness of 0.2 mm or less, resin molding by a
transfer molding method is possible and the molding formation can
be carried out within a certain curing time. Consequently, there is
no difficulty in handling the resin, it is not necessary to take
measures for eliminating floating dusts until the resin is cured,
leaving the resin on a flat plate, or the like, and a long time for
curing the resin also is not required, as in the case of using
liquid resin, thus shortening the process.
[0114] In the case of using liquid resin, the accuracy among
elements must be secured by grinding a surface molded with resin in
order to obtain a uniform thickness of the resin, and the number of
electronic devices that can be formed on a ceramic substrate was
limited. In dicing, due to the irregularity in the resin surface,
it was difficult to allow the resin surface to adhere to a fixing
sheet. However, the formation using a mold for transfer molding
enables such a problem to be solved and the process to be
shortened, and prevents electronic devices from being lost.
[0115] Furthermore, according to the method of manufacturing an
electronic device of the present invention and the apparatus for
manufacturing the same, the pressure applied between the upper mold
and the lower mold can be varied corresponding to the pressure of
the plunger, thus relieving excessive pressure applied to the
substrate of the electronic devices sandwiched between the upper
mold and the lower mold. Thus, the deformation or cracks in the
substrate of ceramic or the like can be prevented.
[0116] The invention may be embodied in other forms without
departing from the spirit or essential characteristics thereof. The
embodiments disclosed in this application are to be considered in
all respects as illustrative and not limiting. The scope of the
invention is indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are intended to be
embraced therein.
* * * * *