Title: Semiconductor power module
Abstract: An insulating substrate (17) includes a surface conductive layer (25) fixedly laminated on a surface of the plate-like semiconductor body (21) via a surface side fixing member (24, 26). The surface side fixing member (24, 26) includes a first fixing portion (26) for fixing one part (25a) of the surface conductive layer (25) located underneath the joint portion (15) of the electrode terminal (14), and a second fixing portion (24) for fixing the other part (25b) of the surface conductive layer (25) which is not located underneath the joint portion (15), and a fixing strength exhibited by the first fixing portion (26) is smaller than that exhibited by the second fixing portion (24).
Patent Number: 6,984,883 Issued on 01/10/2006 to Yamada, et al.
| Inventors:
|
Yamada; Junji (Tokyo, JP);
Saiki; Seiji (Fukuoka, JP)
|
| Assignee:
|
Mitsubishi Denki Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
671592 |
| Filed:
|
September 29, 2003 |
Foreign Application Priority Data
| Dec 12, 2002[JP] | 2002-360730 |
| Current U.S. Class: |
257/690; 257/691; 257/678; 257/701; 257/584; 361/728; 361/772; 174/52.1; 174/52.4 |
| Current Intern'l Class: |
H01L 23/48 (20060101) |
| Field of Search: |
257/690,691,701,584,678
361/728,772
174/521,524
|
References Cited [Referenced By]
U.S. Patent Documents
| 4704320 | Nov., 1987 | Mizunoya et al.
| |
| 4727454 | Feb., 1988 | Neidig et al.
| |
| 5328751 | Jul., 1994 | Komorita et al.
| |
| 5466969 | Nov., 1995 | Tsunoda.
| |
| 5521437 | May., 1996 | Oshima et al.
| |
| 5869890 | Feb., 1999 | Nishiura et al.
| |
| 5956231 | Sep., 1999 | Yamada et al.
| |
| 5967858 | Oct., 1999 | Yamada.
| |
| 6787900 | Sep., 2004 | Shinohara et al.
| |
| Foreign Patent Documents |
| 5-15439 | Feb., 1993 | JP.
| |
| 10-173126 | Jun., 1998 | JP.
| |
| 11233696 | Aug., 1999 | JP.
| |
| 2001-68623 | Mar., 2001 | JP.
| |
| 2002043510 | Feb., 2002 | JP.
| |
Primary Examiner: Thomas; Tom
Assistant Examiner: Chu; Chris C.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
What is claimed is:
1. A semiconductor power module comprising:
a metallic base;
an insulating substrate fixedly laminated on the metallic base, the insulating
substrate including a plate-like insulating body and a surface conductive layer
fixedly laminated on a surface of the plate-like insulating body via a surface
side fixing member;
a power semiconductor element mounted on the insulating substrate; and
an electrode terminal plate fixed to the insulating substrate via a joint portion,
wherein the surface side fixing member includes a first fixing portion for fixing
one part of the surface conductive layer located underneath the joint portion of
the electrode terminal, the first fixing portion formed of a first material including
a metal, and a second fixing portion for fixing the other part of the surface conductive
layer which is not located underneath the joint portion, and
wherein a fixing strength exhibited by the first fixing portion is smaller than
that exhibited by the second fixing portion.
2. The semiconductor power module as claimed in claim 1, wherein the first fixing
portion is formed by providing a fixing member only on its peripheral portions
while its central portion is formed as an unfixed clearance portion.
3. The semiconductor power module as claimed in claim 1, wherein a boundary portion
between the first fixing portion and the second fixing portion is tightly sealed.
4. The semiconductor power module as claimed in claim 2, wherein a boundary portion
between the first fixing portion and the second fixing portion is tightly sealed.
5. The semiconductor power module as claimed in claim 1, wherein the first fixing
portion is quadrangular having four peripheral portions, and one of the four peripheral
portions located at a boundary portion with respect to the second fixing portion
is not provided with a fixing member but only the remaining three peripheral portions
are provided with the fixing member while its central portion is formed as an unfixed
clearance portion.
6. The semiconductor power module as claimed in claim 5, wherein in the three
peripheral portions of the first fixing portion, a width of an opposite peripheral
portion located on an opposite side of the boundary with respect to the second
fixing portion is larger than a width of the remaining two peripheral portions
of the first fixing portion.
7. A semiconductor power module comprising:
a metallic base;
an insulating substrate fixedly laminated on the metallic base, the insulating
substrate including a plate-like insulating body and a surface conductive layer
fixedly laminated on a surface of the plate-like insulating body via a surface
side fixing member;
a power semiconductor element mounted on the insulating substrate; and
an electrode terminal plate fixed to the insulating substrate via a joint portion,
wherein the surface side fixing member includes a first fixing portion for fixing
one part of the surface conductive layer located underneath the joint portion of
the electrode terminal, and a second fixing portion for fixing the other part of
the surface conductive layer which is not located underneath the joint portion,
a fixing strength exhibited by the first fixing portion is smaller than that
exhibited by the second fixing portion, and
the first fixing portion is quadrangular having four peripheral portions, and
one of the four peripheral portions located at a boundary portion with respect
to the second fixing portion is not provided with a fixing member but only the
remaining three peripheral portions are provided with the fixing member while its
central portion is formed as an unfixed clearance portion.
8. The semiconductor power module as claimed in claim 7, wherein in the three
peripheral portions of the first fixing portion, a width of an opposite peripheral
portion located on an opposite side of the boundary with respect to the second
fixing portion is larger than a width of the remaining two peripheral portions
of the first fixing portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a power semiconductor device, and
particularly to a joint assembly structure of an insulating substrate and electrode
terminals of a power semiconductor device used in a power converter or the like.
2. Description of the Prior Art
A power semiconductor device (hereinafter, referred to as "semiconductor power
module", or more simply "power module") is generally arranged to convert a direct
current input into an alternating current output of an arbitrary frequency by using
a semiconductor element, and is employed in, for example, an inverter used for
motor control or different purposes and also for use in an uninterruptible power
source (UPS).
In a conventional semiconductor power module, a semiconductor (element) chip
is
fixedly mounted onto an insulating substrate and one end of each electrode terminal
is fixedly joined to a specified portion on an upper surface portion of the insulating
substrate through a joint material, and an electrode terminal plate is extended
to be directly connected to a circuit pattern.
In order for preventing a breakage of a joint portion between the electrode terminal
and the insulating substrate in the presence of a stress caused through temperature
changes or similar factors, an S-shaped structure is employed for the electrode
terminal that is fixedly attached to the insulating substrate to thereby achieve
a stress relaxation structure (see, for instance, Patent Reference 1: Japanese
Utility Model Laid-Open Publication No. 5-15439 (1993)).
There is also disclosed an arrangement for achieving stress relaxation by extending
each electrode terminal in a plate beam-like manner (see, for instance, Patent
Reference 2: Japanese Patent Laid-Open Publication No. 10-173126 (1998)).
In another disclosed arrangement, a clearance is provided in a non-fixed condition
between a surface conductive pattern of the insulating substrate and the insulating
body, and electrode terminals are joined to the conductive pattern to thereby achieve
the stress relaxation. Alternatively, such a clearance is formed to be large so
as to easily discharge residues occurring during manufacture of the power module
(see, for instance, Patent Reference 3: Japanese Patent Laid-Open Publication No. 2001-68623).
When assembling such a semiconductor module of the above arrangement, the electrode
terminal plates and the semiconductor chip are electrically connected where the
electrode terminal plates form a laminated structure together with the insulating
layer disposed underneath thereof while the electrode terminal plates are insulated
from each other.
Each electrode terminal plate extends outside of a resin case to form, for instance,
a P terminal, an N terminal or an alternating current terminal of main circuit
terminals for external connection, on an upper surface of the semiconductor power
module. It is noted that a filler material such as silicon gel is filled in an
interior space surrounded by the resin case.
However, in the conventional semiconductor power module as disclosed in
Patent Reference 1, stress relaxation is achieved by forming electrode terminals
to be of S-shape for preventing breakage of joint portions between electrode terminals
and the insulating substrate. Therefore, there arise drawbacks such that the electrode
terminals will be of elongated shape in the height direction which is inconvenient
in view of reducing the size of the power module and which also leads to cost up
of the electrode terminals.
In the arrangement as disclosed in Patent Reference 2, stress relaxation is achieved
by extending the electrode terminals in a plate beam-like manner such that the
electrode terminals become long in the horizontal direction. This is problematically
inconvenient when considering reduction in size of the power module.
On the other hand, in the arrangement disclosed in Patent Reference 3, the electrode
terminals are joined with the surface conductive pattern of the insulating substrate
while the surface conductive pattern and the insulating body are in non-fixed condition,
and therefore fluid or gas used during manufacturing processes of the power module
will remain in the non-fixed portions. Thus, there arise drawbacks such that, when
such residues are dispersed in the power module during use thereof to thereby affect
characteristics of the semiconductor chip.
In an arrangement in which the clearance of the non-fixed portion is formed to
be large for easily discharging such residues during manufacture of the power module,
there arise drawbacks such that thermal conduction for discharge heat from the
metallic substrate generated in joining of the electrode terminals is undesirably
blocked by the clearances of non-joined portions, which makes the joining of electrode
terminals difficult and accordingly degrade the production efficiency.
SUMMARY OF THE INVENTION
The present invention has been made for solving the above problems, and it is
an object of the present invention to provide a semiconductor power module that
may be manufactured to be of a small size and at a low cost while preventing a
crack at a solder-joint portion and flexes or fractures of an insulating substrate
and also preventing fluid substances used in manufacturing processes from remaining
and discharging in the usage thereof.
For achieving the above object, the semiconductor power module according to the
present invention includes a metallic base and an insulating substrate fixedly
laminated on the metallic base. The insulating substrate includes a plate-like
insulating body and a surface conductive layer fixedly laminated on a surface of
the plate-like semiconductor body via two kinds of surface side fixing members
having different fixing strengths. The power module further includes a power semiconductor
element mounted on the insulating substrate and an electrode terminal plate fixed
to the insulating substrate via a joint portion.
In this construction, the two kinds of the surface side fixing members include
a first fixing portion for fixing one part of the surface conductive layer located
underneath the joint portion of the electrode terminal, and further includes a
second fixing portion for fixing the other part of the surface conductive layer
which is not located underneath the joint portion, and a fixing strength exhibited
by the first fixing portion is smaller than that exhibited by the second fixing portion.
Thus, by setting different fixing strengths for the right and left region of
the surface side fixing member and by fixing the electrode terminals and the insulating
body immediately below thereof with a weak strength, no substances will reside
during manufacturing processes since a fixed condition is reliably established
in manufacturing stages of the power module.
Further, by forming a stress relaxing structure in which only the first
fixing portion having a weak fixing force is easily peeled off upon receipt of
an initial stress when using the product, breakage of the joint portion of the
electrode terminal can be prevented. Since it is possible to omit forming a stress
relaxing structure at the electrode terminals themselves, the electrode terminals
can be formed at a low cost, enabling to provide a power module of a low cost, accordingly.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will be readily
understood from the following detailed description taken in conjunction with preferred
embodiments thereof with reference to the accompanying drawings, in which:
FIG. 1 is side-sectional view illustrating an entire structure of a semiconductor
power module according to a first embodiment of the present invention;
FIG. 2 is an enlarged sectional view illustrating an essential part of a structure
of an insulating substrate shown in FIG. 1;
FIG. 3 is a perspective top plan view of an essential part of FIG. 2;
FIG. 4 is an enlarged sectional view illustrating an essential part of a structure
of an insulating substrate of a semiconductor power module according to a second
embodiment of the present invention;
FIG. 5 is a perspective top plan view of an essential part of FIG. 4;
FIG. 6 is an enlarged sectional view illustrating an essential part of a structure
of an insulating substrate of a semiconductor power module according to a third
embodiment of the present invention;
FIG. 7 is a perspective top plan view of an essential part of FIG. 6;
FIG. 8 is an enlarged sectional view illustrating an essential part of a structure
of an insulating substrate of a semiconductor power module according to a fourth
embodiment of the present invention; and
FIG. 9 is a perspective top plan view of an essential part of FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the description proceeds, it is to be noted that, since the basic structures
of the preferred embodiments are in common, like parts are designated by the same
reference numerals throughout the accompanying drawings, and repetitive explanations
are omitted for simplification purposes.
Embodiments of the present invention will now be explained with reference
to the accompanying drawings. While the embodiments of the present invention are
explained as an example of using a semiconductor power module shown in the drawings,
the present invention is not limited to this arrangement. The present invention
is also applicable to a case of using other complex types of semiconductor devices
in which a plurality of semiconductor chips are mounted in a single package.
(Embodiment 1)
The first embodiment will be now explained with reference to FIGS. 1 to 3. FIG.
1 is side-sectional view illustrating an entire structure in section of a semiconductor
power module according to the first embodiment of the present invention. FIG. 2
is an enlarged sectional view illustrating an essential part of a basic structure
of an insulating substrate shown in FIG. 1, and FIG. 3 is a perspective top plan
view of an essential part shown in FIG. 2.
A major different point between a semiconductor power module
1 according
to the first embodiment of the present invention and a conventional semiconductor
power module resides in the following fact. That is, in the first embodiment, an
insulating substrate structure is constructed in that, in a joint portion between
a surface conductive layer on the insulating substrate and an insulating body thereof,
a fixing strength of an area immediately below a connected part of an electrode
terminal plate on the insulating substrate is set to be smaller than that of the
other area of the joint portion.
In the semiconductor power module
1 as illustrated in FIG. 1, reference
numeral
11 denotes a metallic base of Cu or other material,
17 an
insulating substrate adhered onto an upper surface of the metallic base in a laminated
structure,
13 a semiconductor chip (element) such as an IGBT chip fixedly
mounted onto the insulating substrate
17 with a soldering material or the
like,
14 an electrode terminal plate, and
16 a resin case for protection
provided on the metallic base
11.
A lower end of the electrode terminal plate
14 is fixedly joint to a specified
portion on the upper surface portion of the insulating substrate
17 through
a conductive joint material
15 such as a solder while the other end thereof
is fixed and inserted to the resin case
16. A silicon resin gel or a like
material is filled in the resin case
16 for protecting the semiconductor chip.
In the basic structure of the insulating substrate
17 as illustrated in
FIGS. 2 and 3, reference numeral
21 denotes a plate-like insulating body,
23 a lower conductive layer that is fixedly formed onto the rear surface
(downward side in the drawings) of the plate-like insulating body
21 via
a lower fixing layer
22, and
25 a conductive pattern of an upper
conductive layer that is fixedly formed onto the upper surface (upward side in
the drawings) of the plate-like insulating body
21 via an upper fixing layer
24.
The conductive pattern of the upper conductive layer
25 may be made of
Cu or Al material. The lower fixing layer
22 and the upper fixing layer
24 may be formed of the same material (which is referred to as "first brazing
material", hereinbelow), and a material of Al—Si, Ag—Cu or Ag—Cu—Ti
may be used as the first brazing material. The joint of the upper and lower conductive
layers
25 and
23 to the plate-like insulating body
21 may
be constructed by a known active metal joint method or direct joint method.
The electrode terminal plate
14 may be formed by press molding or etching
process of, for example, a Cu plate or Al plate plated with Ni, and the joint material
15 may be a soldering material of such as Sn—Pb type, Pb—In
type or Ag—Sn type. The plate-like insulating body
21 may be formed
as a ceramic substrate made of alumina (Al
2O
3) or aluminum
nitride (AlN).
In the above arrangement, the side-sectional shape of the electrode terminal
plate
14 has a L-shaped beam structure which is comprised of a vertical extending
portion
14a and a base portion
14b, where the base
portion
14b is fixed onto a surface of a first conductive portion
25a of the upper conductive (pattern) layer
25 via the joint
material
15. The first conductive portion
25a corresponds
to a region of the upper conductive layer
25 underneath the base portion
14b. A region of the upper conductive layer
25 other than
the first conductive portion
25a is referred to as "second conductive
portion
25b", hereinbelow.
In the present embodiment, a specified fixing member
26 (referred to as
"first fixing member", hereinbelow) is interposed between the first conductive
portion
25a of the upper conductive (pattern) layer
25 and
a first insulating body portion
21a of the plate-like insulating
body
21, where the first insulating body portion
21a corresponds
to a region of the plate-like insulating body
21 underneath the base portion
14b of the electrode terminal plate
14. A region of the plate-like
insulating body
21 other than the first insulating body portion
21a
is referred to as "second insulating body portion
21b", hereinbelow.
Thus, the bonding between the first conductive portion
25a and
the first insulating body portion
21a is implemented by the first
fixing member
26.
On the other hand, the upper fixing layer
24 serving as a second fixing
member is interposed between the second conductive portion
25b of
the upper conductive (pattern) layer
25 and the second insulating body portion
21b of the plate-like insulating body
21.
Thus, the bonding between the second conductive portion
25b and
the second insulating body portion
21b is implemented by the second
fixing member
24 (i.e., the upper fixing layer
24).
Specifically, in the insulating substrate structure
17, a fixing
strength by the first fixing member
26 is set to be smaller than that by
the second fixing member
24. As the first fixing member
26, there
may be used an active metal or the like material having a weak joining force. In
this construction, the first fixing member
26 and the second fixing member
24 are closely contacted with each other at a boundary portion therebetween
in a sealed condition with respect to an exterior of the device.
Thus, in the structure of fixing the electrode terminal plate
14 onto
the first insulating body portion
21a of the plate-like insulating
body
21, since the fixing strength by the first fixing member
26
is set to be smaller than that by the second fixing member
24, the conductive
layer
25 is reliably fixed to the insulating body
21 at a stage of
manufacturing the power module, and there remain no substance generated in the
manufacturing process.
Moreover, in the present embodiment, the insulating substrate structure
is constructed to have a stress relaxing structure in which only the first fixing
member
26 having a weak fixing force can be easily peeled when an initial
stress is generated in a usage of the product. With this arrangement, breakage
of the joint portion
15 of the electrode terminal plate is effectively prevented
while the electrode terminals can be arranged at a low cost since it is not necessary
to form a stress relaxing structure such as a S-shape of an electrode terminal
plate, and it is accordingly possible to reduce a cost of a power module compared
to a conventional one.
(Embodiment 2)
The second embodiment of the present invention will now be explained with reference
to FIGS. 4 and 5. FIG. 4 is a partially enlarged sectional view illustrating a
basic structure of an insulating substrate
17 of a semiconductor power module
according to the second embodiment of the present invention, and FIG. 5 is a perspective
top plan view of FIG. 4.
The second embodiment of the present invention is a modified example of the first
embodiment, and the basic structure thereof is similar to that of the first embodiment.
The different point of the second embodiment resides in the fact that the first
fixing member underneath the connected portion of the electrode terminal plate
is provided only at peripheral portions thereof.
More particularly, as illustrated in FIGS. 4 and 5, a non-fixed clearance portion
27 having no fixing member
26 filled therein is formed in a central
portion surrounded by the first fixing member
26 provided underneath the
connected portion of the electrode terminal plate. In this insulating substrate
structure
17, at the joint portion between the first conductive layer portion
25a and the first insulating body portion
21a of the
plate-like insulating body
21, only the peripheral regions thereof is provided
with the first fixing member
26 having a smaller fixing strength than that
of the second fixing member
24 (i.e., upper fixing layer
24) while
the central portion
27 thereof is formed as a non-fixed clearance portion.
In this construction, the first fixing member
26 and the second fixing
member
24 are closely contacted with each other at their boundary portion
so that the non-fixed clearance portion
27 is formed in a sealed condition
with respect to an exterior of the module.
With this arrangement, it is possible to achieve the same effects as those of
the first embodiment. Moreover, since the area for filling the first fixing member
26 of smaller fixing strength is further limited to only the peripheral
portion thereof, there can be obtained an effect of preventing substances residues
during the manufacturing process. In addition, it is further possible to arrange
the electrode terminal plates with reduction in cost and weight.
Furthermore, since the insulating substrate is formed to have a stress
relaxing structure, only the first fixing member
26 of a smaller fixing
strength can be easily peeled when an initial stress is generated in usage of the
product. Thus, only the first conductive layer portion
25a underneath
the joint portion of the electrode terminal plate is allowed to partially separate
from the plate-like insulating body
21, which exhibits the effect of reliably
preventing breakage of the joint material portion
15 under the base portion
14b of the electrode terminal plate
14.
(Embodiment 3)
The third embodiment of the present invention will now be explained with reference
to FIGS. 6 and 7. FIG. 6 is a partially enlarged sectional view illustrating a
basic structure of an insulating substrate of a semiconductor power module according
to the third embodiment of the present invention, and FIG. 7 is a perspective top
plan view thereof.
The third embodiment of the present invention is another modified example of
the first embodiment. The basic structure thereof is similar to that of the second
embodiment, where the different point thereof resides in the fact that, among the
four peripheral portions provided with the first fixing member, the peripheral
portion that is located at the boundary portion with respect to the second fixing
member
24 is not provided with the first fixing member but only the remaining
three peripheral portions are provided with the first fixing member
26.
More particularly, as illustrated in FIGS. 6 and 7, the non-fixed clearance
portion
27 having no fixing member filled therein is formed at a central
portion of the joint fixing portion underneath the electrode terminal plate.
In this insulating substrate structure, in the joint portion between the first
conductive layer portion
25a and the first insulating body portion
21a underneath the electrode terminal plate
14, only three
peripheral portions among the four peripheral portions other than the peripheral
portion located at the boundary portion with the second fixing member
24
are provided with the first fixing member
26 having a smaller fixing strength
than that of the second fixing member
24. Meanwhile, the central portion
27 and the peripheral portion located at the boundary with the second fixing
member
24 are formed as a non-fixed clearance portion.
With this arrangement, since the first fixing member of weak fixing strength
is not provided at a boundary portion on the side that is strongly fixed by the
second fixing member and that does not contribute to preventing residues of substances
during a manufacturing process, it is possible to achieve the same effects as those
of the second embodiment. Further the cost and weight can be reduced in arranging
the electrode terminal plates and to achieve a stress relaxing effect in an initial
design in which the first fixing member can be easily peeled when an initial stress
is generated in the usage of the product.
(Embodiment 4)
The fourth embodiment of the present invention will now be explained with reference
to FIGS. 8 and 9. FIG. 8 is a partially enlarged sectional view illustrating a
basic structure of an insulating substrate of a semiconductor power module according
to the fourth embodiment of the present invention, and FIG. 9 is a perspective
top plan view thereof.
The fourth embodiment of the present invention is still another modified example
of the first embodiment. The basic structure thereof is similar to that of the
third embodiment, where the different point thereof resides in the fact that, the
widths (that is, the areas) of the joint fixing portions of the three peripheral
portions are defined to be different in size between the longitudinal portions
and the lateral portion.
More particularly, as illustrated in FIGS. 8 and 9, the non-fixed clearance
portion
27 having no fixing member
26 filled therein is formed at
a central portion of the joint fixing portion underneath the connected region of
the electrode terminal plate.
In the insulating substrate structure, only three peripheral portions among the
four peripheral portions other than the peripheral portion located at the boundary
portion with the second fixing member
24 are provided with the first fixing
member
26 having a smaller fixing strength than that of the second fixing
member
24, while the central portion
27 and the peripheral portion
located at the boundary with the second fixing member
24 are formed as a
non-fixed clearance portion, which is similar to the insulating substrate structure
of the third embodiment.
In the fourth embodiment, the width (that is, the area) of the fixing portion
26a in the lateral direction among the first fixing members
26
provided at the three peripheral portions is made to be larger than the width (that
is, the area) of the remaining two fixing portions
26b and
26c
in the lengthwise direction.
It is, for instance, possible to employ an insulating substrate structure in
which
the width of the fixing portions
26b and
26c in the
lengthwise direction is 1 mm while the width of the fixing portion
26a
in the lateral direction is 3 mm.
The boundary portions between the two fixing members
26b and
26c
in the lengthwise direction and the second fixing member
24 are closely
contacted with each other so that the non-fixed clearance portion
27 is
in a sealed condition with respect to the exterior.
Since a force applied during manufacturing processes is conventionally to be
mainly applied to a side opposite to a side strongly fixed by the upper fixing
layer
24, that is, a weakly fixed side by using the first fixing members
provided on the end portion side, such portions would peel in the presence of a
stress during manufacturing processes, and therefore substance residues are problematically
caused during the manufacture.
In the arrangement of the fourth embodiment, the width (that is, the area) of
the fixing portion
26a in the lateral direction provided on the end
portion side that is opposite to the side strongly fixed by the second fixing member
24 is arranged to be larger than the width (that is, the area) of the remaining
two fixing portions
26b and
26c in the lengthwise direction.
Accordingly, it is possible to achieve the effects of the third embodiment and
further to achieve the effects of preventing substance residues during manufacturing processes.
As described above, according to the present invention, the fixing strength between
the electrode terminal plate and the insulating body portion is defined to be smaller
than the joining strength of the fixing members of remaining regions so that reliable
fixing is achieved during a manufacturing stage of the power module and no substances
of manufacturing processes will remain.
A stress relaxing structure is further formed in which only the fixing member
of
weak fixing strength is easily peeled off in the presence of initial stress when
using the product. With this arrangement, breakage of joint portions of the electrode
terminal plates can be reliably prevented. Moreover, it is possible to omit forming
a stress relaxing structure such as a S-shape at the electrode terminal plates,
enabling to arrange the electrode terminal plates to be of low cost, and it is
possible to provide a power module that is of a lower cost than those of the prior art.
Although the present invention has been described in connection with the
preferred embodiments thereof with reference to the accompanying drawings, it is
to be noted that various changes and modifications will be apparent to those skilled
in the art. Such changes and modifications are to be understood as included within
the scope of the present invention as defined by the appended claims, unless they
depart therefrom.
*
