Power semiconductor module with a plurality of semiconductor chips

On a metal base, an insulated wiring substrate is fixed, and, on a conductive layer on the insulated wiring substrate, semiconductor chips are disposed. Above the semiconductor chips, a controlling substrate is provided, and the signals produced in this controlling substrate are supplied to electrodes on the surfaces of the semiconductor chips via bonding wires passing through openings provided in the controlling substrate.

BACKGROUND OF THE INVENTION 
The present invention relates to a power semiconductor module constituted 
in such a manner that a plurality of semiconductor chips and a control 
circuit for controlling the plurality of semiconductor chips are housed in 
the same case. 
FIG. 1 shows the structure of a conventional power semiconductor module, 
wherein the reference numeral 1 denotes a metal base, and numeral 2 and 2 
denote insulated wiring substrates, respectively. The insulated wiring 
substrates 2 are each formed in such a manner that, on the front and back 
surfaces of a ceramics substrate, conductive layers composed of a metal 
such as, e.g. Cu are formed. The insulated wiring substrates 2 are each is 
fixed onto the metal base 1 by soldering the conductive layer formed on 
the back surface thereof. On the conductive layer formed on the front 
surface of each of the insulated wiring substrates 2, a plurality of 
semiconductor chips 3 are fixed by soldering, respectively. 
The metal base 1 is fixed to a resin case 4, and electrode pads on the 
semiconductor chips 3 and the conductive layers on the front surfaces of 
the respective insulated wiring substrate 2 are connected to electrodes 5 
provided on the resin case 4 through bonding wires 6. Further, the 
electrodes 5 on the resin case 4 are led to external terminals 8 provided 
in the upper portion of the resin case, through wirings 7 composed of a 
metal such as Cu or the like and buried in the resin case 4. 
Further, within the resin case 4, a plurality of support pillars 10 in each 
of which a pin (electrode) 9 is buried are provided in a state projecting 
from the bottom. By the plurality of support pillars 10, a controlling 
substrate 11 is supported, and, the pins 9 extend through predetermined 
patterns on the controlling substrate 11 and are soldered thereto, whereby 
the fixation and electrical connection of the controlling substrates 11 
are effected. On the controlling substrate 11, various parts such as IC 
(integrated circuits) etc. are mounted, these parts being coupled to one 
another by wiring patterns (not shown) to form a control circuit; and, by 
this control circuit, signals for controlling the semiconductor chips 3 
are generated. The signals generated by the control circuit constituted on 
the controlling substrate 11 are fed to the electrode pads on the 
semiconductor chips 3 via the wiring patterns (not shown) on the 
controlling substrate 11, the pins 9, the electrodes 5 and the bonding 
wires 6. 
FIG. 2 is s plan view of the conventional power semiconductor module shown 
in FIG. 1, wherein the controlling substrate 11 is not shown. In this 
conventional case, the semiconductor chips mentioned above each constitute 
an IGBT (Insulated Gate Bipolar Transistor) formed in such a manner that, 
on the back surface of the chip, a collector electrode is formed, while on 
the front surface of the chip, a plurality of (four, in this embodiment) 
emitter electrode pads 4 and one gate electrode pad G are formed. 
As shown, the gate electrode pad G on the front surface of each 
semiconductor chip 3 is connected to the electrode 5 on the resin case 4 
through the bonding wire 6, and further, the electrode 5 is connected to 
the controlling substrate 11 through the pin 9. 
In the case of the conventional power semiconductor module shown in FIG. 1 
and FIG. 2, the circuit must be composed by connecting the bonding wires 6 
to the electrodes 5 on the resin case, and, in case of feeding the 
respective semiconductor chips 3 with the control system signals generated 
on the controlling substrate 11, there must be provided a space for signal 
connection in the resin case 4 as in the case of a main signal. Due to 
this, there has arisen the problem that, when a plurality of semiconductor 
chips are used, the module as a whole is increased in size, thus resulting 
in an increase in the manufacturing costs. 
As a result of the limitation on the connection with the resin case 4, a 
limitation is also placed on the disposition of the semiconductor chips 3; 
and thus, there has arisen the problem that the inductance component of 
the wirings is increased, thus resulting in the occurrence of the adverse 
effect that the reliability falls. 
Here, as for the fact that the electrodes of the control signal system 
(gate control signal) are provided on the resin case disposed around the 
semiconductor chips, it is because the wire bonding connection steps can 
be continuously carried out as one step. 
The reason why the module as a whole is large in size is that, as shown in 
FIG. 2, spaces for provision of the gate-relaying electrodes (electrodes 
5) and the pins 9 need to be provided. 
Further, as for the increase in the inductance component, the wiring length 
of the collector/emitter wirings plays a big role. 
BRIEF SUMMARY OF THE INVENTION 
Thus, it is the object of the present invention to provide a power 
semiconductor module which is small in size and has a low-inductance 
characteristic, the power semiconductor module being constituted in such a 
manner that the control electrodes on the semiconductor chips are directly 
connected, by means of bonding wires or the like, to the wiring 
patterns--other than the electrodes on the resin case--formed on a 
controlling substrate disposed above the semiconductor chips, whereby an 
ideal semiconductor chip arrangement is realized. 
According to an embodiment of the present invention, there is provided a 
power semiconductor module, comprising a metal base, an insulated wiring 
substrate fixed on the metal base, at least one semiconductor chip which 
is fixed on the insulated wiring substrate and has control electrode on 
the upper surfaces thereof, a controlling substrate disposed above the at 
least one semiconductor chip and having a plurality of parts mounted 
thereon, the plurality of parts constituting a control circuit for 
controlling the at least one semiconductor chip, the controlling substrate 
having at least wiring pattern formed thereon, and at least one bonding 
wire which electrically connect the control electrode of the semiconductor 
chip and the wiring pattern on the controlling substrate to each other, 
respectively. 
According to another embodiment of the present invention, there is provided 
a power semiconductor module, comprising a metal base, an insulated wiring 
substrate fixed on the metal base, at least one semiconductor chip which 
is fixed on the insulated wiring substrate and has control electrode on 
the upper surfaces thereof, a controlling substrate which is disposed 
above the semiconductor chip and has a plurality of parts mounted thereon, 
the plurality of parts constituting a control circuit for controlling the 
semiconductor chip, the controlling substrate having at least one wiring 
pattern formed thereon, and at least one wiring which has one end and the 
other end, the one end being connected by soldering to the control 
electrode for controlling the semiconductor chip, the other end being 
connected by soldering to the wiring pattern on the controlling substrate. 
According to still another embodiment of the present invention, there is 
provided a power semiconductor module, comprising a metal base, an 
insulated wiring substrate fixed on the metal base, at least one 
semiconductor chip which is fixed on the insulating substrate and has a 
control electrode on the upper surface thereof, a controlling substrate 
which is disposed above the semiconductor chip and has a plurality of 
parts mounted thereon, the plurality of parts constituting a control 
circuit for controlling the semiconductor chip, the controlling substrate 
having at least one wiring pattern formed thereon, and a pressure 
contacting mechanism which is provided between the control electrode of 
the semiconductor chip and the wiring pattern on the controlling substrate 
to electrically connect the control electrode and the wiring pattern to 
each other. 
According to still another embodiment of the present invention, there is 
provided a power semiconductor module, comprising a metal base, an 
insulated wiring substrate having an insulating substrate which has first 
and second surfaces opposed to each other and first and second conductive 
layers formed on the first and second surfaces of the insulating 
substrate, the first conductive layer being fixed by soldering onto the 
metal base, at least one IGBT chip which has first and second surfaces 
opposed to each other, a collector electrode being formed on the first 
surface, a gate electrode and emitter electrodes being formed on the 
second surface in a state electrically separated from each other, the 
collector electrodes being fixed by soldering onto the second conducive 
layers of the insulated wiring substrate, a controlling substrate which is 
disposed above the IGBT chip and has a plurality of parts mounted thereon, 
the plurality of parts constituting a control circuit for controlling the 
IGBT chip, the controlling substrate having at least one wiring pattern 
formed thereon, and at least one bonding wire which electrically connect 
the gate electrode of the IGBT chip and the wiring pattern on the 
controlling substrate to each other. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out 
hereinafter.

DETAILED DESCRIPTION OF THE INVENTION 
Embodiments of the present invention will now be described by reference to 
the drawings. 
FIG. 3 is a sectional view of the power semiconductor module according to a 
first embodiment of the present invention. In the description to follow, 
the constituent portions which correspond to those of the conventional 
power semiconductor module are referenced by the same reference numerals. 
Numeral 1 denotes a metal base, and numeral 2 denotes insulated wiring 
substrates. The insulated wiring substrates 2 are each formed in such a 
manner that, on the front and back surfaces of a ceramics substrate, a 
conductive layer composed of a metal such as, e.g. Cu is formed. The 
insulated wiring substrates 2 are each fixed onto the metal base 1 by 
soldering thereto the conductive layer formed on the back surface thereof 
to the metal base 1. Numeral 3 denotes semiconductor chips; and, over the 
whole back surface of each of the semiconductor chips 3, an electrode is 
formed, while on the front surface thereof, a plurality of electrode pads 
are formed in a state electrically separated from one another. The 
semiconductor chips 3 are each fixed onto the insulating substrate 2 in 
such a manner that the electrode formed over the whole rear surface 
thereof is soldered onto the conductive layer formed on the front surface 
of each of the insulated wiring substrates 2. 
The metal base 1 is fixed to a resin case 4. The electrical connection 
between specific electrode pads on the front surfaces of the semiconductor 
chips 3, the electrical connection between specific electrode pads on the 
front surfaces of the semiconductor chips 3 and the conductive layers on 
the front surfaces of the insulated wiring layers 2, the electrical 
connection between the conductive layers on the front surfaces of the 
insulated wiring substrates 2 and the electrodes 5 provided on the resin 
case 4, and the electrical connection between specific electrode pads on 
the front surfaces of the semiconductor chips 3 and the electrodes 5 
provided on the resin case 4 is made through bonding wires 6a. Further, 
the electrodes 5 on the resin case 4 are led to external terminals 8 
provided in the upper portion of the resin case 4, via wirings 7 composed 
of a metal such as Cu or the like and buried in the resin case 4. 
Further, on the inner side of the upper portion of the resin case 4, 
stepped portions 12 are provided, and, on these stepped portions 12, a 
controlling substrate 11 is disposed and fixed by the use of an adhesive 
or the like. 
On the controlling substrate 11, various parts such as an IC (integrated 
circuit) etc. are mounted as in the conventional case; and these parts are 
connected to each other by wiring patterns (not shown) to constitute a 
control circuit. By this control circuit, signals for controlling the 
semiconductor chips 3 are produced. 
Further, in the controlling substrate 11, a plurality of openings 13 are 
formed, so that the signals produced on the controlling substrate 11 are 
fed to the semiconductor chips 3 via bonding wires 6b extending through 
the openings 13 so as to directly connect the wiring patterns (not shown) 
on the controlling substrate 11 and specific electrode pads on the 
semiconductor chips 3 to each other. 
Further, on the controlling substrate 11, a plurality of electrodes 14 for 
receiving signals from outside are provided in a projecting state. 
FIG. 4 is a plan view of the power semiconductor module shown in FIG. 3, 
wherein the controlling substrate 11 is not shown. In this embodiment, the 
semiconductor chips 3 each constitute an IGBT formed in such a manner that 
a collector electrode is formed as an electrode provided over the whole 
rear surface of the chip, and a plurality of (four, in this embodiment) 
emitter electrode pads E and one gate electrode pad G are formed on the 
front surface of the chip. 
As shown, the emitter electrode pads E on the front surfaces of the 
respective semiconductor chips 3 are finally connected to the external 
terminals 8 on the resin case 4 through the bonding wires 6a. On the other 
hand, the gate electrode pads G are directly connected, by the bonding 
wires 6b, to predetermined wiring patterns (not shown in FIG. 4) on the 
controlling substrate 11. 
FIG. 5 and FIG. 6 are plan views of different embodiments of the 
controlling substrate 11. The controlling substrate 11 shown in FIG. 5 is 
what is used in the embodiment shown in FIG. 3; and, in the controlling 
substrate 11, a plurality of electrodes 14 are formed besides the openings 
13, and the plurality of parts 15 are mounted. Further, numeral 16 denotes 
a cut-away recess formed in one side portion of the controlling substrate 
11. The bonding wires 6b may be disposed so as to extend through this 
cut-away recess 16 to electrically connect the wiring patterns on the 
controlling substrate 11 to the gate electrode pads G on the front 
surfaces of the semiconductor chips 3. 
The above-mentioned stepped portions 12 provided on the resin case 4 may be 
provided on all of the four sides of the resin case 4 in case the plane 
shape of the resin case 4 is square as shown in FIG. 5 or in some (for 
instance, two opposed sides) of the four sides. 
The controlling substrate 11 shown in FIG. 6 is constructed in such a 
manner that, in order to allow the passage there through of the bonding 
wires 6b, the controlling substrate 11 itself is divided into a plurality 
of portions (three portions, in this embodiment) in place of providing the 
openings 13. In this case, the bonding wires 6b are made to extend through 
gaps 17 between the substrate portions. 
FIG. 7 is an equivalent circuit diagram of the power semiconductor module 
according to the above-mentioned embodiment. In the controlling substrate 
11, a plurality of (two, in this embodiment) ICs (integrated circuits) 21 
and three resistors 22, one end of each of which is connected to the 
output of the respective IC, are provided as the parts 15. The other ends 
of the resistors 22 are connected to the gate electrodes of the 
semiconductor chips 3 (six IGBTs in this embodiment), respectively. The 
six semiconductor chips 3 are divided into two sets each consisting of 
three semiconductor chips 3. The collector electrodes of the three 
semiconductor chips in one set are connected to an external terminal P to 
which a positive power supply voltage is supplied, while the emitter 
electrodes thereof are connected commonly to an output external terminal 
OUT. The collector electrodes of the three semiconductor chips 3 in the 
other set are connected commonly to the external terminal OUT, while the 
emitter electrodes thereof are connected commonly to an external terminal 
N to which the earth potential is supplied. 
With this constitution, the electrodes 5 (the relating electrodes 5) on the 
resin case 4 which are used in connecting gate electrode pads G as shown 
in FIG. 2 are disused, so that it becomes possible to dispose the 
semiconductor chips in an ideal arrangement; and thus, the apparatus as a 
whole can be miniaturized. Further, the external terminals 8 which are 
connected to the collector electrodes C and the emitter electrode pads E 
of the semiconductor chips 3 can be disposed at positions closer to the 
semiconductor chips 3, so that the bonding wires 6a for connection of the 
collectors and emitters can be reduced in length, whereby a reduction in 
the inductance of the wirings can be realized. 
Further, in place of the controlling substrate 11, a metal wiring body may 
be used. In case the control circuit is mounted by the use of the metal 
wiring body, the metal wiring body itself serves as wirings, and 
therefore, it is necessary to work the metal wiring body into a 
predetermined shape. In this case, the respective parts constituting the 
control circuit are provided outside the module in some cases; in such a 
case, the controlling substrate is used only as wirings. 
Further, finally, the open portion, above the controlling substrate, of the 
resin case is covered with a cover plate, whereby the module is completed. 
In this case, the electrodes 14 are placed in a state projecting out 
through the cover plate. 
FIG. 8 is a sectional view of the power semiconductor module according to 
another embodiment of the present invention. In the case of this 
embodiment, the connection between specific electrodes (the gate electrode 
pads G in FIG. 4) on the semiconductor chips 3 and the wiring patterns on 
the controlling substrate 11 is made by the soldering of wirings 18. 
Further, the connection between specific electrodes (the emitter electrode 
pads E shown in FIG. 4) on the front surfaces of semiconductor chips 3 and 
the electrically conductive layer on the front surface of the insulated 
wiring substrate 2 onto which the different semiconductor chips 3 are 
fixed, and the connection between specific electrodes (the emitter 
electrode pads E shown in FIG. 4) on the front surfaces of the 
semiconductor chips 3 and the electrodes 5 on the resin case 4 are made by 
the soldering of metal wiring plates 19. By improving the disposition of 
the electrodes on the surfaces of the semiconductor chips 3, such ways of 
connection becomes possible. 
According to this embodiment, the electrical connection between the 
conductive layer on one insulating wiring substrate 2 and the external 
terminals 8 is realized by forming the external terminals 8 integrally 
with the conductive layer on the front surface of the insulating wiring 
substrate 2, without using bonding wires as according to the conventional 
technique. 
FIG. 9 is a sectional view of the power semiconductor module according to 
still another embodiment of the present invention. In the case of this 
embodiment, the electrical connection between the wiring patterns on the 
controlling substrate 11 and the respective electrode pads on the front 
surfaces of the semiconductor chips 3 as well as the conductive layer on 
the front surface of one insulated wiring substrate 2 is effected by the 
use of a pressure contact mechanism. In this pressure contact mechanism, 
pressure-contacting pins 20 are used. 
Further, in the respective embodiments mentioned above, the electrical 
connection between the conductive layer on the front surface of the 
insulating wiring substrate 2 which is connected to the collector 
electrodes on the semiconductor chips and the external terminals 8 can 
alternatively be effected by means of welding. 
FIG. 10 is a sectional view of the power semiconductor module according to 
still another embodiment of the present invention. This embodiment is 
constituted in such a manner that, as the metal base 1 shown in FIG. 3, a 
plate-shaped metal base is not used, but a metal radiation fin 23 based on 
various cooling systems such as the self-cooling, water-cooling, 
air-cooling, etc. is used. Also in the cases of the embodiments shown in 
FIG. 8 and FIG. 9, the radiation fin 23 can be used as the metal base 1. 
It is a matter of course that the present invention is not limited only to 
the above-mentioned embodiments but can be variously modified. For 
instance, the embodiment shown in FIG. 3 has been described with reference 
to the case where, in order to fix the controlling substrate 11 to the 
resin case 4, the stepped portions 12 are provided on the inner side of 
the upper portion of the resin case 4, and the controlling substrate 11 is 
disposed on the stepped portions 12 and fixed by the use of an adhesive or 
the like, but the embodiment can be modified in such a manner that, in 
addition to the provision of the stepped portions, stripe-shaped support 
portions are formed integrally with the resin case 4, and, on the 
stripe-shaped support portions, the controlling substrate 11 is placed and 
fixed, in which case care should be taken to ensure that the openings 13 
in the controlling substrate 11 are disposed so as not to overlap the 
stripe-shaped support portions. 
As described above, according to the present invention, there can be 
provided a power semiconductor module which has an ideal semiconductor 
chip arrangement, is small in size and, in addition, has a low-inductance 
characteristic. 
Additional advantages and modifications will readily occurs to those 
skilled in the art. Therefore, the invention in its broader aspects is not 
limited to the specific details and representative embodiments shown and 
described herein. Accordingly, various modifications may be made without 
departing from the spirit or scope of the general inventive concept as 
defined by the appended claims and their equivalents.