Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-10-17
2003-02-18
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C257S724000, C361S328000, C361S707000, C361S735000, C361S734000, C361S715000
Reexamination Certificate
active
06522544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power module structure and, more particularly, to a power module structure including a smoothing capacitor for smoothing a DC supply voltage to be externally applied to a power semiconductor device such as an IGBT.
2. Description of the Background Art
FIG. 28
is a schematic top plan view of a structure of a background art power module body portion
100
. Output terminals
111
U,
111
V and
111
W are arranged along a first side of a top surface of a case frame
106
, and a P-terminal
108
P and an N-terminal
108
N are arranged along a second side of the top surface of the case frame
106
which is parallel to the first side.
FIG. 29
is a cross-sectional view showing a cross-sectional structure taken along the line X
100
—X
100
of FIG.
28
. The case frame
106
made of resin is disposed on a base plate
101
made of metal. A case lid
116
made of resin is disposed on the case frame
106
. An insulating substrate
102
made of ceramic is soldered, as shown at
103
, onto the base plate
101
. A plurality of power semiconductor devices
105
such as IGBTs are soldered, as shown at
104
, onto the insulating substrate
102
. Circuit elements (not shown) such as switching elements are mounted on the top surface of the insulating substrate
102
, and a predetermined circuit pattern (not shown) is formed on the top surface of the insulating substrate
102
.
A control substrate
114
formed with a control circuit for controlling the power semiconductor devices
105
is disposed within the case frame
106
. The control substrate
114
is soldered to first ends of respective interconnection electrodes
112
. Second ends of the respective interconnection electrodes
112
are connected through aluminum wires
109
to the power semiconductor devices
105
. An anti-noise shield plate
113
is disposed between the control substrate
114
and the insulating substrate
102
within the case frame
106
. An interior space of the case frame
106
below the shield plate
113
is filled with a silicone gel
115
.
The N-terminal
108
N is disposed on the top surface of the case frame
106
. The N-terminal
108
N is connected to a first end of an N-electrode
107
N. A second end of the N-electrode
107
N is connected through the aluminum wires
109
to the power semiconductor devices
105
. The P-terminal
108
P (not shown in
FIG. 29
) is also disposed on the top surface of the case frame
106
. The P-terminal
108
P is connected to a first end of a P-electrode
107
P. A second end of the P-electrode
107
P is connected to the power semiconductor devices
105
through the aluminum wires
109
and the circuit pattern formed on the insulating substrate
102
. The output terminal
111
V is disposed on the top surface of the case frame
106
. The output terminal
111
V is connected to a first end of an output electrode
110
. A second end of the output electrode
110
is connected through the aluminum wires
109
to the power semiconductor devices
105
.
FIG. 30
is a schematic cross-sectional view showing the overall construction of a background power module, as viewed in side elevation. A smoothing capacitor
120
for smoothing a DC supply voltage to be externally applied to the power semiconductor devices
150
is disposed over the power module body portion
100
. An N-electrode
121
N and a P-electrode
121
P (both designated by the reference numeral
121
in
FIG. 30
) of the smoothing capacitor
120
, and the N-terminal
108
N and the P-terminal
108
P (both designated by the reference numeral
108
in
FIG. 30
) of the power module body portion
100
are connected to each other through a connecting conductor
124
. The connecting conductor
124
has conductor plates
122
N and
122
P opposed to each other, with an insulation plate
123
therebetween. The conductor plates
122
N,
122
P and the N- and P-terminals
108
N,
108
P are fastened to each other with respective screws
125
.
FIG. 31
is a schematic cross-sectional view showing a structure of connections between the smoothing capacitors
120
and the connecting conductor
124
, as viewed in top plan. The conductor plate
122
N is in contact with the N-electrodes
121
N, and the conductor plate
122
P is in contact with the P-electrodes
121
P. The conductor plate
122
N has openings
126
provided partially to avoid contact with the P-electrodes
121
P, and the conductor plate
122
P has openings
127
provided partially to avoid contact with the N-electrodes
121
N.
However, the above-mentioned background art power module requires the connecting conductor
124
including the conductor plates
122
N,
122
P and the insulation plate
123
for connection between the N- and P-electrodes
121
N,
121
P of the smoothing capacitors
120
and the N- and P-terminals
108
N,
108
P of the power module body portion
100
. This presents problems in the large number of parts and in complicated assembly.
Another problem is an increased circuit inductance because of a long wiring path between the smoothing capacitors
120
and the power semiconductor devices
105
. In the operation of the power module, the high-speed switching of the power semiconductor devices
105
causes a large pulse-shaped current proportional to the amount of current change (di/dt) to flow between the smoothing capacitors
120
and the power semiconductor devices
105
, thereby to develop a voltage proportional to the circuit inductance, which in turn is applied as noise to the power semiconductor devices
105
. Further, the increase in circuit inductance requires the increase in electrostatic capacitance of the smoothing capacitors
120
for suppression of ripple voltage. This results in the increase in the size of the smoothing capacitors
120
and accordingly the increase in the size of the power module itself. Therefore, the circuit inductance is preferably low.
Furthermore, the background art power module which comprises the large-sized smoothing capacitors
120
disposed over the power module body portion
100
is too low in resistance to vibration for use as a vehicle-mounted power module, for example.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a power module comprises: a substrate with a power semiconductor device mounted thereon; a case having an interior in which the substrate is disposed; an N-terminal and a P-terminal arranged along a first side of a main surface of the case and electrically connected to the power semiconductor device; and a smoothing capacitor having a first electrode connected to the N-terminal and a second electrode connected to the P-terminal for smoothing a voltage to be externally supplied to the power semiconductor device, wherein the smoothing capacitor has a main surface level with the main surface of the case, and is disposed in contact with a side surface of the case including the first side of the main surface of the case, and wherein the first electrode and the second electrode are disposed on the main surface of the smoothing capacitor and in proximity to the N-terminal and the P-terminal, respectively.
Preferably, according to a second aspect of the present invention, in the power module of the first aspect, the smoothing capacitor comprises: an enclosure; a plurality of capacitor elements disposed in the enclosure, each of the plurality of capacitor elements having a first electrode abutting against the first electrode of the smoothing capacitor and a second electrode abutting against the second electrode of the smoothing capacitor; and a hold-down plate for pressing the plurality of capacitor elements against the enclosure to fix the plurality of capacitor elements in the enclosure.
Preferably, according to a third aspect of the present invention, in the power module of the second aspect, the enclosure has a single heat sink for dissipating heat generated by the plurality of capacitor elements.
Preferably, according to a fourth aspect of the present invention, in the power module of the second or third asp
Fukada Masakazu
Kimoto Nobuyoshi
Koga Masuo
Majumdar Gourab
Nakajima Dai
Mitsubishi Denki & Kabushiki Kaisha
Thompson Gregory
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