Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – With extended latchup current level
Reexamination Certificate
2000-07-25
2002-01-15
Flynn, Nathan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
With extended latchup current level
C322S046000, C323S207000, C327S438000, C327S440000, C257S156000
Reexamination Certificate
active
06339231
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gate commutated turn-off thyristor module, and more particularly to an improvement for reducing electric resistance and inductance components in a path for a gate current and simplifying an assembly.
2. Description of the Background Art
A gate turn-off thyristor (which will be hereinafter referred to as a “GTO” thyristor) has widely been utilized as a device suitable for application to large-capacity power electronics. However, the GTO thyristor has had a problem in that a snubber circuit is required and it is hard to prevent a snubber loss from being increased with a rise in an operating voltage. Instead, a gate commutated turn-off thyristor (hereinafter referred to as a “GCT thyristor”) which has been developed as another device has an advantage that an operation can be carried out without the snubber circuit and the snubber loss can be eliminated.
The GCT thyristor serves to raise a rate of increase in a gate reverse current to approximately one hundred times as high as the GTO thyristor and to cause all main currents to flow to a gate circuit (that is, commutate all the main currents), thereby carrying out a turn-off operation. In order to carry out this operation, a GCT thyristor module incorporating a GCT thyristor and a driving device thereof has such a structure that the GCT thyristor and the driving device are connected to each other through a gate terminal plate provided like a ring in the GCT thyristor.
FIG. 9
is a partially sectional side view showing a conventional GCT thyristor which is the background of the present invention. As shown in
FIG. 9
, a GCT thyristor
90
comprises a semiconductor substrate
28
. In the semiconductor substrate
28
, a plurality of (for example, several thousand) minute thyristor elements (not shown) connected in parallel with each other which are referred to as segments are arranged concentrically in a plurality of stages (for example, eight stages). Each thyristor element can be turned on and off by a gate current. Each cathode electrode
29
b
is formed in a position corresponding to each segment on a lower main surface of the semiconductor substrate
28
, and a gate electrode
29
a
is formed in the vicinity of an outer peripheral portion of the lower main surface.
A cathode distortion buffer plate
30
and a cathode post electrode (main electrode)
31
are sequentially provided under the cathode electrode
29
b.
On the other hand, an anode distortion buffer plate
32
and an anode post electrode (main electrode)
33
are sequentially provided above an anode electrode (not shown) which is formed on an upper main surface of the semiconductor substrate
28
.
Furthermore, a ring-shaped gate electrode
34
is provided in contact with the gate electrode
29
a,
and a gate terminal plate
1
formed as a ring-shaped metal plate is provided to slidably come in contact with the ring-shaped gate electrode
34
on an inner peripheral edge surface thereof. The gate terminal plate
1
and the ring-shaped gate electrode
34
are pressed against the gate electrode
29
a
by means of a ring-shaped elastic member
35
. The elastic member
35
has a configuration of a ring-shaped belleville spring or corrugated spring and presses the gate terminal plate
1
through a ring-shaped insulator
36
.
A sheet-shaped insulator
37
is provided along wall surfaces of the cathode distortion buffer plate
30
and the cathode post electrode
31
. The insulator
37
serves to insulate the ring-shaped gate electrode
34
from the cathode distortion buffer plate
30
and the cathode post electrode
31
.
A cathode flange
26
is fixed to an edge portion of the cathode post electrode
31
and an anode flange
40
is fixed to the anode post electrode
33
. An insulating cylinder
2
constituted by an insulator such as ceramic is provided between the cathode flange
26
and the anode flange
40
to surround a main part of the GCT thyristor
90
. The insulating cylinder
2
is divided vertically into two portions with the gate terminal plate
1
interposed therebetween, and further has a projection
42
to increase a creeping distance. The gate terminal plate
1
has an outer peripheral portion protruded like a ring from a side surface of the insulating cylinder
2
to the outside and can be thus connected to the outside. The insulating cylinder
2
is fixed in close contact with upper and lower surfaces of the gate terminal plate
1
.
A ring-shaped connecting plate
43
a
is fixed to a lower end face of the insulating cylinder
2
. The connecting plate
43
a
is further fixed to the ring-shaped cathode flange
26
. Similarly, a ring-shaped connecting plate
43
b
is fixed to an upper end face of the insulating cylinder
2
. The connecting plate
43
b
is further fixed to the ring-shaped anode flange
40
. Thus, the GCT thyristor
90
has a package structure in which a housing chamber for accommodating the semiconductor substrate
28
and for being held airtightly with the outside is defined on the inside. The air in the housing chamber is substituted for an inert gas.
A plurality of mounting holes
21
are provided at a predetermined interval along an edge portion of the gate terminal plate
1
. The GCT thyristor
90
has a disc-shaped appearance, which is not shown. The cathode post electrode
31
, the cathode flange
26
and the gate terminal plate
1
are concentrically provided in order as seen from the lower surface. Moreover, the anode post electrode
33
, the anode flange
40
and the gate terminal plate
1
are concentrically arranged in order as seen from the upper surface.
FIG. 10
is a plan view showing a driving device to be connected to the GCT thyristor
90
. The driving device includes a gate driver
15
acting as a circuit section and a connecting substrate
70
. The connecting substrate
70
is a portion where a circuit substrate (not shown) belonging to the gate driver
15
is extended toward the outside on the side of the gate driver
15
, has a wiring pattern (not shown) and serves to electrically relay the gate driver
15
and the GCT thyristor
90
.
The connecting substrate
70
is provided with a thyristor inserting section
71
which is an opening for inserting the GCT thyristor
90
. Around the thyristor inserting section
71
are provided a plurality of through holes
21
A through which screws for fixing the gate terminal plate
1
of the GCT thyristor
90
penetrate. The cathode post electrode
31
is inserted into the thyristor inserting section
71
to be disposed on the underside, and thereafter, the GCT thyristor
90
is fixed to the connecting substrate
70
with a screw. Thereby, a GCT thyristor module is completed.
FIG. 11
is a partially enlarged plan view showing a part of the periphery of the thyristor inserting section
71
which is obtained after the GCT thyristor
90
is fixed to the connecting substrate
70
and the GCT thyristor module is assembled.
FIG. 12
is a sectional view taken along the line A—A in
FIG. 11
, and
FIG. 13
is a sectional view taken along the line B—B in FIG.
11
.
As shown in
FIGS. 11
to
13
, the GCT thyristor
90
is fixed to the connecting substrate
70
through two kinds of screws
8
A and
8
B, three kinds of metal rings
7
A,
7
B and
7
C and a metallic cathode electrode plate (main electrode plate)
10
. Each of the metal rings
7
A,
7
B and
7
C and the cathode electrode plate
10
has a high electric conductivity.
The gate terminal plate
1
fixed to the insulating cylinder
2
through a soldering
2
a
is interposed between the upper metal ring
7
A and the middle metal ring
7
B, and is fixed thereto with the screw
8
B. The cathode electrode plate
10
abutting on the lower main surface of the cathode post electrode
31
and the connecting substrate
70
are interposed between the middle metal ring
7
B and the lower metal ring
7
C and are fixed thereto with the screw
8
A. Consequently, the GCT thyristor
90
and the connecting substrate
70
are fixed to each other.
The connecting substrate
Flynn Nathan
Wilson Scott R.
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