Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With large area flexible electrodes in press contact with...
Reexamination Certificate
1998-12-18
2001-11-27
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With large area flexible electrodes in press contact with...
C257S139000, C257S147000, C257S689000, C257S181000, C257S182000, C257S150000, C257S726000, C257S730000, C257S718000
Reexamination Certificate
active
06323547
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pressure contact type semiconductor device used for a power converter.
2. Background of the Invention
In the field of large-capacity power electronics devices, a snubberless GCT (Gate-Commutated Turn-off) thyristor with the maximum cut-off current of 4000 A and a turn-off storage time of 3 &mgr;s or less has been realized to be an alternative to a conventional GTO (Gate Turn-Off) thyristor. The operating principles and the structure of the GCT thyristor is disclosed, for example, in European Patent Publication No. EPO785627A2, Japanese Patent Laid-Open No. 8-330572A, or Mitsubishi Electric Technical Report Vol. 71, No. 12, pp. 61-66. The features of the GCT thyristor are summarized as follows: In the GCT thyristor, a gate terminal which is in contact with a ring gate electrode and extends to the outside of an insulation cylinder is changed from lead-shaped to ring-shaped; and a connection between the GCT thyristor and a gate drive circuit is improved from a lead wire structure to a laminated circuit board structure, as compared with the conventional GTO thyristor. Thus, an inductance of the gate terminal and a metal gate contact is reduced to about one hundredths of an inductance of the GTO thyristor. This makes possible an isotropic supply of reverse gate current to be passed at the time of turn-off, from all the circumferential surfaces of a gate electrode, and also a reduction in the turn-off storage time. Further, in a wafer structure of the GCT thyristor, several thousands of segments are concentrically located in parallel with each other in a several-stage configuration, and a gate electrode region forming an interface with the gate electrode is located at the outermost peripheral portion.
FIG. 4
is a longitudinal cross-sectional view of the structure of a conventional GCT device, including a gate driver. Since a GCT device
1
P has a structure bilaterally symmetrical on a central axis CA, only one side of the structure is shown in FIG.
4
.
Each reference numeral or character in
FIG. 4
indicates each element as follows:
2
is a gate drive device for controlling the GCT device
1
P;
3
is a stack electrode for pressurizing the GCI device
1
P and drawing current; and
4
indicates a semiconductor substrate (wafer). On the peripheral portion of a first major surface of the semiconductor substrate
4
, a ring-shaped gate electrode
4
a
of aluminum is formed in contact with a gate electrode region, and on the inner portion of the first major surface outside the gate electrode
4
a
, a plurality of cathode electrodes
4
b
are concentrically formed. The reference numerals
5
and
6
are a cathode distortion buffer plate (or cathode metal plate) and a cathode post electrode, respectively, which are sequentially stacked one above the other on the cathode electrodes
4
b
on the semiconductor substrate
4
. Across a second major surface (opposite to the first major surface) of the semiconductor substrate
4
, an anode electrode (not shown) is formed on which an anode distortion buffer plate (or anode metal plate)
7
and an anode post electrode
8
are sequentially stacked one above the other. The reference numeral
9
is a ring gate electrode which is, at its first surface (bottom surface), in surface to surface contact with the gate electrode
4
a
on the semiconductor substrate
4
. The reference character
10
P is a ring-shaped gate terminal made of a metal plate. The inner end portion of an inner plane portion
10
PI of the ring-shaped gate terminal
10
P is slidably located on a second surface (opposite to the first surface) of the ring gate electrode
9
. Further, an elastic body
11
such as a disc or wave spring pushes the ring gate electrode
9
against the gate electrode
4
a
via a ring insulator
12
, in conjunction with the inner end portion of the inner plane portion
10
PI of the ring-shaped gate terminal
10
P. This establishes an electrical connection between the gate electrode
4
a
, the ring gate electrode
9
, and the ring-shaped gate terminal
10
P. The reference numeral
13
is an insulation sheet for insulating the ring gate electrode
9
from the facing cathode distortion buffer plate
5
and the facing cathode post electrode
6
. In addition to the inner plane portion
10
PI, the ring-shaped gate terminal
10
P includes an intermediate or fixed portion
10
PF and an outer plane portion
10
PO. In a portion of the inner plane portion
10
PI which is not in surface to surface contact with the ring gate electrode
9
, a bent portion
10
P
d
is formed, and in the middle of the outer plane portion
10
PO, a bent portion
10
P
a
is formed.
The reference numeral
14
is an insulation cylinder of ceramics which is divided so as to sandwich the intermediate portion
10
PF of the ring-shaped gate terminal
10
P from above and below. The insulation cylinder
14
further has a protrusion
14
a
. The fixed portion
10
PF of the ring-shaped gate terminal
10
P and the insulation cylinder
14
are hermetically fixed to each other by brazing. Further, in a portion of the outer plane portion
10
PO of the ring-shaped gate terminal
10
P which is spaced slightly inward from the outer end portion, a plurality of mounting holes
10
P
b
for coupling the ring-shaped gate terminal
10
P to the gate drive device
2
are equally spaced along the circumference. Further, an end portion
14
b
1
of a first L-shaped portion which is protruded above the upper surface of the insulation cylinder
14
, bending outwardly, and one end portion of a first ring-shaped flange
15
are hermetically fixed to each other by arc welding. Likely, an end portion
14
b
2
of a second L-shaped portion which is protruded below the lower surface of the insulation cylinder
14
and one end portion of a second ring-shaped flange
16
are hermetically fixed to each other by arc welding. The other end portions of the first flange
15
and the second flange
16
are fixed to cut portions of the cathode post electrode
6
and the anode post electrode
8
, respectively. Thus, the GCT device
1
P is enclosed to be kept from the outside. The interior of the device can be replaced by inert gas.
Further, the reference numeral
17
is a plate control electrode made of a ring metal plate which is located to be concentric with the ring-shaped gate terminal
10
P. The stack electrode
3
allows the plate control electrode
17
to be in pressure contact with the cathode post electrode
6
. Further, like the plate control electrode
17
, a plate control gate electrode
18
made of a ring metal plate is located to be concentric with the ring-shaped gate terminal
10
P. An inner end portion of the plate control gate electrode
18
is electrically connected to the outer end portion of the outer plane portion
10
PO of the ring-shaped gate terminal
10
P. This electrical connection is established by the following members
19
and
20
:
19
is an insulating sleeve for insulating the ring-shaped gate terminal
10
P and the plate control gate electrode
18
from the plate control electrode
17
; and
20
is a coupling part including bolts and nuts, for electrically connecting the ring-shaped gate terminal
10
P and the plate control gate electrode
18
via the insulating sleeve
19
between the plate control electrode
17
and the plate control gate electrode
18
. Each bolt of the coupling part
20
comes through a mounting hole
10
P
b
, and a mounting hole provided on the plate control gate electrode
18
corresponding to the mounting hole
10
P
b
. Thus, the plate control electrode
17
and the plate control gate electrode
18
are directly coupled to the gate drive device
2
.
As the material for the ring-shaped gate terminal
10
P, an alloy of iron and 42% nickel having a similar thermal expansion characteristic to a thermal expansion coefficient of alumina and relatively high processability and strength has been generally used to obtain high fixing strength of the brazed joint between the ring-shaped gate terminal
10
Bessho Mikio
Kawamura Toshinobu
Satoh Katsumi
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Williams Alexander O.
LandOfFree
Pressure contact type semiconductor device with ringshaped... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pressure contact type semiconductor device with ringshaped..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pressure contact type semiconductor device with ringshaped... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2593912