Pressure-contact semiconductor device

Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – With housing or external electrode

Reexamination Certificate

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Details

C257S151000, C257S153000, C327S440000

Reexamination Certificate

active

06423988

ABSTRACT:

TECHNICAL FIELD
The present invention relates to the structure of a pressure-contact type semiconductor device used for a power converter.
BACKGROUND ART
In the field of bulk power electronic devices, a snubberless GCT (Gate-Commutated Turn-off) thyristor having a maximum breaking current of 4000 A and a turn-off storage time of not more 3 &mgr;s is being implemented as that substituting for a conventional GTO (Gate Turn-off) thyristor, in order to satisfy requirement for a higher withstand voltage and a higher current.
The operation principle of the GCT thyristor and its structure are disclosed in European Patent Laying-Open Gazette EP0785627A2 (Japanese Patent Laying-Open Gazette No. 9-201039), Japanese Patent Laying-Open Gazette No. 8-330572 and Mitsubishi Denki Giho Vol. 71, No. 12, pp. 61-66, for example. The characteristics thereof are summarized as follows: That is, in the GCT thyristor, the shape of a gate terminal coming into contact with a ring gate electrode and drawn out from an insulator tube is changed from a lead shape of the conventional GTO thyristor to a ring shape while connection between the GCT thyristor and a gate drive circuit is also improved from a lead wire structure of the GTO thyristor to a structure by a multilayer substrate. Thus, the inductance of the gate terminal and a gate wire is reduced to about 1/100 of the inductance of the GTO thyristor and it is possible to isotropically supply a gate current of an opposite direction fed at a turn-off time from the overall circumferential surface of the gate electrode while reduction of the turn-off storage time is also enabled. As to the wafer structure of the GCT thyristor, thousands of segments are concentrically arranged in a parallel manner in a several-stage structure and a gate electrode region forming an interface with the gate electrode is arranged on the outermost peripheral portion thereof, similarly to the wafer structure of the conventional GTO thyristor.
FIG. 3
is a longitudinal sectional view showing the structure of a conventional GCT device
1
P inclusive of an external gate driver
2
P for controlling the GCT device
1
P. Since the GCT device
1
P has a laterally symmetrical structure in relation to a central axis CAP, only the structure of one side thereof is shown in FIG.
3
.
Each reference numeral in
FIG. 3
denotes the following each element: That is, stack electrodes
3
P are electrodes for pressurizing the GCT device
1
P and taking out a current.
4
P is a semiconductor substrate (wafer), and a gate electrode
4
Pa of aluminum coming into contact with a gate electrode region is formed in the form of a ring on the outermost peripheral portion of its first main surface, while a plurality of cathode electrodes
4
Pb are concentrically formed on the first main surface of the semiconductor substrate
4
P inside the gate electrode
4
Pa.
5
P and
6
P are a cathode distortion buffer plate and a cathode post electrode successively loaded on the cathode electrodes
4
Pb of the semiconductor substrate
4
P respectively, a non-illustrated anode electrode is fully formed on a second main surface (surface opposite to the first main surface) corresponding to the rear surface of the semiconductor substrate
4
P, and an anode distortion buffer plate
7
P and an anode post electrode
8
P are successively loaded on this anode electrode.
9
P is a ring gate electrode whose first surface (lower surface) comes into surface contact with the gate electrode
4
Pa of the semiconductor substrate
4
P,
10
P is a ring-shaped gate terminal of a metal plate (which is an iron-42% nickel alloy, for example), and an inner peripheral side end portion of its inner peripheral plane part
10
PI is slidably arranged on a second surface (upper surface opposed to the aforementioned first surface) of the ring gate electrode
9
P. Further, an elastic body
11
P such as a belleville spring or a waved spring presses the ring gate electrode
9
P against the gate electrode
4
Pa through an annular insulator
12
P along with the aforementioned end portion of the inner peripheral plane part
10
PI of the ring-shaped gate terminal
10
P. Due to this pressing, the gate electrode
4
Pa, the ring gate electrode
9
P and the ring-shaped gate terminal
10
P are electrically connected with each other.
13
P is an insulating sheet for insulating the ring gate electrode
9
P from the opposed cathode distortion buffer plate
5
P and the cathode post electrode
6
P. The ring-shaped gate terminal
10
P is further formed by an intermediate part or fixed part
10
PF and an outer peripheral plane part
10
PO in addition to the aforementioned inner peripheral plane part
10
PI, and a bent part
10
Pd is provided on a portion not in surface contact with the ring gate electrode
9
P in the inner peripheral plane part
10
PI while a bent part
10
Pa is formed also on an intermediate portion of the outer peripheral plane part
10
PO.
On the other hand,
14
P is an insulator tube consisting of ceramics, which is vertically divided through the intermediate part
10
PA of the ring-shaped gate terminal
10
P and has a projection part
14
Pa. The fixed part
10
PA of the ring-shaped gate terminal
10
P and the insulator tube
14
P are airtightly fixed to each other by braze bonding. In a portion of the outer peripheral plane part
10
PO of the ring-shaped gate terminal
10
P drawn outward from the outer peripheral side surface of the insulator tube
14
P slightly closer to the side of the inner peripheral portion than the outer peripheral end thereof, a plurality of mounting holes
10
Pb for coupling this ring-shaped gate terminal
10
P to the gate driver
2
P are provided at prescribed intervals toward the circumferential direction. Further, an end part
14
Pbl of a first L-shaped portion bent to project outward from the upper surface of the insulator tube
14
P and one end portion of a ring-shaped first flange
15
P are airtightly fixed by arc welding, and an end part
14
Pb
2
of a second L-shaped portion projecting from the lower surface of the insulator tube
14
P and one end portion of a second flange
16
P are also airtightly fixed similarly by arc welding. Other end portions of the first and second flanges
15
P and
16
P are fixed to parts of notched portions of the cathode post electrode
6
P and the anode post electrode
8
P respectively. Thus, the GCT device
1
P is in a structure closed against the exterior. This interior is replaced with inert gas.
Further,
17
P is a plate-shaped control electrode formed by an annular metal plate arranged to be concentric with the ring-shaped gate terminal
10
P, and brought into pressure contact with the cathode post electrode
6
P by the stack electrode
3
P. A plate-shaped control gate electrode
18
P formed by an annular metal plate is arranged to be concentric with the ring-shaped gate terminal
10
P similarly to the plate-shaped control electrode
17
P, and electrically connected in its inner peripheral side end portion with the outer peripheral side end portion of the outer peripheral plane part
10
PO of the ring-shaped gate terminal
10
P. Both electrodes
17
P and
18
P are rendered to form a multilayer substrate through an insulating substrate
30
P. Connection of both electrodes
17
P and
18
P to the GCT device
1
P is implemented by the following members
19
P and
20
P: That is,
19
P is an insulating sleeve for insulating the ring-shaped gate terminal
10
P and the plate-shaped control gate electrode
18
P from the plate-shaped control electrode
17
P,
20
P is a connection part formed by a bolt, a nut and the like for electrically connecting the ring-shaped gate terminal
10
P and the plate-shaped control gate electrode
18
P with each other between the plate-shaped control electrode
17
P and the plate-shaped control gate electrode
18
P through the insulating sleeve
19
P, and the nut in the connection part
20
P passes through a mounting hole provided in the plate-shaped control gate electrode
18
P in correspondence to the mounting hole
10
Pb and the mounting hole
10
Pb. The

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