| 摘要 |
1,254,500. Semi-conductor devices. MITSUBISHI DENKI K.K. 25 Aug., 1969 [24 Aug., 1968 (2)], No. 42176/69. Heading H1K. A main semi-conductor device 10, such as a thyristor, a bidirectional switch or a transistor, is protected against overheating at its junctions by the provision of an auxiliary device 50 mounted on the main device 10 and having an electrical characteristic, e.g. breakover voltage in the case of the PNPN switch shown, which changes significantly at a lower temperature than that at which a characteristic, e.g. breakover voltage, of the main device 10 changes. In the arrangement shown the breakover voltage of the auxiliary device 50 reduces to zero at a temperature below that at which that of the main device 10 changes, and the device 50 then acts as a short-circuit to a firing signal applied between terminals 103 and 113 to prevent the main device 10 from firing in the presence of an alternating load current and thus to prevent overheating. The main device is made of Si having Ga-diffused P-type regions 12, 13 and an annular P-diffused N-type region 16. The vapour deposited Al gate electrode 19 and cathode electrode 18 are preferably annular, the auxiliary device 50 being mounted centrally on the device 10 through a layer 22 of Al. The region 12 of the device 10 is brazed to a Mo disc 21 through an Al foil. The auxiliary device 50 is a Si PNPN diode made by diffusion or epitaxy, and has its outer junctions shorted by Al electrodes. The device 50 may alternatively be a 5-layer device, a thyristor or a transistor. |
