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Durable substrate subassembly for transistor switch module

  • US 5,895,974 A
  • Filed: 04/06/1998
  • Issued: 04/20/1999
  • Est. Priority Date: 04/06/1998
  • Status: Expired due to Term
First Claim
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1. A durable composite substrate subassembly useful in electronic switching modules comprising:

  • a ceramic wafer having first and second opposed major faces and a coefficient of thermal expansion close to a thermal expansion coefficient of a selected semiconductor material, said first and second faces being metallized;

    a first metal tab on said first metallized face that extends away from the ceramic wafer for electrical connection to a terminal member;

    a semiconductor switching device chip of said selected semiconductor material thermally and electrically conductively bonded to said first metallized face, wherein a first region of said device chip is in low electrical resistance connection with said first metal tab;

    a first ceramic layer bonded to a portion of said first metallized face adjacent said device chip, said first ceramic layer having a metallized upper surface;

    a second metal tab on said metallized upper surface of said first ceramic layer that extends away from the ceramic wafer for electrical connection to a terminal member;

    a metal foil conductively bonded to electrodes on an upper surface of said device chip and also to said metallized upper surface of said first ceramic layer, wherein a second region of said device chip is in low electrical resistance connection with said second metal tab, said metal foil having an upper surface; and

    a second ceramic layer bonded to said metal foil upper surface, said second ceramic layer being disposed over said device chip, said ceramic layer and said copper foil forming a composite material having a coefficient of thermal expansion close to that of said selected semiconductor material;

    effective to provide a durable heat conductive subassembly that includes an electrical and thermal connection to an upper surface of said device chip that has a composite coefficient of thermal expansion close to that of said device chip.

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