Power switching device having improved heat dissipation means

A power control assembly, comprising a solid state device including a heat generating portion, an electrically insulating thermally conductive substrate having a first side operatively connected in heat transfer relation to said heat generating solid state portion, a heat sink having an outer surface abutting a second substrate side spaced from said first side for dissipating heat from said solid state device, an electrically insulating housing having a first side including an outer wall surrounding an opening providing a recessed inner wall spaced from said outer wall with said substrate enclosing said opening and spaced from said inner wall to form a cavity about said solid state device, said inner wall including a terminal opening extending from said cavity to a second side of said housing, means for mechanically clamping said substrate to said heat sink without subjecting said solid state device to compressive forces, and electrical conductor means including a first conductive portion attached for electrical connection to said solid state device and including a bendable terminal strip including a first part substantially normal to said substrate and a second part connected to the first part and generally normal to said first part and parallel to said substrate and a second conductive portion extending through said terminal opening and providing external electrical access to said solid state device and including a lead wire attached to and soldered to said second part.

A method of attaching lead wires to a power control device whose major parts are a ceramic substrate on which electric circuit means are adhered and an insulating housing for said substrate, which device is preliminarily fabricated to the extent of having conductive film bands bonded to said substrate and a lead frame comprised of thin sheet metal strips bonded to selected bands and having electric circuit components connected to selected ones of the strips to form an electric circuit mounted to said substrate, said method including the steps of:

• providing said lead frame with thin strips that extend laterally from and substantially coplanar with the lead frame after preliminary fabrication, which strips have first and second parts, the first of which is nearest to the lead frame,
• bending said strip part on a line intermediate said first and second strip parts such that said second part is generally normal to said first part,
• soldering the end of a lead wire to each of said second parts and bending said first part on a line intermediate said first part and said lead frame to thereby dispose said first part generally normal to said lead frame and said lead wires generally normal to said second part,
• then inserting said substrate with lead wires attached into a recess in the bottom of said housing such that said lead wires extend through openings in said housing and the bottom of said substrate is exposed.