Patent ID: 7956455

Claim:
A power transistor package comprising: a rectangular ceramic base; one or more die affixed to an upper surface of the ceramic base; and a rectangular non-conductive cover overlying the ceramic base, the cover including: a marginal frame including an inner stair-stepped portion defining a recess configured to receive the ceramic base, the inner stair-stepped portion of the marginal frame having a bottom surface laterally outward of the ceramic base facing an upper surface of the heat sink; at least two bolt holes in the marginal frame arranged to receive bolts on opposite sides of the recess to secure the ceramic base to a heat sink outward of the recess; and a boss forming a peripheral stair-stepped portion protruding from the bottom surface of the inner stair-stepped portion of the marginal frame adjacent each bolt hole at a location spaced laterally outward toward a periphery of the marginal frame such that the adjacent bolt hole is between the recess and the boss; each boss protruding from the bottom surface of the inner stair-stepped portion of the marginal frame, so that the bottom surface of the inner stair-stepped portion of the marginal frame is spaced by the bosses above the heat sink when unbolted and, when bolts are tightened in the bolt holes, the bosses serve as pivots to exert a downward-bending moment in the cover laterally inward of the bolts.