TEARDROP SHAPED LEAD FRAMES

摘要

A lead frame for use in solid state relays has a teardrop shaped frame. The frame has a small rounded portion connected to a large rounded portion. A power semiconductor is mounted in the large rounded portion. The teardrop shape eliminates sharp corners found in rectangular frames and allows heat to dissipate radially in all directions. More metal in close proximity to the power semiconductor, maintaining a lower aspect ratio of length to width, allows the semiconductor to run cooler at any given load. Several vent holes are located in the small rounded portion, which act as exhaust ports for the fumes generated in the heating stage of the solder re-flow, increasing solder coverage and improving reliability. The life of solder junctions utilizing the teardrop shaped lead frame which are subjected to temperature cycling while under load is increased, thus extending the life of the solid state relay.