MCT packaging

An effort was made to develop a hermetic MCT (MOS controlled thyristor) packaging approach in which the package does not limit the switching efficiency of the power semiconductor chip itself. This was accomplished by the development of the hermetic thin-pack (HTP) packaging approach, which results in a hermetic package outline not much bigger than the chip itself. This is achieved by the replacement of the traditional aluminum wire bonds with small (0.040-in) copper spheres which make the connections to the chip topside contacts (gate and anode) through holes cut directly through the ceramic (alumina) lid. Electrical contact is made to the chip by means of thermocompression and hard solders and to the lid by means of hermetically bonded direct-bond copper foil. The HTP approach has so far been applied to MCT chips as large as 0.500 on edge. The package thickness can be as small as 0.050 in. The package resistance is 0.35 Ω/cm² and the inductance is 1 pH/cm²