In its simplest form the thin Pak as illustrated in figure is a soldered assembly of a large power device usually at least a size and a thin ceramic lid The lid is metalized on the bottom side to mate to large and small device electrodes gate pilot cathode source etc which are connected by metalized vias to a more rugged and convenient pattern of top side metal If the lid material is a good thermal conductor and or the lid vias are very dense the thinPak lidded device can be cooled from both sides or treat ed as a flip chip device but with no restrictions on achiev able breakdown voltage The low impedance small size and weight and rather large mechan ical tolerances permissible on the top of the lid are convenient
Vic Temple