Envelope design for semiconductor devices

Semiconductor devices have high-current low-voltage characteristics, are very temperature dependent, are basically very small and robust and must be hermetically sealed. Further, they cover a frequency range up to about 100Gc/s, voltages up to thousands of volts, currents up to hundreds of amperes and a temperature range of the order of ±200°C. The effect of these factors on the envelope design is discussed and the choice of metals and insulators for the envelope is considered. A strong case is made out for the extensive use of copper. Its high electrical and thermal conductivities, the ease with which it can be cold welded, its ready availability in a high-purity state and the availability of copper-sealing glass are all enlarged upon. Of the three possible insulators, glass, ceramics and plastics, the case of glass is discussed in some detail. Finally, some thought is given to mechanical standardization of outline dimensions of semiconductor devices with similar electrical characteristics made by different manufacturers. The difficulties are noted and possible degrees of standardization are indicated.