New stacked-wafer micromodule techniques have been developed by Sylvania Electric Products Co., Inc., under an independent research program. Multi-component, hermetically sealed wafers are stacked one on top of the other and interconnected by printed circuit wafers. Each wafer, measuring less than one-half in. sq. and about 10 mils thick, is capable of carrying a stage of circuitry.
Spacers used to separate stages are fused to the circuit wafers to provide sealing. Glass spacers are used, and the wafers are about 96% alumina ceramic. Individual modules are connected by a printed interwiring board, so that wires are not required.
A low-frequency radio transmitter is being built to illustrate the potential of the concept. Special transistors have been produced for the transmitter, and inductance will be provided by wound toroidal cores.The technique can be easily adapted to automated production, according to Sylvania. (Electronic Design, June 8, 1960, p. 5)
Among the hot topics of the first half of the '60s were miniaturization and hybrid microcircuits. At that early stage of monolithic ICs, hybrids offered many advantages over monolithics.