Thermal and Electrical Properties of Coated Conductive Substrates for Integrated Circuit Chip Mounting

A necessary component in realizing the potential of integrated circuit technology is the substrate upon which the integrated circuit chip is mounted. The substrate must meet several requirements to avoid deterioration of the system's performance: (i) The substrate must act as a rigid, reliable mounting platform for the chip. 1151 1152 T H E BELL SYSTEM TECHNICAL J O U R N A L , J U L Y - A U G U S T 1970 (it) The substrate must allow the dissipation of heat produced on the chip without causing an increase in temperature which would detrimentally effect circuit operation. (iii) The substrate must permit electrical connections to and interconnections between chips in a manner compatible with desired circuit performance. (iv) The substrate fabrication and chip mounting must be realizable at a cost consistent with the cost requirements of the system. Presently used substrates (for example, 0.625 mm thick A1203 ceramic wafers) are limited in their attainment of objectives ii and iii outlined above. Heat sink capability is limited by the low thermal conductivity and relatively large thickness of material necessary for mechanical rigidity and by the difficulty in extracting heat from the substrate itself. High frequency ( > 5 0 0 MHz) performance of beam-leaded integrated circuits suffers from the transmission line mismatch necessary with conventional substrates as is discussed below. A new materials configuration, as shown in Fig. 1, is envisioned which would simultaneously satisfy the four basic substrate requirements listed above.