Development of a Thermally Conductive Ceramic Component Board

This paper describes the development and evaluation of a ceramic component board having all circuit connections electrically insulated but thermally grounded. Individual circuits are encapsulated in epoxy parallelopipeds having large diameter leads of nickel clad copper wire. The leads in turn are resistance welded to metallic (Kovar) studs which have been brazed into an inorganic (Beryllium Oxide Ceramic) wafer having exceedingly good thermal conductance. Interconnections between weld studs are accomplished by metalized plated runs. The component board assembly was then evaluated under simulated operating conditions, i.e., edge clamped to an infinite heat sink and in a vacuum environment. Internal heat rise within the circuit modules was monitored and compared to that found in another module which had not been welded to the board, and plots of the thermal gradients across the ceramic wafer were made.