Random vibration testing and analysis of a large ceramic substrate assembly

Hermetic chip carriers (HCC) are increasingly used in electronic equipment to obtain greater packaging densities. In order to avoid thermal expansion mismatch, the HCC which is basically made of ceramic, is soldered to a ceramic substrate. The ceramic substrate, in turn, is soldered to a printed wiring board which is usually mounted in a metallic chassis. The ability of the ceramic substrate to withstand the rigors of a high level random vibration environment is of great importance. An investigation was conducted with the objective to determine the fragility level of a large ceramic substrate in a random vibration environment by step-stressing the part until structural failure resulted. The substrate tested was 3.3 inches x 3.45 inches x .040 inches thick and contained 44 HCCs on each side. A ceramic substrate assembly was mounted to a printed wiring board. The overall assembly was mounted into a vibration fixture which simulated the mounting conditions of an actual chassis.