Differential thermal expansion in microelectronic systems

Structures used in microelectronics systems, ranging in size from the individual device level to complete printed circuit boards (PCBs) involve ceramic, metallic and polymeric materials in intimate physical contact. Thermal cycling during normal operation can give rise to thermal fatigue at the various material interfaces, cause defect propagation, and lead to premature failure of the structures, either directly or through subsequent environmental degradation. The author reviews this technologically important problem by taking examples from each of the `packaging levels´ of microelectronic systems. The examples used include silicon oxidation and GaAs-on-silicon heteroepitaxy, ceramic or polymeric encapsulants of fabricated structures, PCBs, and on the solder connections used in mounting components on PCBs