Material issues in electronic interconnects and packaging

Electronic packages consist of metallic, polymeric, and sometimes ceramic materials as integral entities. Individual physical and mechanical properties of these constituents, and their influence on each other's behavior, affect the overall reliability of the electronic packages. The most common failures in electronic interconnects arise from thermomechanical fatigue of the solder joints. Mismatches in coefficient of thermal expansion (CTE) that exist between these constituent materials are the main cause of such failures. Several approaches such as alloying and composite methodology are being explored to improve the reliability of the solder, which is metallic in nature, by improving its mechanical attributes. Other avenues such as matching the CTE of the constituent materials are also being considered. In addition, the metallization of the electrical components and electrically non-conducting polymeric/ceramic layer to make it solderable has also been a source of concern regarding the joint reliability. Another concern relates to the high CTE of polymeric boards. This can cause significant CTE mismatch problems if silicon chips are directly mounted on them. Some of our significant findings in these respects are presented.