Physics and materials challenges for lead-free solders

Abstract

At present, the electronic industry is actively searching for Pb-free solders due to environmental concerns over Pb-containing solders. Solder joints are widely used to bond chips to their substrates for electrical connection and packaging. Lacking reliability data, many electronic companies will be reluctant to adopt Pb-free solders in the advanced products. Hence, it is timely to review our understanding of structure-property relationship and potential reliability issues of Pb-free solders. A brief history of solder joint processes in electronic manufacturing is presented to serve as a background for the review. It emphasizes the unique phenomenon of spalling of interfacial intermetallic compound in solder reactions. Challenges for Pb-free solders from the point of view of physics and materials are given since the reliability issues of solder joints will remain with us when advanced Cu/low k dielectric interconnect technology is introduced into microelectronic devices.