Electrocodeposition of Silver Particles with Tin for Fabrication of Lead-Free Solder Bumps

Solders based on tin-lead alloys are used extensively in semiconductor packaging. Electrodeposition is a favored solder- application process in flip-chip packaging because it provides superior thickness control and is easily scaled down to small pitch sizes. However, industrial processing and consumer use of lead-bearing products is a recognized public-health hazard, and the international trend toward regulation is driving demand for lead-free alternatives such as the Sn/Ag eutectic. Direct alloy deposition and stack deposition have been used to produce Sn/Ag bumps. Electrocodeposition, in which metallic or dielectric particles suspended in the plating bath are incorporated into a metal electrodeposit is potentially more economical. In this study, electrocodeposition of silver particles with tin was used to generate Sn/Ag composites and alloys.