Investigation of UBM systems for electroplated Sn/37Pb and Sn/3.5Ag solder

For the future electronic packaging, a high density and environmentally friendly interconnection technology is urgently needed. This paper suggests a Pb-free electroplated bumping process for high density interconnection. We describe a newly defined eutectic Sn/3.5Ag solder bumping process using an alloy electroplating method and introduce the UBM (Under Bump Metallurgy) study for electroplated Sn/3.5Ag bumps. Four different types of UBM layers were selected and investigated. The bumping process and UBM interface reactions of Sn/3.5Ag were compared with those of Pb/63Sn which is most commonly used as a solder bumping material.