An intermetallic study of solder joints with Sn-Ag-Cu lead-free solder

This paper focuses on the intermetallics study of reliability tested solder joints between the Sn-3.5Ag-0.75Cu lead-free solder balls and Sn-plated Cu pads on molded BGAs. In the solder joints, /spl eta/ phase (Cu/sub 6/Sn/sub 5/) was the initial intermetallic observed on the Cu substrate, followed by /spl epsiv/ phase (Cu/sub 3/Sn) between /spl eta/ and Cu. This paper described observations on intermetallic thickness and its growth over the anneal timeframe. It also covers the impacts of reliability tests on joint integrity and mechanical failure mode. The results obtained were compared against Sn-36Pb-2Ag solder in order to provide a more comprehensive understanding of the Sn-Ag-Cu lead-free solder.