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Formation of AuSn_x intermetallic compounds (IMCs) in laser reflowed solder joints was investigated.The results showed that few IMCs formed at the solder/0.1μm Au interface.Needlelike AuSn_4 IMCs were observed at the solder/0.5μm Au interface. In Sn-2.0Ag-0.75Cu-3.0Bi and Sn-3.5Ag-0.75Cu solder joints,when the laser input energy was increased,AuSn_4 IMCs changed from a layer to needlelike or dendritic distribution at the solder/0.9μm Au interface.As for the solder joints with 4.0μm thickness of Au surface finish on pads,AuSn_4,AuSn_2,AuSn IMCs,and Au_2Sn phases formed at the interface.Moreover,the content of AuSn_x IMCs,such as,AuSn_4 and AuSn_2,which contained high Sn concentration,would become larger as the laser input energy increased.In the Sn-37Pb solder joints with 0.9μm or 4.0μm thickness of the Au surface finish on pads,AuSn_4 IMCs were in netlike distribution.The interspaces between them were filled with Pb-rich phases.
Formation of AuSn_x intermetallic compounds (IMCs) in laser reflowed solder joints was investigated. The results showed that few IMCs formed at the solder / 0.1μm Au interface. Needlelike AuSn_4 IMCs were observed at the solder / 0.5μm Au interface. In Sn-2.0 Ag-0.75Cu-3.0Bi and Sn-3.5Ag-0.75Cu solder joints, when the laser input energy was increased, AuSn_4 IMCs changed from a layer to needlelike or dendritic distribution at the solder / 0.9μm Au interface. As for the solder joints with 4.0 μm thickness of Au surface finish on pads, AuSn_4, AuSn_2, AuSn IMCs, and Au_2Sn phases formed at the interface. More over, the content of AuSn_x IMCs, such as, AuSn_4 and AuSn_2, which contained high Sn concentration, would become larger as the laser input energy increased. In the Sn-37Pb solder joints with 0.9 μm or 4.0 μm thickness of the Au surface finish on pads, AuSn_4 IMCs were in netlike distribution. interspaces between them were filled with Pb-rich phases.