No abstract

Sn-8Zn-3Bi solder paste and Sn-3.2Ag-0.5Cu solder balls were reflowed simultaneously at 240°C on Cu/Ni/Au metallized ball grid array substrates. The joints without Sn-Zn-Bi addition (only Sn-Ag-Cu) were studied as a control system. Electrical resistance was measured after multiple reflows and aging. The electrical resistance of the joint (R 1 ) consisted of three parts: the solder bulk (R solder bulk , upper solder highly beyond the mask), interfacial solder/intermetallic compound (R solder/IMC ), and the substrate (R substrate ). R 1 increased with reflows and aging time. R solder/IMC , rather than R solder bulk and R substrate , seemed to increase with reflows and aging time. The increase of R 1 was ascribed to the R solder/IMC rises. R substrate was the major contribution to R 1 . However R solder/IMC dominated the increase of R 1 with reflows and aging. R 1 of Sn-Zn-Bi/Sn-Ag-Cu samples were higher than that of Sn-Ag-Cu samples in various tests.