Enhancement of the wettability and solder joint reliability at the Sn-9Zn-0.5Ag lead-free solder alloy-Cu interface by Ag precoating

摘要

The enhancement of the wettability and solder joint reliability at the Sn-9Zn-0.5Ag solder alloy-Cu interface by Ag precoating has been investigated. The wettability of the Sn-9Zn-0.5Ag solder alloy-Cu interface has been improved by Ag precoating. The adhesion strength of the solder alloy-Ag precoated Cu interface increases from 4.11+- 0.56 to 6.92 +- 0.85 MPa as dipped at 250 deg C for 10 s. When the dipping time is prolonged from 10 to 30 s, the interfacial adhesion strength increases from 6.92 +- 0.85 to 13.62 +- 0.73 MPa. The interfacial adhesion strength is enhanced by the rod-like Cu-Zn intermetallic compound (IMC) formed close to the interface. The diffusion coefficients of Sn and Zn in the IMC layer are determined as 5.76 X 10~(-10) and 9.50 X 10~(-11) cm~2/s at the Sn-9Zn-0.5Ag-Cu and Sn-9Zn-0.5Ag-Ag precoated Cu interfaces, respectively.