Comparison of wetting properties for Sn-based solders on copper and aluminum substrates

The wetting properties of four typical Sn-based solders,i.e.Sn-37Pb,Sn-3.0Ag-0.5Cu,Sn-0.7Cu and Sn-9Zn,on copper and aluminum substrates at 250,260 and 270 ℃ were evaluated adopting wetting balance method.The experimental results show that the wetting times of all solders on copper substrate are less than on aluminum substrate,the wetting forces of the solders with copper substrate are bigger than with aluminum substrate except Sn-9Zn solder.The wetting properties of the solders on aluminum substrate increases with the elevation of soldering temperature,the wetting force of Sn-9Zn increases most obviously among four solders and reaches 3.68 mN at 270 ℃.The experiments also show that the wetting properties of solders on copper substrate mainly depend on surface tension of solder alloy,however,depend on both surface tension of solder alloy and interaction with aluminum substrate on aluminum substrate.