Effects of Sb addition on the properties of Sn-Ag-Cu/(Cu, Ni) solder systems

The wetting characteristics and microhardness of the Sn-Ag-Cu (SAC) near eutectic alloy and the effects of a small addition of antimony on these properties have been investigated. The contact angle measurements on the two Sn-rich alloys, i.e. the Sn-1.8Ag-0.7Cu and Sn-1.9Ag-0.4Cu-2.1Sb (in wt %) in contact with Cu and Ni substrates have been performed by using a sessile drop apparatus. Although the two solders investigated exhibit different spreading kinetics on Cu and Ni substrates, their final contact angle values indicate a good wetting of these alloys on both substrates. The melting behaviour of two SAC type alloys and the interfaces between these solders and substrates have been characterised by DSC and SEM/EDS analyses, respectively. The results obtained were explained qualitatively by means of the corresponding phase diagrams. The microhardness of SAC solders investigated slightly increases with Sb addition.