The effect of Ni,Ge elements on microstructure and mechanical properties of Sn-Ag-Cu solders

Sn-Ag-Cu solder alloys have been widely used as lead-free solders following the enactment of the 2007 RoHS Directive. Recently, the content of Ag has been demanded to decrease in the solders for wave soldering process as the cost of Ag has already become very expensive. On the other hand, it was considered that the mechanical strength of the solder tends to be not enough as the amount of Ag decreases. Therefore, the low-Ag solders must be carefully developed to keep the mechanical properties. In this paper, we study the effect of adding small amount of (Ni, Ge) elements on microstructure and mechanical properties of the low-Ag lead-free solders of which the amount of Ag is 0.3 wt% and 1.0 wt%. Indentation testing method was used to obtain mechanical properties including elastic, plastic and creep deformations in this study.