Influence of rapid solidification on microstructure, thermodynamic characteristic and the mechanical properties of solder/Cu joints of Sn-9Zn alloy

Rapidly solidified Sn-9Zn alloy foils were prepared by the melt-spinning method. The effects of rapid solidification process on the microstructure, thermodynamic characteristic, electrochemical corrosion properties and spreading properties of Sn-9Zn solder alloys were analyzed. The mechanical properties and fracture behaviors of the solder/Cu joints were also investigated. The results showed that the rapid solidification process could obviously refine the solidification structure of Sn-9Zn alloy and a fine netlike dendrite structure was formed due to the rapid branch of Sn phase. The Zn phase was distributed in Sn matrix in granular form. After rapid solidification, the pasty range decreased from 7 K to 4 K, the wettability was modestly improved, and the corrosion resistance of the rapid solidified alloy was improved significantly. The tensile shear strengths of the joints using the rapidly solidified solder were obviously higher than that of the joints using the as-solidified solders result from the formation of fine-grained intermetallic compound (IMC) with a needle pattern and more uniform IMC layer at the interface.