Wetting Properties and Interfacial Reactions of Mechanically Alloyed Cu5Zn8-Bearing Pb-Free Solders on a Copper Substrate

Abstract

For enhanced wetting properties of Zn-doped solder alloys, this paper proposes Cu5Zn8-bearing solders. A mechanical alloying process with controlled milling time and rotational speed was used to successfully fabricate Cu5Zn8-bearing powders with a diameter of 50 mu m to 70 mu m. Their composition was identified by inductively coupled plasma atomic emission spectroscopy. After the powders were made into a paste with a rosin-activated type of flux, the wetting angles of the Cu5Zn8-bearing paste solders on a Cu substrate were compared with the wetting angles of bulk solder alloys with the same amount of Cu and Zn alloying elements. The reason for the enhanced wetting properties of Cu5Zn8-bearing solders is explained by thermodynamic calculations and differential scanning calorimetry experiments. In addition, the interfacial reactions and the shear strength with Cu substrates are also discussed.