Experimental and theoretical analysis of the classification of Sn0.3Ag0.7Cu lead-free solders powder

Classification experiments using Sn0.3Ag0.7Cu lead-free solder powder prepared by supersonic gas atomization were conducted by turbo air classifier. The effects of rotor cage rotary speed on the cut size and partial classification efficiency of Sn0.3Ag0.7Cu solder powder were investigated. The relationship between cut size and rotor cage rotary speed was calculated through curve fitting. Results showed that cut size and median diameter of fine powders decreases exponentially with an increasing of the rotor rotary speed. The “fish-hook effect” existed in the turbo air classification process of Sn0.3Ag0.7Cu solder powder. The “fish-hook effect” weakens and classification efficiency increases with the rotor cage rotary speed decreasing. The efficiency of classifier was evaluated with the classification size ratio (CSR) index. It shows that higher rotor cage rotary speed is beneficial to the separation of coarse and fine powders adequately, and the classification is difficult when the size distribution of material fed is narrow.