Effect of ultrasonic power on wettability, porosity and mechanical properties of ultrasonic-aided laser reflow soldering

Abstract

Wettability, porosity and mechanical properties of ultrasonic-aided laser reflow soldering lead-free solder Sn-3.0Ag-0.5Cu (SAC305) on Cu pad have been investigated at ultrasonic vibration (USV) of different power. The parameters of laser reflow soldering are determined by the wetting experiment, and the effects of different ultrasonic powers on the performance of the solder joint are studied. Results showed that USV can improve wettability without keyholes on top of the solder joint, and the contact angle between the solder joint and the substrate decreases first and then increases as the ultrasonic power increases. The cavitation effect caused by USV effectively reduces the porosity of the solder joints. When the ultrasonic power is 225 W, the porosity of the solder joint is reduced from the initial 13.2% to 5.2%. Through X-ray Diffraction (XRD) analysis of the solder joint matrix, all solder joints have diffraction peaks of [Formula: see text]-Sn, Cu6Sn5 and Ag3Sn, and the solder joints show higher diffraction peak intensity with USV treated. Furthermore, the solder joints prepared by ultrasonic-aided laser reflow soldering show better shear strength compared with laser reflow soldering.