Effect of ultrasonic vibration on the wetting behavior of molten tin on copper substrate

The wetting behavior of molten tin solder on copper substrate under ultrasonic vibrations was investigated by the wetting balance method at 250 degrees C. The cross-section morphology and microstructure of the specimen were analyzed after the wetting test. The grain size and thickness of intermetallic compounds (IMCs) at the interface were measured by an image-pro software. The ultrasonic sound pressure distribution in the molten tin solder was simulated by finite element analysis. The results showed significant effect of ultrasonic vibrations on the wettability of the molten tin solder on the copper substrate. The wettability was conjunctively determined by the driving and additional forces caused by an interfacial reaction and acoustic streaming, respectively. Acoustic cavitation expedited the interaction of interfacial atoms and facilitated the interfacial reaction, resulting in an increased driving force that contributed to the spreading of the molten tin solder on the copper substrate.