Kinetics of Ultrasonic and Current Coupling-Enhanced Dissolution of Copper in Liquid Tin

Abstract

With the development trend of high speed, light weight, continual miniaturization, and multifunctionality of microelectronic products, the size of solder joints continues to shrink. Therefore, higher requirements are being placed on soldering techniques. This study used the immersion method to investigate the dissolution kinetics of copper in liquid tin at temperatures in the range of 240–300°C with ultrasonic and current coupling. The amount of dissolution and the thickness of the interfacial intermetallic compound (IMC) layer were measured and the dissolution activation energy was calculated. Results showed that the composite fields of ultrasonic and current coupling accelerated copper dissolution in liquid tin and decreased the dissolution activation energy. The dissolution rate was 5–7 times higher compared to that without ultrasound and current, and was 2–3 times higher compared to that using only current. At a certain temperature, with the increase in immersion time, the thickness of the interface IMC layer demonstrated parabolic growth. The sound pressure caused by the ultrasound and the temperature gradient caused by current in the liquid tin were simulated by finite element modeling. The results show that the sound pressure distribution in liquid tin was uneven, and the temperature gradient inside the liquid tin increased with current.