Cavitation Characteristics in Ultrasonic Soldering and the Erosion Effect

In this work, the cavitation characteristics of the solder sonocapillary action during ultrasonic soldering were studied by a high-speed camera. The effects of ultrasonic power and time on the acoustic pressure, cavitation characteristics, and erosion effects were also investigated. Results showed that cavitation occurred throughout the entire sonocapillary action. Two kinds of bubble structures were observed. The steady bubbles had large sizes and long life periods. The transient bubbles had small sizes and short life periods. The steady bubbles preferentially appeared at the primary filling stage, while the transient bubbles dominated the entire cavitation field. The sonocapillary action was divided into the primary filling stage, the intermediate filling stage, and the completion filling stage. The primary filling stage had low acoustic pressure but high bubble density because the air content in the solder was high and some additional air entered the solder through the triple interface caused by ultrasonic vibration. Higher ultrasonic power resulted in stronger cavitation and, thus, better erosion effect on the substrate.