Effect of ultrasonic power on the wire bonding strength

Abstract

The PZT driver signal during bonding process and the shear test force of the corresponding wire bonding point are acquired as the indicator of ultrasonic power and bonding strength respectively in the large aluminum wire wedge bond- ing experiments.The bonding force,temperature and time are 4.7 N,room temperature and 100 ms respectively,which are selected according to industrial practice.The effect of ultrasonic power on large aluminum wire wedge bonding strength is stud- ied by changing the ultrasonic power rate,which is defined as the rate between set and maximum ultrasonic power.1 000 times bonding experiments in 20 groups are done,with 20 kinds ultrasonic power rate set between 15%～100%.Correlation be- tween the ultrasonic power and the bonding strength is found. When ultrasonic power is less then 1.0 W,the bonding strength will increase with the power increase while the fail bonding will decrease,and the opposite will happen when ultrasonic power is larger than 1.6 W.Only when ultrasonic power is between 1.0 W and 1.6 W,can stable and high yield bonding be reached. And when larger then 3.5 W,there are no obvious rules. Moreover,ultrasonic power is effect by ultrasonic power ratio and other uncontrolled factors such substrate quality,restricts between tool and wire,and so on.