Lift Off Defect Analysis In Wirebonding Process

Abstract

Lift off defect was occurred a lot in wirebonding area during September 2023, with fishbone and FMEA analysis, writer concluded that the main reason of it are ultrasonic force and clamp power failure. Ultrasonic force shear test is done to see how the forces affect the shape of the bonded wire and also the power of the wire itself. With 6 different parameters applied, writer gains different results for each parameter which are: 40KHz, 45KHz, 50KHz, 55KHz, 60KHz, 65KHz. The standard of wire strength is 1900g – 2900g or even more as long as there is no deformed bondfoot occur. 40KHz - 45KHz Ultrasonic force causing lift off defect the most, with only 1870g - 2010g wire strength, 50KHz – 60KHz is a stable parameter for bonding with wire power results between 1980g – 2890g with no liftoff, for 65KHz ultrasonic power the highest result of wire strength 3880g causing the wire to get deformed. Therefore, the range between 50KHz – 60KHz ultrasonic force is recommended. Meanwhile clamp power is divided into two, bolts clamp and vacuum clamp. Bolts clamp monthly failure is 3 while vacuum clamp is 7, the vacuum clamp receiving much more failure is caused by unstable vacuum pressure that happen sometimes while bolts clamp is less failed due to the stable hold by the bolts. After the rootcauses are found, the corrective action is made as a preventive way to avoid further failure, such as machine condition checking, one module checking, and further machine settings for technicians.