F. Schneider
Y. Long
H. Ohrdes
J. Twiefel
M. Brökelmann
M. Hunstig
A. Venkatesh
J. Hermsdorf
S. Kaierle
L. Overmeyer

Effect of laser assistance in ultrasonic copper wire bonding

Lasers in Manufacturing (LiM)
26.-29. Juni
Type: Konferenzbeitrag
Due to the required low forces and the necessity of short cycle times in industrial production of electronic interconnections, the use of the established ultrasonic wire bonding is limited for hard materials such as copper. To reduce the applied forces and the cycle times, an additional energy source is applied to the process. This is implemented by integrating a near infrared laser source to the wire bonding setup. The laser radiation is focused on the workpiece during or immediately before the bonding process for heating the wire. This approach enables locally applied energy to be increased during the process without affecting surrounding materials. Thick copper wires with 400 μm diameter are used for bonding to rolled copper plates. For evaluation, the mechanical strengths of the bonds are tested afterwards and the bonding interface is microscopically examined. To prevent the hazard of oxidation of the bond partners during the process, the influence of shield gas is considered as well. The results show a direct relation between the applied laser power and the examined bond strength. This approach opens the opportunity to obtain bonds equivalent in strength to standard ultrasonic wire bonds but with reduced forces and/or bonding times. Hence the attempt to combine ultrasonic and laser power shows an advantage over the individual processes in terms of the resulting bond strength and the handling of the materials and tools.