Early-state crack detection method for heel-cracks in wire bond interconnects

Reliability of electronic systems is finally limited due to thermo-mechanical fatigue of interconnections. Besides soldered interconnections wire bonding is one of the most commonly used interconnection technology in electronics. Due to thermo-mechanical loading wire bond technology suffers from cracking in the heel region and delamination in the interface. To increase lifetime and lower ecological impact of electronic systems, a condition monitoring concept is needed, which is able to determine the remaining lifetime of an interconnection. The scope of this paper lies in the development of a parameter measurement system for early-state crack detection in the heel region of wire bond interconnections. This parameter measurement system uses signal components generated by cyclic opening and closing of growing cracks. So it becomes possible to determine the remaining lifetime of the interconnection, which is directly connected to the lifetime of the whole system. Furthermore an analytical model is presented, which supports the experimental setup. Measured cracks are investigated by metallographic cross-sectioning of wire bonds and focused ion beam (FIB).