A fast mechanical test technique for life time estimation of micro-joints

A novel accelerated mechanical testing method for reliability assessment of micro-joints in the electronic devices is presented as an alternative to time consuming thermal and power cycling test procedures. A special experimental set-Lip in combination with an ultrasonic resonance fatigue testing system and a laser Doppler vibrometer is used to obtain fatigue life curves of micro-joints under shear loading. Using this method fatigue life curves of Al wire bonded micro-joints were obtained up to 10(9) number of loading cycles and discussed with regard to micro-mechanisms of the bond failure. Failure analysis of the fatigued micro-joints showed that the predominant failure mechanism of power cycling tests, bond wire lift-off, was reproduced by the mechanical testing procedure. Life time of the micro-joints was modelled using a Coffin-Manson type relationship and showed a good correlation to lifetime curves obtained by power cycling tests. The major advantage of the proposed fast mechanical testing method is the significant reduction of the testing time in comparison with conventional thermal and power cycling tests. Furthermore subsequent examination of the failure surface provides a reliable tool for improvement of the bonding process. The proposed high frequency fatigue testing system can be applied as a rapid qualification and screening tool for various kinds of interconnects in electronic packaging. (C) 2008 Elsevier Ltd. All rights reserved.