Space tether produced to strength specification

A non-contact method to determine the quality of an ultrasonic weld was developed for wire-to-wire bonding purposes. Relative wire movement during the bonding process was monitored with a laser-doppler-vibrometer. This movement provides information about the bond development. Such information permits predicting the final quality of the bond. Signals from N=5000 bonds were analyzed to find tell tale characteristics that predict the final strength of the bond. A bond that eventually will end up failed (un-attached) can be recognized as early as 2 ms into the bonding process. A distinction between poor quality (maximum sustainable pull-force below 8 g) and good quality (pull-force above 10 g) bonds can be recognized within 6 ms from the bonding start. A real-time feedback system was implemented to reduce the uncertainty in final bond quality and to actively augment the quality during the bonding process. The purpose of this study was to confirm that real-time quality assurance (produce to specification) is feasible in wire-to-wire bonding. This work is part of our efforts towards the produce to specification concept in the ESAIL programme.