An instrument recently constructed for Goddard Space Flight Center involved stacked chip memory modules having about six thousand 1 mil gold wires, each between 4.6 mm and 6.1 mm long. Four of these bond wires fractured during the final box-level random vibration test which had spectral power to 850 Hz. Investigation determined that these wires have fundamental resonant frequencies in the range from 1.4 kHz to 2.3 kHz, with quality factors up to 300, when the bonds at each end are rigid. However, a nearly severed top bond decreases the lead's fundamental frequency to the range 600 Hz to 750 Hz. The lowered mode is strongly excited by the box-level vibration test, leading to fatigue-fracture of that already weakened bond during the several minutes of the vibration test. However, spectral power in the region from 600 Hz to 750 Hz. An unfractured 1 mil gold wire was still intact after 12 days (1.4 billion oscillations) at 1.4 kHz at a root-strain of 0.2%, while several (deliberately) nearly fractured wires failed after less than a minute (less that 41,000 oscillations) at 680 Hz at the same drive stress.

Key words: resonance, fatigue, fracture, wire bond.