Wire-bonds failures induced by resonant vibrations in the CDF silicon detector

Abstract

Unrecoverable internal failures of modules in the CDF Run2 silicon detector have been observed since its installation in early 2001. A fraction of these failures have been categorized as infant mortality because they were detected right after installation or in the first few months of data taking. Another fraction occurred during the second year of operation and they were strongly correlated with anomalous trigger conditions. These failures are explained by wire-bonds breaking due to fatigue stress induced by resonant vibration. These resonant vibrations are a direct consequence of the oscillating Lorentz forces induced by the 1.4 T magnetic field on wire-bonds earning non-DC current. Changes have been implemented in data taking procedures in order to minimize occurrences of such failures and to prolong the lifetime of the detector itself. A more general analysis of the topic has been pursued. Changes in the packaging and assembly processes for future applications have been investigated and are proposed in order to avoid this failure mode.