Electromigration driven failures on miniature silver fuses at the Large Hadron Collider

Spurious faults were observed on the miniature silver fuses of electronic cards used for the cryogenics instrumentation in the LHC (Large Hadron Collider) accelerator at CERN. By applying analytical tools and techniques such as Scanning Electron Microscopy, spectrometry and Weibull reliability calculations and by the knowledge of operating temperatures and operational time of each unit, the origin of the problem has now been understood and can be attributed to electromigration. The selected fuse was operated at moderate temperature and load conditions and was considered as a “lifetime” component. However, it turned out to have a smaller than expected MTTF with failures following a Weibull distribution of $\beta = 3.91$ and $\eta = 2323$. The literature describes extensively the effects of electromigration, but there are only limited references referring to the impact of this phenomenon on miniature silver fuses for electronic circuits.