Burn in Hours That Remove the Steepest Early Drift
Thermal burn-in under active electrical bias removes early non-linear drift, locking in long-term calibration stability before sensors reach the field.
Bond Wire Voiding
Interface Degradation
Microscopic Kirkendall void formation along semiconductor wire interconnects leads to mechanical separation and electrical resistance growth at the weld interface. Occurrences of bond wire voiding stem from unbalanced atomic diffusion rates between dissimilar metals under elevated temperature conditions. This structural defect reduces the effective contact area between the gold or copper wire and the aluminum bonding pad.
The boundary of this failure mode occurs at the metallurgical junction, excluding stress fractures driven purely by mechanical vibration.
Intermetallic Growth
Interdiffusion of gold and aluminum atoms at elevated temperatures generates intermetallic compounds with distinct lattice structures and diffusion rates. Vacancies accumulate on the side of the interface with the higher diffusion rate, coalescing into sub-micron voids that expand under sustained thermal stress. As thermal aging continues, these voids grow into continuous sub-surface channels that weaken the bond post.
The reduction in contact area increases local current density, which accelerates localized heating and promotes further void coalescence. Over extended operational lifetimes, this thermal cycle creates severe structural embrittlement across the entire contact zone.
Resistance Increase
Void formation alters the electrical path by restricting current to narrow material bridges. The accumulation of bond wire voiding produces a gradual increase in series resistance that manifests as output voltage offset and calibration drift in sensor circuits.
Verification Standard
Quality assurance protocols verify bond integrity through destructive pull tests and non-destructive acoustic microscopy inspection. Acceptance limits set by microelectronics standards define maximum allowable resistance shifts following high-temperature storage testing. Test reports record structural void area percentages to confirm compliance prior to device packaging.