Nickel dendrites: a new failure mechanism in ceramic hermetic packages

Abstract

A new failure mechanism, nickel dendrites, was identified in hermetic ceramic packages. Nickel dendrites resulted from an unauthorized change in the supplier's assembly process. The change caused lots to be produced with package ambient moisture levels ranging from 10% by volume to 20% by volume. Device cooling in the system application reduced the package temperature below the dew point of the internal package ambient and allowed water to condense. The liquid water absorbed materials from the ambient atmosphere and reacted with the nickel underplating of the package conductors. Normal operating voltages provided the electrical potential necessary for the growth of nickel dendrites. Burn-in was not effective in screening out this failure mechanism because temperature during burn-in was above the dew point of the package ambient. The supplier revised their assembly procedures to prevent unauthorized process changes of this type. UNISYS purged all devices in the suspect date code range from the factory and field inventory. Corrective actions were implemented by UNISYS and the supplier with the result that this failure mechanism was eliminated from both field and factory. The nickel dendrite failure mechanism has not been reported in any literature. Hermetic ceramic packaging is widely used. The existence of a new failure mechanism has tremendous potential impact on product reliability, process controls, reliability prediction, and failure analysis.