In Situ Interconnect Failure Prediction Using Canaries

A physics-of-failure-based canary approach for early identification of solder interconnect failures has been developed. The canary is composed of a resistance path formed by a near-zero ohm ceramic chip resistor soldered to pads designed to produce failure earlier than standard pad resistors, which are the target structures. The time to failure of the canary can be adjusted by adjusting the printed wiring board pad dimensions and, hence, the solder interconnect area. The developed canary approach is demonstrated through temperature cycling of the resistors. The pad width of a standard resistor is reduced by 80%, thereby reducing the interconnect life. The results from the temperature cycling experiment prove that the developed canary approach provides advanced warning of failures of the standard pad resistors. The FEA results suggest that there is a 78% increase in the strain range in the canary resistor, as compared with the standard resistor. The Engelmaier model, a physics-of-failure-based model for solder interconnect life estimation under thermal cycling, is modified to take the solder interconnect area into account. The model provides time to failure estimates for the canary and target structures. A comparison of the results from the Engelmaier model and temperature cycling experiment shows that the model provides a good estimate of time to failure of standard resistors and a conservative estimate of time to failure of the canary resistors.