Use of prognostics in risk-based decision making for BGAs under shock and vibration loads

Leading indicators of failure have been developed based on high-frequency characteristics, and system-transfer function derived from resistance spectroscopy measurements during shock and vibration. The technique is intended for condition monitoring in high reliability applications where the knowledge of impending failure is critical and the risks in terms of loss-of-functionality are too high to bear. Previously, resistance spectroscopy measurements [Constable 1992, Lizzul 1994, Prassana 1995] have been used during thermal cycling tests to monitor damage progression due to thermo-mechanical stresses. The development of resistance spectroscopy based damage pre-cursors for prognostication under shock and vibration is new. In this paper, the high-frequency characteristics, and system transfer function based on resistance spectroscopy measurements have been correlated with the damage progression in electronics during shock and vibration. Packages being examined include ceramic area-array packages. Second level interconnect technologies examined include copper-reinforced solder column, SAC305 solder ball, and 90Pb10Sn high-lead solder ball. Assemblies have been subjected to 1500g, 0.5 ms pulse [JESD-B2111]. Continuity has been monitored in-situ during the shock test for identification of part-failure. Resistance spectroscopy based damage pre-cursors have been correlated with the optically measured transient strain based feature vectors. High speed cameras have been used to capture the transient strain histories during shock-impact. Statistical pattern recognition techniques have been used to identify damage initiation and progression and determine the statistical significance in variance between healthy and damaged assemblies. Models for healthy and damaged packages have been developed based on package characteristics. Data presented shows that high-frequency characteristics and system-transfer characteristics based on resistance spectroscopy measurements can be used for- - condition-monitoring, damage initiation and progression in electronic systems. A positive prognostic distance has been demonstrated for each of the interconnect technologies tested.