Prognostication of solder-joint reliability of 0.4mm and 0.5mm pitch bgas subjected to mechanical shocks up to 10,000G

Due to the reduced size and geometry constraints imposed on electronics in various applications there has been tremendous need for use of very fine pitch surface mount electronics. Fine pitch BGAs of 0.4mm and 0.5mm pitch are finding applications in military and defense applications. Fine pitch BGA electronics in aerospace applications they may be subjected to high-g levels in the neighborhood of 10,000g of mechanical shock during normal operation. Survivability and design envelope of fine pitch semiconductor packages under high-g mechanical shock is unknown. In addition, the efficacy of the traditional supplemental restraint mechanisms such as underfills in mitigating the risk of interconnect failure under 10,000g mechanical shock, is not available. A circular board with an annular ring typical of projectile applications has been designed with fine pitch daisy chained packages. Packages studied have package interconnects in the range of 84-360 I/D. Two configurations of the test board have been studied including non-underfilled, and underfilled assemblies. Full-field strain on the board assembly has been measured and the strain histories at the corner of the component locations extracted. The change in the resistance of the second-level interconnects has been monitored during the shock event using high speed data acquisition system. Resistance spectroscopy in conjunction with Kalman Filter has been used to identify the onset of failure and prognosticate remaining useful life.