The use of impedance spectroscopy, SEM and SAM imaging for early detection of failure in SMT assemblies

Abstract

We propose complementary solutions to improve the evaluation of PCB under specific stresses using electrical and physical indicators adapted to a given part of the board. For ceramic capacitors, the residual piezoelectricity provides an impedance signature at resonance allowing detection of local physical defects. Solder joint fatigue criticity under thermal cycle can be predicted using combined analytical and FEM simulations, while the lead phases coarsening provides a good early degradation indicator. At last, ball inspection of BGA packages using shear waves in scanning acoustic microscope lead to an interesting improvement of resolution.