Research on the influence of dimpled ceramic SMD on mechanical strength of solder joint in LTCC-based BGA packages

It is generally known that the thermal fatigue damage is the main failure mode of ball grid array (BGA) packages, which caused by the mismatch of the coefficient of thermal expansion between low temperature co-fired ceramic (LTCC) and print circuit board (PCB). The thermal mismatch would subject the solder joints to in-plane shear and out-of-plane bending loads. To ensure the reliability of BGA packages, it must enhance the mechanical strength between solder ball and LTCC substrate, which can be improved by structure optimization. In this paper, the influence of dimpled ceramic solder mask defined (SMD) construction on the mechanical strength of solder joint in LTCC-based BGA package have been investigated using non-linear finite element analysis and experimentation. A series of dimpled ceramics SMD constructions are applied to BGA packages to carry out the ball shear tests. It could be observed that the existence of dimpled SMD has the effect of increasing the interfacial mechanical strength between pad and LTCC substrate. Averaged equivalent stress and plastic strain analyses were carried out to reveal the failure mechanisms. The results of this work can be recommended as the optimization plan for the high reliability LTCC-based BGA packages.