Experimental study on CBGA assembly in various environmental temperatures using moire interferometry

Solder joints between a ceramic ball grid array (CBGA) and a printed circuit board (PCB) generally suffer important thermal strains and stresses during the operation of devices as well as under temperature variations. Mainly, these tend to increase the thermal stress concentration in solder joints. In this study, moire interferometry is used to measure the power-induced thermal displacement in the CBGA assembly. The experimental study is performed under various environmental temperatures using different power levels. Two types of thermal strain distributions are found in the assembly, depending on the thermal loadings. The stress concentrations are located in the CBGA assembly. Then, based on the relative displacement between the CBGA and the PCB, the shear stress on the solder ball is determined. Moreover, the effects of different thermal loadings on the CBGA as well as their impact on the reliability of CBGA solder balls are discussed in details.