Effects of component stand-off height on reliability of solder joints in assembled electronic component

The structural performance of electronic devices depends immensely on the standoff height of the components used to assemble them. The component standoff height (CSH) of electronic assemblies can be varied either by changing the settings of the reflow profile parameters or by varying the diameter of bond pad on the printed circuit board (PCB). The continued desire by electronic manufacturing industries to improve the reliability of their devices has driven researchers to seek in-depth understanding of the contribution of CSH on the integrity of solder joints in these assemblies. This is coupled with the fact that there is no industry standard for CSH, for electronic components. This investigation studies the effect of CSH on the shear strength and failure mechanism of assembled Ball Grid Array (BGA) electronic components. Five different CSHs were investigated using a number of test vehicles. The various CSHs were achieved by varying the bond pads on the PCB while keeping the reflow profile parameters constant. These test vehicles were subjected to shear stress using a Dage 4000 series bond tester. The results obtained demonstrate that the different vehicles produce different load profiles and their shear strength increases with decrease in their CSH. It was found that the mechanics of failure of the specimen is both by crack propagation at the interface between solder bulk and the intermetallic layer; and by pad lifting. These findings would be useful to benchmark the CHS for B GAs, for their optimal mechanical reliability.