Board level solder joint failures by static and dynamic loads

Quasi-static bend tests and drop tests of surface mounted MCMs on printed circuit boards (PCBs) are conducted to compare the failure patterns from the two types of tests. The boards are 120 x 90mm in dimension. The modules are 40 x 40mm with a brass heat spreader of the same dimension on top. Five-point bend tests are conducted with different ramp-rates from 0.1 to 10.0mm/min to determine the effect of different PCB strain rates on the reliability of the solder interconnections. Drop tests are conducted for the same batch of PCBs at 1.0m and 1.5m drop heights and PCB strains from drop tests are compared with those taken from the quasi-static tests. A failure analysis is also conducted to determine the possible mechanisms of failure. Findings show that solder joint failure in five-point bend tests is dependent on the ramp-rate. The tests also show that mass inertia of the heat-spreader may cause solder joints to fail at lower PCB strain levels than expected especially for packages with heavier heat-spreaders which are needed for higher heat dissipation.