Accurately simulate the thermal cycling test with improved mechanical reliability test for electronic components

Accelerated thermal cycling (ATC) test, though time-consuming, is currently the most widely used reliability test for electronic components. However, a much faster mechanical bend test is often adopted as an alternative for the ATC test. But it is a general guideline that the mechanical reliability test results are meaningful only if the mechanical stresses applied on the test components are either the same or identical to those thermal stresses found in the ATC test. However, those mechanical stress test machines currently used were just those general purposes material test machines. Normally, it could apply only half of the full stress cycles (from heating to cooling) of the ATC test, not even the dwell time in ATC test can be simulated. Besides, it was bulky and over capacity for today's miniaturized electronic components. With the motivation in improving these drawbacks, the study developed a miniaturized testing machine for electronic components that was capable of applying both positive and negative stresses as well as the dwell time at the peak displacement of each cycle that resemble the stress states in the ATC test. The developed machine was verified through a series of cyclic bend test on flip chip ball grid array (FCBGA) components. Under the same displacement settings, the resulting reliability test cycles with the improved test method were found to be only one-tenth of those with the conventional mechanical test machine. The stress conditions on the solder balls were found to be much closer to those from ATC test when checked with the finite element analysis (FEA). Therefore, the developed machine and the corresponding loading profile in the test method are believed to be more accurate and is proposed to be used as a new alternative for the mechanical stress test in the future.