The experimental study for the solder joint reliability of high I/O FCBGAs with thermal loaded bend test

In this study, the reliability of flip-chip ball-grid array package (FCBGA) is explored by a cyclic four-point bend test executed at different controlled temperature. The test vehicle is put in a heated chamber and the resulting daisy chain resistance and strains variations are monitored to check its failure. The strain gauges are mounted near the component corners to get the strains of the test boards when under bending. A data logger records the daisy chain resistance simultaneously during the test. The component failure is detected with a self-written program by judging when the failure resistance of the daisy chain is larger than 20% of its initial resistance. The test results at various temperatures showed that the component life cycle is reduced with the increase of the temperature during the cyclic bend test when under a fixed maximum deflection setting. If tested at room temperature by varying the maximum deflections, the component life cycle is also reduced with the increase of the maximum deflection in the cyclic bend test. Through the fitted curve of all these test data, it is then possible to get relating equations among the variables of temperature, deflection, and life cycle. An extra test is conducted to verify these deduced equations with an error of only 6% approximately. Furthermore, the optic microscope is utilized to observe the failure mode of the FCBGA component after the test. It is found that all the failures are the delamination at the interface of solder balls and substrate. Also, from the results of tested curves, it can be used to predict the component life cycle at elevated temperatures based on the results tested at room temperature.