The objectives of the present studies are to design and test representative commercial off-the-shelf plastic encapsulated microcircuits, including various types of ball grid array (BGA) components, chip scale package, flip chip, lead flat pack, and leadless capacitor, over military random vibration levels. The approach is to demonstrate the solder joint reliability performance of these components through the design of an electrical daisy-chain pattern printed wiring board (PWB) assembly test vehicle (TV), in which the design and manufacturing variables are included. The three variables, including BGA underfilled materials, solder pad sizes on PWB, and BGA rework, with each having either two or three levels of variation are used to address test criteria and to construct 14 different types of TV configurations. All TV configurations are then subjected to random vibration tests while continuously monitoring solder joint integrity. Based on the measured results, a destructive physical analysis is then conducted to further isolate the failure locations and determine the failure mechanisms of the solder joints. Test results indicate that the 352-pin tape BGA and 600-pin super BGA are more susceptible to failure than plastic BGAs under the same conditions, and that the use of underfilled materials appears to improve the life expectancy of all the components. The stiffer packages of tape BGA and super BGA, which have copper heat spreaders, may account for higher BGA solder joint stress/strain during random vibration tests. Test data also shows that only a limited number of electrical opening are observed. This indicates that the test modules are robust enough to survive the random vibration inputs. One possible reason is that the test modules are very stiff, whose 1st mode of natural frequency is about 550 Hz. Therefore, the curvature changes of the test modules are minimal, which resulted in smaller relative motion between the package and the PWB, and less solder joint stresses. All these test results are recommended to be used for calibrating BGA solder joint vibration fatigue life prediction models, which will be presented in other publications.
Based on the virtual experiment study of the impact of load sequence on the calculation process of random vibration fatigue damage.
