COTS BGA Thermal Fatigue Test for Avionics Applications

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, and flip chip over military thermal environment. 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 variables, including the types of PWBs, conformal coating, and BGA underfilled materials, with each having either two or three levels of variation are used to address test criteria and to construct 12 different types of TV configurations. All TV configurations are then subjected to temperature cycling tests (−55°C to +125°C) 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. Based on the lesson-learned from the above TV, a second TV (defined as TV2) has been designed, constructed and tested. The four selected parameters in TV2 are BGA under-fill materials, conformal coating, solder pad sizes on PWB, and BGA rework, with each also having either two or three levels of variation. Test results from these two groups of TVs indicate that the influence of these design and manufacturing parameters on fatigue life is dependent on the particular package, in some instances improving the fatigue life tenfold. All these test results are recommended to be used for calibrating BGA solder joint thermal fatigue life prediction models, which will be presented in other publications.