A Combined Methodology to Include System Effects in Board-Level Stress Simulations

The development of automotive electronics towards autonomous driving applications generates various challenges, in particular also on the reliable functionality of components originally designed for consumer products. In addition to use with higher environmental loadings, e.g. higher temperatures, the microsystems must also stay reliable in other mounting situations. For analysis of these effects a methodology has been developed combining FEA and high precision optical measuring techniques for determination of in-plane and out-of-plane (warpage) deformations. A systematic study on mounting effects, i.e. on "3
^rd
level reliability", is reported New test setups were constructed to investigate effects of mounting. The “3
^rd
level” component loadings are either from screwing on aluminum plates or from four-point bending loading stages. For both test setups, a mismatch loading from the aluminum-baseplate is superimposed on the component-board mismatch loading. Sensor systems in QFN packages were chosen from the spectrum of characteristic CE packages. Both in-plane and warpage effects are studied from 1
^st
to 3
^rd
level by the combined method Simulation assumptions are discussed From the results it is shown that intrinsic deformations and warpages need to be considered directly in AE system design and indirectly when evaluating stress risks, e.g. for solder fatigue.