Ultra-Thin Package Board Level Drop Impact Modeling and Validation

Board level reliability during drop impact is a major concern for electronic packages. The impact force generated as the casing strikes the ground can cause electronic device failures in handheld products. The full drop testing procedure is costly and time-consuming due to complex sample preparation and test set-up procedures. Failure analysis also requires significant manpower to conduct. Therefore, an impact modeling method to predict the results of board level drops is highly desirable. We propose a dynamic modeling approach to describe the transient response of the package during impact based on an Input-G loading method with an implicit solver algorithm. The dynamic response of an ultra-thin package is obtained experimentally using a drop tester with accelerometer, strain gauge, and resistance monitor. For the Input-G method, the acceleration response of the impact pulse is then converted into a velocity form, and is taken as the loading input to a finite element (FE) model in this paper. The time dependent PCB strain, spectrum analysis, and modal analyses are used to correlate with the FE model and used to understand drop impact behaviors. Spectra of impact pulse and PCB dynamic strains are obtained by using the Fast Fourier Transform (FFT) technique. The extracted bending shape and frequency are consistent with the modal analysis results. The bending shape is mainly determined by the first mode. Knowledge about the spectra of PCB dynamic responses are required to understand the bending characteristics, which affect the package drop reliability. This FE model provides an accurate and reliable way to understand failure physics, and to help to achieve service life improvements in early development stage.