Modelling vibration of printed circuit board assembly to predict component damage

Abstract

Failure of electronics due to mechanical damage is a prevalent issue in product development. Predicting and preventing failure is difficult without expensive and time consuming physical testing. The aim of this thesis was to develop a model for simulating the mechanical behaviour of printed circuit boards (PCBs). The purpose of the model was to predict the lifetime of ball grid array (BGA) components when subjected to vibration-induced fatigue. The developed model was calibrated based on experimental results, and was able to predict eigenfrequencies, mode shapes and board strains in a satisfactory manner. However, care had to be taken to note whether the relevant deformations were linear or not. If the geometry was nonlinear, this had to be compensated for. Fatigue experiments were also performed with both harmonic and random vibrations, in order to develop a relationship between board strain and number of cycles to failure. Such a relationship, an EN-curve, was established for both harmonic and random vibrations. While these curves can be used to give an indication of a BGA’s lifetime, the spread in results is not insignificant. This highlights the difficulties in predicting a lifetime, especially for a new design without experimental data available.