Dynamic modeling and measurement of personal computer motherboards

Abstract

This paper addresses basic modeling issues regarding the mechanical shock and random vibration response of a typical personal computer motherboard. Finite element modeling of an ATX-style motherboard was used to estimate the modal characteristics and dynamic response. Locally stiffened regions, such as sockets and large components, were modeled as simple blocks. The elastic modulus for these regions was determined by performing a 3-point bend tests on samples removed from the motherboard. The mode shapes and natural frequencies of the motherboard were computed and correlated with measurement. The dynamic response, due to random base excitation of the motherboard, was predicted by the model and showed very good correlation with measured acceleration response values. Mechanical shock response analysis was approached using two methods: direct time integration and the shock response spectrum method. Both provided good correlation with the measured peak acceleration response to an applied half-sine shock pulse. In addition, the predicted transient response was well correlated with acceleration time history measurements made during shock loading. It was observed that the shock response was dominated by the fundamental mode of the motherboard. Simple guidelines are presented for modeling of personal computer motherboards subjected to random base excitation and shock loads.