Optimal Design of Thermal Variant Stress Spectrum Based on Virtual Accelerated Life Test of the Circuit Board

The spectrum design and lifetime evaluation of high reliability and long lifetime aerospace electronical products has been a puzzled problem for engineering and scientific researcher. The fatigue of these products are caused by complicated environmental and operational conditions. The specific works in this study involve the establishment of fatigue life model of the circuit board under the thermal variant stress, model fatigue virtual accelerated life test (VALT) based on thermal variant stress spectrum, calculation and analysis of model accelerated life based on VALT data, and the method of stress spectrum optimization based on accelerated model.

In this study, focused on the weak node of the circuit board, the fatigue failure model is constructed, and the fatigue life of the model is predicted by accelerated stress spectrum and Coffin-Manson formula. Furthermore, the fatigue degradation data of the model under thermal variant stress are obtained by VALT. Considering that the coefficients of Coffin-Manson formula should be adjusted to different accelerated models, the study combines S-N curve and simulation data to fit the formula parameters, and calculates the optimal stress spectrum of the accelerated model by using the modified Coffin-Manson formula. Finally, the fatigue life of the model under the optimal accelerated stress is obtained. The method and result can be referred to the ALT design for similar products.

Keywords: Thermal variant stress, Virtual accelerated life test, Accelerated life calculation, Coefficient fitting, Optimal design.

Download PDF