Applicability of Different Cycle Counting Methods in Thermal Fatigue Life Analysis of BGA Solder Joints under Asymmetric Temperature Cyclic Load

In the fatigue life analysis of asymmetric temperature stress load, different cycle counting methods are used to count the load, and different cumulative frequency distributions will be obtained, so as to obtain different predicted life. Therefore, understanding the applicability of these cycle counting methods is of great significance to improve the accuracy of fatigue life prediction. In this paper, the thermal fatigue failure life of BGA solder joints is studied by using three groups of different temperature cycle accelerated tests, and the thermal fatigue cumulative failure function of BGA solder joints is obtained; Based on the reliability index requirements of asymmetric temperature cyclic load test, the temperature stress damage of a single identification test section of three different cycle counting methods including rain flow counting method, maximum and minimum cycle counting method and simple range counting method, is calculated by comprehensively applying coffin Mason solder joint life model and Miner linear damage accumulation model; Combined with the finite element simulation results of temperature stress damage of a single identification test section under direct loading and simple range counting method, it is considered that the simple range counting method is more suitable for load statistical counting in the thermal fatigue life analysis of BGA solder joints under asymmetric temperature cyclic load in this study.