Application of PSO Method to Identification of Creep Material Constants Using Indentation Load Relaxation Curves

Abstract

In the design of high-density mounting boards, the strength reliability of solder joints should be evaluated by conducting finite element analyzes (FEAs) considering the distribution of creep properties in the joints. To conduct such FEAs, a testing method that can evaluate the creep properties of the solder joints in-situ must be developed. The indentation creep test is an effective method for the evaluation, however, there are some problems with the method such as the creep law obtained by this method does not coincide with that obtained by tensile creep tests. Therefore, we previously proposed a new indentation test including the indenter depth maintenance process in which creep properties are evaluated by using the load relaxation curve given by the maintenance process. However, we have not developed a systematic method to estimate material constants in creep law based on the test results yet. Then, in this study, we proposed a method using the particle swarm optimization (PSO) method to estimate creep material constants from the load relaxation curve due to maintaining indenter depth. To discuss the availability of the proposed method, elastic-plastic-creep FEAs were conducted as the numerical experiments of the indentation test including the indenter depth maintenance process for an Sn-Ag-Cu (SAC) solder.