Three-dimensional surface-mount assemblies (SMA) (leaded chip carriers (LCC) and self-stretching flip chip (SSC)) are modeled in this study by an effective finite element method to analyze the thermal conduction and thermal stress during the power-cycling. In this method the solder joints and leads are modeled by a special element, called the solder joint element. Since the solder joints and leads have the same shape, the stiffness matrix or thermal conduction matrix can be given by a unitized matrix for every solder joint element Based upon an influence function method, the stiffness matrix and thermal conduction matrix are determined by finite element analyses. And then with the solder joint elements, finite element analyses of the global model of the surface-mount assembly are carried out to investigate the whole-field temperature distributions and displacement distributions. As an example evaluation, power cycling (power on without ambient temperature change) simulation is carried out. The computed temperature distributions are utilized to analyze the displacement fields for every solder joint and the stress distribution in the printed circle board (PCB). The displacement fields are then used as the imposed displacement boundary conditions for computing the stress and the strain of every solder joint. It is shown that the proposed method can be used as a rapid estimating tool to investigate the temperature distribution of the SMAs and thermal stress-strain distribution in the solder joints.
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