Parametric Models of Thermal Transfer Impedances within a Successive Node Reduction Based Thermal Simulation Environment

Abstract

In this paper we present a new, direct computational method for calculating thermal transfer impedances between two separate locations of a given physical structure, aimed at the implementation into a field-solver based on the SUNRED (SUccessive Node REDuction) algorithm. We tested the method symbolically with a simple 2D example with multiple combinations of Dirichlet and Neumann type boundary conditions. Also, for time domain transient analysis different types of thermal loads such as prescribed unit-step change in dissipation or temperature were assumed. A model of a typical MCPCB assembled LED was also created. With that model we studied the inverse problem of predicting the thermal conditions at the junction (the "driving point") from the transient signal measured at the thermal test point on the MCPCB (the "monitoring point") which is a typical task in simple LED thermal management designs. Results obtained by the proposed new calculation method and results obtained by conventional numerical simulations differ less than the uncertainty of the traditional solution method itself. The drawback of the accuracy is the high computational cost. This increased computational need can be mitigated by introducing the combination of the balanced model reduction and the SUNRED algorithms