A thermal analysis has been made of 40 pin leadless chip carriers (LCC) surface mounted on an alumina substrate. Finite element (FE) codes have been used to numerically simulate the problem. We show both theoretically and experimentally that the junction to case temperature is not a convenient parameter for thermal characterization of the heat transfer processes in the complex geometry under consideration. The geometrical complexity of the problem together with the uncertainty of the thermophysical properties and heat transfer coefficients make accurate thermal characterization difficult for parametric study and design analysis. A method, based on homogenization or simplification of a complex region by introducing an effective homogeneous material, is proposed for thermal analysis of complex geometries and its range of applicability is presented. Using this method, different models of heat transfer can be lumped together and various available computer codes can be utilized for rapid thermal design analysis of microelectronic devices.

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