Implementing compact thermal models under non-symmetric trace routing conditions

Compact thermal models (CTMs) are used to reduce the size and time required to solve system thermal models while still maintaining a high level of simulation accuracy. Methods for developing and validating CTMs under symmetrical boundary conditions are well understood. However, they do no always accurately predict the thermal solution for nonsymmetrical boundary conditions arising from either developing flow and/or non-uniform trace routing conditions. Presented in this study is a detailed analysis of a super ball grid array (SBGA) and a carrier array ball grid array (CABGA) style packages. Also presented are two-resistor models, symmetric and non-symmetric compact models. Two-resistor models were shown to underestimate the thermal resistance while Delphi style compact models tend to overestimate the thermal resistances for the SBGA and CABGA packages considered in this study. A method of accounting for non-symmetrical printed circuit board (PCB) routing conditions is also presented.