A time-domain method for the analysis of thermal impedance response preserving the convolution form

The study of the thermal behavior of complex packages as multichip modules (MCM's) is usually carried out by measuring the so-called thermal impedance response, that is: the transient temperature after a power step. From the analysis of this signal, the thermal frequency response can be estimated, a nd consequently, compact thermal models may be extracted. We present a meth od to obtain an estimate of the time constant distribution underlying the o bserved transient. The method is based on an iterative deconvolution that p roduces an approximation to the time constant spectrum while preserving a c onvenient convolution form. This method is applied to the obtained thermal response of a microstructure as analyzed by finite element method as well a s to the measured thermal response of a transistor array integrated circuit (IC) in a SMD package.