The electrical transient testing method has become popular as a useful thermal analysis tool because of its accuracy, high repeatability and rich information content compared to the use of traditional steady state thermal characterization techniques. This paper presents a thermal study of a 16-chip memory module using transient testing. The two variables in this study are the thermal boundary conditions of and the power distribution within the module. By applying the method of network identification by deconvolution (NID) to a transient temperature measurement, we can identify the structure function, which is the dynamic thermal resistance versus capacitance along a particular heat flow path for a given boundary condition and power distribution. Comparisons of the structure functions reveal differences in the heat flow paths for the cases of one chip and multiple chips dissipating heat. We have successfully used transient testing on a three-dimensional memory module, and determined the contributions to the overall dynamic thermal resistance by each of the components including the heat spreader (HS), socket and even thermal interface material (TIM). This information about a 3-D assembly is often difficult to obtain using steady state techniques. Thermal engineers can use such information to differentiate the relative merit of materials and heat transfer mechanisms in a cooling solution to optimize the overall thermal budget.