A quick method for estimating junction temperature profiles in transient applications

In disk drive applications, IC packages are often required to dissipate very high power levels for short periods of time. It is crucial to evaluate the IC junction temperature T_j(t). The standard IC package transient thermal characterization data do not reflect T_j(t) in real applications. Obtaining T_j(t) experimentally is relatively time consuming. In addition, one has to rely on the availability of measurement hardware. Therefore, it is desired to develop a method which can be used to quickly estimate the T_j(t), based on the standard transient thermal characterization data. In this work, a new method is proposed to calculate the junction temperature for a general power input. This method is based on linear superposition of the standard package thermal characterization data. This method is demonstrated by an example of the power TQFP package subjected to a multiple pulse power input. The calculated results have excellent agreement with the experimental data. It is shown that with the new method, T_j(t) can be calculated very easily with good accuracy without additional physical measurements or simulation