An effective methodology for thermal characterization of electronic packaging

An effective and novel methodology that integrates infrared (IR) thermography measurement and a three-dimensional (3-D) finite element (FE) model is proposed for thermal characterization of packages in a steady state under a natural convection environment based on JEDEC specification . To perform surface temperature measurement using an IR thermometer, a black paint coating is applied on the surface of packages so as to calibrate the surface radiation. The associated emissivity is approximately assessed using a simple calibration experiment, and an appropriate thickness of the coating is determined. By using a typical 100-lead Thin Quad Flat package (TQFP) as the test vehicle, the proposed methodology is benchmarked by a thermal test die measurement in terms of the junction-to-ambient (J/A) thermal resistance and the chip junction temperature. To demonstrate the accuracy of the benchmarked data from the thermal test die measurement, a corresponding uncertainty analysis is performed. It is found that the worst possible uncertainty in the measured power, based on the specific power supply, is about 0.005 W and that of chip junction temperature measurement is about 0.78°C. Additional studies are performed to evaluate the feasibility of the correlation models for convective heat transfer coefficients on typical TQFP packages. It turns out that for a small device such as the TQFP package, these correlation models are fairly reliable.