Thermal imaging for detecting thermal interface issues in assembly and reliability stressing

This paper describes the development of a non-destructive thermal imaging technique to detect thermal interface material defects in integrated heat spreader in advanced microprocessors. This technique allows capturing the surface infrared emission response as a function of time using high speed infrared camera. The infrared response of the surface of the integrated heat spreader is captured immediately after powering up the silicon die internally or applying pulsed external heating to the surface. With the presence of thermal interface material defects, the heat flow is disrupted and is reflected on the surface thermal distribution of integrated heat spreader. Since the thermal response of the heat spreader is affected by the thermal interface material defects underneath, the technique can be used to evaluate thermal interface material defects and thermal degradation. We show the successful application of this technique to capture various types of artificially created defects such as voiding. We also show that post thermally cycling and stressing, the thermal signature degrades for all units tested. This paper discusses the results obtained using the internal die heating only as it provided better results for all cases, as compared to pulsed external heating