Non-Destructive Analysis of Voiding in Thermal Interface Material of High-Performance Computing Devices Using B-Mode Scanning Acoustic Microscopy (B-SAM)

C-mode scanning acoustic microscopy (C-SAM) is a robust, non-destructive technique used for inspecting coverage of thermal interface material (TIM). While C-SAM images effectively reveal voids in planar views, it lacks depth information necessary for assessing the volumetric coverage of TIM. This paper proposes the use of quantitative broadband acoustic microscopy (Q-BAM) for further analysis of TIM coverage. The experimental results presented in this paper suggest that Q-BAM extracts void depth information from TIM specimens, providing a quick solution to assess TIM volumetric coverage. Experiments were conducted on both newly assembled (T0) unit and high-temperature storage (HTS) stressed unit. Comparing the Q-BAM measurement results with physical cross-sectional depth measurements, an average percentage difference of 35.93% was observed for the T0 unit and 19.42 % for the HTS unit. The accuracy of Q-BAM is limited by the resolution of the transducer and acoustic reflectance properties giving rise to challenges in detecting minor voids and complex geometries. Nonetheless, Q-BAM offers rapid imaging capabilities with depth information obtained within 5 minutes, enabling quick TIM assembly process fixes for enhanced product reliability and better thermal management.