Investigation of BGA underfill process based on multipositional computed tomography

Abstract

Abstract In this paper, defect inspection related to an epoxy underfilling process between integrated circuits (ICs) and printed circuit boards (PCBs) is presented utilizing the data fusion of multipositional computed tomography (DFMCT). The work aims to verify the existence of underfilling epoxy which was not possible utilizing standard computed tomography due to strong metal artifacts created by ball grid array (BGA) packages. By interpreting the results obtained from the scanned samples, we were able to correlate the excess epoxy defects and the success of the underfilling process. We present the data fusion approach as an alternative method when traditional metal artifact reduction methods would be insufficient. The study was commenced by making a proper radiographic simulation using aRTist simulation software. The simulation enabled us to choose the right mounting positions which produce less metal artifacts for the experimental study. The DFMCT was achieved by acquiring multiple computed tomographic scans at different sample orientations. The reconstructed volumes were then aligned, and the fused volume was obtained by combining the corrected data and suppressing the disrupted data of the reconstructed volumes.