X-ray inspection methods for controlling PCBA potting process — 2DX and partial angle computer tomography

Abstract

High performance X-ray inspection systems are widely used in the PCBA manufacturing process. These include 2DX systems with sub-micron feature recognition that are equipped with 3D micro-CT (Computer Tomography) and Large Board CT 1-2 (also called Partial Angle CT and PCT). The Large Board CT functionality is extremely important in order to be able to perform 3D CT inspection of regions of interest within a large PCBs in a completely non-destructive way and still provide very high resolution and detail. The micro-CT is mostly effective for small samples and not for large PCBAs. In this paper we share our experience for verifying the quality of a potting process using completely nondestructive X-ray methods (2DX and Large Board CT/PCT). The defects we verify for are voiding and incomplete potting curing. Traditionally, the standard way of controlling the potting process has been a destructive sampling (mechanical cross-sectioning) that results in board damage and scrapping. We compared our X-ray inspection results (2DX and PCT) with mechanical cross section results and proved that the non-destructive X-ray techniques provide completely satisfactory testing solution that gives good confidence to our customers. The X-ray inspection provides clear 2D and 3D images of the defects and it is easy to optimize. In addition, the X-ray inspection (2DX and PCT) of potting process resulted in a significant cost savings for our customers. This is due to the fact that the X-ray techniques are completely non-destructive and also much faster, compared to the mechanical cross-sectioning. In addition, using X-ray inspection we can offer 100% testing solution that is not possible using mechanical cross section. Naturally, as a future project, we will be looking to fully automate the X-ray inspection and provide a fully automatic, extremely fast and completely non-destructive solution for PCBA potting process verification.