Definition

X-ray inspection uses X-ray imaging to examine solder joints that are hidden from optical inspection, particularly under BGA, QFN, and LGA packages where joints are beneath the component body. X-ray reveals voids in solder joints (acceptable up to 25% for most applications), head-in-pillow defects, bridging between BGA balls, and incomplete joints under QFN thermal pads. Automated X-ray inspection (AXI) systems provide 2D or 3D tomographic imaging for production inspection. For PCB designers, X-ray inspection capability means BGAs and QFNs can be used confidently - the hidden joints are verifiable. Specify X-ray inspection in your assembly requirements for boards with hidden-joint components.