2D X-ray imaging is primarily used for PCB assembly defect detection because it allows for the observation of all layers of a PCB simultaneously. This service is non-damaging and allows for solderability inspections on any components of which the solder joint is not inspectable via microscope, AOI, or other “superficial” means of inspection. These components include but are not limited to BGAs, LGAs, and QFNs. 2D X-ray imaging is primarily used for looking for solder bridging, solder voiding, and taking area calculations of solder voiding.
3D computed tomography (CT) imaging is used for qualitative and quantitative defect analysis on an entire PCB and its components. CT can resolve each layer of a PCB individually so disconnects, delamination, and other defects can be detected within the PCB itself. It is possible to do volumetric, quantitative calculations for the solder fill on individual SMD and T/H components, thermal pads of QFNs and individual balls of BGAs and calculate bond wire defects, thickness and lengths. CT also allows for full 3D rendering of a component and its inner workings, such as bond wires. The CT process requires the sample to be clamped to a spindle and rotated 360 degrees while being held above the x-ray tube, so this is best used for small, light weight samples.
3D Laminography imaging is used to acquire much of the same data as CT imaging but is faster and can be used for much larger and heavier samples. There are a few downsides to using laminography versus CT in terms of resolution and noise levels. This imaging is taken by placing the sample on a rotating table and with 2D images taken at nearly every degree (360) which are afterwards reconstructed into a single model.