Radiographic Projection
X-ray imaging provides a volumetric view of flat electronic components by rotating the source and detector in parallel planes rather than tilting the object. Computed laminography isolates horizontal layers within a high-density assembly to reveal features obscured by overlapping structures. This technique avoids the mechanical interference typical of standard rotation stages when inspecting large printed circuit boards.
It requires a planar reconstruction algorithm to convert a series of limited-angle projections into a depth-resolved slice.
Assembly Verification
Solder joint integrity assessment relies on this method to detect head-in-pillow defects and internal voiding in ball grid arrays. Engineers use these cross-sectional images to verify the wetting behavior of components mounted on dense multilayer substrates. Optical inspection systems cannot penetrate the underside of area array packages, whereas this X-ray approach slices through the board to expose hidden connections.
Geometric Limitation
Spatial resolution degrades in direct proportion to the distance between the target layer and the focal spot of the X-ray source. Shadowing artifacts occur if the surrounding material density varies too sharply, as secondary scattering creates noise that mimics structural discontinuities. Software filters minimize these unwanted signals during the reconstruction phase to maintain signal contrast.
Precise alignment of the rotation axis ensures that geometric distortion stays within the tolerances required for microelectronics failure analysis.
