Spatial Position
Geometrical layout of X-ray inspection systems relies on the physical gap between the tube focal spot and the sample under inspection to establish the base parameters of image acquisition. This clearance, known as the focus to object distance, dictates how the radiation cone spreads as it intersects the printed circuit board assembly. Shortening this path increases the area of the board projected onto the sensor.
Magnification Effect
Altering the position of the board relative to the source allows inspectors to change the size of the captured features. A small focus to object distance yields high geometric magnification, revealing tiny defects like solder voids or micro-cracks inside ball grid array joints. If the board resides closer to the sensor, the image remains at a lower resolution but captures a broader view.
System operators adjust this gap to balance inspection speed and detail level.
Collision Avoidance
Physical limits restrict how closely a board can approach the X-ray tube without damaging delicate components on the assembly surface. Because the focus to object distance cannot be reduced past the thickness of the tube window and component height, mechanical clearance sensors must actively monitor the motion axes during high-magnification runs. If a collision occurs, it can rupture the beryllium window of the tube or destroy the board under test.
High-end automated systems use software-defined safety zones that calculate the minimum safe gap based on component heights and fixture geometry, protecting both the expensive source and the board from physical impact.
