As PCB assembly densities climb, BGA packages have become standard equipment in modern electronics manufacturing. But the solder joints that hold those packages to the board sit beneath the chip body, out of reach of the naked eye and even of conventional optical microscopes. When a board develops an unexplained open or short, X-ray inspection systems are what allow engineers to see through the package and into the joint itself.
Traditional in-circuit test and automated optical inspection are built around the component surface. For BGA, CSP and similar bottom-terminated packages, those methods are largely blind to the joints that matter most. X-ray inspection exploits the high penetrative power of X-rays to pass through package material and render the internal solder geometry in detail.
Systems such as the MX1 X-ray inspection platform use high-resolution imaging to capture fine defects inside multilayer boards and complex packages in real time, including bridging, voiding and missing balls. The result is a view of the joint that no optical method can deliver.
For any X-ray system, imaging quality sets the ceiling on defect-detection accuracy. The MX1's published specifications illustrate what that looks like in high-density assembly work:
| Specification | Detail |
|---|---|
| X-ray source voltage | 80 kV |
| Focal spot size | 10 μm |
| Contrast resolution | Resolves 0.001 in. gold wire |
| Spatial resolution | 100 line-pairs/mm |
| Optical magnification | 4X to 225X |
| Stage travel | 14 in. x 14 in. (356 mm x 356 mm) |
The 10 μm focal spot is the decisive figure. Compared with a conventional 35 μm spot, a tighter spot sharply reduces image blur, which allows small BGA voids and fine bridging to be identified rather than guessed at.
Beyond straight-down inspection, the MX1 carries a 45-degree wedge block that supports angled viewing. Those oblique views matter when a defect is complex. A BGA offset, for example, may not be fully resolved from a single top-down angle, since the direction of displacement can be ambiguous.
Tilting the sample makes the solder ball geometry easier to confirm. Geometric magnification shifts to 15X when the wedge block is in use, but the depth information gained is often the difference between a confident call and an uncertain one.
