QPE Blog: X-ray inspection: examining hidden solder joints in PCB assemblies
Visual inspection provides valuable information about a PCB assembly, but some connections are concealed beneath component bodies.
For components such as Ball Grid Arrays (BGAs), the solder joints sit underneath the package. These connections cannot be fully assessed using conventional visual inspection or Automated Optical Inspection (AOI) alone.
At QPE, our Nikon X-ray inspection system helps us examine these hidden areas, providing an additional layer of inspection where the assembly requires it.
Why hidden connections need closer inspection
BGA packages use an array of solder connections beneath the component to connect it to the PCB. This arrangement allows many connections within a compact footprint, but it also limits access for optical inspection.
A component may appear correctly positioned from above while an issue exists beneath it. X-ray imaging allows us to examine the concealed solder connections without removing the component.
This helps our team assess features that would otherwise remain hidden.
What can X-ray inspection reveal?
Our Nikon system uses high-resolution X-ray imaging to help identify potential soldering defects, including:
Solder bridges: unwanted solder connections between adjacent joints.
Voids: gaps within the solder that may affect joint performance, depending on their size, position and the application requirements.
Irregular solder formations: variations that may need further investigation.
The images support assessment of the assembly against its inspection requirements. A visible feature does not automatically mean a joint is unacceptable; findings need to be interpreted in the context of the component, application and relevant acceptance criteria.
How X-ray complements other quality checks
Different inspection methods provide different information.
AOI checks visible assembly features, while X-ray imaging helps examine concealed solder connections. Electrical and functional testing provide further information about how the assembly performs.
Used together where appropriate, these methods give a more complete assessment than any single inspection technique can provide.
What this means for customers
For customers whose designs include hidden solder joints, X-ray inspection provides additional insight into assembly quality. It helps identify potential issues before products progress further through manufacture and supports investigation when a connection needs closer examination.
Our investment in Nikon X-ray technology gives our team the means to inspect increasingly complex assemblies and make informed quality decisions.
It is another part of QPE’s approach to combining controlled manufacturing processes with inspection and testing suited to the product.
Does your PCB design include BGAs or other hidden solder connections? Contact QPE to discuss your inspection and manufacturing requirements.
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