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PCB Assembly

Printed Circuit Board Assembly X-Ray Inspection

X-ray inspection in PCB assembly is to provide access to the internal geometries and structures of the soldering of a component without the need for physical disassembly. Which enables non-destructive verification of hidden solder joint integrity through high-resolution imaging.

Why X-Ray Inspection is Critical for Modern PCB Assembly

In today’s electronics manufacturing, Automated X-Ray Inspection (AXI) has become essential for ensuring reliability in high-density PCB assemblies. As components shrink to microscopic sizes—such as 01005 chips and 0.3mm-pitch BGAs—traditional inspection methods like Automated Optical Inspection (AOI) can no longer detect hidden defects.

Key Challenges Solved by AXI:

BGA/CSP Solder Joints

– Inspects voids, cracks, and bridging under the package

Microvia Integrity

– Detects plating voids in HDI (High-Density Interconnect) PCBs

3D Package Stacking

– Verifies solder connections in complex multi-chip modules

X-ray inspection image with quantitative analytics highlighting solder voids (air pockets) within the ball grid array (BGA) solder joints, measuring void location, size, and percentage against IPC standards.
Side-by-side comparison of X-ray inspection images showing an actual solder joint defect versus a false call caused by component geometry or imaging artifacts, annotated to highlight the differentiating features.
X-ray inspection station integrated into a fast-turnaround PCB assembly line, showing a freshly assembled board being scanned to ensure quality without delaying rapid delivery timelines.
X-ray inspection image of a PCB assembly highlighting solder joint quality that meets or exceeds the stringent acceptance criteria of IPC-A-610 Class 3 for high-reliability electronic products.
X-ray inspection image of a Quad Flat No-lead (QFN) package on a PCB, clearly showing solder fillet formation, voiding under the thermal pad, and alignment of the perimeter solder joints.
Illustrated guide showing how X-ray inspection reveals hidden PCB solder defects like BGA voids, QFN heel fillet gaps, and insufficient through-hole fill, with side-by-side comparisons of good and faulty joints.

Based on its working principles and capabilities, AXI is applied to test circuit boards containing components with array-style packaging or fine pitch packaging including BGAs, CGAs (Column Grid Arrays), CSPs (Chip Size Package), etc. AXI is usually placed in the assembly process, just after the last soldering no matter wave soldering or reflow soldering. Furthermore, AXI is usually applied coupled with boundary scan test, ICT and functional test in order to obtain optimal inspection results.

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AXI features: some advantages as a type of structural test and inspection

Some defects can be found in the early stage of printed circuit board assembly process;
It is contributive to the cost reduction of defects;
It stops defects from flooding among remaining PCB assembly or even clients’ practical projects.

AXI equipment is classified into two categories: 2D and 3D equipment. For 2D AXI equipment, WellPCB uses model VIEWX2000, responsible for inspecting PCBA manufacturing defects including opens, shorts, insufficient solder, excessive solder, missing electrical parts, misaligned components, solder voiding etc.

PCB assembly QFN X-Ray Inspection

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Although AXI and AOI have the same working principles and play similar roles in PCB assembly production line, defects they can detect differ to some extent.

Inspection capability comparison between AXI and AOI

Defect TypeAOIAXIICT
Faulty component×√√
Missing component√√√
Incorrect component value××√
Lifted Lead√√√
Misaligned/Misplaced component√√√
Open Soldering Circuits√√√
Solder bridges√√√
Solder shorts√√√
Insufficient solder√(not heel of joint)√×
Solder void×√×
Excess solder√√×
Solder quality×√×
BGA and CSP shorts×√√
BAG and CSP open circuit connections×√√

Why Choose WellerPCB for X-Ray Inspection?

  • IPC-A-610 Certified Inspectors
  • 24-Hour Turnaround for X-Ray reports
  • AI-Powered Defect Classification (Reduces false calls)

Automated X-ray inspection is a critical quality control procedure of many electronics manufacturing organizations. X-ray inspection can provide a fast and accurate and thorough inspection of internal soldering quality passing the production facility and by this way provide real-time feedback that have the production system to be optimized to produce high quality and reliable electronics assembly. Generally, the cost of AXI is more expensive than some other forms of inspection, but it has many advantages and these need to be carefully balanced against the costs to ensure whatever choices is made, it is reasonably correct for the particular production and manufacturing environment.

 
WellerPCB’s AXI system caught a 9% voiding issue in our medical device BGAs—saving $500K in potential recalls.

– Medical Device Manufacturer, ISO 13485 Certified

FAQ – PCB Assembly X-Ray Inspection

Yes! AXI works perfectly with SAC305, SnAgCu, and other lead-free alloys.
AXI has higher upfront costs but saves 60% in rework/recall expenses for complex boards.

Absolutely. Our low-dose systems comply with FDA radiation safety limits.