X-ray inspection reveals hidden solder joint defects, internal component structures, and assembly problems that automated optical inspection or standard visual inspection cannot detect.
It is especially important for inspecting BGAs, QFNs, CSPs, LCCs, and other components with solder connections located underneath the package.
Some of the most expensive printed circuit board failures begin in solder joints that appear perfect from the outside. A board may pass visual inspection and still contain voids, bridging, insufficient solder, incomplete reflow, or other hidden defects.
Excel Electronics uses high-resolution X-ray inspection to identify these issues before assemblies are shipped or to investigate the root cause of a board failure.
What Is PCB X-Ray Inspection?
PCB X-ray inspection is a non-destructive testing method that uses X-ray imaging to examine solder joints, component connections, and internal structures inside a printed circuit board assembly.
Unlike optical inspection, X-ray inspection can see through components and circuit board materials. This makes it possible to evaluate connections that are hidden underneath electronic packages.
X-ray inspection is commonly used for:
- BGA and micro-BGA solder joints
- QFN and LCC packages
- Chip-scale packages
- Hidden thermal pads
- Dense, multilayer circuit boards
- Component authenticity analysis
- PCB failure analysis
- Reflow process validation
Why Can Optical Inspection Not Inspect BGA Solder Joints?
A BGA, or Ball Grid Array, has an array of solder balls located underneath the component package.
Once the BGA is mounted to the circuit board, its electrical connections are no longer visible from above or from the side. Automated optical inspection can verify the component’s placement, alignment, orientation, and external condition, but it cannot directly inspect the solder joints beneath it.
X-ray inspection is required to evaluate those hidden connections.
What PCB Defects Can X-Ray Inspection Detect?
PCB X-ray inspection can detect several defects that may not be visible through other inspection methods.
Solder Voids
A solder void is an empty area or air pocket inside a solder joint. Excessive voiding can weaken the connection, reduce thermal transfer, and affect long-term reliability.
Solder Bridging
Solder bridging occurs when solder unintentionally connects two adjacent pads or BGA balls. This can create an electrical short.
Insufficient Solder
Insufficient solder may prevent a component terminal or BGA ball from forming a complete and reliable electrical connection.
Incomplete Reflow
Incomplete reflow occurs when solder does not heat, flow, or bond correctly during the reflow process. The resulting connection may be weak or intermittent.
Cold Solder Joints
A cold joint forms when solder does not properly wet or bond to the component or PCB pad. Cold joints may create intermittent electrical failures.
Head-in-Pillow Defects
A head-in-pillow defect occurs when a BGA solder ball and the solder paste deposit fail to fully merge during reflow. The joint may appear connected but can fail under mechanical or thermal stress.
Misalignment and Open Connections
X-ray inspection can identify BGA balls, pads, or internal connections that are misaligned, missing, or electrically open.
QFN Thermal-Pad Voiding
QFN components often use a large thermal pad underneath the package. X-ray inspection can measure solder coverage and identify excessive voiding beneath that pad.
What X-Ray Inspection System Does Excel Electronics Use?
Excel Electronics uses the Glenbrook Technologies JewelBox-70T/70LC, a high-resolution, real-time X-ray inspection system designed for electronics manufacturing, PCB diagnostics, process control, and failure analysis.
The system allows our quality team to inspect complete circuit board assemblies and then magnify individual solder joints or component structures for detailed analysis.
What Are the Capabilities of the Glenbrook JewelBox-70T/70LC?
Magnification from 7X to 2000X
Continuously variable geometric and optical magnification supports inspection ranging from a full-board overview to detailed analysis of individual solder joints.
Microfocus X-Ray Source
The system uses an 80 kV microfocus X-ray source with a 10-micron focal spot. This produces sharp, high-contrast images of dense assemblies and fine-pitch components.
Five-Axis Motorized Positioning
Motorized X, Y, and Z movement, combined with 360-degree rotation and 45-degree tilt, allows solder joints and components to be viewed from multiple angles.
Multi-angle inspection can help distinguish overlapping features and provide a clearer understanding of a suspected defect.
Automated BGA Analysis
The GTI-5000 workstation includes tools for automated BGA ball analysis. These tools help identify and document abnormalities in ball shape, size, spacing, and solder distribution.
QFN Void Measurement
The system can measure voiding beneath QFN packages and exposed thermal pads. This supports objective process evaluation rather than relying only on visual judgment.
Fully Shielded Enclosure
The X-ray system is housed in a CE-approved, fully shielded enclosure designed to support safe operation in an electronics manufacturing environment.
What Components Should Be Inspected with X-Ray?
X-ray inspection is particularly useful for components with hidden or difficult-to-see solder terminations.
These include:
- Ball Grid Arrays
- Micro-BGAs
- Chip-Scale Packages
- Quad-Flat No-Lead packages
- Land Grid Arrays
- Leadless Chip Carriers
- Bottom-terminated components
- High-density integrated circuits
- LED assemblies with internal wire bonds
Can X-Ray Inspection Identify Counterfeit Components?
X-ray inspection can support counterfeit and suspect component analysis by revealing internal structures that may differ from those found in an authentic component.
Inspectors may compare:
- Die size and position
- Internal wire bonds
- Lead-frame structure
- Internal construction
- Package density
- Component consistency
X-ray inspection is one part of a broader component authenticity and supply chain quality process. It does not replace traceability, supplier qualification, or electrical testing, but it can reveal internal differences that justify further investigation.
How Is X-Ray Used for PCB Failure Analysis?
X-ray inspection provides a non-destructive method for examining a failed PCB before components are removed or the assembly is altered.
It can help determine whether a failure is related to:
- A hidden solder joint
- A BGA connection
- A solder bridge
- Excessive voiding
- Incomplete reflow
- Internal component damage
- Process variation
- Component misalignment
Because the board remains intact during inspection, the quality team can gather evidence before deciding whether to rework, destructively analyze, or reject the assembly.
How Does X-Ray Support PCB Process Validation?
X-ray inspection can be used during prototype builds, first articles, new product introductions, and production runs to verify that the manufacturing process is producing acceptable hidden solder joints.
It can help evaluate:
- Reflow profiles
- Solder paste volume
- Stencil design
- Component placement accuracy
- BGA collapse
- QFN thermal-pad coverage
- Void percentage
- Production consistency
This information can be used to refine the assembly process before a defect becomes a recurring production issue.
Does X-Ray Inspection Replace AOI?
No. X-ray inspection does not replace automated optical inspection.
AOI and X-ray inspection evaluate different types of defects.
Automated optical inspection is effective for visible features, including:
- Component presence
- Component orientation
- Polarity
- Placement
- Visible solder fillets
- Tombstoning
- External bridging
- Surface defects
X-ray inspection is effective for hidden features, including:
- BGA solder balls
- QFN thermal pads
- Internal voids
- Hidden bridges
- Incomplete reflow
- Internal component structures
The strongest PCB quality programs use both technologies.
How Does Excel Electronics Inspect Circuit Boards?
Excel Electronics uses a layered inspection and testing process.
- Automated Optical Inspection
Our Mirtec MV-6e OMNI 3D AOI system inspects visible components and solder joints during the surface-mount assembly process.
- X-Ray Inspection
High-resolution X-ray inspection evaluates hidden solder joints and internal structures that cannot be inspected optically.
- Functional Testing
Custom full-function test fixtures verify that the completed circuit board performs according to the customer’s specifications.
Each inspection layer is designed to detect a different category of defect.
Why Is Layered PCB Inspection Important?
No single inspection method can detect every possible PCB defect.
A component may be correctly placed but have a defective hidden solder joint. A solder joint may appear acceptable but fail electrical testing. A board may pass functional testing initially but contain a process defect that reduces long-term reliability.
Layered inspection combines visual, X-ray, and functional testing to reduce these risks.
For OEMs producing high-reliability electronics, layered inspection can help:
- Reduce escaped defects
- Improve process consistency
- Identify root causes
- Support production documentation
- Reduce field failures
- Improve long-term product reliability
When Should an OEM Ask for X-Ray Inspection?
An OEM should discuss X-ray inspection with its contract manufacturer when a circuit board includes:
- BGAs or micro-BGAs
- QFNs or LCCs
- Chip-scale packages
- Leadless components
- Hidden thermal pads
- Fine-pitch components
- Dense PCB layouts
- High-reliability requirements
- New or unproven assembly processes
- Unexplained field failures
- Intermittent electrical failures
X-ray inspection is also valuable during first-production runs, prototype validation, process troubleshooting, and failure analysis.
What Industries Benefit from PCB X-Ray Inspection?
PCB X-ray inspection is particularly valuable in industries where electronic reliability, traceability, and process control are critical.
These industries include:
- Medical devices
- Industrial controls
- Specialty vehicles
- Powersports
- Transportation electronics
- LED lighting
- Office furniture electronics
- Commercial equipment
- High-reliability embedded systems
What Should You Ask a Contract Manufacturer About X-Ray Inspection?
When evaluating a PCB contract manufacturer, ask:
- Do you perform X-ray inspection in-house?
- What X-ray system do you use?
- Can you inspect BGAs and QFNs?
- Can you measure solder voiding?
- Do you document inspection findings?
- Is X-ray used for first articles or production sampling?
- Can you perform failure analysis?
- How is X-ray integrated with AOI and functional testing?
- Who reviews and interprets the X-ray images?
- How do inspection results affect process adjustments?
Owning X-ray equipment is only part of the requirement. The contract manufacturer must also have trained personnel, defined inspection criteria, and the process discipline to act on the findings.
PCB X-Ray Inspection at Excel Electronics
Excel Electronics is an ISO 9001:2015-certified electronics contract manufacturer located in Elkhart, Indiana.
We provide PCB assembly, inspection, testing, diagnostics, and manufacturing support for OEMs across multiple industries. Our team brings more than 300 years of combined printed circuit board manufacturing experience to customer projects.
Our quality capabilities include:
- Mirtec MV-6e OMNI 3D automated optical inspection
- Glenbrook JewelBox-70T/70LC X-ray inspection
- Custom functional test fixtures
- Process validation
- Failure analysis
- Production quality documentation
Talk to Excel Electronics About Your PCB Assembly
If your circuit board design includes BGAs, QFNs, leadless components, or other complex packages, Excel Electronics can review the design and determine whether X-ray inspection is appropriate for the application.
Submit a QUOTE REQUEST or call 574-206-2627.
Excel Electronics responds to quote requests within 24 hours and will provide a direct assessment of the inspection, testing, and manufacturing requirements for your PCB assembly.
Does X-ray inspection replace automated optical inspection?
No. Automated optical inspection evaluates visible components, placement, polarity, solder fillets, and surface defects. X-ray inspection evaluates hidden solder joints and internal structures. The two technologies are complementary and are often used together.
What X-ray inspection system does Excel Electronics use?
Excel Electronics uses the Glenbrook Technologies JewelBox-70T/70LC, a high-resolution real-time X-ray inspection system designed for electronics manufacturing, PCB diagnostics, process control, and failure analysis.
How is X-ray inspection used for PCB failure analysis?
X-ray inspection allows a failed circuit board to be examined without removing components or damaging the assembly. It can help identify hidden solder joints, BGA connection problems, solder bridges, voiding, incomplete reflow, internal component damage, and component misalignment.
Does X-ray inspection replace automated optical inspection?
No. Automated optical inspection evaluates visible components, placement, polarity, solder fillets, and surface defects. X-ray inspection evaluates hidden solder joints and internal structures. The two technologies are complementary and are often used together.
Does X-ray inspection replace functional testing?
No. X-ray inspection evaluates the physical condition of hidden solder joints and internal structures. Functional testing verifies that the completed circuit board operates according to the customer's design requirements.
How does Excel Electronics combine X-ray inspection with other quality controls?
Excel Electronics uses a layered quality process that combines 3D automated optical inspection for visible components and solder joints, X-ray inspection for hidden connections, and custom functional testing to verify board performance.