In short
BGA X-ray inspection lets an engineer examine solder connections hidden beneath the package. A suitable image can reveal features such as bridging, missing balls, solder distribution and voids. It is most useful when those hidden-joint questions affect the build; AOI covers visible features, while electrical and functional tests answer different questions about connectivity and operation.
For hidden solder joints, review placement and inspection in the BGA assembly overview.
BGA solder joints sit beneath the component, beyond the view of normal optical inspection. X-ray imaging opens a useful window into those connections, helping engineers examine ball pattern, bridges, missing joints and void-related features. The inspection plan should name the feature and image criteria of interest, then pair X-ray with electrical or functional checks when those are also needed.
Use this guide when a BGA or other hidden-joint question may require X-ray. For the wider choice among SPI, AOI, X-ray, ICT, flying probe and functional testing, use the PCB inspection methods overview. For a project route, begin with quality control and PCB assembly testing.
What can BGA X-ray inspection show?
On a BGA board, an X-ray image can show the solder-ball pattern and signs of bridging, missing balls, uneven solder distribution or voids. Package construction, board layers, viewing angle and image quality determine what can be distinguished. Infineon's BGA assembly guidance notes that some broken joints may still be hard to detect; use an electrical or functional check when the question is whether a connection works.
| Question | Useful X-ray view | Pair it with |
|---|---|---|
| Are BGA balls present and aligned? | Ball pattern and missing-ball indications beneath the package | AOI for visible placement and polarity |
| Are bridges or voids visible? | Imageable solder bridges and void features from the selected angle | Project-specific criteria for the feature and its significance |
| Did reflow leave a hidden anomaly? | Changes in the hidden joint pattern or solder distribution | SPI or AOI for paste and visible assembly features |
| Does the assembled board work? | X-ray does not test powered behavior | ICT, flying probe or functional test as appropriate to the design |
AI-generated illustration: BGA PCBA inside an X-ray inspection workstation.
When should you request BGA X-ray inspection?
Specify X-ray when the risk review, drawing, customer requirement or pilot finding creates a hidden-joint question that cannot be answered from the optical view alone. BGA, QFN and other bottom-terminated packages are common reasons to review the question, but package name alone does not define coverage or acceptance. Confirm which packages, positions, view angles, image interpretation rules and sampling or unit scope are required.
Do not insert a generic X-ray line into a quote and leave the decision unfinished. A practical requirement identifies the released assembly revision, the feature or defect mode of concern, the applicable acceptance language, who owns disposition and what record is expected. If a formal standard, customer drawing or program-specific class applies, identify the current revision and project applicability; a standard title alone is not a test plan.
Pair X-ray with AOI and electrical testing
AOI evaluates visible placement and solder features configured in its approved recipe. X-ray addresses defined hidden features. Electrical methods such as ICT, flying probe or functional test evaluate only their reachable nets or specified behaviors. A release plan can combine them, but each method should retain its own question and boundary.
AI-generated illustration: PCB under inspection beside a BGA X-ray image.
Set image criteria before the first build
- Freeze the BGA package, board revision and assembly configuration to be evaluated.
- Name the hidden feature or failure risk that needs evidence.
- Set the image method, views, evaluation basis, scope and reviewer authority.
- Define what record, image reference or disposition is retained for the agreed project scope.
- Pair X-ray with AOI, electrical test or functional test only where those methods answer separate release questions.
- Revisit the affected decision when the package, land pattern, solder route, board stackup, process or acceptance requirement changes.
AI-generated illustration: Engineer reviewing BGA X-ray and electrical test results.
What to send for a BGA inspection review
Send the released fabrication and assembly files, BOM, assembly drawing, package information, target build stage and any customer or product acceptance requirements. Flag the hidden packages and state the evidence you need returned. PCBArise can review the request as part of a project-specific PCB assembly and quote review; X-ray coverage, acceptance and records are confirmed for the actual build rather than presumed from this guide.
FAQ
Common questions
Can AOI inspect BGA solder joints?+
AOI can inspect visible placement and solder features configured in its recipe, but it cannot directly see a solder joint hidden beneath an opaque BGA package. Define a separate hidden-joint evidence method when that question is in scope.
What defects can BGA X-ray inspection find?+
An agreed X-ray method can support review of imageable hidden-joint conditions such as bridging, missing balls, solder distribution or void-related features. The exact features, views and acceptance basis must be defined for the package and project.
Does X-ray prove that a BGA joint is electrically connected?+
No. X-ray produces radiographic evidence of defined physical features. Electrical connectivity and product behavior require their own approved electrical or functional test evidence where required.
Is X-ray inspection required for every BGA?+
No. X-ray is most useful when the acceptance question concerns solder features hidden under the BGA, such as bridging, missing balls or void-related features. Specify the joints or sampling scope and image acceptance criteria before production; use electrical or functional testing for connectivity and behavior, which the radiograph cannot establish.
Who sets BGA X-ray acceptance criteria?+
The project owner and supplier should agree the applicable drawing, customer requirement, standard context or other acceptance basis before production. The criteria, scope and failure disposition should be explicit rather than inferred from a machine name.
What changes require the X-ray plan to be reviewed?+
Review the affected plan after a change to package, land pattern, board construction, solder process, image setup, revision, acceptance requirement or disposition rule.
Technical references
Sources used for this guide
These sources explain the standards, materials or process details discussed above. Check the current revision when applying them to a new design.