Quick answer
BGA X-ray inspection is useful when a project needs evidence about solder joints hidden beneath an opaque package. It can reveal imageable conditions such as bridging, missing balls, solder distribution or void-related features, depending on the image method and review plan. It does not prove electrical connectivity, every crack, or product function. Define the inspected feature, acceptance basis, scope and record before release, then combine X-ray with AOI and electrical or functional evidence where those questions also matter.
BGA X-ray inspection is needed when a release decision depends on evidence from a solder joint that cannot be viewed optically. A radiograph can show selected imageable conditions below an opaque package, but it is not a blanket quality verdict. The useful plan names the feature to inspect, the accepted image characteristics, the unit or lot scope, the reviewer and the resulting record before the board is built.
This page owns the decision for BGA and other hidden-joint X-ray evidence. 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 reveal?
With an appropriate image setup and review method, X-ray can provide evidence about hidden solder-ball geometry and other subsurface features that an optical camera cannot directly see. The exact interpretation depends on package construction, board stackup, projection angle, image quality and the project acceptance basis. Infineon's BGA assembly guidance describes X-ray as useful for hidden terminations while also noting that some conditions, including certain broken joints, are not readily detected.
| Question | Evidence X-ray can support | What it does not prove by itself |
|---|---|---|
| Are hidden BGA joints imageable? | Visible solder-ball pattern, bridging, missing-ball or solder-distribution indications within the agreed view | Every internal defect or the electrical behavior of the assembly |
| Is a void-related feature relevant? | Radiographic evidence of the feature under the defined image method and acceptance basis | A universal acceptable percentage or reliability conclusion without project criteria |
| Did reflow create a visible assembly issue? | Evidence that supports review of hidden-joint conditions in scope | That all visible placement, polarity or paste conditions are correct |
| Does the PCBA work? | No direct product-function evidence | Powered behavior, interface performance or all accessible electrical conditions |
When should a project specify X-ray?
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.
Use X-ray with—not instead of—other evidence
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.
Build an acceptance review before the first image
- 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.
What to provide for an engineering 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.
Engineering review
Prepared and reviewed for project use
Engineering Director
Senior Quality Engineer
Review scope: technical accuracy, evidence wording, standards references, internal links and release readiness. Project requirements remain subject to the released files, applicable acceptance criteria and agreed test documentation.
FAQ
Questions engineers ask before release
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?+
Not automatically. Decide from the package risk, design, customer requirements, pilot evidence, acceptance plan and the evidence needed for the release decision.
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.
Reference points
Sources and verification starting points
External standards and industry references help frame the decision. Confirm current supplier evidence and project-specific requirements before release.