Ultimate PCB Inspection Checklist

AOI systems use high-resolution cameras and pattern-recognition software to compare every solder joint and component against the digital reference design. AOI identifies polarity errors, insufficient solder, and lifted leads faster and more accurately than the human eye. For surface mount assemblies, it provides a repeatable, objective check early in the process. And all of this occurs before boards move to test or final assembly.

Effective inspection starts with preparation. Before testing begins, boards must be fully cured, cleaned, and labeled. Inspection criteria should align with customer specifications and IPC standards such as IPC-A-610 and IPC-6012.

Environmental factors, like lighting, magnification, and ESD control, should also be verified to prevent accidental contamination or handling damage during evaluation. Finally, inspection documentation and checklists should be approved and traceable to each production batch, establishing a clear quality record for future audits.

• Verify uniform wetting, correct fillet shape, and absence of voids or bridges.
• Check for dull, grainy, or cracked joints that may indicate cold solder or contamination.
• Inspect for excessive solder that could cause shorts or mechanical stress.

• Confirm alignment to pads, especially for fine-pitch and polarized components.
• Validate that all part numbers match the bill of materials (BOM).
• Check for tombstoned resistors, lifted leads, or skewed parts caused by reflow imbalance.

• Ensure that mask openings align with pads and vias, preventing solder bridging.
• Confirm legible, accurate silkscreen markings for reference designators and polarity.
• Check for mask bleed, voids, or contamination that could affect assembly or rework.

• Inspect traces for nicks, cuts, or over-etching.
• Verify pad adhesion and copper thickness in high-current areas.
• Check for damage near connectors or plated through-holes that may weaken the circuit.

• Examine surfaces for flux residue, dust, fibers, or metallic debris.
• Confirm ionic contamination is within limits per IPC J-STD-001.
• Verify cleaning methods and solvents have not damaged coating or markings.

• Ensure uniform coverage, correct thickness, and full cure without bubbles or peeling.
• Verify masking accuracy, which means no coating on connectors, test points, or contact pads.
• Inspect overmolded assemblies for voids or incomplete encapsulation that could trap moisture or compromise flexibility.

• Check board flatness, connector alignment, and mounting hole accuracy.
• Inspect standoffs, fasteners, and mechanical supports for torque and fit.
• Confirm assemblies meet defined tolerances for insertion force and dimensional stability.

Inspection is the safeguard to identify defects and prove compliance. Each verification point must be recorded with lot codes, inspection dates, and operator sign-offs. Visual data, such as AOI or X-ray images, should be archived for traceability.

For regulated industries, documentation must link inspection results to material batches, calibration records, and final acceptance criteria. At EI Microcircuits, inspection data is digitally logged and integrated into our manufacturing execution system (MES), ensuring full visibility from incoming material to outgoing shipment.

Even experienced teams can overlook subtle risks during inspection. Common issues include:

• Relying solely on visual inspection for hidden defects.
• Skipping intermediate AOI checks between SMT and final assembly.
• Failing to recalibrate test equipment or update test programs after engineering changes.
• Inconsistent documentation across production shifts or facilities.

Avoiding these pitfalls requires both process discipline and cross-team communication. And inspection should never function as an isolated task, because it’s part of a continuous quality loop that includes design, assembly, and corrective action feedback.

At EI Microcircuits, inspection is embedded into every phase of production. Each assembly moves through defined verification stages supported by advanced inspection technologies, experienced technicians, and closed-loop process control.

• AOI and X-ray verification confirm solder integrity for all SMT and through-hole builds.
• Flying probe and ICT testing validate continuity and circuit function before integration.
• Functional testing and environmental stress screening replicate real-world conditions to verify performance over time.

All inspection data is logged and traceable through our quality management systems that are certified to ISO 9001, ISO 13485, and AS9100D. Our documentation protocols support full audit readiness for all our customers, including medical, aerospace, and defense.