Questions to Ask When Reviewing a PCB Microsection

A microsection can reveal features hidden inside a printed circuit board, but a photograph is not a complete acceptance decision. Its meaning depends on what was sectioned, where the cut passed through the feature, how the specimen was prepared, and which requirement is being evaluated. Ask these questions before treating an attractive image as proof of an entire lot’s quality.

Identify the sample and the purpose

IPC’s public standards resources describe dedicated coupon structures for evaluating plated-hole integrity, including through holes and microvia structures. That distinction matters: a coupon designed for one assessment should not be assumed to demonstrate every property of a different structure. IPC: standards-related resources and coupon information.

Request the board part number, revision, lot or panel identifier, coupon designation, and sampled feature type. State the question the section is intended to answer. Examples include wall copper, an internal connection, a filled structure, or the location of a backdrill termination. If the purpose is failure analysis, identify whether the sample came from a failed board, a passing control, or a production coupon.

Check the evidence in the image

1. Locate the feature of interest and establish the orientation of the section.
2. Confirm that a scale or calibrated measurement is available.
3. Ask where each reported dimension was taken and whether a minimum, average, or individual value is being reported.
4. Review whether preparation artifacts could affect the interpretation.
5. Compare the observation with the exact drawing or agreed acceptance requirement.

For example, a plated hole may show a clear wall on one image but no visible internal land on the layer under discussion. Before concluding that the connection is missing, confirm the cut location and ask for the relevant view. Conversely, a single favorable wall measurement should not be described as the minimum across an entire panel unless the sampling procedure supports that statement.

Keep sampling separate from acceptance

Record how samples were selected and which delivered boards they represent. Sampling can provide useful process evidence without inspecting every feature. Its limits should remain visible in the report. When a finding raises concern, define the affected population and the next investigation step instead of extrapolating from one image without context.

Close the loop with a disposition

A useful report preserves the original images, annotated measurement locations, numerical results, applicable criteria, and reviewer conclusion. If the feature is outside the agreed requirement, request a documented disposition and cause assessment. If an image is ambiguous, ask for additional preparation or another method rather than forcing a pass or fail decision. For critical products, the customer’s quality plan may require specific test methods and accredited evaluation; a general explanatory guide does not replace those contractual requirements. The goal is traceable evidence that answers a defined engineering question.