A cross section is useful only if it intersects the intended feature. Before cutting a valuable failed board, agree on the target and the evidence needed to know that preparation has reached it. A polished image from a nearby region cannot answer a question about a particular failed connection.
Locate the target in three dimensions
Mark board side, layer sequence, feature identifier and the intended viewing direction. Use available nondestructive evidence to connect the observed fault to a physical location. Preserve photographs with recognizable neighboring features so the laboratory can locate the target after the board has been divided.
Struers’ microelectronics preparation guidance describes controlled material removal to reach small targets and warns that preparation can miss a unique feature. It also identifies cutting damage as a concern. These points support planning the target before starting destructive work.
Agree on the stopping decision
| Question | Evidence to establish |
|---|---|
| Which feature? | Unique location and reference images |
| Which plane? | Orientation relative to the suspected interface |
| When to stop? | Recognizable target geometry or another approved indicator |
| What to retain? | Remaining specimen and intermediate images |
The laboratory should choose cutting, mounting and removal settings appropriate to the specimen. A customer location sketch is not a substitute for a qualified preparation method, but it defines what that method must reveal.
Use intermediate observations deliberately
Record progress where the target is approached. If the feature begins to appear unexpectedly, pause for interpretation before continuing to the nominal plane. A narrow crack or irregular connection may not follow the idealized geometry shown in the layout.
For example, a via known to fail at one internal connection may require a different section direction from a routine hole-wall thickness coupon. Explain the failure question instead of simply asking the laboratory to section a via.
If several suspect features exist, allocate them before preparation. Preserve another location for confirmation where possible rather than consuming every candidate in the first exploratory cut.
State what the resulting plane can show
Label the final image with the actual section location, not only the intended one. If the target was missed or partially removed, state that limitation. An attractive image does not justify calling an unobserved interface acceptable.
Connect the conclusion to electrical and other evidence from the same board. A section is a local view, and its interpretation should not silently become a claim about every corresponding feature on the production panel.
The filled-via section plan addresses sampling positions, while preparation artifact review separates specimen condition from damage introduced during examination.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist