A section through a filled via shows a particular plane through a three-dimensional feature. Before preparing samples, decide what question the examination must answer and which hole population it represents. A convenient polished image is weak evidence if its location cannot be connected to the reported concern.
Define the filled-hole population
Separate holes by construction, size, depth, material and process route where those differences matter to the investigation. Identify the affected panels and physical coordinates. Keep production holes distinct from specially prepared demonstration structures.
Eurocircuits distinguishes via filling from plugging and asks customers to identify which holes require filling. That distinction should also survive inspection: a report needs the intended construction, not merely the word closed beside an image.
Write the sample map before cutting
| Selection field | Purpose |
|---|---|
| Panel and coordinate | Identifies the original physical feature |
| Selection reason | Separates random, representative and suspect samples |
| Section direction | States the planned plane through the feature |
| Processing state | Identifies whether later cap and finish are present |
Include comparison samples from a relevant unaffected region when investigating a local problem. Mark their selection reason so they are not later mistaken for evidence of an unrestricted production sampling plan.
Preserve observation and interpretation separately
Describe the observed boundary, cavity or material feature before assigning a cause. Record the examiner’s confidence in the preparation and the ability of the method to distinguish different materials.
For example, a cavity intersected by one section provides evidence at that plane. Its full volume and shape require additional justified examination; they should not be inferred from a single area measurement without an agreed basis.
Apply the actual acceptance requirement
- Identify the drawing and applicable specification revision.
- Confirm that the required feature was examined.
- Compare observations using the specified definition.
- Escalate ambiguity before assigning acceptance.
- Retain images, locations and disposition together.
A percentage from another supplier’s capability page is not an automatic acceptance limit for the current product. The type of fill, required cap and intended use can change which characteristic matters.
If the investigation expands, give additional samples their own identifiers. Preserve the relationship between the original suspect feature and later comparison sections instead of replacing the first report with a more favorable image.
Retain a plan-view photograph before sectioning when possible. It helps another reviewer identify which member of a close-spaced array was examined and distinguish a documented target from an adjacent hole that happened to appear in the prepared plane.
The surface review guide covers the region around a filled hole. The solder-land guide connects the inspected construction to its assembly purpose.
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