After resin filling and surface finishing, a via location may look smooth without yet representing the completed solder land. The review should distinguish the filled-hole surface, surrounding copper and any later metallization. Each belongs to a different stage of the manufacturing route.
Identify the inspected stage
Eurocircuits’ resin-filling description places filling, cure and brushing within a larger production sequence. Its route is an example, not a universal recipe. Ask the actual fabricator where the proposed surface examination occurs relative to fill cure and subsequent copper processing.
Retain the fill material and hole identity. A report labeled only as a via-in-pad inspection can leave it unclear whether the image shows resin, a copper cap or the final surface finish.
Define the physical comparison
| Observation | Reference needed |
|---|---|
| Local recess or projection | Agreed neighboring surface and measurement direction |
| Remaining copper | Layer and stage at which it is evaluated |
| Cap condition | Completed metallization and applicable requirement |
| Finished land | Assembly-facing surface after all operations |
Choose a method that can distinguish the concern. A reflected-light photograph can document a visible ring, but it should not be reported as a direct height or remaining-copper measurement.
Compare representative feature arrangements
Include the relevant hole sizes, spacing and panel locations in a process trial. Keep the relationship between an inspected coupon and the product explicit. Do not substitute an easy isolated via if the concern occurs in a dense local array.
For example, when a depression is seen after the final finish, preserve a cross-section and available earlier-stage evidence. This can help determine whether the feature existed after fill finishing or appeared during a later operation.
Release the final requirement separately
- Approve the intermediate surface criteria with fabrication.
- Check that subsequent metallization meets its requirements.
- Examine the finished land at the assembly interface.
- Record unresolved limitations before product disposition.
A smooth intermediate surface does not replace evaluation of the completed cap. Conversely, a satisfactory solder joint on one sample does not reveal the condition of unexamined filled holes elsewhere in the panel.
Keep preparation details with section images. Removing material to expose a feature can change its apparent relationship to the original surface, so the examiner should identify the section plane and any relevant artifact.
If the process is adjusted to remove a projection, review the adjacent copper as well as the filled region. Accepting only a reduced projection could overlook an unintended change to the surrounding layer that matters later in conductor formation.
The filled and capped land guide defines the finished feature, while section-location planning supports a deliberate inspection sample.
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