A coverlay opening can match its nominal outline while adhesive extends into the exposed land. Inspection should identify the remaining solderable area and the boundary that limits it. Measuring only the cut film opening can miss the feature that the assembly process actually encounters.
Distinguish the visible boundaries
Epec’s coverlay explanation notes that lamination can produce adhesive squeeze-out into openings. This supports treating the film edge and adhesive edge separately. It does not establish an acceptance allowance for a particular flex drawing.
Locate the copper land, coverlay film and any visible adhesive boundary using an agreed examination method. Record uncertainty if clear adhesive cannot be identified reliably under the available lighting.
Relate the measurement to the joint
| Feature | Question |
|---|---|
| Film opening | Is its location consistent with the released construction? |
| Adhesive extension | Where does the actual exposed land begin? |
| Terminal footprint | Which area is required for the intended connection? |
| Remaining web | Is the neighboring insulation geometry preserved? |
Evaluate individual sides of the opening where relevant. An overall width may conceal a local encroachment near the end of a solder land or around a hole.
Investigate registration and flow separately
Compare the opening position with the copper pattern, then evaluate the adhesive relative to the film edge. Retrieve the material construction and lamination history before choosing a correction. A shifted film and excessive local adhesive extension can coexist.
For example, enlarging an opening to recover one land may remove a narrow insulating web elsewhere. Review the entire affected pattern and the finished exposed area rather than approving a uniform expansion from one measurement.
Validate the agreed correction
- Confirm the required land exposure from the drawing and applicable specification.
- Define the material or process change.
- Inspect representative openings after complete lamination.
- Verify the relevant assembly result.
- Retain the accepted boundary definition for production inspection.
Do not adopt a numerical squeeze-out limit from a different product class or an outdated summary. The product’s actual requirement should control the disposition.
Keep original sample photographs before any proposed adhesive removal. Cleaning or scraping changes the condition under investigation and may affect both the land and nearby insulation.
When the coverlay material changes, recheck the exposed geometry even if its nominal film thickness remains the same. The coating transition guide addresses another protective boundary, while bond-interface review supports investigation of local adhesion concerns.
Record the material designation with both its film and adhesive construction. Two catalog variants can share a film thickness while providing different adhesive layers, so recording only the visible film dimension leaves the proposed substitution incompletely defined.
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