Printed carbon contacts need a controlled relationship to the underlying copper and surrounding insulation. A dark printed shape can look complete while being shifted from its intended location. Define which boundaries matter to electrical connection and separation before deciding whether registration is acceptable.
Show the complete contact construction
Release separate, aligned data for copper, soldermask and carbon as applicable. Identify the intended copper overlap and the region that must remain isolated. Do not ask a supplier to reconstruct the functional geometry from a single combined screenshot.
Eurocircuits’ carbon-contact explanation describes conductive carbon printing and registration measurement against a reference in the copper pattern. Its published manufacturing limits belong to its service; agree on the actual supplier’s supported geometry for the design being ordered.
Choose an inspection reference that survives production
Use identifiable copper features or agreed registration targets. Explain the relationship between the production target and the functional contact. A target outside the delivered board may support process control, but the final board still needs an appropriate acceptance method.
| Boundary | Question |
|---|---|
| Carbon over copper | Is the required conductive connection retained? |
| Carbon between contacts | Does the required separation remain? |
| Carbon near soldermask | Does the released overlap arrangement remain valid? |
| Contact opening | Is the intended working surface accessible? |
Inspect the edges that control function
A single center-position measurement may miss a distorted or locally incomplete print. Review representative contact edges and any narrow spaces defined by the design. Retain images with the correct layer references when investigating a shifted print.
For example, carbon may still cover the center of a copper land after a lateral shift while reducing separation to the next contact. The overlap check and the isolation check therefore answer different questions.
Identify whether the approved inspection occurs before or after later soldering and cleaning. A board inspected only immediately after printing has not yet demonstrated the condition of the delivered contact surface.
Connect geometry to electrical evidence
Use the product’s specified electrical test for contact resistance, continuity and isolation as applicable. Passing one of these tests does not eliminate the need to meet the released geometry; conversely, correct alignment does not establish every electrical property of the printed material.
Keep the ink identity, artwork revision and cure route traceable when a print change is evaluated. A registration correction should not conceal an unrelated change in the contact material.
The carbon-contact measurement guide addresses test geometry, while peelable-mask removal review covers temporary protection that may be used later.
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