Conformal Coating Design Hub
Design Guidelines Index
| Design Topic | More | Article |
|---|---|---|
| Keep-Outs & Masking-Friendly Layout β coating-free zones and mask access | π | β |
| Clearance & Creepage β coating influence on electrical spacing (IEC/IPC) | π | β |
| Component Selection & Orientation β shadowing, venting, standoffs | π | β |
| Edge Coverage & Drain Paths β meniscus control and pooling avoidance | π | β |
| Coating Thickness Targets β defining ranges by chemistry and function | π | β |
| Material Compatibility β silicones, labels, adhesives, flux residues | π | β |
| Test Coupons & Witness Boards β coverage & thickness validation tools | π | β |
| Inspection Aids & Labelling β making conformal coating easy to verify | π | β |
| Design Checklist (DfM/DfCC) β pre-release conformity review | π | β |
Keep-Outs & Masking-Friendly Layout
Define coating-free zones early to minimise masking time and prevent leakage.
- Mark keep-outs for connectors, test points, switch shafts, heat sinks and gold fingers in CAD and drawings.
- Allow enough space between coated and uncoated areas for tape or boots.
- Add cover pads or maskable flats if components sit too close to no-coat zones.
- Ensure physical access for masking and selective coating valves.
Clearance & Creepage
Coating can improve surface insulation, but electrical safety distances must still be designed correctly.
- Use IEC 60664 and IPC-2221 for baseline creepage/clearance rules.
- Only apply βcoating creditβ if thickness, uniformity and chemistry are validated.
- Document assumptions in design files and drawings, including pollution degree and material group.
- Avoid dust traps and sharp edges that reduce creepage after coating.
Component Selection & Orientation
Avoid shadowing, trapped coating and blocked drainage by selecting and orienting components wisely.
- Rotate tall components to avoid blocking spray paths.
- Use components with standoffs or reliefs to allow drainage and air escape.
- Vent covers, relays or shields to prevent solvent retention.
- Check selective coating valve reach and clearance during PCB layout.
Edge Coverage, Meniscus & Drain Paths
Manage coating behaviour around edges to prevent thinning, cracking or pooling.
- Break sharp PCB edges; coating pulls away from 90Β° corners.
- Design drain points so excess coating flows away from critical circuitry.
- Use solder dams or barriers to prevent wicking under components.
- Consider gravity flow direction when positioning boards for spray or dip coating.
Coating Thickness Targets & Tolerances
Define coating thickness during designβnot after manufacturing.
- Acrylic: 25β75 ΞΌm | Polyurethane: 50β150 ΞΌm | Silicone: 50β200 ΞΌm | Parylene: 5β20 ΞΌm.
- State nominal, minimum and maximum thickness ranges on drawings.
- Specify measurement method (coupon, gauge, optical reflectometer, etc.).
- Indicate where critical thickness must be maintained (edges, underside, leads).
Material Compatibility & Adhesion
Certain materials interfere with adhesion and must be designed out or treated.
- Avoid silicones, oils, mould-release agents and plasticisers near coating areas.
- Specify approved label types that resist solvents and UV inspection.
- Add notes for surface preparation (plasma, corona, primers) where needed.
- Ensure flux residues and ionics are controlled before coating.
Test Coupons & Witness Boards
Use conformal coating test coupons and witness boards to validate coverage, edge definition and thickness before risking production hardware. They replicate real PCB challenges and provide a consistent way to check process stability.
- Include representative features such as vias, fine-pitch pads, vertical edges, gaps and connector-style geometries.
- Use UV inspection to verify uniform coverage and meniscus behaviour.
- Measure coating thickness on dedicated pads, steps or fins.
- Align coupon pass/fail criteria with your production acceptance standards for full traceability.
Inspection Aids & Labelling
Designing with inspection in mind ensures coating can be verified quickly and consistently.
- Keep reference designators and polarity markings visible after coating.
- Add fiducials and orientation marks to aid manual and automated inspection.
- Include UV tracer requirements in notes if coating chemistry supports it.
Design for Coating Checklist
Use this checklist before PCB release for manufacture:
- β Keep-outs defined and labelled on drawings/Gerbers.
- β Masking feasibility (tape/boots/selective path) confirmed.
- β Creepage & clearance documented (with/without coating credit).
- β Edge breaks or drains included to avoid meniscus thinning and pooling.
- β Coating thickness targets and measurement method specified.
- β No silicone, release agents or incompatible materials in BOM.
- β Coupons/inspection legends used if required.
- β Notes added to fabrication drawing for coating/masking requirements.
Need Help with Coating Design or DFx Reviews?
Prevent coating failures before production. SCH can review your PCB layout, create mask strategies and ensure IPC/IEC/UL compliance.
π Consultancy & Design Support
- Design-for-Coating (DFM/DFX) review of schematics and layouts.
- Masking strategy and selective-coating path validation.
- Standards alignment (IPC-A-610, IPC-CC-830, IEC 60664, UL).
π Team Training
- Design for Coating workshops for PCB and hardware teams.
- Inspection and coating acceptance to IPC standards.
- Thickness, cleanliness and adhesion control training.
β Talk to our Consulting Team |
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Need Process Support?
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- Training & Consultancy on coating processes
- Support Equipment including inspection booths, thickness measurement systems, and curing solutions
- Direct technical support from our global team
Why Choose SCH Services?
Partnering with SCH Services means more than just outsourcing β you gain a complete, integrated platform for
Conformal Coating, Parylene & ProShieldESD Solutions, alongside equipment, materials, and training, all backed by decades of hands-on expertise.
- βοΈ 25+ Years of Expertise β Specialists in coating technologies trusted worldwide.
- π οΈ End-to-End Support β Selection of chemistry/process, masking strategies, inspection, and ProShieldESD integration.
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