Conformal Coating Design Hub

Designing a PCB correctly for conformal coating reduces masking time, prevents defects and eliminates rework. This hub explains how to design boards that are easy to mask, easy to coat, and compliant with IPC/IEC/UL requirements. Whether using manual spray, selective coating or Parylene, applying these rules during design saves cost and improves reliability.

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.

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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 “coating credit” 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.

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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.

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Edge Coverage, Meniscus & Drain Paths

Manage coating behaviour around edges to prevent thinning, cracking or pooling.

  • Break sharp PCB edges; coating pulls away from 90° 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.

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Coating Thickness Targets & Tolerances

Define coating thickness during design—not after manufacturing.

  • Acrylic: 25–75 μm | Polyurethane: 50–150 μm | Silicone: 50–200 μm | Parylene: 5–20 μm.
  • 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).

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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.

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Test Coupons & Witness Boards

Use representative coupons to verify coverage, thickness and adhesion before full production.

  • Include sample vias, gull-wing leads, fine gaps or PCB materials on coupons.
  • Use UV-trace coating to visibly confirm coverage on test boards.
  • Align coupon pass/fail criteria with production acceptance standards.

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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.

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Design for Coating Checklist

Use this checklist before PCB release for manufacture:

  • ✔ Keep-outs defined and labelled on drawings/Gerbers.
  • ✔ Masking feasibility (tape/boots/selective path) confirmed.
  • ✔ Creepage & clearance documented (with/without coating credit).
  • ✔ Edge breaks or drains included to avoid meniscus thinning and pooling.
  • ✔ Coating thickness targets and measurement method specified.
  • ✔ No silicone, release agents or incompatible materials in BOM.
  • ✔ Coupons/inspection legends used if required.
  • ✔ Notes added to fabrication drawing for coating/masking requirements.

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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.

🛠 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).

🎓 Team Training

  • Design for Coating workshops for PCB and hardware teams.
  • Inspection and coating acceptance to IPC standards.
  • Thickness, cleanliness and adhesion control training.

→ Talk to our Consulting Team |
→ Explore Training Options

Explore Topic Hubs

Conformal Coating Processes Hub
Explore core conformal coating processes—spray, dip, selective robotic, and Parylene. Compare strengths, limits, and selection tips to match volume, cost, and reliability.

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Equipment & Application Methods Hub
Configure application equipment—spray guns & booths, dip systems, and selective valves/robots. Standardise recipes and fixtures to stabilise throughput and yield.

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Masking Hub
Master masking strategies for keep-outs: dots & tapes, reusable boots, custom shapes, and latex sealing. Apply barrier vs shielding correctly for spray, dip, and Parylene.

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Conformal Coating Design Hub
Learn design-for-coating (DfCC / DFM) principles—keep-out zones, component layout, creepage & clearance, masking access, drainage control, and coating thickness planning to eliminate rework and defects before manufacture.

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Inspection & Quality Hub
Build a robust inspection & quality plan: UV coverage checks, thickness verification (AQL, coupons, SPC), adhesion tests, and documentation aligned to IPC/UL.

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Removal & Rework Hub
Choose the right removal & rework method: wet stripping for liquid coatings, precision micro-abrasion for Parylene, and controlled repair workflows that protect pads & leads.

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Parylene Coating Hub
Dive into Parylene coating: dimer grades, deposition parameters, vapour-phase masking, and optical thickness control. See when Parylene outperforms liquid coatings.

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Defects & Failure Mechanisms Hub
Prevent common coating defects—pinholes, dewetting, orange peel, cracking, delamination, corrosion/ionic contamination, and wicking—with root-cause fixes.

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Need Process Support?

Optimising electronics coating methods requires the right combination of materials, equipment, and operator training. Partner with SCH Services for:

Why Choose SCH Services?

Partnering with SCH Services means more than just outsourcing — 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.

  • ✈️ 25+ Years of Expertise – Specialists in coating technologies trusted worldwide.
  • 🛠️ End-to-End Support – Selection of chemistry/process, masking strategies, inspection, and ProShieldESD integration.
  • 📈 Scalable Solutions – From prototypes to high-volume production.
  • 🌍 Global Reach – Responsive support across Europe, North America, and Asia.
  • ✅ Proven Reliability – Consistent results across services, equipment, and materials.

📞 Call: +44 (0)1226 249019
✉ Email: sales@schservices.com
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