Capillary (Wicking) Around Components in Conformal Coating

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Capillary flow (wicking) occurs when conformal coating is drawn away from target areas and pulled into gaps, underneath components or leads, or into interfaces. The result is a patchy, uneven finish with thin or bare regions that can compromise protection and reliability.

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Article Quicklinks

Topic	More
Definitions: what capillary wicking is and why it matters	🔗
Root Causes of capillary/wicking	🔗
Prevention: viscosity, film build, setup	🔗
Troubleshooting & Diagnosis	🔗
Related Defects	🔗

What is Capillary Flow (Wicking) in Conformal Coating?

• Definition: Coating is drawn into gaps/interfaces (e.g., under component bodies) and away from open surfaces, leaving patchy coverage.
• Main issue: Bare/thin regions reduce insulation resistance and increase moisture ingress risk, especially around fine-pitch and underfills.

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Causes of Capillary / Wicking in Conformal Coating

• Low viscosity / high wetting drive — coating readily flows into micro-gaps and interfaces.
• Over-wet films — excessive deposit re-distributes before solvent flash-off.
• Low surface energy or contamination — preferential wetting around components rather than across laminate.
• High coating surface tension relative to substrate finish and geometry.
• Geometry & orientation — narrow gaps, capillary channels, and vertical features pulling film.

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How to Prevent Capillary Effects

• Increase effective viscosity — higher-viscosity mix or staged passes with flash-off.
• Reduce film build — lighter coats; avoid pooling around component bodies and leads.
• Improve cleanliness — raise surface energy via validated clean/rinse/dry cycles.
• Match chemistry — select coatings with suitable flow/level properties for geometry (solvent-based often easier to tune).
• Board orientation & fixturing — tilt to discourage draw into gaps; add edge dams/masking where practical.
• Thermal conditioning — controlled pre-warm and flash to shorten capillary dwell time before cure.
• Selective application tweaks — reduce flow rate and pass overlap near capillary-prone features.

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Troubleshooting & Diagnosis

• UV/white-light inspection — map thin/bare zones around components and along gap lines.
• Thickness checks — coupons and on-board features to confirm under-build around edges/leads.
• Viscosity/solids monitoring — restore target windows; check for solvent loss.
• Application recipe review — head type, distance, pressure/flow, overlap strategy.
• Orientation trials — A/B test tilt/fixture changes and flash intervals to suppress wicking.
• Masking aids — temporary dams/latex seals near problematic gaps.

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Where Capillary Wicking Sits Among Other Defects

Wicking is a flow/geometry issue driven by viscosity, surface energy, and orientation. Orange peel is flow/level; de-wetting is surface energy/contamination; pinholes/bubbles/foam are entrapped air/skinning; cracking/delamination are stress/adhesion. Correct diagnosis avoids rework and field returns.

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Related Defects

• Pinholes, Bubbles & Foam
• Orange Peel
• De-wetting
• Delamination
• Cracking
• Corrosion & Ionic Contamination

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Training on Conformal Coating Defects & More

SCH offers conformal coating training that goes beyond theory—recognising and preventing wicking, de-wetting, orange peel, pinholes, bubbles, foam, cracking, delamination, and corrosion. We cover process analysis, troubleshooting, materials, and application methods.

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Industry Standards We Work To

SCH Services follows international standards across all our coating services, training, equipment supply and materials. Our processes are aligned to the relevant IPC standards, including:

• IPC-A-610 – Acceptability of Electronic Assemblies
• IPC-CC-830 – Qualification & Performance of Conformal Coatings
• IPC-HDBK-830 – Conformal Coating Handbook (guidance and best practice)

For further details on IPC standards, visit:
electronics.org/ipc-standards ↗

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 by aerospace, medical, defence, automotive, and electronics industries worldwide.
• 🛠️ End-to-End Support – Guidance on coating selection, Parylene grades, masking strategies, application methods, inspection, and ProShieldESD integration.
• 📈 Scalable Solutions – From small prototype batches to full-scale, high-volume production, SCH delivers flexible capacity that grows with your needs.
• 🌍 Global Reach – Responsive technical support and supply coverage across Europe, North America, and Asia.
• ✅ Proven Reliability – A strong reputation built on quality, consistency, and customer satisfaction across services, equipment, and materials.

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✉ Email: sales@schservices.com
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Note: This article provides general technical guidance only. Final design, safety, and compliance decisions must be verified by the product manufacturer and validated against the applicable standards.