De-wetting in Conformal Coating

De-wetting in conformal coating occurs when the wet film refuses to wet the surface evenly, leaving bare patches or “islands.” Preventing de-wetting is critical to maintain uniform protection and PCB reliability.

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Collage showing de-wetting defects in conformal coating on PCB surfaces under UV and visible light inspection

What is De-wetting in Conformal Coating?

  • Definition: The coating refuses to wet the surface uniformly, producing holes, craters, or “islands.”
  • Main issue: Bare areas provide pathways for moisture/contaminants, undermining insulation resistance and long-term protection.

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Causes of De-wetting in Conformal Coating

  • Low surface energy / contamination (most common).
  • Board manufacture residues — silicone surfactants from solder mask, HASL rinse contamination.
  • Component residues — mould-release agents and process oils.
  • Silicone oils/adhesives transferred during handling and masking.
  • Soldering residues and flux activators (even “no-clean” can interfere).
  • Contaminated cleaning baths or poor rinsing leaving films that repel coating.
  • Operator handling — fingerprints, hand creams, FOD.

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How to Prevent Conformal Coating De-wetting

  • Control incoming cleanliness — specify low-residue laminates, masks, and components.
  • Validated cleaning — qualified solvent/aqueous cycles with proper rinsing and dry-out.
  • Surface energy checks — routine dyne pens/contact angle; set accept/reject criteria.
  • Housekeeping — segregate silicones, use clean gloves, manage FOD and handling.
  • Local rework — strip affected area, re-clean, and re-apply to spec.

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Troubleshooting & Diagnosis

  • Surface energy testing — dyne level / contact angle before coating.
  • Residue analysis — ionic contamination tests and spot solvent swabs for non-ionic films.
  • Bath audits — verify cleaner concentration, rinse quality, and bath life.
  • Material segregation — check for silicone sources (sealants, sprays, tape adhesives).
  • Witness coupons — run coated coupons alongside builds to isolate line issues.

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Where De-wetting Sits Among Other Defects

De-wetting is primarily a surface energy/contamination problem. By contrast, orange peel is a flow/level issue (viscosity/film build), pinholes/bubbles/foam come from entrapped air or skinning, and delamination points to adhesion/cure issues. Fixing the correct mechanism prevents rework and protects reliability.

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Training on Conformal Coating Defects & More

SCH offers conformal coating training that goes beyond theory—recognising and preventing de-wetting, orange peel, pinholes, bubbles, foam, delamination, and cracking. 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 ↗

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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 – Guidance on coating selection, masking, inspection, and ProShieldESD integration.
  • 📈 Scalable Solutions – From prototype to high-volume production.
  • 🌍 Global Reach – Support across Europe, North America, and Asia.
  • ✅ Proven Reliability – Built on quality, consistency, and customer satisfaction.

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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.