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.

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 tendency of the coating to refuse uniform wetting of the surface, producing holes, craters, or “islands.”
  • Impact: Non-coverage creates routes for moisture/contaminants and undermines insulation resistance and protection.

Causes of De-wetting in Conformal Coating

  • Non-ionic contamination lowering surface energy (common root cause).
  • Board manufacture residues such as silicone surfactants from solder resist and HASL rinse contamination.
  • Component residues including mould-release agents.
  • Silicone oils from adhesives used in production.
  • Soldering processes introducing residues.
  • Contaminated cleaning baths / poor rinsing.
  • Operator handling adding contaminants.

How to Prevent Conformal Coating De-wetting

  • Control incoming cleanliness – select low-residue materials and manage laminate/component cleanliness pre-assembly.
  • Clean before coating – validated cleaning and rinsing to ensure a high-energy surface.
  • Rework locally if needed – strip the de-wetted area and re-apply coating to specification.

Conformal Coating Defects and Their Importance

Conformal coating protects printed circuit boards (PCBs) against moisture, dust, corrosion and electrical leakage.
However, defects such as de-wetting, orange peel, pinholes, bubbles, foam, delamination, and cracking
can compromise that protection. Even small imperfections provide pathways for contaminants, lower insulation resistance, and increase the risk of premature failure.

These coating defects arise from issues such as incorrect viscosity or film thickness, trapped air or solvent,
poor surface preparation, unsuitable spray settings, or stress during cure. Understanding these failure mechanisms is essential for process control, quality assurance, and long-term reliability. By recognising how and why these defects form, manufacturers can optimise application methods, materials, and operator technique to eliminate rework, improve yield, and ensure consistent performance.

Training on Conformal Coating Defects & More

SCH offers conformal coating training that goes beyond theory. Our courses teach you how to recognise and prevent defects such as de-wetting, orange peel, pinholes, bubbles, foam, delamination, and cracking. We also cover process analysis, troubleshooting, materials, and application methods.

Explore Conformal Coating Training →

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.

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