Cracking in Conformal Coating

Cracking in conformal coating occurs when the cured film fractures, creating fissures that expose the PCB surface. These cracks undermine protection, allowing moisture and contaminants to penetrate and reducing electrical insulation performance.

Collage of conformal coating cracking defects on PCB surfaces under UV and visible light inspection

What is Cracking in Conformal Coating?

Definition: Cracking is the formation of surface fractures and fissures in the cured coating that can expose the underlying board.
Impact: These cracks create leakage pathways, compromise moisture resistance, and may lead to premature PCB failure under thermal or mechanical stress.

Causes of Cracking in Conformal Coating

  • Excessive cure temperature or overly fast thermal ramping.
  • Insufficient room-temperature drying before oven cure, trapping solvents.
  • Excessive coating thickness creating internal stress and CTE mismatch.
  • Incompatible coating chemistry with poor flexibility for service conditions.
  • Thermal cycling and harsh operating environments causing mechanical fatigue.

How to Prevent Conformal Coating Cracking

  • Reduce cure stress: Use lower initial oven setpoints and controlled thermal ramps.
  • Allow RT drying: Ensure adequate solvent evaporation before heat cure.
  • Optimise thickness: Keep film build within supplier recommendations.
  • Select flexible materials: Choose chemistries with wider temperature tolerance and elongation before break.
  • Process validation: Test coating and cure profiles under thermal shock and cycling conditions.

Conformal Coating Defects and Their Importance

Conformal coating is designed to protect printed circuit boards (PCBs) from moisture, corrosion, and electrical leakage. However, defects such as cracking, delamination, de-wetting, orange peel, pinholes, bubbles, foam, and capillary wicking can compromise that protection.

Even small imperfections create pathways for contaminants, lower insulation resistance, and increase the risk of premature failure. These defects may result from incorrect viscosity, poor surface preparation, unsuitable spray settings, or stress during curing.

Understanding and preventing these issues is essential for process control, quality assurance, and long-term reliability.

Training on Conformal Coating Defects & More

SCH provides conformal coating training that goes beyond theory. Our courses teach engineers and operators how to recognise, prevent, and repair defects such as cracking, delamination, de-wetting, and orange peel. We cover:

  • Failure mechanism recognition.
  • Root cause analysis & troubleshooting.
  • Materials, masking, and application techniques.
  • Process optimisation and inspection methods.

Explore Conformal Coating Training →

Why Choose SCH Services?

Partnering with SCH Services gives you a complete platform for conformal coating, Parylene, and ProShieldESD solutions:

✈️ 25+ Years of Expertise – Trusted by aerospace, medical, defence, automotive, and electronics industries worldwide.

🛠️ End-to-End Support – Guidance on materials, masking, application, inspection, and troubleshooting.

📈 Scalable Solutions – From prototype batches to full-scale production.

🌍 Global Reach – Technical support and supply coverage across Europe, North America, and Asia.

✅ Proven Reliability – Reputation built on quality, consistency, and customer satisfaction.

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