Corrosion & Ionic Contamination in Conformal Coating

Corrosion and ionic contamination are serious failure mechanisms in conformal coating. Contaminants left on PCB surfaces can react with moisture and bias, leading to electrochemical migration, dendrite growth, and metal degradation. Preventing corrosion is critical to ensure long-term circuit reliability.

Conformal coating corrosion and ionic contamination defects on PCB under inspection

What is Corrosion in Conformal Coating?

Definition: Corrosion is the chemical or electrochemical reaction between a material, usually a metal, and its environment that deteriorates the material and its properties.
Impact: Ionic residues and moisture under the coating create leakage paths, dendrites, and metallic degradation, compromising insulation resistance and PCB performance.

Causes of Corrosion & Ionic Contamination

Factors that influence corrosion and electrochemical migration usually revolve around the cleanliness of a PCB. Contaminants may arise from:

  • Board fabrication residues.
  • Contaminated or unclean components.
  • Residues from assembly equipment.
  • Soldering flux and paste residues.
  • Operator handling introducing oils or salts.
  • Incorrect or incomplete cleaning processes.

How to Prevent Conformal Coating Corrosion

  • Effective cleaning: Implement validated cleaning and rinsing to remove ionic residues before coating.
  • Incoming inspection: Check boards and components for solderability and cleanliness.
  • Operator discipline: Ensure gloves and ESD-safe handling at all times.
  • Low-residue processes: Use “low residue” no-clean fluxes, pastes, and wires for rework.
  • Process control: Fine-tune soldering windows, control reflow systems, and validate processes.
  • Material compatibility: Ensure fluxes, cleaning chemistries, and coatings are compatible.

Ultimately, corrosion can be controlled with good process design and rigorous quality control.

Conformal Coating Defects and Their Importance

Conformal coating protects printed circuit boards (PCBs) from moisture, corrosion, and electrical leakage. However, defects such as corrosion, ionic contamination, 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 corrosion, cracking, delamination, and ionic contamination. 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 ›