Surface Preparation & Cleanliness for Reliable Coating

How to prevent adhesion failures, corrosion and electrical leakage before coating

Effective surface preparation and cleanliness are critical for conformal coating reliability. Contaminants such as flux residues, oils, and ionic salts can cause adhesion loss, corrosion, or electrical leakage. This guide covers cleaning methods, cleanliness testing, adhesion promoters, and industry standards.

Illustration of PCB surface preparation showing cleaning spray, plasma treatment glow, and adhesion promoter bottle for reliable conformal coating

Why Surface Preparation Matters

  • Adhesion: A clean, dry surface ensures coating bonds strongly to substrates.
  • Electrical reliability: Ionic contamination can lead to dendritic growth, leakage currents, or corrosion.
  • Consistency: Proper preparation reduces defects like dewetting, bubbles, and delamination.

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Surface Preparation Methods

  • Cleaning: Aqueous, semi-aqueous, and solvent systems remove flux and oils.
  • Plasma treatment: Improves surface energy, ideal for Parylene adhesion and difficult plastics.
  • Micro-abrasion: Removes oxides, residues, or old coatings in rework (use with containment and process control).
  • Adhesion promoters: Silanes such as A-174 or chemistry-specific primers can increase bonding and reduce edge-lift risk.

Rule of thumb

  • Liquid coatings: cleanliness + dryness + handling discipline usually dominate outcomes.
  • Parylene: surface energy control (often plasma) + correct adhesion promoter selection are frequently critical.
  • Rework parts: remove residues and any weak/aged coating edges before you “repair over” them.

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Cleanliness Testing

  • ROSE / Ionic contamination test: Measures total ionic residues (often reported as µg NaCl/cm²).
  • Ion chromatography: Identifies specific contaminants (chlorides, sulfates, weak organic acids) and is better for root-cause.
  • Dyne pen / contact angle: Evaluates surface energy and wetting risk (useful for dewetting diagnosis and plastics).

Important

  • Pick test methods that match the failure mode: ROSE for overall control, IC for diagnosis, dyne/contact angle for wetting issues.
  • Define the sampling plan in your control plan (where on the board/coupon, how often, pass/fail rules).

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Standards & Guidance

  • IPC-5704 – Cleanliness requirements for printed boards
  • IPC-A-610 – Acceptability of electronic assemblies (cleanliness & coating coverage)
  • IEC 60664 – Insulation coordination & pollution degree context
  • Customer specifications may define tighter ionic, surface energy, or adhesion requirements

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SCH Surface Preparation Solutions

We provide surface preparation tools, training, and consultancy:

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Need support with conformal coating surface preparation?
SCH provides cleaning systems, adhesion promoters, and training for reliable coating performance.

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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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.