How to Dip Coat a PCB | Conformal Coating Step-by-Step Guide

Dip tank setup, viscosity control, withdrawal rate, curing and inspection

Dip coating delivers uniform, wrap-around coverage for complex assemblies when viscosity and withdrawal rate are controlled.

This guide shows you how to prepare, mask, set tank variables, dip and cure a PCB with conformal coating while avoiding common pitfalls such as capillary wicking, runs/sags and edge pooling.

PCB being dip coated in conformal coating bath showing controlled withdrawal and drainage

1) Tools & Materials You’ll Need

  • Conformal coating (dip grade): per your specification and environment.
  • Dip tank + lift/withdrawal control: consistent speed and repeatable dwell timing.
  • Viscosity & temperature control: Zahn cup (or equivalent) and thermometer (record every check).
  • Filtration & tank covers: reduce contamination and solvent loss.
  • Masking materials: tapes/dots, liquid mask, reusable boots/shields.
  • PPE & safety: gloves, goggles and appropriate extraction/booth.
  • Inspection & QC: white/UV light, wet film gauge, dry thickness gauge (e.g., PosiTector) β€” see thickness measurement tools.

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2) Step 1 – Clean & Prepare the PCB

Coating only adheres to clean, dry surfaces. Remove flux residues, dust, oils and ionic contamination (IPA wipe, DI wash + bake, ultrasonic, or engineered cleaners). Ensure moisture is fully removed from connectors and under components. Avoid handling cleaned areas with bare hands.

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3) Step 2 – Mask Keep-Out Areas

Mask all features that must not be coated: connectors, sockets, switches, test points, gold fingers and keep-outs.

  • Barrier masking: tapes/dots or liquid mask β€” fast to apply; seal edges thoroughly.
  • Shield masking: reusable boots/caps β€” ideal for repeat work; consistent and quick.
  • Design consideration: vent and seal masking to reduce capillary draw into housings/headers.

Learn about masking strategies and how to mask for barrier protection in the Masking Hub.

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4) Step 3 – Set Viscosity & Tank Conditions

  • Viscosity: measure with a Zahn (or equivalent) and adjust per datasheet/validated process window.
  • Temperature: hold the coating within the recommended range for consistent film build.
  • Agitation: gentle only β€” avoid foam; allow entrained bubbles to dissipate before dipping.
  • Filtration/cleanliness: use filters and covered tanks; strain coating when needed.
  • Pot life/contamination: track usage; replace or top-up per your control plan.

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5) Step 4 – Dip & Withdraw

Technique: Immerse the PCB steadily to the required depth. Dwell briefly for full wetting beneath components, then withdraw at a constant rate to achieve target wet film. Hold above the tank for drain/flash-off and to avoid drips.

  • Validate your withdrawal speed against the required thickness (coupon/witness-board verification).
  • Use multiple thin dips rather than one heavy dip to reduce runs, edge pooling and solvent entrapment.
  • Orient the board to minimise capillary wicking into connectors and cavities.

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6) Step 5 – Flash-Off & Cure

  • Drain/flash-off: allow solvent to drain and flash between dips (per datasheet).
  • Multiple coats: build up in thin layers to the specified thickness.
  • Cure: air dry or force-cure at the recommended temperature/time.

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7) Inspection & Quality Control

  • Visual: confirm wrap-around coverage without voids under components.
  • Edges & features: check for edge pooling, bridges and coating drawn into connectors.
  • Thickness: measure using wet film gauge or dry gauge (e.g., PosiTector) per your plan.
  • Standards: verify to IPC-A-610 and IPC-CC-830 acceptance criteria.

Tools: thickness measurement.

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8) Common Defects and How to Prevent Them

Defect: Capillary / Wicking

Typical cause: capillary draw into gaps/vents/connectors during immersion and drain.

Prevention: improve masking/vent sealing; adjust orientation and withdrawal rate; validate dwell; avoid over-wet conditions.

Defect: Runs / Sags

Typical cause: excessive film build, too slow withdrawal, insufficient flash-off/drain.

Prevention: use thinner dips; optimise withdrawal; extend controlled drain/flash-off.

Defect: Edge pooling / Bridging

Typical cause: high wet film and drainage behaviour concentrating at edges/features.

Prevention: reduce film build (multiple coats); optimise viscosity; check orientation and drain time.

Defect: Dewetting / Fish Eyes

Typical cause: surface contamination (oil/flux/silicone) and poor surface energy control.

Prevention: improve cleaning/handling; verify cleanliness; consider adhesion promoter where appropriate.

Defect: Cracking

Typical cause: excess thickness, rapid solvent loss, cure mismatch and stress.

Prevention: apply thinner films; control flash-off/cure; meet thickness spec (validate by measurement).

Explore more in the Defects Hub.

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9) Training & Industry Standards

If you need repeatable, audit-ready dip processes, formal training helps operators control viscosity, withdrawal rate and masking for complex builds. SCH delivers hands-on training in dip coating, masking, inspection and IPC-A-610 / IPC-CC-830 acceptability.

For official acceptance criteria and guidance, refer to the IPC standards:

To discuss training or a validation plan for your team, contact us here.

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Why Choose SCH Services?

Partnering with SCH Services means more than just outsourcing β€” 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.
  • πŸ› οΈ End-to-End Support – Coating selection, masking, inspection and process validation.
  • πŸ“ˆ Scalable Solutions – From prototypes to high-volume production.
  • 🌍 Global Reach – Responsive support across Europe, North America and Asia.
  • βœ… Proven Reliability – Built on quality, consistency and customer satisfaction.

πŸ“ž Call: +44 (0)1226 249019
βœ‰ Email: sales@schservices.com
πŸ’¬ Contact Us β€Ί

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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.