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.

Related process control article: Dip coating reliability depends not only on the coating itself, but on preparation, contamination control, drying discipline and process stability. For the wider causes of repeat failures in coating operations, see Why Conformal Coating Processes Fail.
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.