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

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 spec and environment.
  • Dip tank with lift/withdrawal control – steady speed and dwell timing.
  • Viscosity & temperature control – Zahn cup (or equivalent), thermometer.
  • Filtration & covers – reduce contaminants and solvent loss.
  • Masking materials – tapes/dots, liquid mask, reusable boots/shields.
  • PPE & safety – gloves, goggles, extraction/booth.
  • Inspection & QC – white/UV light, wet film gauge, dry thickness gauge (e.g., Positector):
    See thickness measurement tools.

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.

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 – fast to apply; seal edges thoroughly.
  • Shield masking: Reusable boots/caps – ideal for repeat work; consistent and quick.
  • Design consideration: Vent masking to prevent capillary draw into housings/headers.

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

4) Step 3 – Set Viscosity & Tank Conditions

  • Viscosity: Measure with a Zahn (or equivalent) and adjust per datasheet/validated spec.
  • Temperature: Keep coating within the recommended range for consistent film build.
  • Agitation: Gentle only – 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 control plan.

Related reading: Viscosity in Process Control.

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 onto the floor.

Tips:

  • Slower, consistent withdrawal generally builds thinner films; validate your rate vs target thickness.
  • Use multiple thin dips rather than one heavy dip to increase thickness, reduce runs and edge pooling.
  • Orient the board to minimise capillary wicking into connectors and cavities.

See also: Application Processes Overview.

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 spec thickness.
  • Cure: Air dry or force-cure at the recommended temperature/time.

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 with wet film gauge or dry gauge (e.g., PosiTector). Typical dry film 25–75 µm (per spec).
  • Standards: Verify to IPC-A-610 and IPC-CC-830 acceptance criteria.

Tools: thickness measurement.

8) Common Defects and How to Prevent Them

Defect Cause Prevention
Capillary / Wicking Around Components Capillary draw into gaps, vents or connectors during dip Improve masking/vent sealing; adjust orientation and withdrawal rate; reduce dwell
Runs / Sags Excess film build; too slow withdrawal; insufficient flash-off Use thinner dips; optimise withdrawal; extend drain/flash-off
Edge Pooling / Bridging Surface tension accumulates coating at edges and sharp features Round edges where possible; reduce viscosity/film; split into multiple coats
Dewetting / Fish Eyes Surface contamination (oil/flux/silicone); poor surface energy Thorough cleaning; adhesion promoter where appropriate
Cracking Excess thickness; rapid solvent loss; thermal mismatch Apply thinner films; control cure; meet thickness spec

9) Training & Industry Standards

If you need repeatable, audit-ready dip processes, and want to learn how to dip coat a pcb, then 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.

10) Useful Links & Next Steps

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 worldwide.
  • 🛠️ End-to-End Support – Coating selection, masking, inspection and process validation.
  • 📈 Scalable Solutions – From prototypes to high-volume production.
  • 🌍 Global Reach – Responsive support across Europe, North America and Asia.
  • ✅ Proven Reliability – Built on quality, consistency and customer satisfaction.

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