Conformal Coating Thickness Measurement: Wet, Dry & Optical Methods

How to verify coating thickness for reliability, compliance and process control

Accurate conformal coating thickness measurement underpins reliability, cost control, and compliance. This guide explains when to use wet film gauges, dry film gauges (after cure), and optical film thickness measurement for Parylene and ultra-thin coatingsβ€”plus setup, verification, and common pitfalls.

Conformal coating thickness measurement with a dry film gauge – SCH Services UK

Why Thickness Control Matters

  • Reliability: Meeting the specified micron window reduces early-life failures.
  • Compliance: Supports acceptance criteria aligned with IPC-A-610.
  • Cost: Prevents over-application (waste) and under-application (scrap/rework).
  • Process stability: Enables SPC monitoring and faster first-time yield.

Measurement Methods

Wet Film Measurement for Conformal Coating Processes

Use a wet film gauge at the point of application to set passes, speed, and viscosity so the final dry thickness lands on target consistently.

  • Immediate feedback during spray/dip setup
  • Best for liquids (acrylic, urethane, silicone, epoxy)
  • Pair with cure factors to estimate final dry film

View Wet Film Thickness Gauges β€Ί

Dry Film Gauges for Conformal Coating Thickness Control

After curing, use a dry film gauge (e.g., PosiTectorΒ 6000) on suitable substrates and coupon panels to verify coating windows for QA release.

  • Rapid QA checks and data logging for traceability
  • Use representative flat areas or dedicated coupons
  • Ideal for routine verification during inspection

See PosiTectorΒ 6000 Dry Film Gauges β€Ί

Optical Film Systems for Parylene & Ultra-Thin Coatings

For Parylene and very thin transparent films, use optical film thickness measurementβ€”a fast, non-destructive method suited to coupons or flat, representative areas.

  • Non-destructive; ideal for Parylene C/N and ultra-thin liquids
  • Supports process development and SPC
  • Best on smooth, flat surfaces or dedicated coupons

Explore Optical Thickness Measurement β€Ί

Wet film thickness gauge used during conformal coating application – SCH Services UK
Optical film thickness system for Parylene and ultra-thin coatings – SCH Services UK

Which Method Should I Use?

  • Setting up the process: Wet film gauge
  • Routine QA after cure (liquids): Dry film gauge
  • Parylene or ultra-thin films: Optical thickness

Many teams use a combination: wet film for setup, dry film for QA, and optical for thin films and Parylene.

Set-Up, Verification & SPC

  • Coupons: Use representative test panels for repeatable readings.
  • Sampling: Define sampling plan and measurement points in your work instruction.
  • Records: Log results for traceability and trend analysis (SPC).
  • Correlation: Calibrate wet-to-dry factors during process development for each coating/process.
Illustration of conformal coating thickness measurement methods showing wet film comb gauge, dry film probe, and optical laser measurement on a PCB

Common Pitfalls (and How to Avoid Them)

  • Measuring on rough/uneven areas: Prefer flat coupons or planar board areas.
  • Assuming wet = dry: Validate conversion factors for each coating and process window.
  • Ignoring cure effects: Under/over-cure can change thickness readings and performance.
  • Parylene with contact gauges: Use optical methods; contact methods are generally unsuitable.

Download the Technical Bulletin

Prefer the PDF version of this article? Download it here:

πŸ“„ Conformal Coating Thickness Measurement – Technical Bulletin 2025

Request a Quote

Whether you need thickness measurement equipment, operator training, or outsourced inspection services, SCH can help. We supply wet film gauges, PosiTector dry film gauges, and optical systems alongside our coating services.

Contact SCH to discuss thickness control β€Ί

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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 by aerospace, medical, defence, automotive, and electronics industries worldwide.
  • πŸ› οΈ End-to-End Support – Guidance on coating selection, Parylene grades, masking strategies, application methods, inspection, and ProShieldESD integration.
  • πŸ“ˆ 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.
  • βœ… 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.