Conformal coatings are used in a variety of industries to protect electronic circuit boards and components from harsh environmental factors. However, there are times when the protective coating needs to be removed, such as during repairs or rework.

What is a Conformal Coating Stripper?

A conformal coating stripper is a chemical solution specially formulated to safely remove cured conformal coatings from printed circuit boards and other electronic assemblies. Different strippers work best for different types of conformal coatings, such as acrylics, silicones, or urethanes.

Strippers dissolve the protective coating through a chemical reaction, breaking down the bonds between the coating and substrate. This allows the coating to be wiped away without damaging sensitive components underneath. It's important to use a stripper specifically designed for the type of coating being removed.

Choosing the Right Stripper

There are a few key factors to consider when selecting a Conformal Coating Stripper:

Coating Type - As mentioned, strippers are formulated for specific coating materials like acrylic, silicone, urethane, etc. Use a stripper matching your coating's chemistry.

Safety - Always check and follow the stripper's safety data sheet (SDS) for proper handling and PPE requirements. Some contain flammable or hazardous solvents.

Substrate Compatibility - Ensure the stripper won't harm common substrates like FR-4, copper, or components. Some may corrode or dissolve certain plastics or metals over time.

Dwell Time - The amount of time needed for the stripper to fully dissolve the coating can vary. Shorter dwell formulas save time but may be less effective on thicker coats.

Ease of Removal - Strikers with slicker, less-viscous formulas make coating removal easier with less scrubbing or wiping required.

Cleanup - Consider strippers that rinse away cleanly with water or solvents to simplify post-removal cleanup. Some leave messy residues.

Application Methods for Conformal Coating Strippers

There are a few primary methods used to apply conformal coating strippers:

Immersion - Submerge the entire coated board or assembly in a stripper bath. Effective for thorough, even removal but wets all areas.

Spray Application - Spray stripper directly onto coated surfaces using an aerosol or pump spray bottle. Targets specific problem zones.

Brush Application - Manually brush stripper onto coated areas using a small paint brush or swab. Allows direct, controlled application.

Vapor Degreasing - Suspend coated items above a heated stripper vapor bath inside a sealed chamber. Strips with minimal wetting.

Choosing the right application method depends on factors like coating thickness, size of parts, accessibility, and desired removal control. Multiple techniques may be combined as needed.

Conformal Coating Stripping Procedure

Once the proper stripper and application method is chosen, follow these general stripping procedure steps:

1. Prepare Work Area - Cover surfaces, add ventilation, mix fresh stripper solution.

2. Apply Stripper - Immerse parts, spray or brush on stripper generously to coat surfaces.

3. Allow Dwell Time - Let stripper chemically break down coating per manufacturer duration guidelines.

4. Remove Coating - Wipe away loosened coating with solvent-safe wipes or rinse with compatible solvent or water as needed.

5. Inspect - Check for any remaining coating patches and reapply stripper if needed.

6. Rinse - Thoroughly remove all stripper residues to preclude contamination.

7. Dry - Air dry or use compressed air to evaporate all remaining moisture before continuing work.

8. Dispose - Discard used stripper solution per environmental regulations. Never pour down drains.

Stripping Tips and Tricks

Here are some additional tips to help ensure an effective and safe stripping process:

- Agitate parts in a stripper bath by gently rocking or stirring for even coating removal.

- Consider localized heating (up to 55°C max) to accelerate chemical stripping reactions.

- Scrub with non-abrasive tools like brushes or swabs on stubborn coating areas.

- Reapply fresh stripper if the solution becomes saturated and less effective over multiple uses.

- Work in a well-ventilated area and always wear appropriate personal protective equipment.

- Small coated parts can be placed in an airtight container with stripper-soaked wipes or rags for prolonged dwell times.

- Rinse thoroughly with distilled or deionized water to flush residues from any crevices before inspection or further work.

Taking time to properly select and apply the right conformal coating stripper solution is key to safely and effectively removing protective coatings for repair or rework needs. Adhering to manufacturers' instructions and general best practices will help ensure an efficient, contaminant-free stripping process every time. With the right tools and techniques, conformal coating removal need not be a daunting task.

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