Thinners

Conformal coating thinners are specially formulated solvents that help you fine-tune how a conformal coating behaves during application. By reducing viscosity, they make the coating easier to brush, dip, or spray, allowing it to level out smoothly and create an even, defect-free finish.

Beyond just thinning the material, the right thinner also improves flow, helps prevent bubbles or streaking, and ensures the coating adheres properly to delicate electronic assemblies. When used correctly, thinners support the coating’s ability to protect circuits from moisture, dust, and other environmental stresses without compromising its electrical insulation or long-term reliability.

Frequently asked questions

What are Conformal Coating Thinners?

Conformal coating thinners are solvent blends designed to reduce the viscosity of liquid conformal coatings, improve flow, and support proper application by spraying, dipping, or brushing. They help achieve smooth, defect-free films without compromising coating performance.

Why are thinners used with conformal coatings?

Thinners are used to adjust viscosity, enhance leveling, prevent bubbles, maintain consistent film thickness, and ensure that coatings apply evenly across complex electronic assemblies. They are also used for cleaning tools, spray equipment, and lines when compatible with the coating chemistry.

What types of thinners are available?

Thinners are formulated to match specific coating chemistries. Common types include acrylic thinners, polyurethane thinners, silicone thinners, and epoxy thinners. Each type has a specific evaporation rate and compatibility profile to ensure proper application and coating performance.

Can any thinner be used with any conformal coating?

No. Thinners must be chemically compatible with the coating. Using an incorrect thinner can cause whitening, poor adhesion, incomplete cure, or material defects. Always use the thinner recommended by the coating manufacturer to maintain product integrity.

How do thinners affect the application process?

Thinners adjust the coating’s flow and atomization during application. For spraying, they help achieve fine atomization and even coverage. For dipping, they maintain consistent withdrawal viscosity. For brushing, they reduce streaking and improve leveling.

What is the role of evaporation rate in thinners?

The evaporation rate determines how quickly a thinner flashes off during application. Fast-evaporating thinners support quick drying, while slower thinners improve leveling and help prevent bubbles. Choosing the right rate depends on the coating method and environmental conditions.

Can thinners be used for cleaning equipment?

Many thinners can be used to clean spray guns, pumps, brushes, and coating lines, but not all are intended for cleaning purposes. Some are viscosity reducers only. Always verify whether the thinner is compatible and safe for cleaning to avoid contamination or damage.

What safety precautions should be taken when using thinners?

Thinners are volatile solvents and should be used with proper ventilation, PPE, and safe handling procedures. Containers must be kept sealed to prevent evaporation, and waste should be disposed of according to local environmental regulations.

How should thinners be stored?

Store thinners in tightly sealed containers, away from heat or ignition sources. Prevent prolonged exposure to air to reduce evaporation loss. Proper storage ensures consistent viscosity performance and prevents contamination.

How much thinner should be added to a conformal coating?

Recommended thinning ratios vary by coating type and application method. Typically, thinning ranges from 5% to 30% by volume. Adjustments should be made gradually while measuring viscosity with a Zahn or DIN cup to ensure process consistency.

Learn more

Conformal coatings are formulated with a specific viscosity optimized for certain application methods. However, environmental conditions, coating thickness requirements, equipment setups, or storage time can make the coating too thick for proper use. This is where thinners come in.

Why Thinners Are Used

Conformal coating thinners allow you to:
Reduce viscosity for spray, dip, or selective-coating equipment
Improve leveling and flow-out to avoid bubbles, orange peel, and streaks
Control film thickness for precise technical requirements
Extend pot life during long production runs
Clean tools, lines, and equipment when compatible with the coating chemistry
Restore aged coatings that have partially evaporated or become too thick

Important thinners properties per conformal coating chemistry

Different coating conformal coating chemistries require different thinner properties. For different

Acrylic

Fast, clean evaporation rate
High solvency strength for acrylic resins

Urethane

Controlled/medium evaporation rate
Isocyanate-safe formulation

Silicone

Slow to moderate evaporation rate
Low polarity & compatibility with silicone oils/resins

Rubber

Strong solvency for elastomeric polymers
Plasticizer-compatible formulation

How Thinners Affect Application

Achieve consistent atomization
Prevent dry spray and overspray roughness
Improve edge wetting on densely populated boards

Maintain consistent withdrawal viscosity
Reduce runs or dripping
Ensure uniform coating thickness

Improve flow and minimize brush marks
Adjust open time for larger boards or rework

Equipment Cleaning vs. Viscosity Adjustment

Some thinners serve dual purposes—both thinning and equipment cleaning. Others are cleaning-only solvents designed to remove uncured coating residue from spray guns, pumps, or lines.

Always check labeling to avoid accidentally introducing contaminants into a production line.