Conformal Coating: How to Choose a Quality Coating, Application Methods and Thickness Measurements

Conformal coating is a liquid, rubberized coating that protects electronic components from harsh environmental conditions. Conformal coatings are also called “liquid encapsulants,” and they can be applied to a variety of surfaces in a multitude of ways. Conformal coatings come in many different types with various properties, application methods, thickness measurements, curing methods and removal methods. There are also certifications and regulatory considerations to take into account when choosing the best type for your project’s needs. In this article we will discuss these topics so you can make an informed decision about which conformal coating is right for you!

Application Methods

Once the type of coating is selected, the next question is how to apply the conformal coating. This decision should be based on the following variables:

• What surface is being coated? Conformal coatings can be applied to a variety of surfaces in a multitude of ways including spraying, brushing, and dipping.
• What kind of environment will the device be used in? Conformal coatings come with different associated environmental ratings including high temperature performance and resistance to water vapor.
• How much space between parts does there need to be? Conformal coatings can take up as much as 5 mm between parts so it’s important to plan your spacing accordingly.

Traditional conformal coatings may be applied in a variety of ways. The following are some of the most common application processes for traditional conformal coatings:

• Manual Spraying – Spraying by hand is an option for small runs. Conformal covering with an aerosol can or a handheld spray gun may be done manually. When capital equipment is not accessible, it’s a good choice for low-volume manufacturing. Because areas that don’t need to be coated must be masked, this method might take longer. Quality and consistency of the finished product are also dependent on the skill of the operator, so variations are common among boards.
• Automated Spraying: Spraying the board using an automated system – A programmed spray system that moves the board on a conveyor under a different spray head that applies a conformal coating.
• Selective Coating – An automated conformal coating technique that employs programmable robotic spray nozzles to cover very particular regions of the circuit board with the conformal coating. The use of this technique is common in high-volume production and can eliminate the need for masking.
• Immersion – The circuit board is immersed first, then removed from the conformal coating solution. The film formation produced by immersion rate, withdrawal speed, and temperature of the coating solution all affect the final film thickness.
• Brushing – A brushing operation is a simple application process that’s often used in repair and retouch procedures. The conformal coating is brushed onto specific sections of the circuit board using a paint brush.

Curing Methods

There are three Conformal Coating Curing Methods: UV Cure, Heat Cure and Room Temperature Vulcanization (RTV). Conformal coating cures when exposed to ultraviolet light. This process is called UV curing. Another common method for activating the curing of conformal coating is heat cure which will activate a chemical reaction that turns the liquid into rubber through either infrared lamps or hot air ovens. The third form of Conformal Coating activation was discovered by NASA scientists who found RTV activated at room temperature without any curing methods needed!

Removal Methods

Conformal Coatings can be removed with organic solvents such as alcohol, acetone or mineral spirits. Conformal Coating removal methods include sandblasting, chemical stripping and heat blasting which are all abrasive in nature. Conformal coatings can also be removed using UV curing equipment that is capable of penetrating the coating to break down its molecular structure then dissolving it into a liquid state where it can easily be cleaned away with soap and water without any damage done to the product underneath!

Certifications

There are several Conformal Coatings certifications you should become familiar with such as UL (Underwriters Laboratories) 94V-0 for resistance against solvents used in industrial settings; ASTM D4329 standardizing electrical insulating liquids applied by dipping or spraying; and ASTM G23 which defines the physical and mechanical properties of Conformal Coating liquids.

Regulatory Considerations

Some Conformal Coatings are non-compliant with regulations such as those from the United States Food & Drug Administration (FDA) or European Union’s Restrictions on Dangerous Substances Directive (RoHS). Other Conformal coatings may be compliant, including those conforming to FDA CFR 175.300 for use in food packaging applications; RoHS exemptions if certain restrictions aren’t present; and UL Standard 94 V0 for insulation performance requirements according to ASTM D120 standards.

Summary

Conformal Coating is a protective layer that can help keep electronic components safe even under harsh environmental conditions. Conformal coatings can be used to protect a wide variety of electronic components from moisture, chemicals and other environmental contaminants. Conformal coating thickness is important because it affects how well the coating protects against various threats. Conformal Coatings are available in different thicknesses depending on its application method and needs. Conformal Coating cures when exposed to ultraviolet light or heat then activated by using RTV that sets at room temperature without any curing methods needed! Conformal Coatings can also be removed with organic solvents such as alcohol, acetone or mineral spirits which includes sandblasting, chemical stripping and heat blasting which all use abrasive removal methods including UV curing equipment capable of penetrating the liquid conformal coating breaking down its molecular structure then dissolving it into a liquid state where easy cleaning can be done with soap and water without damaging the product underneath! Conformal Coatings are available in different thicknesses depending on its application method, curing methods, removal methods certification or regulatory considerations. Conformal coatings that do not follow regulations may pose risks to human health since they contain hazardous substances harmful for humans. Conforming Conformal Coating certifications include UL (Underwriters Laboratories) 94V-0 for resistance against solvents used in industrial settings; ASTM D4329 standardizing electrical insulating liquids applied by dipping or spraying; and ASTM G23 which defines the physical and mechanical properties of Conformal Coating liquids.