Conformal Coating Types

Coatings can be categorised by their base chemistry, each option having its own beneficial properties for the different environments the PCB will be operating in. The most widely used materials are historically solvent-based, the benefits of which include:

• Ease of processing and application
• Simple viscosity adjustment
• Suitability for a range of application methods
• Tailored application and cure

Acrylic Coating

Acrylics combine reasonable price with good environmental protection; they retain clarity and can resist darkening and hydrolysis during extended exterior exposure. They do however have a limited solvent resistance, making them suitable for re-work but not applications where chemical resistance is important.

Key Properties

• Acrylic coatings offer good flexibility and all round protection
• They offer excellent humidity and salt mist protection
• They are easy to apply and remove and dry quickly at room temperature via simple solvent evaporation
• They have a wide operating temperature range.
• They have excellent adhesion to a wide variety of substrates

Polyurethane Coating

In contrast to acrylics, polyurethane coatings offer excellent chemical resistance and superior protection in harsh environments. They also maintain flexibility at very low temperatures. Like acrylics, they are also very versatile covering a broad operating temperature range.

• Good flexibility, particularly at low temperatures
• Excellent chemical resistance
• Polyurethane coatings can be removed using specialist products (CCRG)
• Very good abrasion resistance

Hybrid Coatings

Hybrid coatings are where a mixture of base chemistries are used. These can result in a number of different coating options, tailoring the requirements for specific applications.

Electrolube’s SCC3 range of conformal coatings are polyurethane base resins modified with silicone to enhance the high temperature properties of the resin. These coatings display a wide range of advantages over standard materials and as they are solvent-based, they also provide all the benefits of ease of application. The SCC3 range of coatings offers a wide range of performance benefits without the problems associated with standard silicone coatings; i.e. silicone migration and the effects of low molecular weight siloxanes.

• Extremely wide operating temperature range
• Easy to apply
• Very high chemical resistance
• Can be reworked with specialist coating removers (CCRG)
• Good protection in a wide range of environments

Electrolube also provide other modified silicone technologies which have been specifically designed for the railway industry. These coatings offer a wide range of protection in a both challenging and rapidly changing environments.

• Good all round protection
• Approved to IEC 61086
• Ease of processing and ideal for those applications requiring rework

Electrolube offer a range of hybrid coatings, including low-VOC and non-VOC options.

Water-Based Coating

Water based coatings cure by evaporation of water from the system. They are low-VOC options, replacing the majority of solvent in the system with water. This improves operator safety and also dramatically reduces solvent emissions.

• Reduces solvent use; improves operator and environmental safety
• Electrolube products are NMP free; again offering a safer product
• Electrolube products are hybrid products offering enhanced performance
• Can be applied using standard equipment; dipping and spray versions available
• Can offer a good level of chemical resistance

UV Cure Coating

UV cure conformal coatings are also another example of hybrid coatings. In this case, different chemistry types are often used to produce a dual-cure system, thus avoiding issues with areas shadowed from the UV light during curing. UV cure coatings offer the fastest curing times with coatings curing in seconds under UV light. This is extremely beneficial for high throughput applications and any shadowed areas will cure via the secondary cure system over time. Due to their highly cross-linked structure when cured, they can be difficult to remove and in some cases UV cure coatings are known to suffer from reduced flexibility during thermal changes and therefore must be carefully tested.

• Extremely fast process times
• Secondary moisture cure system used to help shadow areas cure
• Good protection in a range of environments
• Excellent chemical resistance
• Electrolube's UVCL offers good flexibility with frequent and rapid changes in thermal conditions

More Information

• Read more about Conformal Coatings and their application in our latest Blogs
• Read more about Conformal Coatings in our latest White Papers