What are the 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 Coatings

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.

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

Silicone Coatings

Generally speaking silicones are the most resistant coatings to high/low temperatures or temperature fluctuations due to their more flexible nature. These coatings offer a wide range of protection in a both challenging and rapidly changing environments. However they are less resistant to humidity and corrosive gases than other coating technologies.

Good all round protection
Flexible
Wide operating temperature ranges
Approved to IEC 61086 & IPC-CC-830
Ease of processing

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

2K Coatings

2K two part coatings are hybrid technologies combining the best properties of encapsulation resins with those of a conformal coating. These materials offer some of the best protection available while maintaining the processability and cost effectiveness of a conformal coating (compared to a resin).

High Performance
High levels of protection in a range of environments
Applied more thickly than single part coatings
Excellent moisture protection


 2299,    27  Oct  2021 ,   Conformal Coating
PA

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