Conformal Coating
Conformal coating is a protective and non conductive coating that is applied onto the printed circuit board. This protects the electronic assembly from damage that may be due to contamination, salt spray, moisture, fungus, dust and corrosion caused by harsh environments.
How does conformal coating work?
Conformal coating is a barrier that protects electronic components against harsh environments. They are a breathable protective layer that allows moisture trapped in the circuit board to escape. The material tends to be lightweight and helps to increase the strength between conductors which enables the PCB to be small and compact.
Where is conformal coating used?
Often used applications include scenarios where consistent protection is required. This includes against things like moisture, chemicals, salt sprays, temperature changes and mechanical vibrations. The idea behind their use is to enhance product reliability when it comes to reducing cost and damaging effects of failures.
You not only protect your PCB with conformal coating but also enhance your products reliability and therefore reduce the potential future costs. The use of conformal coating is becoming increasingly more common in consumer and domestic applications that can be affected by environmental exposure, including portable devices such as mobile phones.
How do you apply conformal coating?
Conformal coating should completely cover the assembly and provide a good cover of sharp edges and other contours. There are 4 main ways to apply conformal coating; this includes dipping, selective robot coating, spraying and brushing. Once you have applied the coating to your printed circuit board, the next step is to decide the curing method which can include air dry, oven dry or UV light cure. The process of conformal coating is as follows;
1. Make sure the board is cleaned
2. Remove all protected areas such as terminal pins and connectors
3. Apply the conformal coating
4. Cure the coating (this differs according to the coating type)
5. Reassemble any removed parts
6. Undergo a full test to ensure the functionality of board has not been affected.
Types of conformal coating
There is a variety of commonly used conformal coatings available, these include; silicone, acrylic, urethane and paraxlylene. Both physical and chemical properties of the materials differ and in turn offer a different degree of protection.
In regards to printed circuit boards specifically, it is often applied to protect it against various elements so that the end electronic product functions effectively. These are ideal for harsh environments. Printed circuit boards are often expected to perform in many different environments and conditions over the years. Conformal coatings not only protect PCBs from many conditions, they even let trapped moisture escape. The working life of a PCB is paramount to it’s effectiveness.
Philip King
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