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Introduction:
You may have heard of or even observed the presence of PCBs (Printer Circuit Boards) in all electrical and electronic modules like radios, computers, beepers, etc. There are varieties of PCBs, depending upon the applications. PCB is a slim board made out of laminate materials like fiber glass, composite epoxy.
Conformal coating is some non-conductive protective polymeric layer, applied to the contours, relating to PCB components/ assemblies.
There are different types of coatings like acrylic resin (AR), epoxy resin (ER), urethane resin (UR), silicone resin (SR), parylene (XY). Of all these, acrylic is the very common material, used in conformal coating, in view of its properties like excellent moisture resistance, easy to apply, quick curing by physical drying, dielectric strength, protection against dust and fungus and easily repairable.
Properties:
Good electrical properties like dielectric constant/ strength, equalling V 300/ mm, dissipation factor (of 0.01), insulation resistance, dielectric breakdown voltage.
Moisture: While there is a high rated moisture protection through moisture resistant layer, water proof protection cannot be assured 100%. Even if you apply the coating heavily, you may ensure only semi-permeability thereby allowing some amount of moisture. However, current leakage or corrosion arising from ambient moisture can be prevented.
It protects against extreme temperatures (up to 1300 C)
Good Corrosion protection.
Protection:
In order to protect such boards and electronic devices from many vulnerable conditions like moisture, humidity, salt spray, chemicals, temperatures, shocks, vibration, abrasion, contamination, electric failures, Electrostatic Discharge (ESD), corrosion, mould growths, they are coated. Mind you, an uncoated PCB is susceptible to failures, affecting the productivity/ performance of the whole system.
When considering a conformal coating, the following factors should always be borne in mind:
Moisture vapour transmission rate should be low.
Water absorption should be low.
Outgassing should be low.
Good Corrosion protection.
They are non-conductive or insulative.
Typically, it is applied at 10 - 15 μm (micrometers) thickness. Without damaging the PCB, the thickness can be measured using some test probes
The average useful life time of the conformal coating will extend to many years depending on its type (whether N or C)
Advantages:
It is exceptionally and effectively user friendly.
Longevity in working life and functionality are improved.
Production/ maintenance costs will be lower, in the light of labour costs and process complexities.
It prevents premature break down of components
It may be possible to directly solder through these coatings, with normally acceptable resultant finish.
It provides insulation, permitting reduction in Printed Circuit Board conductor spacing.
It avoids damage on account of contamination.
Acrylic coating permits comparatively easy removal with solvents for repair purposes.
It is designed to ensure security and performance reliability of PCBs.
Applications:
It is light application.
The conformal coatings find applications in most of the industries especially, automotive, aerospace, green energy, lighting, marine, military, and so on. Since most domestic appliances involve electronics, they are applied there also.
Further, mobile electronics use them to a great extent.
Conclusion:
In short, you may see that the conformal coatings find applications in vast varieties of electronic devices.
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