What is Conformal Coating?
A Conformal coating is a protective chemical coating or polymer film 25-75µm thick (50µm typical) that ‘conforms’ to the circuit board topology. Its purpose is to protect electronic circuits from harsh environments that may contain moisture and or chemical contaminants. By being electrically insulating, it maintains long-term surface insulation resistance (SIR) levels and thus ensures the operational integrity of the assembly. It also provides a barrier to air-borne contaminants from the operating environment, such as salt-spray, thus preventing corrosion.
The protective nature of conformal coatings also means that they not only protect, but also serve to enhance product reliability and thereby reduce the potential cost and damaging effects of early field failures.
How do conformal coatings work?
A conformal coating is a protective barrier that shields sensitive electronic components against harsh environmental conditions such as moisture, chemicals and debris. They are not designed to be a total sealant. Conformal coatings are a breathable protective layer that will protect against the particular environment requirement but will also allow any moisture trapped in the circuit board to escape.
The particular advantages of conformal coatings can be summarized as follows:
- Insulating properties allow a reduction in PCB conductor spacing of over 80%
- Can help eliminate the need for complex, sophisticated enclosures
- Light weight
- Completely protect the assembly against chemical and corrosive attack
- Eliminate potential performance degradation due to environmental hazards
- Minimize environmental stress on a PCB assembly
Ideally, conformal coatings should exhibit the following characteristics:
- Simple application
- Easy removal, repair and replacement
- High flexibility
- Protection against thermal and mechanical shock
- Protection against environmental hazards including: moisture, chemicals and other corrosive elements
How do you apply Conformal Coating?
To be effective, a conformal coating should completely cover the assembly and provide good coverage of sharp edges (components and component leads) and other contours (solder joints for example). It may even be essential to coat the edges of the board, as these will not even have any solder resist present.
The effectiveness of the coating is, to some degree, influenced by the efficiency of the application method, which also governs the type of coating used (some suppliers offer dedicated versions of the same coating product to suit different application methods).
There are essentially four main ways of applying a conformal coating:
- Dipping – limited to materials that do not cure quickly by moisture, oxidation or light
- Selective robotic coating – such as Asymtek, PVA or DIMA. All coating types can be used if the correct dispense head is selected
- Spraying – hand spray using a spray booth or aerosol can. All coatings can be applied in this way
- Brushing – requires extremely proficient and skilled operators in order to be suitable for production purposes
Finally you will have to consider the curing method determined by the coating selected, air dry, oven dry or UV light cure. The liquid coating should thoroughly wet all surfaces and cure without leaving surface defects. Epoxies are especially sensitive to surface defects. Epoxies can also shrink while setting and may lose adhesion as a result In addition; excessive shrinking during cure can place severe mechanical stresses upon circuit components.
The supplier (Architectural Roof Coatings), to create the special formulation required for a particular application, should be able to modify all of these properties. Other characteristics can also be enhanced. Accessory chemicals and solvents should only be blended with base polymer resins by the coating manufacturer. Plasticizers can also improve mechanical flexibility, and selected solvents in conventional coating formulations can improve adhesion of the cured film.
ARC’s® roof coatings are formulated to provide maximum water resistance
a highly reflective roof surface, and maximum UV protection. With the development of the Styrene Ethylbutlyene Styrene (SEBS) reflective roof coatings, a product emerged that not only withstands ponding water, but also provides high reflectivity and prevents damage by solar ultraviolet radiation.
ARC Roof Coatings®
- APP membranes
- SBS membranes
- Built-up roof membranes
- EPDM or HYPALON roofs
- Metal roofs
- Concrete, concrete block, brick or stucco surfaces for waterproofing.
ARC Reflective Roof Coatings®
- Elongation properties of 600%
- Tensile strength of 1000% psi
- Water absorption rate of 0.004%
“When my team made the switch to the ARC® lineup of products we noticed productivity go way up. Thier roof coating process is just so efficient. It made all the difference.”James CarlsonDallas, Texas
“The quality of the ARC® roof coatings was way above the industry standard. We have used several different roof coating solutions and the ARC® stuff is just plain better than the others. Surprisingly cost effective too. I would highly recommend.”Steven GibbonsChicago, IL.
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