What is Conformal Coating?

What is a Conformal Coating?

What is a Conformal Coating?

Conformal coating is a protective 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 high humidity, a range of airborne contaminants and varying temperatures. 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.

Conformal coatings are a breathable protective layer that will protect against the particular environment the PCA is exposed to by filtering out the airborne contaminants and maintaining long-term surface insulation resistance but will also allow any moisture trapped in the circuit board to escape.

The concept of a conformal coating of electronics was originally proposed and developed through research to meet the demanding requirements of the military decades earlier. HumiSeal was a part of that early research and has remained a pioneer and leader for over 60 years as the technology has expanded to an array of industries today including:

  • Aerospace
  • Automotive, including Hybrid and EV
  • Industrial Controls
  • White Goods
  • Telecoms
  • Energy both Traditional and Renewable

What Are the Advantages of Using a Conformal Coating?
  • Insulating properties can allow a reduction in PCB conductor spacing
  • Can help eliminate the need for complex, sophisticated enclosures
  • Provide extended service life by:
    1. Protecting against humidity, chemical, and physical attack
    2. Protecting against thermal variations and shocks
    3. Protecting against vibration and mechanical shocks
How to You Apply Conformal Coating?

How a conformal coating is applied is dependent mainly upon:

  1. Preferred application method
  2. Existing Available Equipment (Dip/Spray equipment, curing equipment etc..)
  3. Board Design/Complexity/Masking Needs
  4. Desired volumes/cycle times.
Methods of Application: (In order of sophistication)

Methods of Drying and/or Curing Conformal Coatings?

With all four application methods noted above, it will also be necessary to dry and in some cases cure or crosslink the applied coating. Not all methods will be applicable or possible for all chemistries, for example UV curing coatings can only be cured with UV curing equipment.

Advantages and disadvantages of using conformal coatings

How Much Coating Will I Use And What Will The Cost Be?

In order to calculate a cost per circuit board (PCB), it is required that you have the following data available:

  • Length and Width in Millimeters of PCB (or of coated area if not fully coated)
  • Dry thickness of coating in Millimeters (Typically 0.025 to 0.075mm)
  • Decimal percent solids of coating (Ex: 35%=0.35, 100%= 1.0)
  • Price per liter of your coating

Calculation:

mL/PCB = [width (mm) X length (mm) X dry thickness (mm)/ Decimal % solid] / 1000

Cost per PCB ($/PCB) = [cost ($/L) X Volume per PCB (mL)] / 1000

Example: (L=100mm, W=125mm, Dry Thick=0.075mm, %Solids=40%, Price=$100/Liter)

(100mm x 125mm x 0.075)/ (0.40 x 1000)= 2.34 WET mL per PCB

Cost Per PCB= ($50/Liter x 2.34 mL per PCB)/1000 = $0.12 per PCB

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