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What causes bubbles in conformal coating?

Posted by Sean Horn

Wednesday, September 12, 2012 9:41

@ 9:41 AM

One of the causes for failure during conformal coating inspection are bubbles.  Bubbles are trapped pockets of air under coating.  The bubbles can cause voids in the coating and Here we will identify the six largest causes of bubbles.

conformal coating bubbles

  1. When applying the conformal coating the wet film surface can skin over, trapping solvents under the surface which can bubble or burst out.
  2. If the coating is applied too thick or too viscous any bubbles which are created in the process of application can become entrapped in the coating before they settle out.
  3. Air trapped under components by the coating process can be forced out during the drying / curing process and cause bubbles.
  4. Pressure pots with conformal coating inside can absorb air which can manifest as champagne bubbles when applied.
  5. Brush coating with too viscous a material or working the coating can cause bubbles.
  6. Incorrect spray equipment or pressures can cause excessive bubbles or a foam like appearance.


Conformal Coating Defects (And How to Avoid Them)