Definition

Author

  • Dr Lee Hitchens, Nexus

3D effects shadowing reduced size 2Shadowing is where correct conformal coating coverage is not achieved on a section of a board due to a component or part of the board blocking another area of the circuit board.

This can occur when coating is applied by spray method to a circuit board. This can easily occur with 3D components and tall components.

Download our PDF guide Solving conformal coating problems in the application process now.


Causes of shadowing in conformal coating

If the circuit board has an architecture structure that is 3D in nature with large components such as heat sinks, capacitors and through-hole components on the circuit then this is more likely to occur.


How to prevent shadowing problems in conformal coating

Avoiding shadowing can be easily done if you use the correct spray application method that should be adopted for most cases:

  1. Angle the spray gun at 45 degrees so the coating can penetrate easier onto the circuit board.
  2. Spray the PCB in a light coating in a rastered pattern. DO NOT apply the full film thickness on this first pass.
  3. Rotate the circuit board by 90 degrees
  4. Repeat the rastered pattern across the circuit.
  5. Rotate again and repeat until 4 coats have been applied to the circuit.

Examine the PCB for coverage. If the coating coverage is good then the board is coated. If the coating is patchy or too thin then repeat the process after the correct time for the coating to dry enough (to avoid layering issues).

Download our PDF guide Solving conformal coating problems in the application process now.


Links

BlisteringBlushingBubbleContamination
Capillary FlowCorrosionCrackingDelamination
De-wettingDiscolourationFish EyesLayering
MealingOrange PeelShadowingUneven coating