Definition

Author

  • Dr Lee Hitchens, Nexus

A fish eye is a localised de-wetting defect that looks like a fish eye crater on the surface of the conformal coating.

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Examples of conformal coating fish eyes

Examples are shown in the images.

conformal coating fish eye defect
conformal coating fish eye defects


Causes of fish eye defects in conformal coating

Fish eyes are normally caused by a contaminant on the surface prior to application of the conformal coating.

Typically, that contaminant is a substance like a silicon contaminant.

When coating is applied on top of the contaminant, the conformal coating is unable to adhere to the oily surface and a “fish eye” is caused.


How to prevent fish eye problems in conformal coating

  • Cleanliness of Surface: Thoroughly clean the surface of the board before coating. Fish eye is a surface preparation defect. If the surface of the circuit bard has been properly cleaned and degreased, fish eye can usually be prevented completely.

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


 Links

BlisteringBlushingBubbleContamination
Capillary FlowCorrosionCrackingDelamination
De-wettingDiscolourationFish EyesLayering
MealingOrange PeelShadowingUneven coating