In coating, a fish eye is a localised de-wetting defect.
It looks like a fish eye crater on the surface of the conformal coating.
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.
This contaminant is a substance like a silicon residue.
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.
Click to find out how to stop fish eye defects in conformal coating.