De-wetting is where the conformal coating material is applied to a printed circuit board evenly but the coating refuse to stick to the surface that it has been applied to.
Factors that influence de-wetting usually involve non-ionic contamination such as:
- Residues from board manufacture including silicone surfactants from solder resist & HASL rinse contamination
- Component residues like mould release agents
- Silicone oil from adhesives in production.
- Soldering processes
- Cleaning bath contamination where rinsing has failed
- Operator handling adding contaminants
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Conformal Coating cracking is a failure mechanism in processing where the smooth surface fractures into sections with the cracks in the coating leaving the area below exposed to potential contaminants.
Causes of Cracking in Conformal Coating include:
- Cure temperature too high
- Conformal coating heat cured too quickly without allowing enough time for room temperature (RT) drying
- Film thickness too great causing coefficient of thermal expansion (CTE) mismatch and cracks occurring in the coating
- Operating temperature too high or too low causing the conformal coating to flex too much & crack.
To find out more click conformal coating cracking technical bulletin.
Capillary flow in conformal coating is where the coating pulls or runs away from certain areas of a PCB to more favourable sectors due to a combination of effects, leaving a patchy finish on the surface of the board.
To learn more click Common Failure Mechanisms in Conformal Coating Capillary to find out more.
Delamination in conformal coating is where the coating lifts from the surface of the PCB, leaving the area below exposed.
To learn more click Conformal Coating failure mechanisms Delamination to find out more.
Cracking in conformal coating is where the smooth surface of the coating fractures into sections with the cracks leaving the area below exposed to potential contaminants.
To learn more click Conformal Coating failure mechanisms cracking to find out more.
De-wetting is the tendency of the conformal coating material to refuse to wet the surface of the printed circuit boards and components that it has been applied to evenly.
To learn more click Conformal Coating failure mechanisms_de-wetting to find out more.