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3 Methods to Prevent Cobwebbing on Circuit Boards

2024-03-21

Conformal coating, the final step in PCB manufacturing, shields valuable components. However, sometimes things get complicated. Imagine this common scenario:

Your design and testing went smoothly. During production spraying, translucent webs appear, engulfing taller components like a scene from "Arachnophobia." This is cobwebbing, often simple to fix despite its scary appearance.


In this article, we'll explore why cobwebbing happens and offer easy solutions to ensure flawless coating application.

 

Why Do PCB Coatings Cobweb?


Cobwebbing, colloquially known as spider webbing or cotton candy, occurs when coatings or adhesives dry prematurely during spraying. This happens because the solvent evaporates too quickly in midair, leaving strands resembling cobwebs.


What Causes PCB Cobwebbing?

Cobwebbing mainly occurs during spraying, especially atomized spraying. To avoid it, consider alternative methods like dip coating, encapsulation, or manual application with a brush.


How to Prevent Cobwebbing:

 

  1. Lower Air Pressure: Reduce the atomization pressure to the lowest setting. If the coating sprays evenly, you're good. If not, lower it more.
  2. Lower Valve Height: Adjust the valve height so the coating reaches the substrate without evaporating prematurely.
  3. Use More or Slower Solvent: Add more thinner or use slower evaporating solvents to slow down drying.


Cobwebbing is a common issue but easily fixed. Slow drying with proper solvent usage or adjustments during spraying can eliminate it. For assistance in optimizing your process, contact us for unbiased evaluations and reliable solutions.

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