Stop MAsk?

Can me somebody explain what is "Stop mask" in PCB(P-CAD)? For what use this layer? Tnks

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Bojan, I have never heard the term "Stop mask" in regards to PCB design. I can only assume it is some alternate name for soldermask.

The soldermask is typically an epoxy screened on mask layer that is placed over the copper conductors with openings only where there is a pad that requires soldering. It helps stops solder from shorting between two adjacent pads and from wetting along a trace, being pulled away from the pad that was desired to be soldered.

With a soldermask layer you can move the PCB through a solid wave of solder (Wave soldering) without the solder attaching to every trace or copper feature, turning it into a large mass of solder shorting across all traces. When wave soldering the solder will only attach and flow to the exposed PCB pads and component leads. Where there is soldermask the solder will just pull away from the PCB and stay in the wave rather than attaching to all the traces underneath the soldermask.

As a secondary function it also assists in protecting the copper traces from moisture and the resulting oxidation/corrosion during handling, processing and assembly of the PCB.

Brad Velander

Brad Velander.
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Brad Velander

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