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Stop MAsk?

Discussion in 'CAD' started by Bojan, Oct 21, 2006.

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  1. Bojan

    Bojan Guest

    Can me somebody explain what is "Stop mask" in PCB(P-CAD)? For what use this
    layer?
    Tnks
     
  2. 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
     
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