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I am here to clarify my doubt on what is antipad? in padstack creation,and why it is used ? If we create non plated pad then there is necessity of anti pad? Thanks for your good answer .

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The antipad is the space around the via on the plane layers that the via is not meant to connect to.

in padstack creation,and why it is used ?

To avoid shorts between signals routed through vias and power or ground on plane layers that the via passes through.

If we create non plated pad then there is necessity of anti pad?

I'd recommend it.

If you might pass a metallic object like a screw through the drill hole, you might not want it to short to the plane layers.

You also don't want the drilling process to "smear" some copper from one plane in such a way that it shorts to another plane.

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  • \$\begingroup\$ yeah ,but there is no copper in drill hole then how is it possible to short to the plane layers@the photon \$\endgroup\$ – Hari Babu Dec 10 '18 at 9:58
  • \$\begingroup\$ one more doubt is it important to give soldermask top to the non plated holes \$\endgroup\$ – Hari Babu Dec 10 '18 at 9:59
  • \$\begingroup\$ @HariBabu, if you don't provide an anti pad, then there will be copper in the layers you're drilling through. \$\endgroup\$ – The Photon Dec 10 '18 at 15:36
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Anti-pad referes to the area between via and the copper in internal planes. This is necessary to maintain the correct impedance in transmission lines and also to avoid shorts as mentioned in previous answer.

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Source: https://www.polarinstruments.com/support/si/AP8178.html

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