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September 20, 2019 12:29

Is it possible to get coating on a via ?

I need to isolate a via to avoid short circuit. I search in the help but I am not able to find a way to get coating on a via. This via is connected to VDD and there is a risk of short circuit with ground on one of the surface of the pcb.

Thank you in advance for your help.

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September 20, 2019 16:50

If you open up the Design Technology settings, and click on the Layer Types tab, then look at the row for the Solder Mask layer type, and look over to the column labeled Vias, you will see the usual setting, which is Yes. (As in yes, there should be openings in the solder mask layer for the vias.) Toggle that Yes to a No, click Apply, then close the Design Technology dialog, and when you output the manufacturing plots the solder mask will not have explicit openings over the vias. (See the attachment for a screenshot of the dialog with the relevant setting highlighted.)

Note: That does not in itself guarantee there will be no hole in the solder mask over a via, because modern solder masks are thin enough they may not 100% cover the unsupported opening (via hole) in the board. But it should at least cover the pad portion of the via, which should be enough to prevent most causes of shorts (solder bridges to a nearby trace, or a temporary slip of screwdriver or stray wire during debugging). If you need more than that, you would need a filled via. You usually communicate which vias are to be filled by written instructions to the board manufacturer. I found a useful blog post (https://blog.epectec.com/pcb-vias-everything-you-need-to-know) that covers more about the different types of via treatment (tenting, filled, plugged), their characteristics, and how they are made from the standpoint of the board manufacturing. It also includes an example of how to specify the special instructions for the manufacturer.

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