Understanding the via covering process

[Vero]

@retiredfeline

Bear in mind that tented vias are the default and the other options will usually cost extra.

I disagree.

Can you name a serious PCB manufacturer that offers IPC-4761 compliant tented vias as standard? I don’t even know of a manufacturer that still offers the dry film resist (required by IPC-4761) as “standard”.

Even those that do offer dry film resist (on special request) recommend avoiding tenting.

Although many designers submit manufacturing data with “tented” vias, and although many PCB manufacturers don’t argue with their customers, this method is wrong.

The via barrel shall be open when the copper finish (ENIG, HAL etc) is applied to remove residues from previous process steps. Maybe filled and capped vias are an exception to this rule, but if you order these, you don’t need to worry about it anyway.

If you need to close your vias because you are using vacuum fixtures, you should plug them.

If you need small distances between vias and pads, you should uncover just the via hole, so the edge of the annular ring is still covered, but the hole is open. Find a photo here:

Will KiCad pad stacks include solder mask definition for vias?

I think this is a request you should forward to your manufacturer. Since they know the actual drill size, plating thickness and tolerances of their processes. Otherwise you will end up with a partly covered hole or sauce in the hole anyways. The manufacturers I’m using mostly (Eurcircuits, Würth) do this automatically by the way and don’t print over vias.