Solder Masks

Altium globally produces its own solder mask by design rules and Altium does not support true "Pad Stacks".

You cannot control individual solder mask on pads except to use copper on the solder mask layer.

Your fabrication shop will do the gang mask for you if they find any slivers less than their manufacturing tolerances.

Todd,

I have never been concerned with Solder Mask Web Slivers.

Most fabrication shops use Valor Genesis as the front end CAM tool and it rules DRC rule checks for everything you can think of. Every manufacturer has a minimum solder mask to solder mask clearance. The norm is 3 mils or 0.08 mm web width is doable and anything below that web thickness is not.

I leave this up to the fabrication shop.

I've worked as a volunteer for IPC for the past 15 years and every time the subject of Solder Mask Swell comes up the response is always "Solder Mask should be 1:1 scale of the pad size and allow the fabrication shop to swell (oversize) the mask per their manufacturing tolerance.

Altium is slightly different as they DRC check Silkscreen to Solder Mask so you tend to try and swell the solder mask in the CAD tool and then run DRC checks to find violations.

But I agree with IPC and that Solder Mask Swell and Gang Masking is the fabrication CAM operator's job and not the PCB designer's. They know what they can manufacture, they use tools that cost 10 times Altium list price and they have the experience with their equipment.

But if you insist, in Altium (and other PCB design tools), the only way I know how to Gang Mask is to add copper on the solder mask layer.

Todd,

Every manufacturer will modify your Gerber data to match their manufacturing tolerances to insure that the delivered boards match your fabrication notes.

They will swell your outer layer pads, traces and vias to compensate for their etching process.

They will trim all silkscreen that violates solder mask overlap.

They will swell through-hole annular rings to meet IPC minimum annular ring to compensate for their drill machine accuracy and drill drift.

The fabrication shop will always manipulate your Gerber data to increase yield and reduce scrap.