JF,

I can't remember if there is a specification regarding this but I'm sure if I look I would find something.

Now, it all depends.

It's best to keep the soldermask about 10-mils away from the edge of the non-plated hole.
That also means that the copper (no net) should be about 15-20-mils away from the hole so the soldermask covers the copper
If there is a net connected to the copper then you will have to make sure that the head of the screw doesn't come near the copper.  You don't want a short after the assembler toques down the hardware.

If soldermask gets cured in the hole, you may not get your mounting screw through the hole at assembly time.

Then again, if you can drive a Mack truck through the hole you don't have to worry about it.

Cheers
Donald

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of JF
Sent: Monday, February 25, 2013 1:38 PM
To: [log in to unmask]
Subject: [DC] Solder Mask requirements for unplated holes

Hi All,

This should be basic, yet I can't remember the requirement nor where to find the info (which spec).

We have a board with some unplated holes and a copper plane on both the top and the bottom. Of course, the copper planes are recessed from the hole but I can't remember if the Solder Mask should be flush to the holes (some are mounting holes), or just covering the planes + a certain distance.

Thanks in advance!

JF

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