The issue is whether components will be mounted into the holes.

IPC-6012, Qualification and Peformance Specification for Printed Rigid 
Boards (to supersede IPC-RB-276), states that solder mask may tent or 
plug vias or through holes, as long as the hole is not required to be 
solder filled.

If a component is to be mounted through the hole, the mask cannot 
"encroach" upon the barrel of the hole.

Mike Buetow
IPC Technical Staff
2215 Sanders Road
Northbrook, IL 60062
P: 847-509-9700, ext. 335
F: 847-509-9798
[log in to unmask]


On Wed, 28 Feb 1996 [log in to unmask] wrote:

> soldering that side (the actual electronics are on top).  Simple solder mask
> seems to prevent these bumps from being formed.  Is there an IPC
> recommenddaation about soldermasking over thru-hole vias?  The hole may or
> may not be closed by the mask.