SparkFun Forums

[MichaelN]

How much of a border around the pad should I make the solder mask?

I typically use 0.05mm or 0.002". In your case, this would give a 0.1mm wide strip of soldermask between pads. Alignment of the soldermask is often not as good as the copper layers themselves, but you should be OK even if the soldermask encroaches a small amount onto the pads.

EDIT: some people report using even tighter soldermask boundries around pads (eg 0.001"), eg this:
http://www.pcbstandards.com/forums/show ... php?t=1515

I'd say if your PCB house can achieve that sort of accuracy then use 0.001".

[holla2040]

Thanks for the info. I'll ask the board house about your last statement.