Jim Williams wrote:
> 
>      Some designers make an effort to maintain a web of soldermask between
>      the solder pads on SMT devices, where pad spacing permits. When the
>      spacing of fine pitch devices preclude the web, it is omitted. I have
>      heard that the webs are used to reduce solder bridging.
> 
>      Thinking through this issue, I find webs being used where pad spacing
>      is large enough so as to make solder bridging unlikely, while webs are
>      omitted when the pad spacing is close enough to make solder bridging
>      most likely.
> 
>      I am interested in any factual data that supports the reason for, or
>      the value of, soldermask webs.


...don't have any factual data for you, but here's one comment:

I would think the greatest benefit of soldermask webs is during wave 
soldering, and many mixed-technology boards are still wave-soldered, right? 
But from my experience most fine-pitch assemblies use reflow and solderpaste, 
so a soldermask web is of little value. In fact, very thin webs between 
fine-pitch parts can just crack and flake off under high heat, so what's the 
point? Anyone disagree?
							Jack