solder mask dams

[david_c_partridge]

For RF PCB design the solder mask can be a problem as it can change the characteristics of (e.g.) microstrip lines.   One classic solution to this is to create solder mask dams around pads, but not extend the soldermask over the rest of the board.   I cannot see a way to to this in Ultiboard, so assume that this would need to be a "new feature". 

Is that correct?  If so can this be added to the request list, and if not, how can I do this?

Thanks

Dave

[yyao]

Hi David,

I suppose you can use the polygon tool to draw a the solder mask layer. The solder mask layer is a negative layer. That is, any solder mask shape excludes solder mask from being placed at that location when the board is made. That is why you see solder masks on pins and pads. That being said, you can double click on the solder mask layer and use the polygon tool to draw out an area where no solder mask will be placed in the final board for your microstrips. If you place this polygon close to, but not touching a pad opening, you can create solder damns.

I hope that was what you were looking for.

[david_c_partridge]

No, not really, I was hoping to be able to tell Ultiboard to use solder mask dams rather than solder masking everywhere but the pads!

Cheers

Dave