Matthew,

Due to EXACTLY what happened to you, we will use 5/5 for lines and 8 mils for lines to pads.  If you really
need it that tight, you can always spec that the solder mask opening is no larger than the pad and allow a
couple mils of mask on the pad, if not on the whole board, on those pads that are that tight.  Let me know
if you want more info.

Mark


Matthew Sanders wrote:

> Hello all,
>
> I ran into a problem recently where, while following our standard air gap
> design rule of 5 mils, we placed a trace 5 mils from a pad and ended up with
> bridging after assembly. It looks like with the combination of the
> soldermask clearance from the pad (~3.5 mils) and the misregistration
> between the soldermask and the pad, that the edge of the trace was left
> exposed, picked up solder at HAL, and picked up some of the pad's solder
> during assembly.
>
> So, my question becomes, does anyone use different design rules for traces
> next to pads than they would use for two parallel traces?
>
> Thanks,
> Matt
>
> Matthew Sanders
> PWB Procurement Engineer, Trimble Navigation Limited
> [log in to unmask]
> Phone: (408) 481-7817
> Fax: (408) 481-8590
>
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