Is it possible to leave more mask width around some vias, but not others? Or is that only controlled by a general rule in the design software?

But I still don’t see how a thin sliver of mask between two unsoldered vias is an issue, other than for breaking off/FOD.

I know you’re not feeling any shame, Jack! LOL.



From: Jack Olson [mailto:[log in to unmask]]

Sent: Tuesday, February 19, 2019 11:16 AM

To: Stadem, Richard D

Cc: TechNet E-Mail Forum

Subject: Re: [TN] soldermask silvers



We don't rely on the mask for insulation, we rely on a 7 mil clearance copper-to-copper, but that leaves a smaller mask width between them.

For dog bones we do similar, but pad-to-via is the same potential, and those vias are encroached with mask anyway.

not feeling any shame, but thanks for writing back.

(This report also flags "copper slivers" which I've never heard of, but to them it is the thin copper plane that floods between vias!)



On Tue, Feb 19, 2019 at 10:45 AM Stadem, Richard D <[log in to unmask]<mailto:[log in to unmask]>> wrote:

For soldered BGA dog-bone pads, that is a major issue, common within the industry. If the soldermask strip between the via and the BGA pad is too small, there is not enough adhesion and the molten solder runs right under the soldermask strip down into the via hole. Too thin of a strip of soldermask allows solder thieving from the solder ball. But for unsoldered vias not connected to a soldered pad on the opposite side, I cannot imagine what issues there would be. Soldermask is not considered an electrical insulator, so if a designer was depending on a thin sliver of mask to provide insulation between two vias of different potential, shame on them.



-----Original Message-----

From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of Jack Olson

Sent: Tuesday, February 19, 2019 9:58 AM

To: [log in to unmask]<mailto:[log in to unmask]>

Subject: [TN] soldermask silvers



In my experience, what a PCB fabricator would consider a sliver would be

the strip of soldermask material between RECTANGULAR pads being less than a

minimum width.

We got a "DFM report" for a board where minimum distance between ROUND vias

is being reported as slivers.Has anyone ever heard of problems with minimum

mask material between round, unsoldered vias?

I can't imagine any real-world problems that could cause, but I have an

open mind...