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Date: | Thu, 17 Jul 2014 02:24:12 +0200 |
From: | Bernd Walter <ticso AT cicely7 DOT cicely DOT de> |
To: | geda-user AT delorie DOT com |
Subject: | Re: [geda-user] opper ring flag for vias and pins |
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On Thu, Jul 17, 2014 at 02:11:32AM +0200, Bernd Walter wrote: > On Wed, Jul 16, 2014 at 02:22:50PM -0400, DJ Delorie wrote: > > > > > You need to be able to remove inner layer pad annuli completely for > > > signal integrity reasons on some high-speed lines. > > > > Aren't there manufacturability issues if you do that? I.e. voids > > where the copper should be, causing breaks in the barrel? > > Why should there be any? > I can't tell for sure, but when the holes are drilled and plated after > stacking then such a plated hole without inside annular rings should > be just the same as they would be with a standard 2-layer board. > But I just investigated some very high densisty CPU boards I had > within reach and all of them used microvias, but had at least rings > on the outside layers of all vias. > I probably should ask a board manufacturer about their opinions. Just a random manufacturer found by websearch: http://www.eurocircuits.com/index.php/component/content/article/28-glossary/237-ipi-inner-layer-pad-insulation They defines spacing requirements for such a non ringed hole independend if plated or not. So it should be Ok to have non ringed holes in inner layers at least. -- B.Walter <bernd AT bwct DOT de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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