Re: gEDA-user: Metric, Imperial, Rounding, DRC, and board houses
> Use metric grid/unit +1 Pcb's grid is much more precise (it's float point variable) than even internal pcb units (which is small enough but integer), and errors introduced by grid itself (if any) is not cumulative across board items (pins, etc). So simply set grid to 1 mm should give excellent results. ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Metric, Imperial, Rounding, DRC, and board houses
On Tue, 2011-02-22 at 02:37 +0100, Kai-Martin Knaak wrote: > Russell Dill wrote: > > > In addition, my board house rounds everything to > > 2.4 format (0.1 mil). I can envision several scenarios where my design > > meets DRC in PCB, but fails when I send it to the board house. > > > > What is my best option? > > Time to change the board house? Steven is American... and I'd imagine board houses in the US are likely to be the last to abandon imperial units. -- Peter Clifton Electrical Engineering Division, Engineering Department, University of Cambridge, 9, JJ Thomson Avenue, Cambridge CB3 0FA Tel: +44 (0)7729 980173 - (No signal in the lab!) Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me) signature.asc Description: This is a digitally signed message part ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Metric, Imperial, Rounding, DRC, and board houses
Russell Dill wrote: > In addition, my board house rounds everything to > 2.4 format (0.1 mil). I can envision several scenarios where my design > meets DRC in PCB, but fails when I send it to the board house. > > What is my best option? Time to change the board house? > Just use imperial units and cope with weird grids? > > Use metric spacing, but recalculate DRC based on worst case rounding? I'd choose the second option. PCB internal units are 0.01 mil. This adds maximum 10% to the rounding error, the board house introduces anyway. If you do grids that fit the board house metric the rounding error will still happen. The 1mm pitch will make some balls off by 0.05 mill. The internal units are 254 nm. I sincerely doubt that a design better to be etched in 35 µm copper can be that critical. ---<)kaimartin(>--- -- Kai-Martin Knaak Email: k...@familieknaak.de Öffentlicher PGP-Schlüssel: http://pool.sks-keyservers.net:11371/pks/lookup?search=0x6C0B9F53 ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Metric, Imperial, Rounding, DRC, and board houses
I use mil grids, as many boards houses expect mil units, like yours. PCB layout is engineering, engineering involves tolerances... I start my traces from off grid components so that the stub going from the pin/pad is off grid byt quickly becomes on grid after the first 45 degree bend. Steve On Mon, Feb 21, 2011 at 2:44 PM, Stefan Salewski wrote: > On Mon, 2011-02-21 at 15:23 -0700, Russell Dill wrote: >> I'm starting a new design and all my components are metric based, >> including a few 1mm pitch BGA components. I'd really like to do the >> layout in metric, but I'm worried about two factors. The first of >> which is that PCB does not yet have the option to store things >> internally in metric (at least from what I understand) so rounding may >> occur on that end. In addition, my board house rounds everything to >> 2.4 format (0.1 mil). I can envision several scenarios where my design >> meets DRC in PCB, but fails when I send it to the board house. >> >> What is my best option? >> >> Just use imperial units and cope with weird grids? >> >> Use metric spacing, but recalculate DRC based on worst case rounding? >> >> Some other option? >> > > Use metric grid/unit, I guess most of us use that. > Internal resolution is 0.01 mil, which is good. Of course nm would be > better. One problem for me was, that a few 0.01 mil garbage lines were > generated for the layout. Not a big problem. Some not really smart > people have tried to use a very very fine grid, 0.01 mm or so. That is > like using no grid at all, I call that silly. Try to use a useful basic > grid like 0.25mm grid if most of your parts have 0.5mm pitch -- I think > that was what I did, I am not sure. Important: Enable snap to pads/pins, > so you can make good connections to imperial parts which are not on the > metric grid. > >>my board house rounds everything to >> 2.4 format (0.1 mil). > > Strange -- so pitch of metric parts may vary from pad to pad a bit. That > was a problem in very old days of PCB, when 1mil internal units was > used. > > > > > ___ > geda-user mailing list > geda-user@moria.seul.org > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: Metric, Imperial, Rounding, DRC, and board houses
On Mon, 2011-02-21 at 15:23 -0700, Russell Dill wrote: > I'm starting a new design and all my components are metric based, > including a few 1mm pitch BGA components. I'd really like to do the > layout in metric, but I'm worried about two factors. The first of > which is that PCB does not yet have the option to store things > internally in metric (at least from what I understand) so rounding may > occur on that end. In addition, my board house rounds everything to > 2.4 format (0.1 mil). I can envision several scenarios where my design > meets DRC in PCB, but fails when I send it to the board house. > > What is my best option? > > Just use imperial units and cope with weird grids? > > Use metric spacing, but recalculate DRC based on worst case rounding? > > Some other option? > Use metric grid/unit, I guess most of us use that. Internal resolution is 0.01 mil, which is good. Of course nm would be better. One problem for me was, that a few 0.01 mil garbage lines were generated for the layout. Not a big problem. Some not really smart people have tried to use a very very fine grid, 0.01 mm or so. That is like using no grid at all, I call that silly. Try to use a useful basic grid like 0.25mm grid if most of your parts have 0.5mm pitch -- I think that was what I did, I am not sure. Important: Enable snap to pads/pins, so you can make good connections to imperial parts which are not on the metric grid. >my board house rounds everything to > 2.4 format (0.1 mil). Strange -- so pitch of metric parts may vary from pad to pad a bit. That was a problem in very old days of PCB, when 1mil internal units was used. ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
gEDA-user: Metric, Imperial, Rounding, DRC, and board houses
I'm starting a new design and all my components are metric based, including a few 1mm pitch BGA components. I'd really like to do the layout in metric, but I'm worried about two factors. The first of which is that PCB does not yet have the option to store things internally in metric (at least from what I understand) so rounding may occur on that end. In addition, my board house rounds everything to 2.4 format (0.1 mil). I can envision several scenarios where my design meets DRC in PCB, but fails when I send it to the board house. What is my best option? Just use imperial units and cope with weird grids? Use metric spacing, but recalculate DRC based on worst case rounding? Some other option? ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
