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 <m...@ssalewski.de> 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