On Mon, Sep 02, 2013 at 03:45:23AM -0700, Cirilo Bernardo wrote: > Using IDF also gives us another method of specifying the board outline, but > to be honest the specification has severe defects; for example, arcs are not > correctly constrained so for any arc specified in IDF there are 4 different > ways to draw the arc if we assume a circular arc; for elliptical arcs there > are an infinite number of ways to draw the arc and every single one will > conform to the standard as written.
AFAIK IDF is generally used only from ECAD to MCAD, even if it's designed to work both ways. The IPC standard will explicitly add a 'mechanical outline' layer for IDF generation and most probably provisions for attaching a STEP model. However it isn't out yet, but the pattern calculator already generates it (on screen, I don't have licenses for the CAD exporters). I see two problems generating IDF3: 1) correctly finding polygon loops (more or less like for the SPECCTRA board border) and 2) height values; AFAIK the eagle people hack the line width to represent height; a similar special arrangement could be done for the 'body model outline' layer, used for IDF generation. As for the arcs, well, we should fix before the 90 degrees limitation (and do anyone actually use elliptic arcs?) > Nice work Lorenzo. As for how many layers we can ultimately use, I imagine at > least twice as many as the copper layers in a pathological case thanks to > things like 'no route' areas underneath ICs. But with 64 layers total I think > we'll be safe for a long time. We can't raise the copper layer number without breaking things (i.e. renumber layers); IMHO whoever needs to use more than 16 coppers probably should use something more advanced than pcbnew at the moment :P We need *at least* a more complete padstack model to correctly handle modern HDI assemblies... at least different antipads (call them clearances, if you want) for internal layers and even more control for thermals. And of course a script for fanning out BGAs :P The layer increase project (started more than a year ago, IIRC) is more to enable more auxiliary/technical layers (courtyard, assembly, mechanical and electrical clearance to name few), and maybe more user comment layers. -- Lorenzo Marcantonio Logos Srl _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : kicad-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp