> On Sun, Sep 7, 2014 at 1:19 PM, wrote: > > I suspect that you will find free/low priced/hobby packages have layer > > limitations because the underlying code to keep track of everything on > > each layer becomes a big mess if not well designed. Once to get to > > 'serious' packages that cost significant money you can do anything > > with them from laying out silicon for ICs to multilayer PCBs where > > manufacturing technology of the boards sets the maximum layer limits. >=20 > While I agree commercial software is much better suited for doing 12 laye= rs, I > know for a fact the gEDA supports an unlimited number of routing layers. > It is controlled by a compile time variable that is set to 8 by default. > Unfortunately, it does not support blind vias, which I have to imagine is= a > show stopper on high layer count boards. You really only need blind vias in two situations - firstly if doing really= high speed signals where the 'unused' portion of the via becomes a tuning = stub that you don't want putting stray impedance in funny places. Second pl= ace to use them is when dealing with high density high pin count chips like= BGA devices where you also need to go to via-in-pad anyway. Anywhere else = you don't need blind vias unless you are exceedingly cramped for space and = have effectively 2 circuit boards back to back with the only commonality be= ing a ground plane maybe. --=20 Scanned by iCritical. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .