I discovered that the pcb footprint library contains a number of 0603 SMT footprints. The primary ones I am concerned with are:
- 0603 - RESC0603L / RESC0603N / RESC0603M and likewise for 0402. I understand that the IPC standard defines three footprints for these SMT parts, called Least, Nominal, and Most, which are for high-density, medium-density, and low-density designs, respectively. But this leaves me with some big questions: (1) Why is RESC0603L/N/M much smaller than '0603'? (2) Why is there no similarly named set of RESC0805L/N/M for 0805 size? (3) Why does RESC1608M nearly match the '0603' footprint? Is there an imperial/metric naming confusion happening? I thought 0603 was a standard name for this size. Thanks. Below is a message I found in the archives that also asks about the multiple footprints but I don't see that it was satisfactorily answered since 0603 and RESC0603M are so different in size... why? Subject: Re: gEDA-user: Is there a directory of footprints for PCB? From: "John Luciani" <jluciani@xxxxxxxxx> Date: Sun, 26 Oct 2008 16:16:24 -0400 > On Sun, Oct 26, 2008 at 3:25 PM, Kipton Moravec <kip@xxxxxxxxxx> > wrote: > > > newlib -> not_vetted_ingo -> smt0603.ele > > pcblib -> ~geda -> 0603 Standard SMT resistor, capacitor, etc [0603] > > pcblib -> ~geda -> CAPC0603L, Standard SMT resistor, capacitor, etc > > [CAPC0603L] > > pcblib -> ~geda -> CAPC0603M, Standard SMT resistor, capacitor, etc > > [CAPC0603M] > > pcblib -> ~geda -> CAPC0603N, Standard SMT resistor, capacitor, etc > > [CAPC0603N] > > pcblib -> ~geda -> RESC0603L, Standard SMT resistor, capacitor, etc > > [RESC0603L] > > pcblib -> ~geda -> RESC0603M, Standard SMT resistor, capacitor, etc > > [RESC0603M] > > pcblib -> ~geda -> RESC0603N, Standard SMT resistor, capacitor, etc > > [RESC0603N] > > pcblib-newlib -> geda -> 0603.fp > > pcblib-newlib -> geda -> CAPC0603L.fp > > pcblib-newlib -> geda -> CAPC0603M.fp > > pcblib-newlib -> geda -> CAPC0603N.fp > > pcblib-newlib -> geda -> RES0603L.fp > > pcblib-newlib -> geda -> RESC0603M.fp > > pcblib-newlib -> geda -> RESC0603N.fp > > > > There are huge differences in the size of these footprints! > > > > For example, the whole CAPC0603L footprint fits in the space > > between the pads of smt0603.ele > > > > First of all why so many? When would you use one versus another? > > The "L" suffix is for Least material, "N" for nominal and "M" for > most. This is from IPC-7351. You choose between the sizes based on > your manufacturing process and design goals. For hand assembly I would > use either N or M. Regards, Colin _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user