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Re: Tutorial about IPC-7531A



On Wed, 01 Sep 2010, Lorenzo Marcantonio wrote:

> You can see the little diagram in the IPC-7251 working draft which is
> freely downloadable online at
> http://www.ipc.org/committeedetail.aspx?Committee=1-13

I happen to have a bunch of .plb09 library files (all of the
surface mount devices are even IPC-7351B with build dates such
as 02/04/2009).  I suppose I downloaded them for free and
without requiring the acceptance of any license before they shut
them off.  They used to be in separate library update zip files
on PCB Matrix' website.

Do you know of any place where the V2009 (*.plb09) or earlier V6
(*.plb) file formats are documented?  Or, anybody willing to
reverse-engineer the format?

I converted some by hand that I got from gEDA's library.
Someone did the work to recalculate the lands using the
IPC-7351 equations with an m4 script.  I hand converted a bunch
of chip capacitors and resistors to pcbnew modules (pcbnew's
library chip capacitors were wayyyyy wrong).

Rather than write some awk or perl script to generate modules
from the .plb09 files (which might violate some unwritten
copyright, and I say unwritten because there are no copyright
notices on the files or in the archives whatsoever), I was
considering modifying PCBNEW to read the files directly.  Then
rather than distribute the PLB files with PCBNEW, let the user
go get a copy themselves (say, by forking out the $117 for the
standard).  Some vendors (TI/Luminary Micro) actually generate
their own *.plb09 files.  (Which begs the question: where did
they get the format?  Or do they just use LP Wizard or

Ahh, maybe it doesn't matter.  The only thing I really was going
to use them for was SMT chip capacitors, resistors and
inductors: and of these the non-generic ones needed the
manufacturer's recommended land pattern anyway.  Some do not
provide IPC-7351 values on their datasheets.

Do you thing that purchasing the standard would shed some light
on this library format?  Or are the fields in the file just the
(some of the) parameters that get stuffed into the equations?
It seems that there are a lot of non-IPC things too (like silk
screen clearance).

Maybe all we need is a kind-of-a module-editor wizard that
uses the calculations from IPC-7[23]51, A, B to guide the
user and generate (and name) the module under module editor
which can then be customized from there.  It would still be
nice for that wizard to read directly a vendor-supplied PLB

What are your thoughts?


Brian F. G. Bidulock    ¦ The reasonable man adapts himself to the ¦
bidulock@xxxxxxxxxxx    ¦ world; the unreasonable one persists in  ¦
http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
                        ¦ Therefore  all  progress  depends on the ¦
                        ¦ unreasonable man. -- George Bernard Shaw ¦

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