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gEDA-user: land pattern generators vs. verifying footprints

Bert Timmerman wrote:
Hi all, 


a 10000 part library operating a layout service bureau
Take a look at <http://wikicomponents.com> "The worlds first 


Excuse me for having a rather pessimistic view about this site.




IMHO, this flipped "wikicomponents" coin can go just one of two ways:

Head:

It will work, a bazzillion parts get contributed by thousands of
enthousiastic contributors who will produce an error free repo of parts
data.

And then some day someone will realize that the data contributed is a
goldmine and run away with the stuff (gold).



Tail:

Not enough contributors/contributions to gain any/enough leverage against
the bazzillion parts out there.


Bert, I think the efforts to make an open way to share projects is good,
and for footprints and symbols, the LP Wizard approach seems best to copy,
where they base everything on actual part shape plus differences from
various standards or manufacturer's footprint at the user's choice.

They never try to verify manufacturability. They (Mentor Graphics, vendor of LP Wizard)
still leave that to a company's SOP if they want to do that.  That's the
defacto standard -- no feedback publicly.  Any footprint shape feedback to get process control
is internal to one user and depends on the fab you use anyway.

I think contributed parts will always be suspect, and obsolete after a while,
and autogenerated has a chance of becoming an open tool.  Using the
pad shape algorithms to create pads from component shape will let you change the amount
of solder overlap consistently on a project, ( that gets made at one fab) and autogenerate
a library you could use to send to another fab with little effort.  There could be a snag
about putting standards publisher's data in the tool, but that could be worked around
by having the terms more nominal and less for solder amounts instead of the IPC names
most, nominal and least, and having the user do an initial setup to enter the differential
amounts coresponding to the IPC or EIA or IEC standards, (which they borrowed or purchased).

John


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