RE: gEDA-user: Re: LED 100 != 5mm LED ?

["Ostheller, Joel A. " <JOEL.A.OSTHELLER@xxxxxxxx>]

> -----Original Message-----
> From: geda-user-bounces@xxxxxxxxxxxxxx [mailto:geda-user-
> bounces@xxxxxxxxxxxxxx] On Behalf Of Mark Rages
> Sent: Monday, February 12, 2007 5:29 PM
> To: gEDA user mailing list
> Subject: Re: gEDA-user: Re: LED 100 != 5mm LED ?
> 
> On 2/12/07, Kai-Martin Knaak <kmk@xxxxxxxxxxxxxxx> wrote:
> >
> > I trust only footprints I made myself and triple checked for
consistency
> > with the specs. Is this bizarre?
> >
> 
> It seems wasteful for all gEDA users to be doing this.
> 
> Wouldn't you find this bizarre: "I print only with fonts I made myself
> and triple checked for consistency."  If I said that, you might
> consider me a control freak with too much time on my hands.  For
> similar reasons, I think a board design application should come with a
> tested library of popular footprints.  Now, having been burned a
> couple times by broken footprints in pcb, I now check closely before
> sending the board off. I think we can agree that this is an
> undesirable situation.  (I also realize that footprint library
> maintenance is hard work, and I'm not volunteering.)
> 

Assuming you created a perfect footprint for your PCB application with
zero errors, does not equate to that same footprint being exactly
perfect for my application. Depending on board population techniques,
there could be a wide variance into what an acceptable pad excess should
be.  If I am soldering at home without a microscope, I may want 50-80
mils of excess pad to help facilitate soldering. If I have access to my
company's scopes, then 10-40 mills might be needed depending on the
pitch of the part. Pick and place and I may want no excess to help pack
parts. Bottom line, its tough to come up with a one size fits all
footprint IMHO.


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