Re: gEDA-user: OT: I hate footprints

[Dan McMahill <dan@xxxxxxxxxxxx>]

Philipp Klaus Krause wrote:
> It seems the only way to deal with them is to create each footprint from
> scratch eachtime I have to use one. Nearly eachtime I try to use an
> existing footprint things turn out wrong.
> There seems to be nearly no standardization in these things. Each chip
> manufacturer gives them a different name, pcb uses yet another one (if a
> footprint exits). Different manufacturers call different sizes by the
> same name. You never know how wide something calles SOP really is etc.
> So for my latest board I needed something called TSOP-28 in the
> datasheet. I found something by the same name in pcb. I carefully
> checked dimensions. They matched. I created a geda symbol. Today I got
> the chips and started soldering. Then I noticed something seemed wrong.
> The manufacturer had used a different pin numbering.
> 
> Why can't manufacturers just provide footprint and symbol in some
> standard format that all programs could import? I feel like I spend a
> large part of the time it takes to design a pcb drawing symbols,
> footprints, etc.


NIH.  Not Invented Here.

It is a big problem and a headache.  The problem is rampant.  I've been 
burned by footprints from a high dollar cad vendor that were simply 
unmanufacturable, footprints from a company internal library that used a 
generic name "TQFP-xx" without mentioning if it was the 0.4, 0.5, or 
0.65 mm pitch version, footprints where company A used a different 
pinout than company B, etc.

See this forum post which includes a list of something like 50-60 
variations of a sot-23 package.
http://www.pcblibraries.com/Forum/forum_posts.asp?TID=1719

In the end this is part of why I like "heavy" libraries for components 
that will go on a circuit board.  It is way too much work for me to 
re-associate a symbol with a footprint each time when there are so many 
similar but not quite right footprints to choose from.

I think its nuts that semiconductor vendors don't provide at least a 
pinout in an ascii format that you could use to generate a schematic 
symbol.  For these large pin count devices available these days, the 
pain is considerable.

-Dan


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