Re: layout question

On 30 Oct 2006 11:10:13 -0800, the renowned "Michael"
<mkogan1@xxxxxxx> wrote:

Can anybody help me with this?
I lay out my schematics by myself. It was done by outside contractror
once - I had to redo it: few switchers on fairly densely populated
board, one needs to look at the schematic (and understand it) while
doing layout...
Question 1.
how do other EEs do it? Sensitive mix of analog and switching stuff...

I need to lay out another PCB and first thing I have to do is to create
footprints that are not in our library (some QFN packages, few
connectors)...
Question 2.
Has anybody heard of the service/source where we can order the
footprint from? Something that works like this: we send datasheets,
and/or footprints names, give CC number and get either library of 1,
2...10-20 parts..
I do not want to buy library of 10,000 parts and spend hours trying to
find my footprint there.
And it would be nice if I could use the footprints WITHOUT having to
check them (like Samtec QSH footprint I dealt with the other day)
Am I daydreaming?
Thank you for your help!

One time I had to do a PCB layout in a hurry using software I was not
very familiar with (and therefore had not created a library of my
favorite oddball parts), so I paid a layout guy to come up with a
couple of dozen footprints. It was sort-of worth it, and the job got
finished on time.

A lot of the work is just organizing all the information, actually
creating the footprints should go pretty quickly if you're reasonably
good at using the software. Every project typically involves creating
some new footprints and some new schematic symbols. Unless they're
multi-hundred pin chips, it shouldn't be such a big deal, particularly
when you're laying out a lot of the board by hand. It also depends a
bit on how fussy you are about creating schematic symbols- some people
like to see the functionality represented inside, which might take a
lot more time than just a rectangular block with properly labeled
pins.

Getting PCB layouts done by outside contractors can be tricky. Harry
Delamano posted a checklist of how he does it a year or two back,
Google groups should find it. I have also had the experience of having
to redo a lot of the work. Aside from mixed low level and high level
signals, also things like clearances for high voltages, isolation,
minimum trace widths on certain traces and so on.. it's all doable
with good people on both ends, but you do have to be careful.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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