Joe,

If you are really stuck, I am one of many electronic engineers who
designs circuit boards and that can help you as an outsource consultant.

You didn't state what tool you are using, or what part you need a
footprint for.  That could be a great help.  Many manufacturers today
have recommended land patterns in their data sheets, application notes,
or package drawings.  If you cannot find what you want there, you might
purchase a copy of the IPC 7351 calculator at
http://www.pcblibraries.com/IPC-7351/

There are a lot of other issues besides finding a great footprint
library that might hamstring your project, like via sizing, plane
layering, design rule checking.  If you are ever only going to build a
board once, you might go with an outside consultant, but if you will be
doing many boards, there are *many *great websites & books on the subject.

Also, if you have a preferred fab manufacturer and assembler, you should
ask them for their design guidelines.  That will give you many details
such as process capabilities, which include minimum spacings, etc...
You can request one here http://www.sbcinc.com/DsGuide/Guide_Req.htm

Try these websites for general guidelines.
http://www.advancedmsinc.com/guidelines.htm
http://www.pcbstandards.com/

Regards-
Michael Howell
*Howell Electronic Services <http://home.earthlink.net/%7Emhowell777> *
541-601-0887 cell


Joseph Matthews wrote:

>Greetings,
>
>As a hardware engineer I have been tasked with laying out my first real circuitboard in years (first *real* board I guess).  It's proved a bear.  With years of experience designing hardware I am totally unprepared for the leap from the "logical" into the "physical" at this stage in my career.  No less, I am under a crunch (as we all are, right?) and this being a fairly simple board, I figured it's time I dove in and learned...Simply stated, I'm stumped.  Where can I find a comprehensive, clearly defined explaination on how to create *quality* PCB footprints and/or what the terms are used by the Footprint calculator made by PCB Libraries.  I see all of these fields to enter information but I'm not sure what these mean and how to translate what's on the datasheet to these fields.
>
>I have read through a few of the IPC standards (some of the 122x stuff) and still can't say I undertsand much more of what's required.  Is there a more comprehensive standard or something that more clearly deliniates, "do this...don't do this"...or, "if the pad is this big on the datasheet, add n%".  These standards seem fairly high-level and at times seem almost circular.  No less, they are not totally specific and I'm not sure where I can get the very specific information.  I of course am aware that there's probably more to it than simply adding a bit here or a bit there, but assuming I know nothing, can someone offer some straight-forward advice on how to build up a board.  Nothing fancy, just the basics.  I should be smart enough to take it from there.
>
>I hate to inundate people with how-to's but everything I've read, including a book on the fundamentals of PCB layout seems very high-level and seem almost afraid to say anything for certain.
>
>Thanks for your help.
>
>Joe
>

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