One comment: others have well detailed the issues around top and bottom SMT 
pads. Unmentioned was the fact that a pad can live on any layer, including 
non-copper layers.

This can be useful; I've used it to get pads of a component out of the way 
when I was using single-pad "components" to imitate the pins of an FPGA so 
that I could quickly swap them in PCB; that the pads still existed made it 
easy to snap the pseudopads into place so that routing accurately 
terminated on pad center once the original pads were restored to the 
correct (final) layer.

I also have made assembly drawings by taking a photoplot of all the pads on 
each side of the board, reimporting it, and moving all the imported pads 
from each side to a mech layer, together with silkscreen for that side. (I 
used a scratch PCB for the import, then copy and paste once everything was 
on the right layer).

But one should be careful about such uses, as with any use that is outside 
the common envelope; there can be bugs.

For example, don't put holes into surface pads *as part of the pad.* Protel 
does not properly handle this, as I recall. Normally, we would not put 
holes in surface pads at all, for reasons which have been given, and if we 
want to put a hole into such a pad, we would do it with a via, which is 
just fine as far as Protel is concerned.

[EMAIL PROTECTED]
Abdulrahman Lomax
Easthampton, Massachusetts USA

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* To post a message: mailto:[EMAIL PROTECTED]
*
* To leave this list visit:
* http://www.techservinc.com/protelusers/leave.html
*
* Contact the list manager:
* mailto:[EMAIL PROTECTED]
*
* Forum Guidelines Rules:
* http://www.techservinc.com/protelusers/forumrules.html
*
* Browse or Search previous postings:
* http://www.mail-archive.com/proteledaforum@techservinc.com
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Reply via email to