How close can copper and holes be placed next to the edge?

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How close can copper and holes be placed next to the edge?

Postby Lawrence » Thu Feb 10, 2005 8:42 am

How close is a copper trace / pad permitted to be to the edge of the board? Also, how close can the edge of a drilled hole be?
Lawrence
 

Postby sparky » Thu Feb 10, 2005 2:43 pm

If you keep your clearance to 8mil you will be fine.

That's 8 mil between the keepout or border and any holes, pours, or traces.

-Nathan
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Postby Lawrence » Thu Feb 10, 2005 5:03 pm

Cool Thanks!
Lawrence
 

Postby BigRedBee » Thu Feb 17, 2005 12:05 pm

But what if I want copper etches all the way to the edge of the board, can I do that? FOr example, if I'm mounting a DB9 or RF connector where the pins straddle the board, I"d like the pads extending all the way to the edge.
BigRedBee
 

Postby sparky » Fri Feb 18, 2005 9:17 am

Hi,

I know what you mean. You can pour out to the edge, but you don't need to. An 8mil gap between the edge of the pad and the board won't make a difference with your connector - you should still have a 200mil pad connecting the physicals.

On a side note. Why should you avoid running things out to the edge of the board? Read on...

I had a 2 layer PCB where I had a power plane/pour on top, and a ground pour on bottom. It works pretty well if all you've got is two layers to work with. Anyways, this was two years ago before Gold Phoenix was milling the boards apart for us. I had to depanelize our designs with a big cutter. I lined up the board a smidge too close - just inside of the edge where I was supposed to be. I noticed it, but since I didn't nick any signal traces it didn't matter, right? Not until I assembled the board with a DB9 connector on the top side.

Because I had cut into the copper plane, there was a sliver of copper exposed from the end of the PCB - exposed from under the soldermask. You couldn't even see it! But when the power supply kept jumping up to an amp :shock:, I started looking around. Flexing the board it stopped... The metal housing (ground mind you) of the DB9 connector was shorting with the power plane sliver. Very hard to find, a little masking tape to fix. :) Now I make sure my pours are a good 10mils back from the edge.

-Nathan
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