Sorry, I forgot...


Ref my last mail.

For this reason, the clearance via to via and via to throughhole pad
should be set so large, that the openings in the ground plane do not
overlap.
Of course, if they just barely touch, you will get manufacturing
problems so there should be a resonably wide strip of copper between
the vias
This will prevent multiple vis to overlap in the groundplane and thereby
create long slots in the plane which in turn may give you EMI problems.
-as mentioned in my last mail.

I'm aware of a specific design where the first run of the board had
overlapping vias and the second run had not.
The first run failed the  EMI test with over 10dB while the
second run passed the test.
-Of course you can't just transfer this figure to any design but it's
worth noting that it indeed has an impact!

Regards

Per Viklund





Patrick Jabbaz wrote:
>
> I was also wondering what effect do holes have in the ground plane,
> I know that slots are a big problem, but circular holes (such as pad or vias
> clearances) I'm not so sure.
> Could someone clear this up for me.
> Thanks
>
> Patrick Jabbaz
> Halliburton Energy Services
> Circuit Board Designer
> (281) 596-6697
> [log in to unmask]
>

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