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arefeidi
Joined: 06 Sep 2007
Posts: 65
Helped: 2
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 13 May 2008 12:43 Ground planes on two layer PCB |
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I'm doing the layout for a UHF-circuit (~1GHz) on a two-layer pcb. The bottom layer will be used as ground plane, though I'm not sure what to do with the unused areas on the top layer.
a) Should I remove all the copper and leave the areas blank
b) Or should I use them as additional ground, connecting them to the bottom layer with vias?
If the answer is b, how much vias should I use to connect the additional ground areas to the main ground plane – is one via enough per ground area on the top layer, or should I use several vias to connect each ground area?
Thanks alot,
arefeidi
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cyberrat
Joined: 19 Jun 2001
Posts: 884
Helped: 31
Location: In the sewers of the U.K.
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| 15 May 2008 10:45 Ground planes on two layer PCB |
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Go for option B, put a many vias - whatever suits. vias in remote corners etc.
Around the outside edges if you have groundplane both sides put a via in every 10mm or so.
For good manufacturing it is not good to have the copper directly attached to SMT components unless necessary as it alters the cooling of the pads during soldering (use thermal relief & keep copper balanced).
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arefeidi
Joined: 06 Sep 2007
Posts: 65
Helped: 2
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| 15 May 2008 17:23 Re: Ground planes on two layer PCB |
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Thanks alot for your helpful reply, I'll go for additional ground areas on the top layer then.
Let's hope the whole thing will work - my first UHF-layout 
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whiplash
Joined: 22 Jun 2006
Posts: 18
Helped: 2
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| 15 May 2008 17:34 Ground planes on two layer PCB |
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| bit late, but I definitely recommend pouring copper on the top side also. Scatter your vias on a grid where you can. (say a grid of 100 mils or so).
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arefeidi
Joined: 06 Sep 2007
Posts: 65
Helped: 2
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| 15 May 2008 19:51 Ground planes on two layer PCB |
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ok, thanks alot.
As it looks, I'll have to solder my vias "by hand", so I'll probably go to a larger grid of 150 or 200 mil then.
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gabarda
Joined: 16 Feb 2006
Posts: 10
Helped: 1
Location: Philippines
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| 17 May 2008 12:16 Ground planes on two layer PCB |
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| i go for B, since using that copper plane as ground reference and shielding for your critical traces
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