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PCB Layout Technique Question
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PCB Layout Technique Question

by Firebug24k on Sun Feb 10, 2013 3:00 pm

Hello,

I've got a quick question on PCB layout technique. Below are two different screenshots of how I can layout a particular component. One with the ground plane on the top, the other on the bottom. Generally speaking, is one preferred over the other? I feel like the way I laid out the blue one is better, but wanted to get the community's thoughts on this. Thanks!

EDIT: The "case" of the TPS2511 IC is grounded, and is supposed to use the PCB as a heatsink.
Attachments
layout.gif
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Firebug24k
 
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Re: PCB Layout Technique Question

by Zener on Sun Feb 10, 2013 5:11 pm

I prefer ground on top but the guy next to me likes ground on bottom. Oh well. I don't think it matters. In this case here I think you will get lower thermal resistance with the ground on top. Also, are you allowed to put a hole under the part? As far as the right hand view with the ground on top, are you sure about those thermal reliefs? I am not sure they are doing anything to help the solderability. Certainly they will increase the thermal resistance there. But my main question is about solderability in reflow. It is a good question and I don't know the answer, but hopefully someone does.
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Re: PCB Layout Technique Question

by Firebug24k on Mon Feb 11, 2013 2:15 pm

Good point on that thermal relief, I'll take it out. No reason for that on a hand soldered board, which this will be.

As for the hole under the component on the other version, I just want a via there - I think it should be fine, at least when doing it by hand it should be. Thanks for the feedback - I think the gound on the bottom one makes more "sense" to me in this application, as long as the via works out. Once all the Chinese board makers get back from the holiday I'll get something ordered. Thanks for your thoughts!
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Re: PCB Layout Technique Question

by Zener on Mon Feb 11, 2013 4:04 pm

You should use the footprint recommended by the Mfg. How will you hand solder the power pad underneath? I don't think that will work. If you are using thermal vias you will need more than 1.
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Re: PCB Layout Technique Question

by Firebug24k on Mon Feb 11, 2013 4:07 pm

Well, by hand I meant skillet/hot air. TI doesn't have a footprint for that package that I can download, I had to build it myself in Eagle.
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