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So after a very long effort, I think I've finally come towards the end of my PCB board design. It's a two layer board with no ground or VCC plains (Re-routing is not an option) as I can't go though the grief process again.

My question is should I use a copper pour? Currently I have three possibilities which I am contemplating.

  1. Do not use a copper pour
  2. Implement a copper pour connected to nothing (no signal)
  3. Implement a copper pour connected to ground
    A brief example is below.

    Unpoured PCB Unpoured PCB Board



Poured PCB with cross pattern Poured PCB with Cross style pattern

What are your thoughts and why?

Peter H
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3 Answers3

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For signal integrity reasons no pour is better than a pour that is floating. When you have a floating pour you are increasing the coupling capacitance between signals so you are increasing the chance of cross talk. In general the pour that is grounded will perform the best, but you should be aware of image current flow.

In general your pour should also be on both sides of the board and be part of the ground net.

also your pour needs to edited- the circled areas should be removed (as an example - there are many through out your board).

enter image description here

placeholder
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Copper pour has a couple of functions:

  1. Create power & ground planes. These can improve the performance of PCB containing high speed signals. I'm guessing that high speed signals are not a part of your design. Anywhere you're not going to be able to do this without considerable re-layout of your design, probably moving most of the components on the underside onto the top side.

  2. Improve etching. Firstly, having large pour areas (even if they are not connected to anything) reduces the amount of etchant that's used up in the etching process. This means you have to replace the etchant less often, and saves money.

  3. Improve etching again. If you're etching the board yourself, you may notice that the board doesn't etch evenly across its surface. Large areas with no copper are using up the etchant more than areas with lots of copper. This makes the etchant weaker in those areas. By adding hatched copper fill across the board means the copper density varies less, and so it etches more evenly.

So my advice would be:

  • If you're etching it yourself, then add copper pour connected to nothing.
  • If your having it etched by a company, then leave the board without a pour.
Rocketmagnet
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    +1. To add to the above, orphan islands / pours are best avoided, so if connecting the hatch to ground is an option, that would be the way to go. – Anindo Ghosh Mar 02 '13 at 12:35
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    I'll also add that some board houses don't like you making cross-hatched pours - they would prefer that it is solid. – W5VO Mar 02 '13 at 16:00
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Save the environment?

A bug bear of mine is all the DIY PCBs you still see being made/shared that do not have pours. Unpoured PCB above started out life as a solid copper sheet. It's then mostly etched away with all sorts of nasties. Probably in a place when the spent etchant is just dumped into a river with inadequate/no treatment/recovery. Or down the drain at home for those making PCBs themselves.

I can't show you any numbers to substantiate the degree of environmental damage that would be prevented with solid pours though. Modern EDA software makes it pretty simple to add them, so why not?

It just makes me feel better having pours :-)

Terminology doesn't help. It's not a "pour". It's the opposite of a "mass removal". Roll on additive manufacture.

Paul Uszak
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  • Lesson: spend the 1$/£/etc it costs to manufacture in a place that has some respect for environmental protection and, bonus saving, you don't have to ship it half way around the planet as well. – awjlogan Mar 03 '21 at 13:50
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    @awjlogan Is there such a place? It is more like "spend 100€" European PCB manufacturers are seriously outpriced. – Arcatus Mar 03 '21 at 14:30
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    @Arcatus - yes. No affliation on my side, Aisler is well priced, extremely responsive, and high quality for prototype boards. Not "rock bottom" cheap, but not expensive (maybe you have to skip a takeaway coffee). Again, no affliation, Eurocircuits were pretty reasonable for bigger runs. Depends if you're happy to just shift your pollution elsewhere for the sake of saving a few € and forget about it, I guess :) – awjlogan Mar 03 '21 at 14:45
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    @awjlogan Just read [this](https://aisler.net/help/getting-started/what-are-your-environmental-standards). Thanks. – Paul Uszak Mar 03 '21 at 15:54