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Why use ground fill on PCB?

colporteur

I'm looking for some insight into Ground Fill, extending the copper pour when manufacturing a PCB  to create a ground plane. I've just completed a PCB layout in Fritzing that uses an Arduino Mega. There is plenty of empty PCB real estate. I thought why not fill it.

I seem to recall doing some reading on Ground Fill. I have never used the technique before but have seen it used on PCB's. I found a number of benefits in my search but no downside. Methinks the PCB manufactures would want extra coins for this! I'm curious is there a use case where you would not use Ground Fill?

If Ground fill is used should it cover both sides of the PCB or limit it to one side?

I've used the Fritzing function and it appears to work. Looking for some experience to chime in.

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  • 0

    Aside from electrical reasons for ground planes, they can influence your PCB process in producing better quality cards, especially if you etch them yourself. When you have to etch a large area of copper to create a bare patch on a PCB it will etch slower than thin traces, so by the time the large area is clear of copper, the thin traces are over-etched. This is a reason to avoid large bare areas of PCB. Sometimes polygon fills are created using a hatched pattern to avoid large bare areas. If you fill everywhere with copper then you can save on etchant - it will take less acid to etch and it will get etched quicker - so all around cheaper, quicker and more eco-friendly.

    It sounds all good right, but there are of course numerous problems with fills that warrant a larger discussion, which is why I don't use them unless they are electrically necessary.

    Such as the extra design time needed, the fact that most CAD systems, even expensive CAD software, can't generate a perfect pour and can't flag all pour issues and often it is very difficult to edit a layout after a pour is done.

  • 0 in reply to dougw

    I can appreciate the ground fill on do-it-yourself PCBs. I haven't dabbled in that in 30 years but I do recall the scenario of over etching the traces and having to do repairs.

    I was wondering about about the PCB manufactures. They are laying down more copper on a ground fill board so I would assume the cost is more.

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  • 0 in reply to colporteur

    I don't know the process for modern PCB manufacturing, I assume they start with copper clad FR4, mask it and "grow" the copper layer wherever it is needed, including vias, then grow solder to be used as a mask for etching away copper that is not needed. PCBs with more than 2 layers are more complicated, I don't know if the middle layers have copper growing stages. The shops I use don't seem to charge differently depending on the amount of copper surface added or removed. They seem to only care about the total surface area of the PCB and the number of layers. Maybe it is different for high volume orders.