Platform forum

copper poor

ljo , 05-02-2017, 08:48 AM

i have recently designed a 4 layer pcb with a stm32f429 microcontroller. i m a newbie. i used kicad to do it. i sent the gerber files to seedstudio to make my pcb.
Today i receive a mail from them asking me if i don't forget the copper poor in layer 1 and 4. i didn't understand. that 's why i have a question:

is copper poor(power) mandatory in outer layers if i use inner layers for power?

here is my layout:
power vcc

mairomaster , 05-02-2017, 09:38 AM
You don't really need the pours if you have the internal PWR and GND planes.
ljo , 05-02-2017, 09:45 AM
ok thank you. That's what I thought.
By the way, i like this forum. Because it is very reactive and helpful! thank you! I learn a lot from it.
ljo , 05-03-2017, 01:14 AM

another answer from seedstudio:
"I recommend you to use copper pout in all layers. It will make your PCB more flat and stable"

What do you think?
mairomaster , 05-03-2017, 01:39 AM
I don't think it matters at all with small PCBs with symmetrical stackup. In theory you might get the board bent because of the thermal expansion during manufacturing. That normally happens if you have difference in the copper density between the two halves of the stackup. For example you have planes on layer 1 and 2 and you have tracks only on 3 and 4. However with you case it is symmetrical so it's OK. Also your board is very small, the problem is more common with big board, logically they can bend more easily. Apart from that, the problem in general has been much more often in the past than it's nowadays.

Sometimes the manufacturers recommends using fills so they don't need to etch off too much copper. Long etch times might be a problem with small details (thin tracks, fine differential pairs) than need a good control of the etch time to be produced accurately. I can't see this being a problem with your board as well.

You can either decide to go with their advice and be absolutely safe (takes some effort to create and maintain the fills) or just tell them that it is fine like that. If they can really have problem with such a simple board, they would be quite a bad manufacturer.
ljo , 05-03-2017, 01:24 PM
Thanks a lot for your answer!
Finaly Seedstudio told me that is ok for a prototype. So they will fabricate my board.
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