Author Topic: Layout question for DIY PCB  (Read 300 times)

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Online zimmTopic starter

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Layout question for DIY PCB
« on: Yesterday at 07:04:04 pm »
Hi,

I'm working on a PCB which has the traces on the bottom layer and the top layer is an almost uninterrupted ground plane:
2911906-0

My question is, is it ok to place the SMD resistors on the top-left side on the top layer surrounded by the ground pour? Would it be better to move them on the bottom layer and have a completely uninterrupted ground pour on the top layer?
The resistors are just for pull-up and voltage divider.

Thanks
 

Offline negativ3

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Re: Layout question for DIY PCB
« Reply #1 on: Yesterday at 07:54:51 pm »
There are many opportunities for more effective routing by reducing outer pad diameters and routing between in some instances.
You provide no circuit diagram or design intent which makes further comment tricky however with the current information, no bad things will happen as-is with your resistors.
 

Online zimmTopic starter

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Re: Layout question for DIY PCB
« Reply #2 on: Yesterday at 09:01:48 pm »
Thank you for confirming, the circuit is just an ESP32 dev board connected to 2 TMC2209 stepper drivers + filtering caps and various resistors (for pull-up and a voltage divider). I wasn't sure if it's mandatory, or at least strongly preferred, to have a ground copper pour for all components.

The reason I have those pad sizes and clearances is because I'll make the PCB with the toner transfer method then etch it with ferric chloride and it's my first time, so I prefer to have plenty of space between traces/vias/components. If I were to have it made at a commercial manufacturer, yes I know everything could be a lot smaller and more efficient. But I can't make through-plated vias or solder mask layers at home so I chose distances/clearances that hopefully I can manage with my not-so-great manufacturing and soldering skills.

 

Offline negativ3

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Re: Layout question for DIY PCB
« Reply #3 on: Yesterday at 09:15:36 pm »
Thank you for confirming, the circuit is just an ESP32 dev board connected to 2 TMC2209 stepper drivers + filtering caps and various resistors (for pull-up and a voltage divider). I wasn't sure if it's mandatory, or at least strongly preferred, to have a ground copper pour for all components.

The reason I have those pad sizes and clearances is because I'll make the PCB with the toner transfer method then etch it with ferric chloride and it's my first time, so I prefer to have plenty of space between traces/vias/components. If I were to have it made at a commercial manufacturer, yes I know everything could be a lot smaller and more efficient. But I can't make through-plated vias or solder mask layers at home so I chose distances/clearances that hopefully I can manage with my not-so-great manufacturing and soldering skills.

Post up pics of your completed project, I gave toner transfer a shot years ago but found the minute carbide drills difficult not to break! Good luck!
 

Online Doctorandus_P

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Re: Layout question for DIY PCB
« Reply #4 on: Today at 01:47:21 am »
... and the top layer is an almost uninterrupted ground plane:

Euhmm... no. That does not look like a GND plane at all. For a proper GND plane, the sections have to connect in between all the pads of the THT IC's. Looks like KiCad. (which does this by default for some weird reason). A relatively quick way to fix this in KiCad is to change the pads to "oval" and make them narrower. This still leaves enough room for hand soldering.

For the rest, it does not matter much whether this GND plane is on the top or on the bottom, nor does it matter much where you put your SMD footprints. Either top or bottom is fine (for DIY, for ordering assembled boards putting everything on top is easier). Putting SMT footprints on top also offers more mechanical protection.
 

Offline Nusa

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Re: Layout question for DIY PCB
« Reply #5 on: Today at 02:24:22 am »
However, for DIY etching, leaving any large sections of extra copper in place, both sides, is a reasonable practice. First, your etching solution is going to last longer because there's less copper to dissolve. And the process will be a bit faster, because your etching solution remains fresh longer with less copper to dissolve.

I haven't done it in ages. For small boards, it's pretty cheap to send them out these days. And if I need something tomorrow, I'll just do a one-off with a proto board.
 

Online Renate

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Re: Layout question for DIY PCB
« Reply #6 on: Today at 02:29:42 am »
I don't know whether it's your choice or not, but to label those two row modules the same numbers on both sides is crazy.

Since you're using modules that hover over your PCB you might as well take advantage of that.
Since you'll be hand soldering SMDs, why not give yourself some elbow room?
 

Offline PGPG

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Re: Layout question for DIY PCB
« Reply #7 on: Today at 10:06:13 am »
Would it be better to move them on the bottom layer and have a completely uninterrupted ground pour on the top layer?

It would be better to have completely uninterrupted GND but you don't have it if you move these resistors or not.
Much bigger holes in GND are made by rows of pads without GND going between them.

If you look at holes in GND plane it is not the area of hole that counts but the longest dimension. From EMC point of view the 1mm x 5 cm hole is bigger than 3x3cm hole.
 


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