ground plane

Thread Starter

Dadu@

Joined Feb 4, 2022
136
I'm looking some opinions on why designers use PCB grounding plane when designing PCBs. What are the disadvantages of not using a grounding plane ?
 

Papabravo

Joined Feb 24, 2006
18,793
A short path to a ground plane has lower inductance.
Not having to run power and ground traces on signal layers increase the chances for a successful layout.
 

ronsimpson

Joined Oct 7, 2019
2,161
Good engineering practice, which reduces several types of noise.

Making a PCB is not an additive process. They do not add copper! They eat away copper with strong chemicals. The more copper you can leave on the PCB the less chemicals to pollute.
 

nsaspook

Joined Aug 27, 2009
9,987

Listen closely to this part of the video. It might change the way you think of and design circuit boards. My usual mantra, thinking about the fields in electronic design is important but it's critical in PCB design.
 
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crutschow

Joined Mar 14, 2008
30,102
Noise on the ground line due to ground currents can be a problem in many circuits.
This noise is the difference in the ground voltage between different parts of the circuit due to signals flowing through the ground impedance, both resistive and inductive,
A ground plane minimizes the ground impedance, and thus the ground noise.
Designers sometimes use a plane for the circuit power rail(s) for the same reason.

A ground plane may not always be needed, depending upon the circuit sensitivity to noise and the circuit frequencies involved, but you don't want to find that out after you've designed and built the board.
 

Thread Starter

Dadu@

Joined Feb 4, 2022
136
When I look at the any PCB layout I don't understand which terminal of the component is connected to the ground plane

For example Image from link https://pcbdesignworld.com/article/pcb-grounding-techniques-that-every-designer-should-know

1653744436855.png


Is that one terminal of the P3 block is connecting to the terminal of the other component while the other terminal is connecting to ground?

Is that two terminal of the R2 is connecting to the terminal of the Q1 component while the other terminal is connecting to ground?

I guess that the large amount of blue color visible in the PCB is the ground.

How do you know which one is connected to ground and which is connecting to the other component's terminal
 

ronsimpson

Joined Oct 7, 2019
2,161
All the CAD programs I use have a function which lights up all pins connected to a node by name. I can ask for all grounds to be highlighted.
The resolution is low so I cannot see the therminals or where C3 connects.

I used "paint" to change all connected blue to red and it might be better for viewing.
1653746927503.png
 
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nsaspook

Joined Aug 27, 2009
9,987
With a decent CAD program you can easily zoom into the board detail (signals, power, ground), and 3D visualize it before PCB board production.
PXL_20220528_141229824.MP.jpg
PXL_20220528_141325535.jpgPXL_20220528_141634693.jpg
 

ronsimpson

Joined Oct 7, 2019
2,161
If you set the "thermal connection line width" to much larger it will be easy to see. In post #8, see how thin the lines are (bottom left corner).
I solder in a way where thermals are not helpful. I do not use them. I understand hand soldering is harder without.
 

nsaspook

Joined Aug 27, 2009
9,987
@nsaspook i liked your second image

There are many tools available, Which CAD tool do you use for PCB design

@ronsimpson Thank you for nice advice
Fusion360/Eaglecad but most programs are capable of good results with experience on the design platform.
PXL_20220528_135818457.MP.jpg
PXL_20220528_162827833.jpg

3-phase motor drive system with MODBUS and other interfaces. Proper grounds/ground planes and signal integrity factors (device placement, routing, 4 layers) are important on a board with mixed digital, analog and power interfaces.

Eagle is still 'free' for limited 2 layer designs.
https://www.autodesk.com/products/eagle/free-download
 
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sparky 1

Joined Nov 3, 2018
718
A ground plane can remove heat and at the same time can reduce signal interference on nearby circuit components.
When signal strength is much higher than necessary, consider a simple filter to both attenuate and remove harmonics.
It may be useful to draw out the results after probing. This type of drawing involves the board micro field diagrams are directional like the probe orientation with regard to the flat ground plane.
Rather than putting priority on manipulating trace let placement of components reduce issues with parasitic inductance then improve routing where necessary. When you isolate the location of the problems keep your focus on that specific location then zoom out to see where your modification takes you. Often it is only a small change that corrects an issue. It is always preferred to solve issues before all the parts soldered in place but desoldering and rework is common.
 
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MrSalts

Joined Apr 2, 2020
1,832
I don't understand what you are indicating. you made the arrow and you wrote yes and no so I don't know what you are indicating
Your through-hole copper pads are the purplish color that you can barely at the perimeter of each pad.
Your through-hole "solder mask layer" is grey (majority of the pad seen). Solder mask covers the whole side of the PCB EXCEPT where solder mask is shown.

So, anywhere that the blue ground plane touches that purplish edge of a pad means the pad is connected to the ground plane. This is where I have the word "yes".

Your software creates "thermal spokes" when the "copper pour" is used to create the ground plane on the round pads. For some reason, pad P2 is connected to the ground plane with one thin copper trace (lower right corner of the pad) but there are no thermal spokes on this pad.

Pads that are only connected to a single trace (like the one labelled "no" above) and that trace does not connect to ground plane are not connected to ground plane. That is, the pad is surrounded by black space.
 
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