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I've been studying the Arduino Uno layout and noticed that there are about 40 vias that connect the GND polygons on the top and bottom. Here's a picture with the vias circled:
Is this a standard practice? I'm a hobbyist and a novice when it comes to PCB design, but I've never seen this before.. |
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It's called stitching. You want your copper pours (polygons) to be well connected. Any non-connected islands are referred to as "dead copper" and should be removed. Arduino example is a rather moderate one. On multilayer boards, you can have hundreds of stitching vias. |
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It ensures that the copper pour areas can't become unintentional radiators, which would be bad from an EMC point of view. |
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Yes, it is standard. A PCB usually has an even number of layers, so if you have a spare layer around, it never hurts to have another ground. I have also seen a ground layer for every 2-3 routing layers to help reduce crosstalk. Another thing I've done in the past with very high speed differential pairs is to have them sandwiched with a ground layer above and below to help reduce interference from any other clocks in the area. |
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