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I'm currently designing my first PCB, and having done some reading, I understand that the copper pour on the top layer should be grounded as it otherwise just creates a giant antenna.

What would be the best way to connect it to the ground plane on a 4 layer board? Is a simple via enough, or would that be too small (or would multiple vias be required)?

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They are called stitching vias and are used for what you want: -

enter image description here

To avoid EMC problems you may need to have many stitching vias but, without an idea of what your PCB does or what EMC specifications you wish to comply with, it's anyone's guess as to how dense the stitching vias need to be.

It might be as simple as doing something like this: -

enter image description here

I've added red boxes around what look to me like stitching vias. Here's another clearer example: -

enter image description here

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  • \$\begingroup\$ Thanks for the quick answer! The PCB is a data logger / radio transceiver. It's an MCU with 3 UART inputs (which connect to external sensor devices via connectors on the PCB) and a small radio transceiver chip which slots into a SIM card holder on the device (iqrf.org/products/transceivers/tr-72d). The radio transceiver has a built in PCB antenna, which sits above the top edge of the PCB so as to stop any additional interference from the PCB. Top layer looks like this: http://imgur.com/a/UBB4V \$\endgroup\$ – Andy Mills Jan 4 '17 at 14:35
  • \$\begingroup\$ @AndyMills just so you know, I'm not going to do an in-depth analysis of your design in order to determine whether stitching is needed here or there or not at all. Ask your self - how much does a via cost and if you used a hundred (or 500), will that kill your product's profit margin? \$\endgroup\$ – Andy aka Jan 4 '17 at 14:39
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    \$\begingroup\$ Apologies @andy-aka, was just trying to provide as much info as possible in case there was a standout way of doing things based on what I'm working on. Not trying to score a free PCB design consult ;) I appreciate the helpful answer you gave! \$\endgroup\$ – Andy Mills Jan 4 '17 at 14:48
  • \$\begingroup\$ No problems. I'm currently designing a module to go inside NI's cRIO system and I've opted for stitching vias every 5 to 10 mm. It's a 4 layer board and similar to the last picture in my answer (in that there is a daughter module sat on the main PCB). Upshot - try googling stuff that's similar to your product and see if there are pictures that give some clues. \$\endgroup\$ – Andy aka Jan 4 '17 at 14:56

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