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I have been reading alot of questions on this site to clear my understanding on Chassis, Signal Ground, Metal Chassis and Panel.

I have been following the advice given in the selected answer over this link (If I understood it well).

I am working on four layer PCB (Square Shaped 15 X 15 cm). In the first version of the PCB (which is working in my Lab), I had four mounting holes . Three of mounting holes were connected to Signal Ground. The fourth one is connected to CHASSIS Ground copper on the periphery of the PCB (on the bottom layer of my four layer PCB) (See picture below). This Chassis Ground connects the SHIELD of every connector I have in my PCB (USB, Ethernet, SD Card and SIM card).

enter image description here

I was planning to have a metallic enclosure or a metallic sheet (see picture below) for a plastic enclosure. The Metallic enclosure or metallic sheet will connect the SIGNAL Ground and `Chassis Ground together with the help of mounting screws.

enter image description here

I am not sure if I understood the concept well. I am going for another iteration of the design to add more components. I am hoping to rectify the issues with chassis and signal ground if any. Below is the explanation of the terms as understood by me. Please help me with identifying issues with my PCB or understanding of the answer given in this link.

  1. Chassis: It could be a metallic enclosure, metallic sheet (like picture that I have attached in this question), plastic enclosure with inside metallic coating or like the image shown below:

enter image description here

  1. Chassis Ground Layer/Net/Plane on the PCB: It connects every SHIELD of the connectors on PCB. There are some connectors like Ethernet RJ45 Connector which has EMI Fingers on it. Those connectors can be in touch directly with the metallic part of the Chassis and don't need a PCB net (Like I have in my layout posted above).

  2. SHIELD: These are the pins of the I/O Connectors (like USB) which are connected to the SHIELD of the wires (like Woven copper shield of coaxial cable).

EDIT

I have added some comments in my Layout picture:

enter image description here

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