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I would guess so, but I want to make sure.

Edit: After measuring with a multimeter, I suspect that brackets (of most graphics cards) are grounded to the graphics card's ground-plane.

I measured 0 ohm between the traces around the motherboard screw holes and the bracket of a (old) 75W graphics card. (All power from the PCIe x16 slot. No power cable needed. So, graphics card's ground-plane == motherboard's ground-plane.) The motherboard was outside the case, on a wooden table.

On some newer graphics card, a screw (which fastens the bracket to the board) is clearly visible on the back side, suggesting direct contact between the bracket and the graphics card's ground. (This construction also counteracts sagging. A little bit.)

enter image description here

JRE
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    Of course. When you plugged that cars into M/B and screwed it gets connected to the earth. So it should be grounded. – Rohat Kılıç Jan 07 '17 at 11:34
  • @RohatKılıç Yes, then the bracket is grounded, thru the ATX case, to earth. But is the bracket itself (out of the box, before installing) electronically connected to the GND pins of the power-jack on that same graphics card? –  Jan 07 '17 at 11:35
  • Usually the holes that the bracket screws into the card through are plated and connect to ground, much like the holes on a motherboard. – Tom Carpenter Jan 07 '17 at 11:41
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    Measure it with a meter. – Andy aka Jan 07 '17 at 11:51
  • The screws for the DVI connector is what grounds the bracket when unconnected. – winny Jan 07 '17 at 12:09
  • Perhaps it is possible to find one with just DP/HDMI where the bracket is just screwed to the PCB but for EMI and class I product reasons, it's probably an exposed grounded copper area where the bracket in screwed in. What Andy said, measure it. – winny Jan 07 '17 at 16:53

2 Answers2

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The bracket is certainly grounded to the case by mechanical contact when installed.

However, it is up to the card designer as to whether the bracket is directly bonded to the card's power supply ground. I would actually expect that there would be some isolation via some combination of resistor/capacitor/diode in order to avoid creating ground loops through the motherboard. But this would still provide some degree of protection from ESD if you handle the card by its bracket when not installed.

Dave Tweed
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  • If the bracket/faceplate isn't bonded to the graphics card's GND, then touching the bracket won't equalize the charges. So, there could be a potential difference between the graphics card and the motherboard. –  Jan 08 '17 at 18:04
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    All I'm saying is that there will generally be a connection, but not necessarily a direct metallic connection. A connection through a resistor or an inductor still eliminates potential differences (static charges) while limiting the current when needed. – Dave Tweed Jan 09 '17 at 01:02
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In theory, the faceplate of an electronic device with "hot pluggable" cables should not be connected to signal ground directly. The idea behind is that the path of current from any ElectroStatic Discharge (ESD) will go into metal housing (which is normally connected via metal chassis to Earth ground) first, and will not cross board signals. Even if the board ground is made of flooded copper layer and has low impedance, kV-level voltages from ESD can create substantial voltage "bouncing" across the signal ground, exposing signals between internal chips to dangerous overvoltage.

Ale..chenski
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  • Interesting, because i thought that the shield of, for example, an USB-jack (also hot-pluggable) should be connected directly to the GND of that jack. That GND ís the ground of the motherboard. –  Jan 08 '17 at 18:33
  • @Marty, here is an answer about how to connect USB shield, http://electronics.stackexchange.com/questions/269244/structure-of-a-usb-2-0-connector/269313#269313 – Ale..chenski Jan 08 '17 at 19:03