Grounds are created through the ATX 24 pin connection. The is no need for grounding through the case, and in fact, while many THINK that the motherboard tray/case provides grounds through the standoffs, in reality the holes for the standoffs are intentionally shielded from the actual motherboard. If you look closely at any motherboard you will see that there are no leads or traces running to the area around the standoff holes, so no ground could be provided through those points anyhow.
The case itself, while grounded to the PSU through the PSU mounting screws, is simply a redundant feature and is not further redundant by the motherboard fasteners. In fact, in years past, they used to recommend and supply fiber washers that completely kept the screw from even touching the metal reinforced rings around the standoff holes.
Anybody who says standoffs are a required component to the grounding/earth of the system, doesn't understand how the system works, hasn't been building systems since back when they all came with fiber washers under the screws or took a very close look at the fact that the metal reinforcement around the standoff holes does not extend to including any other part of the motherboard than itself.
In point of fact, there was a time when MANY motherboards were mounted to the motherboard tray using push pin style plastic standoffs that popped through the motherboard standoff holes and rested on a plastic "lip" below the split section of the push pin.
If you are still in doubt, you can always cut away an old case and use the remaining back I/O panel and motherboard tray by themselves, IN the wood chassis, as seen here:
I am finishing up my Bartop Arcade and I have all my parts but I want to know the best way to install my motherboard. I've seen people just use some bolts with lots of nuts to raise the motherboard up. Can I do this without drilling completely through the wooden bottom? The wood is 3/4 inch...
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