DUMB motherboard grounding question

[J3anyus]

I figure this is valid for this forum since things generally ground to your case...anyway.

In this thread, UnixFreak said:



<< Make sure the motherboard has at the least, 3 points at which it grounds at the chassis. >>



I've never actually built a box from the ground up before, but will be doing so over the next few weeks. From what I understood before, to mount a motherboard, all you do is put in the correct standoffs, place the motherboard correctly over the standoffs, and screw it in. From what UnixFreak is saying, it sounds like I'll also need to ground my motherboard to my chassis. I'll be using an EPoX 8K7A+ and a Chenbro Junior...so how would I go about grounding my motherboard? I always thought that the ground for the motherboard was supplied on the ground wires coming from the power supply, and that grounding your motherboard to your chassis was a bad thing that would cause all kinds of weird problems. I dunno, any help from anyone would be good...thanks.

J3

 

[dcdomain]

Hmmm, I don't know but I have a similar question... well maybe not similar, but along the same lines...
One of my friends got his mobo and case, but there are no spacers/washers. You need them right so the mobo doesn't touch the case? Are these special washers/spacers or anything or can I just grab some stuff from Home Depot? Plastic/metal?

My other friend is trying to build a computer using mineral oil as his coolant. He's building the case now out of plexiglass, he's going to then seal it, pour in mineral oil and have the entire mobo and all the pci/agp cards submerged. How should he ground the mobo in this situation?

Sorry for intruding on your thread...

 

[L00PY]

Using brass standoffs and metal screws does the grounding. Plastic spacers between the standoffs and the bottom of the mobo can prevent shorts depending on the design.

Honestly, you probably don't need to worry about it. I'd bet 95% of the people here don't assemble everything on an ESD workstation with wrist starps or on even ESD pads. I'm not saying that you'll be okay dragging your feet on shag carpet for 5 minutes right before assembly, but use your common sense and double check your work and you'll be fine.

You can (and probably should) buy spacers from a computer supply store. You want to use them in 99% of the cases out there. Shorting out your mobo is a bad thing.

As for your oily friend, if he doesn't already have this sort of thing thought out, he's likely to make some other silly mistake making the grounding or lack there of a moot point.

 

[boyRacer]

I thought the standoffs did the grounding...?... that's why the motherboard has those grounded holes. I foolishly added more standoffs when I first built my computer thinking that it would help "support" the motherboard...LOL... drove me nuts trying to figure out what the hell was wrong.

 

[XXWoodmanXX]

Come on, guys.

In 99% of cases, the stand-offs DO ground the computer.

Think about it. PSU ground-wire lead attaches to PSU casing. PSU casing is attached to 'puter casing. And, finally, mobo tray is attached to 'puter case. Hence, it is all grounded.

So, if you want to easily attach your ground-plane of your mobo to ground, you can simply take a >18 awg (put 'ring'clamps on it for screwdown capability) and attach it from the mobo(between the stand-off and mobo) to the chassis, OR to the PSU chassis. Either way will work.

WARNING: Be sure that no "thru-hole" solder-points are near the ground wire.

 

[XXWoodmanXX]

Oh yeah. Don't forget....... the mobo is ALSO grounded to the PSU/case via the 20-pin mobo connector.

 

[Jhhnn]

Motherboards get all the grounds they need thru the 20 pin connector, the whole computer can operate just fine with all the parts sitting on a formica table top. Mounting the components to a grounded metal case just serves as a redundant ground & safety, also helps reduce EMI going into and out of the computer.

Some kind of standoffs are necessary to prevent the wrong parts of the board from grounding against the case. It's fine to have the screws ground one in the small areas around the mount holes, that's a design consideration. Some cases use small stamped metal gizmos or plastic push pins, others use screw in brass standoffs, some have appropriate spacers stamped into the backplane.... lots of different ways to create an air space behind the board.