why do cases burn out mobos?

I'm a bit concerned with the system I am currently building... The case makes me nervous. You know how cheap cases usually have those bumps jutting upward on which the mobo is supposed to be mounted? I'm afraid of shorting out a K7S5A. My friend did the exact same thing about a week ago (on a different case, but the similarities made me nervous enough to ask a question or two). What happens when a motherboard gets burned out because of the case? Does it happen because of some sort of contact between the mounting plate and the soldering on the bottom of the motherboard? Does it happen when the little paper washers are not under the screws that mount the mobo? What has to happen in order for a mobo to burn out?

Thanks in advance for the help guys.

-Wesley

MoonWolf said:

Does it happen because of some sort of contact between the mounting plate and the soldering on the bottom of the motherboard? Does it happen when the little paper washers are not under the screws that mount the mobo? What has to happen in order for a mobo to burn out?

Click to expand...

Most of the time I think its because one of the standoffs is just contacting a circuit path. I have taken to insulating it with the paper washers lately to be on the safe side. I have had the problem happen a couple of times, but have never actually destroyed a motherboard. They always seem to work ok when i take them out of the case to test.

Al

If the mobo has solder pads on both sides, then just but a piece of tape over the "bumps" instead of the small paper washers. But if the mobo only has the pad on the underside you should leave a little metal exposed to ensure good grounding. It isn't critical about the grounding, some cases have plastic standoffs, but it can probably help in some cases..

Is tape tough enough to not be pierced by mechanical pressure? I think I'd rather use washers made of fiber, mylar, or nylon.

It does depend on the tape, i forgot to mention it, sorry. Your regular "magic" tape or similar is too thin, but I always has some fiber reinforced, thick tape around that should be just as good as paper/fiber washers.

You can also use regular, small diameter #6 washers - as long as they don't extend out & touch the board traces.

I usually just go with the fiber washers though. They come with the case and might as well put them to good use, plus they're pretty much designed with this kind of problem in mind.

what do you mean burn up a motherboard? most of the time its just your bios that gets burned out and replacing it saves you some big bucks. Ive made cases out of all wood and I made a case out of a granade box (metal) and have never had a mobo go out on me. As for grounding you dont have to worry about that because you mobo is grounded by the black wire in your powersupply and that is grounded by a white wire going to your house

Well as long as you don't screw the mother board down with out spacers you should be ok.I was amazed I knew a kid who did this and it worked for 7days before that killed it.

The problem's not with the fact that the mobo is grounded, the problem is that the bumps that replace the old brass standoffs are too wide. This lets them contact with traces and components away from the holes that aren't meant to be grounded. I had an Abit that had a tiny cap next to the mounting hole in the top left corner, backside, that would do just that.

And while on the subject, while the psu does in fact ground your mobo through the black wires in the power connector, grounding at each mounting bolt is recommended. Considering the power losses through the conectors and components on the motherboard, it only makes sence to give them a much shorter path to the ground plane to lessen some of the resistence in your motherboards power.
Case makers that include the plastic standoffs obviously care little about the power handling that their "bugetizing" is sacrificing. That's irresponsible to the community they are serving, in my opinion.

To keep it from pressing through the electric tape you use to keep it from being a problem, you can add a layer of good old duct tape. The screw itself will still provide a ground if your board has the grounding lugs on the top of the mounting holes.

ARE you using the stand offs?

Usually if I MOBO shorts out the PS is good enough to realize this and kills the power to the mobo.

Rob

Here is what the setup looks like now. Tell me what you think.

The washer needs to be on the other side.

Ok... so the Screw is supposed to come in contact with the motherboard and the case? Is it ok that I have the bumps taped over then?

Since the bump is the spacer you don't need the tape just have the washer in between it and the mother board.The screw can make contact with the mother board.There should be a gray or bown circle around the hole for the screw.

Silver... looks important.

What happens when the little silver ring does not contact the case, and become grounded?

Could any of this have any effect on your +3.3 rail?

Hope these pics help.Should give you a better idea of what to do.




I hate my camera.I would give you clearer pics but this cam sucks when you take close pics.

Like this then?

What about the electrical tape? Can I keep it there or must I take it off?

BTW: How did you put the pictures in your reply like that?

I don' t see any point in using the tape.O and to put a image in click the IMG icon before posting and the put the link in were the image is being hosted.

The tape will wear through after a while. Just do like your latest pic with the fiber washers between the mobo & mounting.

Screw - Mobo - Fiber washer - raised mounting tab

Thanks