Washers for motherboard screws?

[hdtv guy]

Do you need to put non-metallic (fiber or whatever) washers under the
screws that you attach the motherboard to the case with?
Is that necessary for preventing an electrical connection or
something?

 

[km]

Do you need to put non-metallic (fiber or whatever) washers under the
screws that you attach the motherboard to the case with?
Is that necessary for preventing an electrical connection or
something?

The argument for them is to make it more unlikely to short the
motherboard, but there is usually a ring of protection around the hole
to avoid this. I used to put the washers on, with great difficulty in
placing them and not have them fall off - often I resorted to putting
a touch of glue to hold them in place. Eventually I didn't bother and
have had no problems with some 60odd systems I have built.

km

 

[RobV]

Do you need to put non-metallic (fiber or whatever) washers under the
screws that you attach the motherboard to the case with?
Is that necessary for preventing an electrical connection or
something?

No washers. The motherboard holes for mounting to the case have a
solder ring around them so the screw will make electrical contact with
the motherboard and the metal standoffs underneath, providing multiple
grounding points to the case.

 

[johns]

Depends on the case metal. If you are using a
steel case, and the standoffs make contact with
the mobo ground, you can "push" the ground
potential up to 2 or 3 volts .... and really screw
up your performance with lots of blue screens.
Steel is resistive and makes a poor ground.

If the case is aluminum. The standoffs can help
ground the mobo, but after the aluminum corrodes
a bit, you get the same "push". Aluminum oxide
is resistive too.

But .. !!! .... modern power supplies have much
better ground connections at the mobo power
connector now. Generally, this single point ground
is the best conductor, and no current will flow on
the resistive ground connections at the standoffs.
So most techs ignore the problem now.

johns

 

[RobV]

Depends on the case metal. If you are using a
steel case, and the standoffs make contact with
the mobo ground, you can "push" the ground
potential up to 2 or 3 volts .... and really screw
up your performance with lots of blue screens.
Steel is resistive and makes a poor ground.
Nonsense.

If the case is aluminum. The standoffs can help
ground the mobo, but after the aluminum corrodes
a bit, you get the same "push". Aluminum oxide
is resistive too.

Nonsense.

Where do you operate your computer? In a kayak?

But .. !!! .... modern power supplies have much
better ground connections at the mobo power
connector now. Generally, this single point ground
is the best conductor, and no current will flow on
the resistive ground connections at the standoffs.
So most techs ignore the problem now.

johns

The solder rings on the motherboard where the standoffs are used are
connected to the internal ground plane layer of the MB. Having multiple
ground points to the case ensure there is no potential between PSU
ground, MB ground and/or chassis ground. It also helps reduce stray RF
emissions.

 

[jørgen]

The solder rings on the motherboard where the standoffs are used are
connected to the internal ground plane layer of the MB. Having multiple
ground points to the case ensure there is no potential between PSU
ground, MB ground and/or chassis ground. It also helps reduce stray RF
emissions.

It is also worth noting that all the other components you install (psu,
harddrives, pci cards, io shield etc) has a connection to the case. So
even if you use washers for the motherboard screws, you'll end up with
an electrical connection to the case

 

[johns]

All electronic devices must have "single-point"
grounds, or you will dereferece the psupply.
You can get the same effect by running a coax
cable from one building to another where each
building has its own "earth ground". And
you can wind up with 100s of amps flowing
from building to building over the coax ground
cable. I use to pull the ground cable connection
off and reference the cable to the higher dc
voltage to prevent that ... or just leave it
unconnected, and reference each circuit
to its own supply. Ask any radio engineer
.... oops .. that's right ... they don't teach that
any more ... do they

johns

 

[johns]

Sure, but try that in a cheap plastic case ...
run multiple ground connects instead of the
single point psupply ground at the mobo
connect, and you will learn a lot about
ground loops.

johns

 

[jørgen]

Sure, but try that in a cheap plastic case ...
run multiple ground connects instead of the
single point psupply ground at the mobo
connect, and you will learn a lot about
ground loops.

So depending on the case, you will isolate all the points where the
board and other components make contact? Unless you do that, those
washers really don't do anything when talking about isolating the board
from the case

 

[RobV]

Sure, but try that in a cheap plastic case ...
run multiple ground connects instead of the
single point psupply ground at the mobo
connect, and you will learn a lot about
ground loops.

johns

You're talking about steel and aluminum cases in your post, not plastic
(how many people use a plastic case for a computer)? We're (TINW) not
talking about stringing a coax cable between two buildings (something
I'm sure most of us [TINU] would just love to do).

I repeat: your comments about steel and aluminum computer cases are
plain nonsense. Stick to the subject.

 

[ProfGene]

Do you need to put non-metallic (fiber or whatever) washers under the
screws that you attach the motherboard to the case with?
Is that necessary for preventing an electrical connection or
something?

On older motherboards small cardboard washers were used to protect the
board but the newer ones seem to have a built in insulation so washers
are no longer used.