Ken Palmateer said:When installing a motherboard in the case, should it be completely
isolated from any other part of the case? My brother told me that the
mounting holes with the steel rims are grounding points. I am a bit
unsure about this and am looking for informed opinions. Ken
When installing a motherboard in the case, should it be completely
isolated from any other part of the case? My brother told me that the
mounting holes with the steel rims are grounding points. I am a bit unsure
about this and am looking for informed opinions. Ken
Yes. It was a common misconception, that the soft washers often suppliedPhil DeBecker said:You should absolutely not isolate the motherboard from the rest of the
case. Doing so will result in excessive RF noise from the motherboard,
prevent it being grounded properly, and make it run hotter.
Yes, the mounting holes are grounding points. Motherboards are
composed of several layers, one or more of which is a copper layer
designed to connect to an earth ground and to dissipate heat. Providing
a
proper earth ground to the motherboard is important to minimize RF
interference. By mounting the motherboard to the case with metal
standoffs, you provide the motherboard with an earth ground, and the
metal standoffs conduct heat from the motherboard to the case.
This is why it is a good idea to use all of the motherboard mounting
holes
that your motherboard can accommodate.
In the days before the ATX standard, it was common to see motherboards
mounted with plastic or nylon standoffs, but even then, there was always
at least one metal standoff with a screw. Nowadays, most cases include
only metal standoffs. There is never any need to use pads or any kind
of
shield between the screws and standoffs and the motherboard. Just don't
over tighten the screws.
Phil D.
| On Mon, 14 Nov 2005 11:43:07 -0500, Ken Palmateer wrote:
|
| > When installing a motherboard in the case, should it be
completely
| > isolated from any other part of the case? My brother told me that
the
| > mounting holes with the steel rims are grounding points. I am a
bit unsure
| > about this and am looking for informed opinions. Ken
|
| You should absolutely not isolate the motherboard from the rest of
the
| case. Doing so will result in excessive RF noise from the
motherboard,
| prevent it being grounded properly, and make it run hotter.
|
| Yes, the mounting holes are grounding points. Motherboards are
| composed of several layers, one or more of which is a copper layer
| designed to connect to an earth ground and to dissipate heat.
Providing a
| proper earth ground to the motherboard is important to minimize RF
| interference. By mounting the motherboard to the case with metal
| standoffs, you provide the motherboard with an earth ground, and the
| metal standoffs conduct heat from the motherboard to the case.
| This is why it is a good idea to use all of the motherboard mounting
holes
| that your motherboard can accommodate.
|
| In the days before the ATX standard, it was common to see
motherboards
| mounted with plastic or nylon standoffs, but even then, there was
always
| at least one metal standoff with a screw. Nowadays, most cases
include
| only metal standoffs. There is never any need to use pads or any
kind of
| shield between the screws and standoffs and the motherboard. Just
don't
| over tighten the screws.
|
|
Your comments are well made Phil, but it would be my assessment
(having a bit of heat transfer in my background) that the thermal
conductivity between a metal standoff and a solder ring on a
fiberglass motherboard is very low or nominal at best. Assuming the
metallic copper ring about the mounting holes provides a
metal-to-metal contact (preferred for optimum thermal transfer
characteristics) with the metal standoff, one must consider that the
circuit board runner that connects that metal ring (around the hole)
to the mobo ground layer is most likely small in cross-section, and
thus, a poor thermal conduit. In addition, plated-through holes used
to connect surface copper rings about the mounting holes with internal
mobo ground layers are a very thin cross-sectional metallic circuit
connection and not suitable for thermal conductance. Finally, the
mobo itself is essentially a poor thermal conductor due to the
fiberglass or epoxy resin material design thereof. Even if the
metallic mobo layers could conduct heat away, the non-conductive
material of the mobo makes a decent thermal insulator and would tend
to prevent radiation of heat into the air from any internal ground
layer.
As to the OP's question, since RF signals are everywhere in high
frequency computer circuits, good grounding throughout tends to lessen
noise transmitted to adjacent circuits, so use all the grounding metal
standoffs you can with your systems.
And if the motherboard is grounded to the case, how is the case groundedRoger said:Yes. It was a common misconception, that the soft washers often supplied
with cases, were to provide insulation. In fact (if you think about it),
to insulate, you would need a washer both sides of the board, and a tube
round the threads as well. The washers were designed to fit under the
screw head only, to prevent the surface of the board being damaged when
the screw was tightened, and provide a little 'compliance', as the
case/board expanded/contracted.
There is one 'caveat' about grounding though. On some cases which have
large square metal pillars, these extend further from the mounting hole
than is 'normal'. There have been a number of such cases, where some
motherboards had signal tracks relatively close to the mounting hole, and
a signal short could result (one of the older Asus boards had this
problem). This is rare, but makes it well worth visually checking before
assembly, where the nearest tracks actually are...
Best Wishes
And if the motherboard is grounded to the case, how is the case groundedRoger said:Yes. It was a common misconception, that the soft washers often supplied
with cases, were to provide insulation. In fact (if you think about it),
to insulate, you would need a washer both sides of the board, and a tube
round the threads as well. The washers were designed to fit under the
screw head only, to prevent the surface of the board being damaged when
the screw was tightened, and provide a little 'compliance', as the
case/board expanded/contracted.
There is one 'caveat' about grounding though. On some cases which have
large square metal pillars, these extend further from the mounting hole
than is 'normal'. There have been a number of such cases, where some
motherboards had signal tracks relatively close to the mounting hole, and
a signal short could result (one of the older Asus boards had this
problem). This is rare, but makes it well worth visually checking before
assembly, where the nearest tracks actually are...
Best Wishes
And if the motherboard is grounded to the case, how is the case groundedRoger said:Yes. It was a common misconception, that the soft washers often supplied
with cases, were to provide insulation. In fact (if you think about it),
to insulate, you would need a washer both sides of the board, and a tube
round the threads as well. The washers were designed to fit under the
screw head only, to prevent the surface of the board being damaged when
the screw was tightened, and provide a little 'compliance', as the
case/board expanded/contracted.
There is one 'caveat' about grounding though. On some cases which have
large square metal pillars, these extend further from the mounting hole
than is 'normal'. There have been a number of such cases, where some
motherboards had signal tracks relatively close to the mounting hole, and
a signal short could result (one of the older Asus boards had this
problem). This is rare, but makes it well worth visually checking before
assembly, where the nearest tracks actually are...
Best Wishes
And if the motherboard is grounded to the case, how is the case groundedRoger said:Yes. It was a common misconception, that the soft washers often supplied
with cases, were to provide insulation. In fact (if you think about it),
to insulate, you would need a washer both sides of the board, and a tube
round the threads as well. The washers were designed to fit under the
screw head only, to prevent the surface of the board being damaged when
the screw was tightened, and provide a little 'compliance', as the
case/board expanded/contracted.
There is one 'caveat' about grounding though. On some cases which have
large square metal pillars, these extend further from the mounting hole
than is 'normal'. There have been a number of such cases, where some
motherboards had signal tracks relatively close to the mounting hole, and
a signal short could result (one of the older Asus boards had this
problem). This is rare, but makes it well worth visually checking before
assembly, where the nearest tracks actually are...
Best Wishes
And if the motherboard is grounded to the case, how is the case grounded
- through contact with the housing of the power supply, which is
presumably connected to the ground on the AC in? Just curious...
Derek
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.