I just replaced two mobos at work, and just noticed that both of them are bent quite a bit when the processor heatsink assembly is fixed. The boards are a Foxconn G31 and an MSI 945 chipset one. Both processors are Pentium D's with the stock cooler.
Is the flexing of the PCB normal or will it eventually break the copper tracks on the board or something?
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do you have all stand-off's installed for the motherboard.
theintel stock cooler is not very heavy compared to good aftermarket coolers.
it should not be heavy enough to bend your board and it is not good for the board
It's not the weight that bends it, it's the cooler's four pins that pull the board up around the processor. Or if you look at it another way, the cooler pushes the CPU down a few millimeters. I checked for adjustments or anything, but found nothing :S
I glue a strip of plastic, standing on it's edge, to the case or motherboard tray to support the mobo in that area. The strip is about 2" long, 1/8" thick, and as wide as the standoffs are tall. Since it's only 1/8" thick, the strip won't insulate or block cooling to the backside of the board. No more bent motherboards.
Of course this won't work, as described, if you have an opening in the case or tray to allow cooling for the backside of the CPU socket.
Motherboard bending usually happens when system builders don't install special lifters under the motherboard when they're building the system up. Most PC cases come with screws and lifters that allow people to raise the motherboard up and secure the CPU cooler on it without bending.
ive noticed that myself on some builds, its almost as if the push pins are 1mm too short or something so they start bending upwards to make up for the lack of space...
i however dont believe its too good for the mobo considering they were built straight, and not bent
I've observed the same thing before. Almost thought I screwed the mobo into the stand-offs wrong. But, yes, it's the crappy Intel stock heat sink that comes with the CPU that cause this.
It's the worst HSF securing mechanism ever! You push the 4 plastic pins on the corner down to secure the heat sink. It's either too loose, i.e. not touching the CPU right. Or too tight, i.e. bending the mobo around the area of the CPU. This occurs even if you follow their "diagonal pin push down procedure".
I think part of the reason is because the stock heat sink comes with a square of thermal tape on the bottom (approx. 1mm thick), which is what you "suppose" to use. But often we clean that out and put better thermal compounds instead, hence creating a slight difference in contact distance.
That stock heat sink belongs to the trash, IMO. No kidding! Its circular and rough contact surface is no good either.
Anyway, mobos do function even if it's bend like that. But of course, this could reduce the "longevity" of the mobo, and may cause problems later on. It contains multi-layer and sensitive electronic components, not meant to be physically stressed in such way.
This is caused by mounting the heat sink fan assembly before mounting the board in the case.
Always secure the mother board properly using all standoffs and screw securely, then drop processor in socket, apply thermal paste and then lock the heat sink into place.
To the last two posters, please don't assume everyone's stupid. I always mount mobo onto the standoffs in the case / tray first, then install the heat sink. But even that, the bending of the mobo was still observed.
The fact that Intel admitted that bending does occur in the 478 socket stock HSF, meaning the LGA 775 stock HSF is highly probable of doing the same thing. Like I said before (couple posts up), the design of the securing mechanism of the 775 stock HSF is inferior. This plus the habit of most savvy PC builders to replace the no good thermal tape with better quality thermal compound, can cause the mobo to bend after the HSF is installed.
I for sure, if building a PC for myself, will toss that no good stock HSF into the trash bin. Rather instead purchase a quality 3rd party HSF, and it will be well worth the money.
One failure mode is that this localized bending stresses the solder joints on components in the area. It may even cause immediate damage to a joint or joints, but an actual failure may not show up until the joints have had time to oxidize or to further separate due to thermal contraction/expansion by power cycling and CPU thermal cycling.
A seeming contradiction, thermal contraction/expansion may mask the oxidation problem for awhile as well by temporarily "rubbing" off some oxidation in a damaged solder joint.
Ultimately however, such a damaged solder joint will fail, or may be the cause of "unexplainable" random freezes, reboots, data-loss, etc.
This physical flexure could also cause nearby components to "pop" off the mobo. Some of these could be no bigger than a couple square milli-meters. This could happen immediately or again, could be delayed for a bit. If the components happen to be signal conditioners (usu. resistors and capacitors), you could see all sorts of bizarre computer behavior, or you may see no problems at all, or it could negatively impact the ability to overclock the CPU.
edit to add: Diagnostics can be a problem because they may or may not point to the CPU/mobo. It can cause false positives by creating a data error just at the time the diagnostics are testing a specific component (like RAM). In addition, you can turn the system off and let it cool down, then turn it back on again and the problem will be gone. Even when it heats up again, the failure may be gone again and may not return for a short time (minutes) or a long time (months). Can be very frustrating to diagnose.
I agree - this is a VERY dangerous practice - to force the MB to bend. I do not know though what does INTEL say about their unbelievably poor design of the HSA.
Here what I suggest you can do. But warning : this procedure requires a partial destruction of the four plastic mounting studs in heat sink assembly:
- MB = motherboard
- HSA = Heat Sink Assembly i.e. aluminium heat sink and its plastic enclosure
1. Remove the aluminium heat sink from its plastic enclosure.
2. Remove 4 mounting studs (each made of a black outside part and a white inside part) from a standard, crap Intel HSA assembly:
- Unfortunately there are 2 black blocking plastic bits in each of the 4 corners of the HSA (they stop the white part from falling away from its black shell). \
- Break one of those black bits off (it is the one that is facing the HEAT SINK when the stud is turned in LOCKED (clockwise) position) in order to remove the stud from the plastic enclosure.
- Then turn the stud COUNTER CLOCKWISE and gently lift the other black bit up (by a fraction of a millimetre) - this will allow those two (black and white) bits to be separated.
- Push the white bit out of its black shell.
- Remove black and white bits from the plastic enclosure - this will leave the MOUNTING HOLE of the plastic heatsink enclosure empty
- do the above with all 4 studs (corners)
3. Get (buy) 4 plastic screws with nuts - ideally 6-8 mm in diameter. Screws shall be ~ 35 .. 40 mm long. You will also need four 12-14 mm washers as the whole in the heat sink assembly are quite big (~ 10 mm dia)
. This point is optional : get a piece of thick metal strip (~ 10 mm x 4-5 mm x 115 mm) and a bit bigger piece of 1mm thick rubber (or foam). Drill two holes in that piece and pinch two holes in the rubber at the same distance as the diagonal wholes that hold the heat sink assembly in the MB are. Place the rubber strip between the bottom side of the MB and this metal strip.
5. Put the heat sink back into its enclosure
6. Assemble the (5) and  onto the MB using screws etc (3).
7. Now you have the FULL control of how tight the heat sink assembly is fastened to the MB.
8. If you used the optional part (4) then your MB will hardly bend at all.