How sensitive are motherboards?

Robbie Ferraz

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Feb 7, 2017
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Hey, I was just wondering how sensitive are motherboards? Let's say if you drop a screwdriver on to one by accident or you simply scratched it a bit in the process of installing it into the case.
Would this damage affect your PC?
 

Menelaos1996

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May 1, 2016
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As long as the PC is turned off you have no problem dropping metallic items in it because you cannot short anything without Power :). Now scratching is a whole different story if you happen to damage a slope on the board the result will not be pleseant.(Slopes are threse tiny lines on your motherboard).Slopes transfer voltage across you motherboard so damaged slopes equals to shorts and not properly powering components on your mobo and many more.
 

Karadjgne

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There is always potential for damage. You don't even need to scratch the mobo, if the handle hit a component like a capacitor, it's enough to break the solder seal on the legs. Silicon isn't the toughest stuff in the world, it's possible to crack transistors or if chips, separate traces from chips or other components, there's a whole list of possible accomplishments that screwdriver can get up to. Whether it did or not, whether that scratch was enough to break the traces or is nothing more than a light scratch on the protective film is something only you will find out when using the pc. It's entirely possible that there isn't a problem, or if there is one, it's in an area you just don't use.

But to correct a prior post, capacitors are identical to batteries in one respect, they hold power potential, so even if the mobo is in a powered down state, there's componentry on the mobo that is still powered, so a discharge via short is entirely possible, and depending on the cap and exact route of the short, can or might not do anything. Only way I know of to drain the mobo fully is unplug from the wall, then hold the power button down for 5-10 seconds
 

Menelaos1996

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If you are referring to my post Karadjgne I must inform you that if a 10V 500μF capacitor is shorted on your mobo the possibillity of damaging something is close to none even α 3000μF is not going to cause any kind of problem we are not dealing with super capacitors here and how exactly are you going to short the capacitor dropping the metal thing on top of the motherboard the contacts of the capacitors are on the other side of the mobo. Finaly a screwdriver has to be thrown to the motherboard in order to damage the seals on the legs of a capacitor it can only bend the capacitor a litlle bit if dropped.If I am wrong please do correct me.
 

Karadjgne

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Kinda true, but not quite. You base that assumption on Quality of Manufacture, which under normal circumstances is ok-decent-great, but that's not precluding the possibility that the trace, cap leg etc in question is also solid. Doesn't take much at all for metal stress to break a leg off a cap, or crack the housing or if there were solder joints barely hanging onto a connection. You also assume that any low voltage traces, like the 1.3ishv traces from a VRM to the cpu will be fine sending 10v discharge to the cpu. While the caps and other high voltage components will absorb a 10v 3kuf discharge, that's not to say other stuff will too. Not that hard to break a solder joint on a VRM if the screwdriver hits it dead on and shoves the legs straight through the board. If the blade hit a trace dead on, it can crack the trace, especially if the trace was warm/hot. You'll just have to take my word for it that weirder stuff than that has happened for no apparent reason whatsoever. Most of the Ic's on a mobo don't even have solder legs as such, like the bios chip, they use a bead solder, that's just a tiny ball of solder that when heated joins the chip to the board. You could tap on that IC with a fingernail and break the solder seal of half a dozen balls.
 

Menelaos1996

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Well you are right I am referring to good brands like MSI,GIGABYTE,HP e.t.c because I work on a refurbisher company on the service dept and I have never seen something like that.I never said that shorting the caps is the right way to do it you can of course discharge them by pressing the power button.Personally I have dropped many screwdrivers in many cases cause we have to be fast in my job as you may know I have short discharged lots of caps and none of them caused any kind of issue.It is always good to expand your knowledge :) (for me) .Something I didnt understand how are you supposed to discharge 10 volts to the cpu as soon as you touch the + and the - of the cap it will discharge on the screwdriver.
 

Karadjgne

Titan
Herald
It's a screwdriver. Long metal shaft. You can discharge anything, that includes static electricity by any means that contains a difference in potential. A cap will discharge from + to any ground, or anything else it sees as a return path, albeit not fully. It'll discharge enough to balance. So if there's 1.3v on a trace to the cpu for vcore voltage and 10v on a cap, it'll discharge 7v from the anode as the difference in potential. Stand barefoot in a puddle and grab the 12v hot from a car battery. Doesn't have to see the negative terminal.

And yes, it's an almost impossible situation to happen, you'd have to contact both the trace and the cap at exactly the same time. Chances of that exactly happening are close to winning the lottery, if you only ever played it once.

On the flip side, assume it's a transistor not a cap, 12v in, 3v output and there's something else downstream, like the cpu, which will not want to see 12v on that particular part of the circuit. A direct short will drop all 12v down that line instead. Or the backend of a 3v diode, that 12v could easily fry that diode, causing nonfunction of whatever is before it.
 


Speaking from my experience: yes. It's very easy to damage and in ways not always obvious at first.

As it happened in my case I dropped a screwdriver a very small distance (from the mounting screw of the plastic AMD heatsink clips) to the board surface. At first I couldn't see anything but I could FEEL a very fine scratch so I pulled the GPU, got a jeweler's loop and sure enough: there as a bit of bright copper glinting at me from under the mobo's colorized gel coat along one of the hundreds of very fine traces running underneath the GPU socket.

Luckily it ran underneath the x16 connector to the second x16 connector which, when I put my GPU in it, would only operate in x4 mode now. I only run a single graphics card so I avoided disaster. But there are thousands of tiny data traces on the surface of the board protected by gel coat that is tiniest fraction of a mm thick so that's where the damage is most likely to happen.
 

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