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Li-rocchi



Joined: 29/03/06
Posts: 1010
Loc: Norwich, UK
Ways to clean motherboards and PCB boards APART from compressed air... new
      #973981 - 04/03/12 04:26 PM
Hi all

As part of some recent PC problems I've been having, I am taking my PC apart and giving it a good clean out. Aside from compressed air, what other methods are recommended for cleaning the motherboard and other PCB boards? I was thinking/hoping to brush of the dust and dirt, but I presume a synthetic brush would cause static. How about a natural fibre brush like those made from animal hair, etc.? Is it OK to use those?

Are any other methods recommended?

Cheers

Max


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dmills



Joined: 25/08/06
Posts: 2429
Loc: High Wycombe, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #973987 - 04/03/12 05:00 PM
Strip it right down and stick the boards through an ultrasonic cleaner. Use a saponifier in the water followed by a couple of passes with DI water, or use something like trike instead of water.

In extremis I have been known to stick boards in a dishwasher.....

Regards, Dan.

--------------------
Audiophiles use phono leads because they are unbalanced people!


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DGL.



Joined: 28/10/11
Posts: 563
Loc: Portland, Dorset
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #973989 - 04/03/12 05:20 PM
Small paint brushes and a good hoover work wonders, this was one of the things that I used on my city and guilds course on systems support (a numatic and a paint brush gets the dust off wqithout getting dust everywhere) , just be careful and you should have no problems.
Also things like cotton buds are also quite useful for getting in hard to reach areas.

But I would reccommend that you get a grounding strap if you do not have one already, the plug in ones are best, as it means you will never have any static problems.


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Folderol



Joined: 15/11/08
Posts: 3738
Loc: Rochester, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #973993 - 04/03/12 06:31 PM
For a start, I would never consider compressed air for cleaning electronics anyway! You are far more likely to force dirt into crevices than out of them.

I use a medium artists paint brush along with a fairly gentle vacuum. After that, depending on how much greasy crap there is, I'll go over the board with a fatter brush and virtually washing it with iso-polypropylene. Leaving to dry is then usually quite sufficient for almost all domestic stuff.

Probably not relevant for modern PCBs, but for something of any age, don't remove any parts at all unless you are absolutely confident of the condition of the entire assembly. You are likely to end up with a number of dry joints or broken pins. Some plastic clips and plug housings get brittle very rapidly at quite modest temperatures.

Arguably, if a board is that bad it should be junked anyway, but sometimes that's just not an option.

--------------------
It wasn't me!
(Well, actually, it probably was)


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Li-rocchi



Joined: 29/03/06
Posts: 1010
Loc: Norwich, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #973995 - 04/03/12 06:36 PM
@dmills: I'm not sure wikipedia an keep up with that post!!!! Sounds very intriguing but also sounds like I'll need a lot of things that I do not have....

@DGL.: Good to hear that they recommend it on courses. Can't be that bad then. Did they say whether you could use brushes with synthetic bristles or natural ones only?

I do have a ground strap but it is the type you attach to the PC chassis. Maybe I'll look into getting one of the ones you mention which plug into the wall. In the meantime though, the one I have..... Does it only work if the PC is plugged into the mains? Is there something better I could attach it to?

Speaking of mains.... obviously the PC has to be off when working on it, cleaning it, etc. But is there any advantage to keeping it plugged in from a grounding point of view?

Thanks for the helpful replies

Max


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Folderol



Joined: 15/11/08
Posts: 3738
Loc: Rochester, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #973998 - 04/03/12 07:04 PM
Quote Li-rocchi:

@dmills: I'm not sure wikipedia an keep up with that post!!!! Sounds very intriguing but also sounds like I'll need a lot of things that I do not have....

@DGL.: Good to hear that they recommend it on courses. Can't be that bad then. Did they say whether you could use brushes with synthetic bristles or natural ones only?

I do have a ground strap but it is the type you attach to the PC chassis. Maybe I'll look into getting one of the ones you mention which plug into the wall. In the meantime though, the one I have..... Does it only work if the PC is plugged into the mains? Is there something better I could attach it to?

Speaking of mains.... obviously the PC has to be off when working on it, cleaning it, etc. But is there any advantage to keeping it plugged in from a grounding point of view?

Thanks for the helpful replies

Max



With all due respect, a lot of people misunderstand the function of a grounding strap. It is to put you, and what you are working on at the same electrical voltage, so there can be no static discharge between the two.

Not only is it unnecessary for this to be at earth potential, for hand cleaning work like this it can be an advantage to not be earthed. With no power connection at all, there is no safety issue and a lightweight wrist strap with a slim wire to a croc clip on any board ground point is quite adequate.

--------------------
It wasn't me!
(Well, actually, it probably was)


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Li-rocchi



Joined: 29/03/06
Posts: 1010
Loc: Norwich, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974002 - 04/03/12 07:18 PM
Thanks for the clarification, and no disrespect taken at all.... I don't know much about it so all info is very welcomed.

What I'm still unsure about is what part of the motherboard I should connect the croc clip to. And how about if I am cleaning a smaller (disconnected) PCB board like a PCI soundcard?

Cheers

Max


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DGL.



Joined: 28/10/11
Posts: 563
Loc: Portland, Dorset
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974008 - 04/03/12 08:05 PM
For a disconnected PCI board again I would reccommend either a strap connected to a special plug that earths you or just a strap connected to the computers case (with the power to the computer at the wall turned off but with thew plug still in).
As someone who did work experience in a company that had a static safe room (tables earthed, floors earths and you are earthed) it is earthing and not to keep you at the same potential voltage. The problem comes when you build up static and that is discharged into the component in question, this involves a small current but high voltage that fries the chips hence the reason why tyhe strap is nconnected to earth (and why croc clip based straps should be connected to part of the computers case as that is earthed through the power supply and any potetialy harmless voltages sent to earth).
As for brush type, I don't know as we just had whatever was available (poorly funded course with computers found in a cupboard! and computers chucked out from Bournemouth Uni. only got proper computers (cheap dell laptops) at the end)


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Folderol



Joined: 15/11/08
Posts: 3738
Loc: Rochester, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: DGL.]
      #974026 - 04/03/12 10:16 PM
Quote DGL.:

For a disconnected PCI board again I would reccommend either a strap connected to a special plug that earths you or just a strap connected to the computers case (with the power to the computer at the wall turned off but with thew plug still in).



Absolutely do NOT do this under any circumstances.
With you now securely earthed, an accidental nudge of the switch, or a loose/faulty switch will put you at risk of a possibly fatal shock.

Cleaning the kit inside the case is a non-starter anyway - you might as well also wear boxing gloves. You want the board out in the open, away from anything else and most certainly away from any source of power.

I repeat, earthing is irrelevant. Damage is caused by a potential difference developing between you and what you touch. If you and the object are at the same potential, it makes no difference what the rest of the world thinks this is. I've used this principle since before the original 4000 series chips that had no ESD protection at all, when the people trying to be clever and picking them up so carefully by the ceramic body with tweezers, would destroy them by letting just one leg drag a little.

As for where to connect to on the board, surprisingly it doesn't actually matter too much. Almost any large area of copper on the board will be connected to one of the supply rails or to ground, and the impedance between these will be insignificant to potential static charges.

For brushes, as I said, I use artists brushes - I've not come across a half decent one that is synthetic, and I wouldn't want to either.

--------------------
It wasn't me!
(Well, actually, it probably was)


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DGL.



Joined: 28/10/11
Posts: 563
Loc: Portland, Dorset
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Folderol]
      #974030 - 04/03/12 11:03 PM
Actually that was what we were taught by our lecturer at college and what we did at college (worked for barclays and dorset police among others providing IT support had I would have said at least 30 years experience even had an old DEC terminal from when Barclays had them). The plug in type I had from school and consist of a plug connected to the earth (only) on a plug connected to a cable to the wrist strap with a 1meg ohm resistance incorporated. As I have said before it is NOT the electrical potential but static discharge that is the problem (well that was what I was taught in both my L3 systems support course, A level electronics and at the place I did my work experience (as I have said befor they had a static safe room))
Also one flick of a switch WILL NO electricute you as the earth should not ever be carrying any current (anything that would immediatly fails a PAT test and would electricute you just by touching the case when it is on.
For more info see http://en.wikipedia.org/wiki/Static_discharge


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Li-rocchi



Joined: 29/03/06
Posts: 1010
Loc: Norwich, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974035 - 04/03/12 11:16 PM
Well, it's an interesting debate and I can't really take one side over another as I don't know a great deal about it. It would however be great to get the input from others, as I'm guessing one person must be right and the other wrong!

Thanks for all the input and interesting reading from both of you.


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markhodges



Joined: 07/01/07
Posts: 344
Loc: München
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974049 - 05/03/12 03:07 AM
ESD straps are designed to be connected to ground. If they aren't, then although you and whatever you are working on might be at the same potential there is still a chance of discharge if and when things are subsequently grounded e.g. if you take a card out of the PC and put it down, or accidentally touch something that's grounded.

They are often used in conjunction with a dissipative mat that is made of a conductive material with fairly high resistance to ensure that any charges dissipate slowly.

The straps should have a 1 megaohm or so resistor in, that's a safety feature so that you don't fry yourself if you accidentally touch something live when working with low voltages. They are not supposed to be used if working near high voltages e.g. anything over mains.

Leaving a PC plugged in and switching it off using the switch on the back of the PSU is a fairly common practice, I was taught to do it when I worked in a computer factory years ago. It does seem a bit dubious though.


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DGL.



Joined: 28/10/11
Posts: 563
Loc: Portland, Dorset
Re: Ways to clean motherboards and PCB boards APART from compressed air... [Re: markhodges]
      #974063 - 05/03/12 08:05 AM
Switching it off but leaving it plugged in maintains the earth connection through the plug and therefor the earth for the strap, thre is nothing dubious about it and if you disconnect everything from the computers psu (motherboard, drives Etc.)Then even leaving the power on would not be a problem. The only time I would not reccommend this approach is when working on device that either are not earthed (no earth connection of course!) and if the device has an open power supply (such as inside a synth Etc.) where full mains disconnection (remove plug from wall) and a plug in type wrist band would be much better. And es the 1Meg ohm resistance in the cable prevents any chance of electric shock should a device develope a fault and send current down to earth.


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Ojustaboo



Joined: 14/10/11
Posts: 115
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974065 - 05/03/12 09:00 AM
To be safe, surely if you turned the socket on the wall off, you'd still get the ground with the mains cable plugged in with zero chance of touching say part of a transformer that's live?


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markhodges



Joined: 07/01/07
Posts: 344
Loc: München
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974110 - 05/03/12 11:29 AM
In theory it should be fairly safe as even with it switched on everything outside the PSU should be 12V or less. It does increase the risk of it accidentally being switched on though, which can lead to frying stuff by causing a short or plugging/unplugging something without realising.


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Li-rocchi



Joined: 29/03/06
Posts: 1010
Loc: Norwich, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974116 - 05/03/12 11:38 AM
Thanks for all this guys. I currently have all the bits and pieces out of the PC and can therefore clean them one by one. I have a WC I can work in.....! It has lino rather than carpet, and the pipes feeding the small sink have one of those earth link things on them. So can I attach my croc clip to the pipes to give me my earth, and the take one piece of equipment in there at a time to clean with a brush?

The added advantage would be keeping the dust away from the rest of the PC....


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Folderol



Joined: 15/11/08
Posts: 3738
Loc: Rochester, UK
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: markhodges]
      #974253 - 05/03/12 07:41 PM
Quote markhodges:

In theory it should be fairly safe as even with it switched on everything outside the PSU should be 12V or less. It does increase the risk of it accidentally being switched on though, which can lead to frying stuff by causing a short or plugging/unplugging something without realising.



In theory it should be impossible to cut your fingers off with a modern guillotine, but a few years ago a woman did it on a machine that was checked and found 100% compliant with all relevant HSE specs. I don't believe anyone found out exactly how it happened.

If by some freak circumstance you get a fatal shock, you can't get your life sown back on with just some loss of ability. If people really want to take that risk themselves then who am I to stop them? But to advise a newbie to do so is more than irresponsible. With rare, highly specialised exceptions, when I work on any kit I want to have the unplugged end of the power cord in my sight - failing that, the isolator fuses in my pocket.

I've been at the sharp end of CMOS handling on a daily basis since the middle/late 1970s. To date I have a 100% record, even handling SAD1024 BB chips that were notorious for the fragility of the clock inputs. I break most of the ESD 'rules' most of the time, but always have in the back of my mind that you can't get a discharge across things that are connected together.

If I am doing static sensitive work, for choice, I work with a nice soft conductive mat, preferably on an untreated wooden bench. Everything that I'll be handling for job sits on that bench/mat from start to finish. My soldering/desoldering kit runs from 24V. This supply is earthed for obvious safety. The shell of the irons are not. The 'earth' wires run to a strip of copper foil that sits under the mat.

Like that, I will start out resting my hands on the mat then unpack/disassemble what needs to be repaired. With 50x 4000 series chips on a board you often have to cut (quite a lot of) track between chips to find out which of a connected pair is faulty, I just slice through the trackwork with a scalpel having no worries that at least one chip now has a completely floating input. I, my scalpel, the chips and everything else are at the same potential, so where is a rouge chip-murdering discharge going to come from?

Rather than trying to avoid handling the board etc. I take the opposite approach and handle everything as much as possible, right through the faulty parts removal, cleaning up and replacement, then final re-bridging of cut tracks. I make damn sure everything will stay at the same potential. With no interfering dangly bits I work fast.

My chip-pin straightener is a steel rule which I lay the legs along then apply gentle pressure till the body is at 90 deg. (the legs are always splayed for the benefit of auto insertion kit). From my earlier TTL days, I quickly learned that the hand insertion tools you can buy have a habit of suddenly shifting and firing a chip at high velocity over your shoulder. The roller type straighteners are somehow capable of snagging just one errant leg and either wrapping it round its neighbour or snapping it right off.

P.S.
I keep having to tell customers not to smother stuff in bubble-wrap.

--------------------
It wasn't me!
(Well, actually, it probably was)


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markhodges



Joined: 07/01/07
Posts: 344
Loc: München
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Folderol]
      #974321 - 06/03/12 02:26 AM
Quote Folderol:

Quote markhodges:

In theory it should be fairly safe as even with it switched on everything outside the PSU should be 12V or less. It does increase the risk of it accidentally being switched on though, which can lead to frying stuff by causing a short or plugging/unplugging something without realising.




In theory it should be impossible to cut your fingers off with a modern guillotine, but a few years ago a woman did it on a machine that was checked and found 100% compliant with all relevant HSE specs. I don't believe anyone found out exactly how it happened.

If by some freak circumstance you get a fatal shock, you can't get your life sown back on with just some loss of ability. If people really want to take that risk themselves then who am I to stop them? But to advise a newbie to do so is more than irresponsible. With rare, highly specialised exceptions, when I work on any kit I want to have the unplugged end of the power cord in my sight - failing that, the isolator fuses in my pocket.





Rightly or wrongly, grounding via the power cord / PSU for ESD safety IS something that is taught to a lot of computer folk, sometimes as part of a professional certification such as CompTIA.

I said earlier that although it's a fairly standard practice it "seemed dubious", and I was actually trying to explain that there are other good reasons not to leave the machine plugged in aside from personal safety considerations. So just to be clear, although I'd consider the voltages inside a PC outside of the PSU to be fairly safe I'm not advising anyone newbie or otherwise to do anything aside from use a grounded ESD strap when working on their computer.

I'm presuming you don't use any sort of test equipment that has a safety earth e.g. a scope or PSU, otherwise this would be an obvious candidate for something that could lead to a discharge if other things aren't tied to the same ground. A discharge won't necessarily "murder" a chip BTW, it's more likely to lead to a premature failure later on than a failure at the time.


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ef37a



Joined: 29/05/06
Posts: 6865
Loc: northampton uk
Re: Ways to clean motherboards and PCB boards APART from compressed air... new [Re: Li-rocchi]
      #974327 - 06/03/12 08:27 AM
When I went for an interview and soldering test a few years ago at a smallish electronics firm I was given a high R conductive strip that stuck under the heel of my shoe and was tucked into the back to make casual contact with my foot (even zappy nylon socks will have enough sweat in them to be a few tens of megOhms).

Thus "I" was always at ground potential and since everything about me was either on metal benches, conductive pads or in conductive bags no discharges to or from anything were possible.I think RH was kept artificially high as well.

But here, in this forum I have to agree with Will. We cannot be too careful what we say to noobs as WE are not "in the training room" with them! We do not want any Darwinian selection of klutz punters!

Dave.


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