Cleaning circuit boards

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TT
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Cleaning circuit boards

Post by TT » Mon Mar 22, 2004 5:35 am

HI, anyone know of a good way to clean printed circuit boards? I collect a lot of video game and pinball items and some of these boards that are 20-25 years old tend to have collected a lot of dirt and grime over years. I have heard of putting them in the dishwasher but I’m not so sure if that’s a real electro static discharge safe way to go, just wandering if anyone had any decent methods for getting them clean again.

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Externet
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Re: Cleaning circuit boards

Post by Externet » Mon Mar 22, 2004 7:49 am

Hi TT.
Bare boards can be cleaned with soap and water, alcohol, a pencil eraser or commercial cleaners formulated for that use.
Populated boards should be cleaned accordingly to the waterproofing of installed components, preferably commercial cleaners formulated for that use, the ones that leave no residue, brushed while wet and dried in front of a fan. Avoid air above 60°C hot.
Store in ziplock bags.
Miguel
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Re: Cleaning circuit boards

Post by myp71 » Mon Mar 22, 2004 9:45 am

Or if you think that can air will work I have seen the brushes on the end of the nozzle :)

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jwax
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Re: Cleaning circuit boards

Post by jwax » Mon Mar 22, 2004 10:36 am

If you had access to an ultrasonic cleaner, submerge the board in isopropyl alcohol and shake away. Repeat with clean alcohol, dry.

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haklesup
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Re: Cleaning circuit boards

Post by haklesup » Mon Mar 22, 2004 12:11 pm

Assuming you are grounded while handling the boards, washing them will not increase the risk of ESD damage.<p>Extranet was right on by saying that you need to wash loaded boards acording to the compaonents onboard. If it is loaded with all IC devices than a water based bath would be OK but if there are any things like relays or certain types of chokes (with paper based forms) you would not want to submerge it.<p>I've considered using a dishwasher for fixture boards (with no active components) but opted for a bucket since most home dishwashers are already too contaminated with soap, rinse agents and food to be clean enough for my purposes.<p>Also be careful if you use a slovent based cleaner. Flux cleaners work great and are safe for many companents but it will remove any conformal coating that was put on the board, you may not want that. Never use Acetone or solvents known to soften plastic<p>For a soap, a non-ionic, non sudsing soap is best but dishwashing detergent can be used if you dilute and rinse very well. If you can smell it on the board when you are done, it is not clean.<p>Isopropyl alcohol is probably one of the safest solvents you can use. Whatever I use, I normally finish off with a rinse of this stuff. It also speeds dry time.<p>In general dust build up on loaded boards will not necessarily cause poor performance, particularly if the board was conformal coated in the first place. Washing boards without a good reason, can hovever, introduce a host of problems. If I had these boards, I would just blow or vacuum off the loose dirt and wait until I needed one before cleaning the contacts and connectors only

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Chris Smith
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Re: Cleaning circuit boards

Post by Chris Smith » Mon Mar 22, 2004 5:27 pm

A tooth brush and TCE-111, [aka Brake Kleen]

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Re: Cleaning circuit boards

Post by Dean Huster » Mon Mar 22, 2004 7:01 pm

I don't like that canned air and brush idea -- it reeks of monumental ESD problems.<p>It was common practice at Tektronix service centers to wash oscilloscopes using a low-pressure wand (i.e., air at 40-50 psi with a venturi water/detergent draw) and then rinsing with plain water. No DI water, etc., although I'd probably filter some of the water you see coming through a tap these days. Then the scope was put into an oven and dried for a couple of days. You can use your home oven for the same thing (a convection oven is better yet) and set it for a temp where the oven just comes on, maybe around 150°F or so. You won't hurt anything made since 1960 unless you're talking about a beeswax-loaded coil or something. Tek washed stuff including relays, HV and LV transformers, fan motors, switches ... all of it. After the wash, IPA was squirted on the switch contacts and after drying, the motors were oiled.<p>Now in our case, since you probably won't leave a board in the oven for two days, I'd avoid non-sealed relays and stuff like that.<p>I've taken stuff like typewriters, teletypes and tape punches down to the local car wash and worked them over to get all the old grease out and then took them home, dried them up and relubbed them with wonderful results.<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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TT
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Re: Cleaning circuit boards

Post by TT » Tue Mar 23, 2004 12:28 am

Thanks guys, those are all excellent ideas. I may have to give the garden hose a try this weekend; I still might ground the end of it just in case. I have used flux remover and contact cleaner in the past with mixed results and that stuff can be expensive. I wish the boards would fit into an ultrasonic cleaner but most of the old Atari boards run about 22” by 18” in length and I don’t have access to anything that big, I’ll probably dry them supervised outside in the fresh air avoiding direct sunlight for a few days, otherwise the old lady might scalp me for using her oven :eek: I’ll start with one working board and move on from there depending on how it goes, if I do run into a problem I’m sure that I won’t be overly disappointed, I seem to like repairing them more than playing them. Thanks a bunch guys!

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haklesup
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Re: Cleaning circuit boards

Post by haklesup » Tue Mar 23, 2004 5:08 pm

"I may have to give the garden hose a try this weekend; I still might ground the end of it just in case."<p>Grounding the hose is unnessary since the water almost certainly travels through a grounded pipe and contains enough impurities to conduct some electricity. <p>What you should do to avoid ESD damage is ground the boards before you let the water touch them. If the boards are charged (and they wont be if you lay them on damp grass) then the charge will exit the board to the grounded water at the point of first contact. This is the Charged Device Model (CDM) of ESD and is the worst killer of the three models .<p>HBM Human body model has the lowest amplitude and slowest rise time, although it is the most common form experienced by people.<p>CDM represents a situation where a charged device is discharged rapidly to a low impedance ground. This has among the fastest slew rates which allows the energy to penetrate deeper into the circuitry and higher amplitude which causes dielectric breakdown more easily but has less total energy due to the short duration.<p>MM or Machine Model has fallen out of favor but represents a scenario where a charged machine is discharged into a grounded device. <p>FYI Test specifications for the 3 ESD test methods are available for free from www.ESDA.org for a few months (thanks to the competition with JEDEC)

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Re: Cleaning circuit boards

Post by dacflyer » Wed Mar 24, 2004 4:58 am

i work on videogames all the time..and TV's<p>they can get quite nasty especially if they been in smoky bars..cig smoke and hi voltage attract dust etc like a magnet<p>heres how i make boards look brand new<p>purple stuff engine cleaner,most any parts store has this stuff..diluted.. soak the board...once sopmehting is wet,,theres no fear of static at all.. let board soak bout 5 min then hose it off really good.... then dry off with a air hose or blow dryer...inspect then its done...
looks like brand new board...never had any problems yet..

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Re: Cleaning circuit boards

Post by jollyrgr » Wed Mar 24, 2004 6:55 am

Despite what most people think, soapy water and a soft brush (think paint brush) works great. I have used plain old "hand wash" dish soap such as "Dawn". Then rinse with copious amounts of clean water. But you MUST dry the board thoughly afterwards. Using alcohol as a rinse to displace the water is a good idea. And the alcohol evaporates quickly itself. I've never tried engine cleaner but it sounds like a good idea. <p>The Biomed guys where I work use some sort of nearly pure alcohol to dry boards off after washing them. (The stuff they use dries out even your skin!) On really tough jobs I get some of their stuff. Otherwise I use plain old isopropyl alcohol. Rather than let the stuff dry outside unassisted, you might want to use an oven. If you cannot use the "old ladies" oven you might use a small toaster oven set real low. Or at least have a fan blowing on them.<p>[ March 24, 2004: Message edited by: Jolly Roger ]</p>
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Edd
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Re: Cleaning circuit boards

Post by Edd » Wed Mar 24, 2004 5:04 pm

Entry # 10 and with lots of compatible redundancy with others.
Since you would have typical little rework area and considering you to have already taken care of the flux cleanup in those areas. Also, sounds like the main purpose was improving the cosmetic appearance of dirty boards.
What I use is one of their cheapest natural bristle brushes, natural wood handle and matching color bristles from Homeless Despot..2 inch width and marked China origin and is using hog bristles (I think). Then the magical cleansing ingredient “409” and the real kicker…HOT water. I’ve used either a 1 qt Pyrex measuring cup or some of the LARGEST Styrofoam drink cups with the height cut down just enough to go into the microwave and a 10 min warm up. Initially wet both sides of the board then concentrate on the populated side of the board first and spray on your 409 and timely refresh the brush with a hot water dip/or/ use a 50/50 hot water and 409 in a container and dip apply with the brush. Use the brush to vigorously work into every nook and cranny of the board.Work quick and don’t let any initial area dry on you, flip over the board and do the bare side last, as it can be done quickly. Clean all the soap from your brush or have another clean one on hand to use and then go thru the same procedure in rinsing away 409 residue from the board with the balance of your hot water and then a final rinse to your hearts content with cold water. Then you grab the board with a DEATH GRIP, (specifically some finger tips wrapped around some IC’s) and you will be able to sling the majority of any residual water from the board. A board will dry in a hurry, but if impatience onsets me, I have two paper clip wires hanging from the front grill work of a 24 in boxer fan; it will do a drying at high fan speed even faster.
End result…boards glisten.
I had done some repair of gaming machine boards back in the 75-80’ish area and those boards were just chock full of TTL. I thought some of them even approached a 12 x 24 in footprint. My most recent encounter with any of the old kluges was about 2 years ago with a neighbors pool rooms Centipede…,wherein the trouble was in the units monitor, a ring cold solder joint on the kine board, filament supply. <p>73's de Edd
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;) ;)<p>[ March 24, 2004: Message edited by: Edd Whatley ]</p>

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