Electronics cleaning: leaked batteries - Page 1
Forum section: electronics / beginners

author: Chasm
author_rank: Regular Contributor
timestamp: September 10, 2010, 01:32:23 am
content: Hi Forum,not a beginner any more, but some problems seem to catch everyone once in a while...I've managed to f*%& up some cheap and not so cheap electronics with leaking alkaline batteries.Dr. Disassembly says: No major problems, so far.Unfortunately both acid and alkaline damage has the tendency to spread over time...Any ideas do beyond drenching the boards with PCB cleaner and giving the contacts a makeover with the glass fiber pen?PS: A dozen Kodak brand AAA,allof them leaking after 9 months...

author: DJPhil
author_rank: Frequent Contributor
timestamp: September 10, 2010, 02:28:03 am
content: First step is to neutralize the PH, mix a solution of vinegar (alkaline) or baking soda (acid) and mop up the visible mess. After that a thorough cleaning with alcohol should leave things clean. Long term damage is mostly avoidable, you just have to be sure you get all the residue cleaned out. Corrosion and it's byproducts tend to hide in nooks and crannies (this is especially insidious in the convoluted plastic housings of battery spring terminals) and seep out later with the aid of humidity and thermal cycling.The primary threat to PCBs and their residents is oxidation from the alkaline, and this can largely be halted with a good cleaning. It's possible that a compound likedeoxitthat's designed to remove oxidation and leave a coating to help prevent it might be useful. I've also read that Potassium Hydroxide (one of the most common alkaline battery compounds) is reported to be especially mean to aluminum, but I can't speak to that myself.I've got a desktop radio that I rescued from the trash almost twenty years ago. The batteries leaked all over the compartment and it almost got pitched. It's still in service now as my garage radio, and after opening it up about six months ago (looking for a replacement AM tuner chip) I can say it still looks ok inside. After complete disassembly I washed the plastic case out with soapy water (not the best idea) and cleaned the boards with alcohol. Even the sloppy job I did seemed to work out ok. My only complaint is that there's nothing to hear on medium wave here in the US.Hope that helps.

author: Zero999
author_rank: Super Contributor
timestamp: September 10, 2010, 06:49:32 am
content: I can't see anything wrong with washing the plastic case in soapy water.Heck I'd even wash the PCB in water, it's always recommended that you rinse with deionised water before drying but I've never had a problem with tap water. The best way to dry is to put the board in an oven on very low heat 60°C but I know some radios use wax to secure the coils in place and stop them from vibrating so that might not be such a good idea.

author: ElektroQuark
author_rank: Unknown
timestamp: September 10, 2010, 07:10:56 am
content: Quote from: DJPhil on September 10, 2010, 02:28:03 amJust to make it clearer:Vinegar is acid, so use it to neutralize alkaline leaks.Baking soda is alkaline, so use it to neutralize acid leaks.

author: Mambo
author_rank: Contributor
timestamp: September 10, 2010, 11:27:28 am
content: Also with washing PCB's in water, it's possible. What needs to be considered is the edge of the board, if it looks polished then it will handle water alot better than a rough finish. When I say polished, I mean polished. Just because it's not rough to touch does not mean a rough finish. Take a good hard look. Some boards are even sealed against water ingress.

author: Zero999
author_rank: Super Contributor
timestamp: September 10, 2010, 12:09:56 pm
content: I've never seen a board de-laminate or soak up of water - if it does, it can't be very good quality, there again I wouldn't expect a radio PCB to be very good.Another concern regarding cleaning with water is that the tuning capacitors might be difficult to dry out properly.I'm now not sure that soaking the entire board in water would be such a good idea, perhaps it's better to just clean the dirty parts.

author: DJPhil
author_rank: Frequent Contributor
timestamp: September 10, 2010, 01:13:50 pm
content: My apologies, I should have expanded on the soapy water on the case bit. I made two mistakes doing it that way that are avoidable.The first was failing to rinse the soap completely before letting it dry, which resulted in a blotchy film that was annoying but purely cosmetic. Further rinsing cleared that up.The second was failing to take into account what soapy water would do to the thin plastic tuning window that was glued down with the equivalent of rubber cement. It literally came apart! I cleaned up the thin plastic insert with window cleaner and glued it back on with rubber cement. It still bulges a bit at one end, but it's a matter of character now.I also failed to mention that this was the first thing of real value that I ever 'fixed'. I was about ten years old at the time.I used 99% isopropanol (really just rubbing alcohol) for the circuit board, as it was available at my father's work. You can usually find 90% rubbing alcohol at the drug store that's essentially identical, although I'd try to avoid the 70% stuff. I've read of using a dishwasher to clean PCBs for such things as oscilloscopes, but I've never tried it as I'd get strangled if I put the dishwasher to industrial use. The real key I think would be making absolutely sure the board was dry, and a good deal of experimentation has been done along these lines by folks who drop their cellphones in toilets.

author: TopherTheME
author_rank: Regular Contributor
timestamp: September 10, 2010, 05:37:25 pm
content: Did the batteries actually leak or did they vent? There's a difference. If they did in fact leak, then its the electrolyte that leaked out all over the PCB which is acidic. I would first neutralize with baking soda (which is alkaline as corrected above) and then clean with isopropyl alcohol and air dry. If the PCB is one of reasonable quality the solder mask will be made from polyimide which is a relatively chemically stable polymer so there shouldn't be any real damage to the board itself. I would be more concerned about the pads and pins oxidizing on each of the components.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: September 10, 2010, 08:17:13 pm
content: distiled water and one hard brush it will remove any acid ..I have do this countless times , the water it will remove any acid , or better it will mix with the dry acid,and both will be removed ..There is no better chemical than the distiled water about cleaning such a mess , or even car battery poles from dry acid in crystallized form.

author: Zero999
author_rank: Super Contributor
timestamp: September 10, 2010, 11:49:16 pm
content: Quote from: TopherTheME on September 10, 2010, 05:37:25 pmDepends, most dry cells are alkaline nowadays.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 11, 2010, 02:58:13 am
content: NiMH batteries have KOH electrolyte.

author: Chasm
author_rank: Regular Contributor
timestamp: September 12, 2010, 09:36:00 pm
content: Quote from: TopherTheME on September 10, 2010, 05:37:25 pmGood question.Some of the Kodak AAA left the "usual" white crystals behind.But some of them actually leaked fluids. I didn't test for pH value, but it left brown spots on paper.The boards are FR4 with silkscreen, some random SMD stuff and an etched antenna.Cheap remote flash triggers, they are consumables so I'll clean them first with both acidic and alkali solutions and soak them in distilled water. Not too much of a loss if they fail.The other item is much more difficult to clean and abitmore expensive. Found an alkaline in a Speedlite...The alkaline left lots of the white crystals behind, and fsked up the chrome plating of a spring loaded contact really good.The good news is that the battery compartment is sealed relatively good.The bad part is that it is really hard to clean. 0.5mm F4, flex boards, LCD with flimsy connector, a dozen thin wire connections....Of course all of that mounted on the battery compartment and -as Dave loves it- with directly soldered battery connections. (Which is actually areallygood idea, given the near short circuit currents in a modern flashlight using rechargeable batteries.)Disassembly without doing more damage is a quite a challenge.Edit:Lots of wiggling and bending of SMD tweezers later: It came apart.Mostly... No idea how or indeed if the spring loaded contact comes off, probably not.Hmm, 80$ + S&H + import taxes for a new assembly via ebay canada. (Part code CY2-4110-000) Nice to know but not that cheap either. De-solder the boards and soak in cleaner seems to be the easiest way.

author: Peter A
author_rank: Newbie
timestamp: May 22, 2021, 06:27:13 am
content: Hi Forum,An interesting topic.I wonder is there any special cleaning required where a PCBA mounted rechargeable battery has leaked?

author: peteru
author_rank: Regular Contributor
timestamp: May 22, 2021, 01:54:13 pm
content: Maybe Dave @EEVblog could enhance his battery leakage experiment. If/when his batteries eventually leak, he should have various materials exposed to the mess and demo how to clean up the residue and what damage it causes.

author: Fraser
author_rank: Super Contributor
timestamp: May 23, 2021, 11:45:07 am
content: PeterA,Leaking PCB mounted rechargeable cells can be a nightmare if the leakage is not discovered soon after it begins.In my experience, the following issues can occur and require rectification....1. The battery electrolyte travels down the battery leads and attacks the solder joints. The battery needs to be removed and the through-hole solder pads need careful inspection and cleaning. The PCB tracks attaching to those solder pads can be seriously corroded but the damage hidden from view under the solder mask.2. The battery electrolyte migrates across the PCB’s surface and contaminates adjacent solder pads, tracks and component leads. The area around the battery should be carefully inspected for any signs of corrosion and the continuity of the PCB tracks tested for invisible damage like hairline cracks. Corroded component leads may require replacement of the component or careful restoration by cleaning and tinning. Some IC pins can be completely corroded away inside the outer tinning and fall apart when probed !3. Migrating electrolyte will ‘pool’ under components, especially flat bottomed components like Surface mount IC’s. It is very hard to remove that contamination without removing the IC first but an ultrasonic Bath can sometimes work.4. The PCB material and its coating can have an impact on the level of PCB damage caused by an electrolyte leak. A marinised (lacquered) FR4 PCB is less likely to suffer from absorption of electrolyte than the cheap unsealed compressed fibre type PCB’s found in low budget equipment. Once electrolyte enters the layers of the PCB there is the potential for undesirable conduction between component leads, PCB tracks and even metal PCB mounts. I have an expensive protocol analyzer that uses a unsealed FR4 PCB and has suffered a mempac failure through leakage. The PCB’s surface was cleaned of all electrolyte but upon testing, the unit suffered unexplainable crashes and flashes on the LCD display. The problem turned out to be electrolyte absorption into the fibre glass layers of the PCB. The electroluminescent LCD backlight HV driver is over 10mm away from any part of the MEMPAC but the High Voltage is leaking through the PCB and onto the mempac Positive pin ! The result is serious interfereance on the supply rail to the memory that the Mempac supportsthe memory has survived but the solution is to cut an isolating slot around the HV driver transformer and output components or move the HV driver to a new daughter board.THe HV output would then be connected directly to the backlight to avoid HV on the PCB near the Mempac. The PCB will also need to be soaked in IPA for a significant period of time to draw out and dilute the electrolyte within its layers. I should state that this is just a double sided PCB. A multi layer PCB with tracks within the PCB material could suffer long term reliability issues due to continuing corrosion or voltage leakage across adjacent conductors.If electrolyte gets onto or into a PCB, the only solution is removal of that contamination followed by repair of any corroded parts. Failure to remove the electrolyte will lead to ongoing damage to the PCB and/or components.As to how to remove the electrolyte, that has been covered earlier in this thread. Clean water and IPA are your friends as dilution of the electrolyte is a key requirement in the repair process. Neutralisation of the electrolyte is an option if the neutralising agent can get to the contamination and not cause its own contamination issues ! IPA will penetrate the PCB to help ‘flush out’ any liquid or contamination within. Sadly severe contamination of a PCB can be beyond simple flushing however. I will leave a PCB submerged in water and then IPA for days if required in order to leech out the contaminants and any salts. Remove all sources of power to the PCB first though !Hope this helpsFraser

author: Fraser
author_rank: Super Contributor
timestamp: May 23, 2021, 12:21:40 pm
content: Further to my last.......I also use more advanced techniques to clean an electrolyte contaminated PCB......1. A swept frequency ultrasonic cleaning bath filled with either distilled/deionised water or a mixture of distilled/deionised water and PCB cleaning fluid can remove contamination from hidden nooks and crannies that might otherwise be missed. It can help to get the cleaning fluid into the PCB but if a PCB cleaning fluid is used, the process should be repeated with distilled or de-ionised water to remove the cleaning solution. Be warned that hard tap water in an ultrasonic cleaner can cause some cosmetic damage as the lime particles act as an abrasive ! Also be aware that some components do not like to be subjected to high energy ultrasonic vibrations so you may wish to remove Crystal oscillators as a minimum before using such a cleaning technique. Better safe than sorry ! The PCB should be placed in a bath of IPA after the ultrasonic cleaning in order to displace trapped water. The PCB is then dried using mild heat or air drying in a warm room.2. It is a well known and understood technique to apply a vacuum to a material if you want to drive a fluid into its structure. This technique is commonly used to clean and refill the tiny oil pores in Oilite Phosphor Bronze Bearings during servicing. Basically an oil solvent is used to remove the old oil and leave nice clean pores ready for refilling. The bearing is placed in a bath of hot, but not boiling, new oil and a vacuum is drawn on the oil bath. The Vaccum causes the trapped air in the bearing to be pulled out of the pores and as a vacuum is left behind, fresh oil is drawn into the voids to refill the bearing with oil. The oil is heated to make it thinner and more easily absorbed.A similar technique is possible with PCB electrolyte contamination but care is needed to avoid making a bad situation worse ! If a PCB is placed in a bath of IPA or other suitable cleaning solution and then subjected to a vacuum, the cleaning solution will be drawn into the PCB structure wherever voids exist. If the voids contain contamination, this technique can get the cleaning solution to that contamination to dilute it and possibly neutralise it. The problems with this technique should be clearly understood though.....a) Drawing a vacuum on a bare PCB is relatively safe but doing so on a populated PCB can lead to components absorbing the IPA or cleaning solution and suffering a change in characteristics or even failure ! Think about polyester capacitors for instance ! The vacuum will cause almost any air void to become filled with whatever fluid the PCB is immersed in. IPA may be relatively safe but it is still a risk to have it drawn into components as such can lead to high voltage insulation issues and undesirable changes in the component. IPA will also soften some materials and if it cannot be removed after cleaning may cause long term harm. In any case, the PCB must be carefully cleaned of all contamination, whether unintentional or intentional, to avoid future reliability issues.b) Drawing a vacuum on some components can cause them to suffer damage. Make sure that the PCB does not contain any pressure sensitive components.c) The vacuum process will draw the IPA or cleaning fluid into the PCB but it is then inside the PCB and a ‘contamination’ in itself ! Thought needs to be given to the effects of the fluid that is used. IPA and Acetone will be relatively easy to remove through heating of the PCB and they do not leave significant residue from their presence. Other cleaning fluids may leave solids or salts after the PCB is heated and this could cause issues, but possibly not as serious as those caused by the original contamination.In some cases, there is little option but to replace an electrolyte contaminated PCB but in such cases a ‘last ditch’ attempt at recovery can be tried using a combination of free flow flushing, ultrasonic cleaning and vacuum solvent cleaning to achieve the best possible cleansing of the contaminated PCB structure. With little to lose, it is worth a try. In really bad cases, I would remove the components from the PCB first to make the cleaning process more effective and remove the concern over component damage from the cleaning process and chemicals.

author: Peter A
author_rank: Newbie
timestamp: May 25, 2021, 06:40:32 pm
content: Hi Fraser,Thank you for a very comprehensive reply, a lot of food for thought. I am sure that I'll refer to this thread many times, as likely will others.regardsPeterA

author: electr_peter
author_rank: Unknown
timestamp: May 25, 2021, 07:54:13 pm
content: Battery leakage can have long term effects on product. AAA alkaline battery leaked in Fenix LD-01 flashlight few years back. After cleaning it worked fine. From that incident only NiMH rechargeable AAA's are used.A month ago the same flashlight stopped working again - case to spring connection somehow lost continuity, while head unit worked. Some rust was expected, but view of internal spring contact under microscope did not show anything suspicious. WD-40 and IPA bath was used, now flashlight works again. IPA did not help much as spring was clean to begin with, while WD-40 loosened rust a bit.

author: Eaglecrest
author_rank: Newbie
timestamp: June 02, 2021, 10:24:31 pm
content: electr_peter,I am not familiar with Fenix flashlights, what would be the big issue of cleaning battery leakage?

author: wizard69
author_rank: Super Contributor
timestamp: June 03, 2021, 03:06:28 am
content: You have gotten some really good suggestions for cleaning, which is great. Often the bigger problem after the initial clean up is the repair of the damaged components. In some cases the damage to battery contacts and springs can be so bad that you either should replace them or get them re-plated. The corrosion or rust on the contacts just lead to troublesome operation that can be frustrating.Quote from: Chasm on September 10, 2010, 01:32:23 amI know this feeling all too well! This has lead me to outlaw alkaline batteries at my house. I'd suggest doing the same thing as we have better technology these days. One of those technologies in rechargeable batteries such as Sanyo Enloops. The other is the availability of Lithium batteries in AA and AAA sizes. I'm not going out on a limb and say you will never have trouble with these, however your risks are greatly reduced. I use primary Lithiums in things that need to be operable in the extreme cold and may be left unattended for long periods (Car/Truck flashlights, go bags and such). For some things I haven't decided between Lithium primary cells and rechargeable.QuoteContact cleaning effectiveness is depends upon how heavily damaged those contacts are. In some cases it is far better to replace the contacts if that can be done. I've had significant issues with the coil spring type contacts, especially if they are staked to other sheet metal parts. It can be very difficult to clean well some of these parts.Once you get past the battery contacts themselves you can run into other issues that the electrolyte may come into contact with. One example is solution wicking into components and wire, then causing trouble over time. Sometime you may just need to replace wire or other components. Be especially mindful of items such as switches, sockets, SMD and other items that electrolyte can get under and be hard to remove. You need to evaluate the board to determine if your corrosive solution made it to these hard to clean parts. In some cases like push buttons or other types of switches, replacing them may be a good idea. In theory most of the PCB mounted switches are sealed for soldering but they all aren't and that seal might not resist your corrosive fluid. Once that stuff is inside a switch there isn't much you can really do.

author: electr_peter
author_rank: Unknown
timestamp: June 03, 2021, 06:09:22 am
content: Quote from: Eaglecrest on June 02, 2021, 10:24:31 pmFenix LD-01 is smaller flashlight with AAA battery, which consists of LED head and aluminum tube for battery. Aluminum tube fully encloses the battery and actually works as a switch (screw on tighter - turn on) via outer rim as negative contact and battery center as positive. I do not think such construction is specific only to Fenix.Tube is a single piece with spring contact wedged in the end somehow (which later lost contact due to rust). Cleaning leaked battery at the end of a closed narrow tube is not fun.

author: 6gv5
author_rank: Newbie
timestamp: June 05, 2021, 07:27:13 pm
content: Quote from: ElektroQuark on September 10, 2010, 07:10:56 amTrue, and if one lacks vinegar, common lemon juice (I mean squeezed from the fruit, not lemonade!)works equally well as it contains citric acid, with the added benefit of having a better smell

author: peteru
author_rank: Regular Contributor
timestamp: June 07, 2021, 07:05:43 pm
content: And your saliva is acidic too, so why not just spit on it to clean it?

author: Zero999
author_rank: Super Contributor
timestamp: June 08, 2021, 05:16:06 pm
content: Quote from: peteru on June 07, 2021, 07:05:43 pmSaliva is alkaline. If it was acidic, your teeth wouuldn't last long.I agree, using corrosive substances is a bad idea. Especially those which are not volatile, such as lemon, or citric acid and will leave an acidic residue. Vineger is not quite as bad, as it will evapourate eventually, especially white vineger, without leaving a residue, but still not recommended.