(Topic ID: 153565)

TerryB's Guide to Repairing Battery Damage

By terryb

3 years ago

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    #1 3 years ago

    This article has been replaced by the following updated and complete article.


    If you're curious as to why, just read on. If you're not interested in the drama, just follow the link above.

    I see a lot of CPU boards where battery damage is not being treated properly and as a result the alkali continues to eat away at the copper on the board until the board craps out (due to the alkaline damage) and it's sent out for repair (often after being damaged further in an effort to repair it).

    Friendly Reminder: Get the batteries off the CPU board!

    If a board has minor leakage then a flush with vinegar/water/alcohol is good enough. If a board has moderate to severe damage, it requires an involved process, including removing components for proper cleaning and evaluation of the damage. The key is knowing what to look for and how to properly clean and repair the board.

    I should mention first though that moderate to severe alkaline damage is best left to the pro's. You can be assured you will find a lot more damage after removing components. What compounds the issue is the alkali will get under the copper (traces and pads) and eat away at the adhesive that bonds them to the board.

    Even for an experienced solderer it is difficult to work on an alkaline damaged board without lifting a trace or pad--since they're barely hanging on to begin with. And it's worse yet if previous work was done on the board.

    The board below has minor alkaline damage. It is limited to the one small area, and below the batteries the solder joints are still shiny and there are no dark spots showing through the solder mask. In this case properly flushing the board (vinegar/water/alcohol) is sufficient.


    The board below has moderate to severe alkaline damage. While some areas are rather obvious (the damaged components and the solder mask at the bottom of the board) other parts, like the dull solder joints and the dark spots showing through the solder mask, are not. All of that damage needs to be removed and simply flushing the board is not enough. It will require both chemical and mechanical cleaning.


    The board below has alkali (the white powder) that was hidden until J212 was removed. It is unlikely the alkali would have been neutralized by flushing the board and this is why components need to be removed in order to properly clean and evaluate the damage.


    #2 3 years ago

    Prepping the Board for Cleaning

    Before flushing the board there's a couple of things we need to do first.

    Any socketed chip's that will get wet during the flushing process need to be removed. In the case of a WPC CPU board you can usually get away with leaving any chips above the batteries in place if you're careful while cleaning. While you've got the chips out inspect the lower part of the lead for corrosion. If there is any corrosion you need to clean or toss the chip and replace the socket since it likely is corroded internally.

    While we could do this after the flush, I always remove the battery holder and remove any sockets, chips and connectors where I want to inspect the damage and suspect I will need to physically clean the are.

    Note: When desoldering a board with alkaline damage you always want to clean the joints with a fiberglass pen and add flux. It is also common for the solder joints to have been eaten away and be low on solder. In that case you will need to add some solder prior to desoldering.

    I'm not going to go in-depth on the soldering techniques, but do suggest you review my soldering guide, which also covers advanced repairs like jumpers, stitches and eyelets--which will all likely be needed.


    So the big question at this point is which components should be removed. Alkaline damage will travel down from the point of leakage and will often spread out in an upside down V as it progresses. Any sockets, chips or connectors that have corrosion on the pins or brown spots in the surrounding solder mask should be removed. We will worry about dual-lead components later.

    In the last board in the post above the left battery leaked and the alkali traveled down the left side of the board. So I removed J212, J205 and the chips above them, but below the battery holder. In the image below I've already done some cleaning and you can see where the right battery leaked and how the damage spread as it moved down.


    I did remove all of the connectors but there was no alkali damage under the left and center ones.

    One important thing to note is the damage to this board didn't happen overnight. The longer you let a board sit with alkali on it, the more the damage spreads and the bigger the process to repair. So if you swap out a CPU board with battery damage and throw the old one on a shelf, at least take the time to flush the board even if you do nothing else. Someone later on will appreciate it.

    #3 3 years ago

    Importance of Removing all Alkali

    One more thing before we get into the chemical cleaning of the board. If you've never seen it this may surprise you, but alkali will completely eat through a copper trace if left untreated. And when the alkali is under the solder mask it requires mechanical cleaning, which we'll cover later.

    Another thing to understand about alkali is it does not always show up as a white powder. Depending on the stage it is in it can be completely invisible. That is why we look for the results of alkili damage (see the resistor pads in the second image) and even with that approach you can miss the early stages of alkali damage.

    Your best friend when evaluating battery damage is a magnifying glass or microscope so you can catch the damage as early as possible. To he honest, once you see it, you're too late. Not that it can't be fixed, but it's a lot harder.

    The ground plane in the image below should be about a 1/4" longer and the part that is lifted would turn into copper dust as you touched it. You might also correctly guess this is why traces lift so easily on a battery damaged board. This one lifted without heat being applied. You will also note an inductor that needs to be replaced in the photo.

    I'll have more examples of this as we proceed.



    #5 3 years ago

    Neutralizing Alkali

    Everyone has their own little preferences on neutralizing alkaline damage, but they all include (or should) the following three steps.

    1. Neutralize alkali with vinegar.
    2. Flush with water.
    3. Flush with alcohol.

    I use a baking pan (wive's love when you use their kitchen utensils for your projects) to catch the fluids and place a piece of wood under the end I want to keep dry so the board is at a slight angle. A fairly stiff ESD safe brush and a syringe or squeeze bulb will also come in handy.

    During the vinegar stage you want to give it enough time to completely neutralize the alkali. I will spend 3-5 minutes cleaning both sides of the board. Use a syringe or bulb and make sure you get vinegar under any chips and sockets. While the board is soaking you want to scrub the board as this helps loosen and remove the alkali. Keep the board wet as you are working so the vinegar has time to complete the neutralization process.

    I've seen people recommend you dilute the vinegar with water, but you really want if full strength.

    While it is best to use distilled water, tap water is acceptable for the second step. Since all we're doing in this phase is flushing off the vinegar you can move along more quickly and don't need to use a brush. You do want to use a syringe or bulb to get under sockets and chips though.

    The reason our last flush is with alcohol (use 91% or higher) is that it will displace water. Again, no brush needed and make sure you get under any components.

    Once you're done use some canned air or an air compressor to remove any remaining liquid from the board. You will want to do this from a couple of different angles and make sure you get under the components. We could let it air dry, but this is faster.

    #6 3 years ago

    Mechanical Cleaning

    Now that we have the surface alkali neutralized we need to expose any that has gotten under the solder mask. If we don't it will continue to eat away at the copper. Also while we have removed the surface alkali there is still corrosion on the joints which needs to be removed. It is important this is done before we proceed or it will be extremely difficult to reflow or solder any of the dual-lead components.

    The following two images are after chemically cleaning the board.

    In the first image you can see where the alkali has eaten into the board at U20. There are also several damaged traces and through-holes. The trace circled in red was intact, but lifted from the board, and when I prodded it with a solder pick it broke. In addition the area above circled in red has cold solder joints from the alkaline damage.

    I also circled some of the areas where the alkali has gotten under the solder mask.

    In the second image you can see damage to the ground plane and corroded pads where the connector was removed. If these pads are not properly cleaned up solder will never properly flow through the hole and provide a good connection.


    In addition to exposing any alkaline damage under the solder mask during physical cleaning we also need to expose any traces/pads we will be working on or that are suspect.

    #12 3 years ago

    I normally don't talk much about my experience, but in this case I guess I will.

    I have a EE (although my career was in manufacturing and field service) and have been dealing with corrosion on boards for 40 years. Although I will be the first to admit the number of years, or the degree, is not the important issue. My experience is in medical (MRI, Cat-Scan, X-Ray, etc) and aviation electronics where the standards (and training) are a little bit higher than in pinball (no insult to other pinball technicians intended). I've manged a multi-million dollar board repair/rework facility and on average probably spent 4 weeks a year (for twenty years) at seminars and training sessions.

    So you can believe whatever you want clay, and I'm not going to waste my time asking for your sources since every time I do you never provide any proof other than to tell me about your years of experience. As far as your feelings on alkaline, I can assure you that you are in disagreement with the IPC and the entire electronics industry. There is no way that bead blasting, which I was going to cover next--although with proper techniques rather than what you have previously recommended, will get into every nook and cranny and get rid of every bit of alkali. Just not possible.

    We both know this isn't about doing something the right way, it's about your ego since the last time I checked you are not the arbiter of what is and is not correct when working with electronics.

    #15 3 years ago
    Quoted from cfh:

    The problem with chemically treating corrosion is a deep one. It cannot be effectively dealt with by the average person. If chemical neutralization of alkaline damaged boards is your goal you need to know several things.
    First you need to know the basic pH of the alkaline. Because if you were going to neutralize it your acid it needs to be of a similar quality. Nobody here can do chemical analysis of the MPU board to determine exactly what strength of acid will properly neutralize the base.
    The second thing needs to be dealt with is how long to actually neutralize it. Again without knowing your pH numbers this again is just guesswork.
    What happens in most situations is the alkaline is either under treated or over treated. In either case the result is a continuation of corrosion. This is not an effective way for anybody in the pinball world to really deal with corrosion.
    This is why I tell people that using chemicals to try and neutralize corrosion is not a winning scenario. If it makes you feel better go right ahead. But in the end it is not going to really do much.

    I showed that post to a buddy of mine with a Doctorate in Chemistry and he laughed for about 10 minutes and then told me to look up the Dunning–Kruger effect.

    #30 3 years ago

    I've calmed down a little bit (just a little).

    Firstly, I have no issue whatsoever with people asking questions or having a discussion about different opinions. In fact that's how you learn and become more knowledgeable. On the other hand, I'll be damned if I'm going to let two self-professed know-it-alls who don't have 1/100 the professional board repair experience I have--and have probably never attended a professional electronics seminar, training session or conference where things like this are discussed--call me full of shit.

    As I said I've just calmed down a little bit. Although I do still get a laugh every time I think about Clay's suggestion that mustard is better than vinegar in neutralizing alkaline damage and picture someone pushing the mustard under a chip with a toothpick (or maybe a cocktail wienie). I will be telling that story at the next conference I speak at.

    I can confidently state that all professional board repair/rework facilities use acid to neutralize base damage on a board and use a base to neutralize acid damage on a board (as is recommended by the IPC). Of course they don't use vinegar (or mustard), they pay about 10 times as much for something with roughly the same pH. I figured since you have to buy the professional solution by the barrel, most hobbyists would prefer an equivalent solution.

    For those hobbyists who are now totally confused about chemically neutralizing alkaline damage let me explain the fallacies in the previous assertions. After this I'm done with the thread and when I have time will post the information on my website where people can have respectful discussions.

    For anyone interested there's already an article on media blasting on my free website.


    1. You will never get glass bead media into all the nooks and crannies where alkili hide since the beads are thousands of times larger than an alkali molecule. Have a look at the inductor on a WPC CPU board (shown below) and explain to me how the media gets in-between the coils of wire and neutralizes the alkali that have seeped in there. The same is true all over the board.
    2. If you do not chemically clean the board then you will need to remove all of the chips, sockets and connectors. Because if even one has some alkali under it you're screwed since clearly bead blasting will not get under components.
    3. If you bead blast before you neutralize the alkali that is "above the surface" you are in fact spreading the alkali molecules around the board and contaminating other areas. At this point you need to clean the entire board, not just part of it.
    4. If you look at the photos I've posted above you can see where the alkali has gotten under the solder mask. Where else do you think it's hiding that you can't see?

    Now let's talk about bead blasting.

    1. Most hobbyists aren't going to bead blast their boards. Therefore a combination of chemical and physical (sandpaper or whatever) is needed. In fact if Clay would have shut-up and just listened he would have found that I do a three step process: chemically neutralize the damage, bead blast the board and chemically neutralize it again.
    2. According to a study done by NASA, glass beads create an electro-static discharge of -1,764 to -2,097 volts during media blasting. This was deemed to be "unacceptable levels of surface voltages." In other words you are potentially damaging components. Therefore you really should use an ESD safe micro-blaster. The reason for the micro-blaster as compared to using a sand-blasting rig, which is a serious no-no by the way, is so you can control and minimize the media hitting sensitive components (CMOS and other chips for example). You also want to prevent damage to the component packages.
    3. Even the board repair guys aren't going to spend several thousand dollars for an ESD micro-blaster. Although I do have a reasonably priced (home-made) recommendation in my media blasting article above.
    4. Since you should be doing controlled media blasting and not bombarding chips you are not going to remove all alkali. How are you going to get under all of the resistors, for example, without damaging the coating on the resistor. The answer is you can't unless you lightly bead blast in which case you're probably not getting all of the alkali. See the image below where I damaged a resistor package while bead blasting.
    5. Any type of physical cleaning requires you to see where the damage is. As I have previously stated alkali is not always a visible white powder or displayed by dark spots under the solder mask. In other words if you're relying on the physical approach you would have to remove every bit of solder mask on the lower part of the board because any of it could be contaminated.
    6. FYI Clay, glass bead are so 1980's. Most board repair/rework facilities are now using wheat starch.

    Rather than tell everyone they're an idiot if they don't do it my way, I'll leave it up to each of you to make up your own minds based on the information provided.

    This is how you have a discussion Clay, rather than making hyperbolic, ill-informed statements and calling people out. Of course as I said before this isn't about neutralizing alkaline damage, it's about your ego.

    This thread is a perfect example of why Pinside can't have nice things.



    #55 3 years ago
    Quoted from barakandl:

    Corrosion goes deep down. Abrasion is needed hands down... You are foolish to think otherwise.

    Exactly who said mechanical cleaning was not necessary?

    Quoted from vid1900:

    Then you can soda or wheat blast away without worry about spreading the alkali or contaminating reusable blasting media.

    Good point Vid about the contamination.

    Quoted from johnwartjr:

    I expect the people working on those to have a much higher degree of training, better equipment, etc. If every pinball tech had that level of equipment and experience, none of us would be able to afford the pins!

    I agree. If you read any of my guides you will find that I adjust my advice for pinball hobbyists. In my soldering guide I recommended the Hakko digital iron rather than the Metcal we use at work. I've got a bead blasting solution on my website for about $30 that's a whole lot better than using a sand-blasting setup and cheaper than an ESD safe micro-blaster that costs several thousand dollars.

    Quoted from johnwartjr:

    I'm playing with Cratex, a rubberized abrasive in stick format, similar to the socket cleaning sticks that PBR and Marco sells.

    Sounds like a good idea. Look forward to hearing how it works. A fiberglass pen is great when you're working around leads, but not so much on traces and such.

    Quoted from TheLaw:

    Lots of butt hurting in this thread.

    I can't speak for anyone else, but I'm not butt hurt. Although I truly don't understand why two people are so butt hurt (to turn a phrase) about me recommending chemical->mechanical->chemical cleaning.

    I could just put my guides on my website and pinwiki and call it a day, but I enjoy the discussion on Pinside and think it makes the guides better. On the other hand, when someone writes a guide I am very respectful of their efforts and would never consider hijacking it and making it about me.

    I don't write these guides for my benefit, I write them in an attempt to help other people (as Vid, ChrisHibler--on pinwiki--and many others do), but once it's gone completely off the rails I see no point in continuing. Seriously we've got to the point where barakandl is accusing me of saying you should not use abrasion on a battery damaged board (what the hell?). Some pinsiders may enjoy the drama, but I wouldn't read through all of this crap just to get a little information.

    I forgot my point half-way through the last paragraph, so I'll add that I do this for fun, when it ceases being fun I'll quit doing it. This thread has not been fun.

    #58 3 years ago
    Quoted from johnwartjr:

    I keep junk boards to practice on.... I know what I'm trying next!

    You're going to try not using vinegar.

    #62 3 years ago
    Quoted from TheLaw:

    Vid said toilet bowl cleaner and was a genius.

    I didn't give Vid a thumbs up; I'm still trying to figure out if he's serious.

    #80 3 years ago

    I plan on completing the guide on my website with peer reviews. Once it is done I will post it on Pinside en masse (in another thread that I will link here). This is really not my preferred approach since, as I said before, I enjoy the discussion and it makes for a better article. Of course there will be discussion on Pinside, just all at the end of the article. Give me some time, my approach to articles requires some research and due to a bum shoulder I can only work on this a couple of hours a day.

    1 month later
    #100 3 years ago

    Great info john.

    I haven't forgotten about my article, just life's getting in the way at the moment (and for likely the next few months).

    4 weeks later
    #102 3 years ago

    I finally got the article posted at the following link. My apologies again for taking so long to get this done.


    John, I used two of your photos as we discussed. Feel free to add your other photos and experience with the Cratex bullets (it would be nice if it's all in one place).

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