Feedback & Advice on using Ultrasonic Cleaners to Clean Arcade PCBs

[Berty]

I've done some searching on this topic within the forums and more broadly but I am keen to hear the experience of AA users in relation to the use of ultrasonic cleaners for use of PCBs. 

I have a large (15L) ultrasonic cleaner that I use for various bits but not PCBs... yet. 

So who is using these for PCBs and what chemicals / techniques are you using?

[Azure]

I don't have one at the moment, used to (on the long shopping list as I build my workshop back up again slowly).  They are great for pcb cleaning, used to use one back in pc motherboard repair days.  Problem is arcade pcb's are quite large and most single board games will not fit most regular ultrasonic tanks.  Solution depends on what you are trying to achieve, from tidy up cleaning flux on a repaired pcb to doing an initial clean on corrosion and other buildup on an incoming pcb.

[AskJacob]

My main concern is if it is a populated PCB, the ultrasonic action could get your cleaning fluid inside and past some "sealed" items like coils and even electrolytics. Probably rare to happen but just remember it is far more active than just soaking/brushing. It can also take carbon off any trimpots, so care is needed when using it.

I use IPA when cleaning certain electronics as it can also take off some fluxes, and dries taking any moisture with it pretty quickly. Just be aware that warm IPA + electrical equipment could get VERY exciting very quickly.

Edited September 8, 2021 by AskJacob
typo

[Berty]

1 hour ago, Azure said:

I don't have one at the moment, used to (on the long shopping list as I build my workshop back up again slowly).  They are great for pcb cleaning, used to use one back in pc motherboard repair days.  Problem is arcade pcb's are quite large and most single board games will not fit most regular ultrasonic tanks.  Solution depends on what you are trying to achieve, from tidy up cleaning flux on a repaired pcb to doing an initial clean on corrosion and other buildup on an incoming pcb.

Thanks @Azure. I am mainly interesting in using the cleaner to clean grubby boards prior to repair / troubleshooting and then afterwards to remove flux. I'm not sure what to believe online about chemicals for general cleaning. Chemicals to clean up flux tend to be a lot better documented though.

1 hour ago, AskJacob said:

My main concern is if it is a populated PCB, the ultrasonic action could get your cleaning fluid inside and past some "sealed" items like coils and even electrolytics. Probably rare to happen but just remember it is far more active than just soaking/brushing. It can also take carbon off any trimpots, so care is needed when using it.

I use IPA when cleaning certain electronics as it can also take off some fluxes, and dries taking any moisture with it pretty quickly. Just be aware that warm IPA + electrical equipment could get VERY exciting very quickly.

Thanks @AskJacob I want to use the cleaner on boards that have inductors, potentiometers and electrolytic caps. Do you know if it is just a matter of how long these components are submerged and / or does it come down to how the boards are dried post cleaning? 

[Azure]

Places that used them regularly are high volume (for us) and setup appropriately.  They would usually go into a cleansing bath rinse after the ultrasonic in a sealed container with an IPA sort of solution and then after a short rest in free air into a drying oven lowish temp to evaporate any remaining moisture.  After another short rest assembled back into unit and powered up for final testing.

Edited September 8, 2021 by Azure

[AskJacob]

A safe-ish way to use IPA can be to put the PCB in a big ziploc baggie, add enough IPA to ensure it will be covered, squeeze out the air and then put the baggie in the cleaner with plain water in the tank. Of course this needs a cleaner with the size to do that.

As to components getting damaged, basically you just can't chuck the boards in and leave them alone. For potentiometers for example, you want to keep an eye out that there isn't a thin stream of black coming out into solution, as it can be the carbon (not dirt!) being etched away. You can see a simple version of this with a lead pencil by poking the sharpened end into the tank - the lead starts to be eroded away. Of course the potentiometer carbon is harder and will take longer - just don't "set and forget" the clean cycle. Times and so on are really down to the tank volume, ultrasonic power rating and even if you have a basket or baggie in use. Shorter is better - you can always add time but not take it back!

[cwispy]

The usage of an ultrasonic for cleaning circuit boards is very safe. The bigger issue is what is used in the ultrasonic as the cleaning agent. See the other thread about never washing your boards in dishwashers for information about what to use as a cleaner.

 It is extremely unlikely that leaving a circuit board in an ultrasonic for even 1 hour or more will cause any damage to a circuit board. There has been tests done to validate this as well. However a board which is damaged in other ways, will need to be treated with some caution. The decision then will be whether to use the ultrasonic and then be prepared for more comprehensive repairs to the board substrate or tracks, but be confident that the contaminants are gone, or perform probably quicker and simpler clean and repair by hand and risk the board is going to continue to decay further over time due to contaminants that were missed by the hand clean.

Which ever way you go, you should ensure that after cleaning the boards in the ultrasonic, the boards are dried off thoroughly to prevent possible corrosion. Ideally the boards are placed in a drying oven to completely remove all residues. As mentioned in the thread above, we use Electrolube SafeWash Super for board cleaning and we also use it in our ultrasonics and have done for about 10 years without issue.

The best tip for using an ultrasonic with circuit boards is to use the heater to preheat the unit to around 45 - 50 Celsius for the best results. The temperature is not super critical, but it does have a huge difference on how quickly and effectively they work on removing the contaminants.

[Berty]

15 hours ago, cwispy said:

The usage of an ultrasonic for cleaning circuit boards is very safe. The bigger issue is what is used in the ultrasonic as the cleaning agent. See the other thread about never washing your boards in dishwashers for information about what to use as a cleaner.

 

Thanks @cwispy. Do you have any further insight into whether it is safe to place a PCB that has inductors into an ultrasonic cleaner? I am thinking about what @AskJacob mentioned in his earlier post regrading possible water intrusion. 

[Azure]

Most modern electronics is ok to get 'wet' while not powered.  The one part mentioned that I have not dealt with when I was doing it was onboard pots.  The issue would be more around the cleaning agent.  If the cleaning fluid is ok then they could always be relubed or even removed before immersion cleaning and refitted afterwards  Important part of immersion cleaning is to make sure it is dry before powering on.  That is why we both mentioned the rinsing and drying parts.  Don't go all out the first time you give it a try, start with a very light cleaning solution and progressively longer soak times (with ultrasonic and heating on).

[cwispy]

6 hours ago, Berty said:

Thanks @cwispy. Do you have any further insight into whether it is safe to place a PCB that has inductors into an ultrasonic cleaner? I am thinking about what @AskJacob mentioned in his earlier post regrading possible water intrusion. 

Yes it is safe to place inductors, capacitors and potentiometers into the ultrasonic. The issue is ensuring that the board and components are dried out properly after the ultrasonic bath and as Azure said above, using a cleaning agent that is designed to be used for cleaning of electronics. Things like potentiometers will take longer to dry out properly because they are open and moisture can get inside them. Unless an electrolytic capacitor or inductor is physically damaged they are fine to clean in ultrasonics. I would err on the side of caution when it came to paper capacitors and any other 40+ year old type components, but even they typically do not have problems with being cleaned in a ultrasonic.

[wiredoug]

i work on "is it quicker to remove it than worry about it" for any components im not sure on.

[Housematt]

I use a cheap Aliexpress dual frequency ultrasonic cleaner for all the PCBs I make, and any other PCBs small enough to fit into it. 

doesn’t take long, couple of minutes each side if you have dual frequency sweep 

for PCB fabrication I use a specialist ultrasonic PCB cleaning solution in the cleaner to get rid of the flux, then into deionised water bath to get rid of the cleaner , then into IPA bath to get rid of the water, then into the PID toaster oven over night. 

for cleaning old boards I use deionised water in the cleaner, then into ipa bath, then into the dehumidifier over night.

my cleaner is only tiny tho (6L) so a lot of older boards don’t fit

anything with a clock crystal will not survive long in an ultrasonic cleaner

[cwispy]

16 minutes ago, Housematt said:

anything with a clock crystal will not survive long in an ultrasonic cleaner

I have done some tests with some boards with crystals on them, leaving them in the ultrasonic for around an hour and they still worked fine. The only thing that suffered was the silkscreen and solder mask started to come off. Although the boards were not very good quality to begin with.

[Housematt]

1 hour ago, cwispy said:

I have done some tests with some boards with crystals on them, leaving them in the ultrasonic for around an hour and they still worked fine. The only thing that suffered was the silkscreen and solder mask started to come off. Although the boards were not very good quality to begin with.

Nice! I’ve always been diligently desoldering them and soldering them back on because the old-timers told me to 30 years ago and I never questioned it. Progress!