Electronics > Repair
Ultrasonic cleaner size: 10L vs 6L
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SolderOcelot:
So I bought this cheap ultrasonic cleaner from AliExpress as my first ultrasonic cleaner ever to undo liquid damage on laptop motherboards. Yes, I cheaped out, but since these are being sold at big chains in US and UK I thought it might not be too bad as an entry model.

I'm looking for advice from experienced users, specifically on the size. I'm very obsessive about getting the right size and I doubted long and hard and got the 10L instead of the 6L variant. Only the width is different and thus in the 10L variant you can lay the motherboard flat and in the 6L often times you have to lay it at an angle so it fits.


* Basket size 6L: 30cm x 12cm x 15cm (200W heating unit / 180W transducer)
* Basket size 10L: 30cm x 24cm x 15cm (200W heating unit / 240W transducer)
Round 1
So I took a laptop motherboard with some water corosion as a test sample. Here is the process of the first run:

* Fill it with Distilled water / IPA @ 6:1 ratio
* Heat the tank to 60°C
* Let it run for 5 minutes without board to degass because it has no dedicated "sweep mode" for degassing
* Place the board in (damage facing down for optimal agitation) and let it run for 5 minutes
* Result: corosion only ~25% removed
Round 2
I talked to my neighbour and he said that I should have gotten the smaller tank because the agitation / vibration would then reach the board easier and you would need less runtime. So I did a second run with longer agitation time:

* I use the same liquid (lol)
* Heat the tank to 60°C
* Let it run for 15 minutes
* Place the board in (damage facing down for optimal agitation) and let it run for 5 minutes
* Result: the gunk is gone and you can even see factory flux getting removed / displaced as well so effectiveness increased. However, you can see ultrasonic cleaner damage to the paper sticker, see photo. So a 15 minute runtime might be risky.
I have 2 straightforward questions:
1) Do you think the 6L basket size is enough for most laptop motherboards?
2) Is it true that less runtime is needed for the smaller tank and thus is safer for laptop motherboards (or any other populated pcb for that matter?

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SteveThackery:
I'm afraid I cannot contribute anything useful regarding the suitability for a motherboard.  However, I have been using ultrasonic cleaners for 35 years or so.

The ultrasonic power is important, and in particular in relation to the volume of the fluid. Some low cost cleaners use the same circuit board and transducers over two or even three different sized models.  50W of ultrasonic power in a small tank can punch holes in metal foils, but in a larger tank can be insufficient to do a decent clean.

I've never heard of mixing water and alcohol for use in an ultrasonic cleaner, but I must emphasise again that I haven't used an ultrasonic on electronic boards.  In the early days I used trichloroethane 1.1.1, which worked brilliantly, but of course every time you uncapped the bottle you wiped out another cubic mile of ozone (this is an exaggeration, but you know what I mean!).  Nowadays most ultrasonic cleaning fluids seem to be aqueous: surfactants plus water, although those intended for use on metal parts usually have a hydrocarbon base.

In terms of cleaning time, I often let the machine run for up to 30 minutes.  There is a reason: if your cleaner does not have a heating element then the longer you run the cleaner the hotter the fluid gets, and that always (in my experience) helps the cleaning action.  A heating element is definitely worth paying a bit extra for, in my view.

I realise you know this, but I want to emphasise it: the transducers are affixed to the bottom of the tank by a special cement which is glass-hard, in order that it doesn't absorb any energy from the transducers.  It is therefore very important NOT to pour hot water into the tank, because the sudden differential expansion CAN cause the cement to crack.  Not always, but yes, it has happened to me.

Nearly all cleaners use a swept frequency, but usually swept at the mains electricity frequency which I suspect is too fast.  I modified one of my cleaners to sweep much more slowly, and I think it is better because it allows the vibration patterns to build up in the fluid.  Some cleaners offer a manual control over the frequency (you should set it for maximum agitation), and others have a closed loop system where they automatically find the frequency at which maximum energy transfer from the transducers to the fluid takes place.
SteveThackery:
About your question 2 specifically: it isn't a straightforward answer because it depends on the power density in the fluid.  If the same wattage is being concentrated in a smaller tank then yes, the necessary runtime is less.  Otherwise you'll need to compare the watts-per-litre of each machine to compare.

About degassing: perhaps my experience is insufficient, but I've not come across a "dedicated sweep mode" for degassing. All of mine pulse the power at about 0.5Hz and 50% duty cycle to do the degass.  Maybe the more professional ones use special sweep modes?

Edit: I'm too embarrassed to put up yet another post, so I'm going to cheat by adding some stuff to this one!  Another point I want to add: some cleaners have a plastic lid, others a metal one.  In general I've found that the plastic ones tend to be a better fit, and importantly, they mute the horrible noise from the cleaner more thoroughly.  I cannot guarantee this is true for all cleaners, but perhaps you will arrive at your own conclusion.  I can't stay in the room for one of my cleaners because the noise is unbearable - a really harsh, high frequency, teeth-tickling racket.

Be aware, though, that if you do use one with a plastic lid then you probably won't be able to use anything other than water (and some alcohols, maybe?) in the tank. In my experience most solvents eventually end up causing the plastic to fog, craze and - if you wait long enough - crack.  Some make the plastic sag instead.

If you want to put lots of small, and possibly delicate, parts in the cleaner you ought to put them on a platform so they are off the base of the tank.  Plastic trays absorb ultrasonic energy, so something stainless steel would be better. Fine meshes (like a tea strainer) greatly attenuate the ultrasonic vibrations.

One last thing. The design of the cleaner in terms of keeping the cleaning fluid away from the electronics inside is obviously very important, but you'd be amazed by some of the crap designs.  They all have a seal around the top of the tank, but the good ones also have a kind of double-walled arrangement whereby any fluid that does get past the seals is caught and directed to a drain hole underneath the cleaner.

Sorry - this has become a bit of a brain dump.
SolderOcelot:
First of all, thank you for all your input. Although it doesn't directly address my individual issues, still an interesting read.


--- Quote from: SteveThackery on July 08, 2024, 04:31:47 pm --- Some low cost cleaners use the same circuit board and transducers over two or even three different sized models.  50W of ultrasonic power in a small tank can punch holes in metal foils, but in a larger tank can be insufficient to do a decent clean.
--- End quote ---
The 6L variant has 200W heating power and 180W transducer power. The 10L has 200W heating power and 240W transducer power. Seems like they took this into consideration.


--- Quote from: SteveThackery on July 08, 2024, 04:31:47 pm ---I've never heard of mixing water and alcohol for use in an ultrasonic cleaner, but I must emphasise again that I haven't used an ultrasonic on electronic boards.
--- End quote ---
Finding the right recipe is the next project! Here in NL there aren't many ready made stuff to be found.


--- Quote from: SteveThackery on July 08, 2024, 04:31:47 pm ---In terms of cleaning time, I often let the machine run for up to 30 minutes.  There is a reason: if your cleaner does not have a heating element ...
--- End quote ---
True, but mine does! :-) it takes 45 minutes to heat from 24C to 60C.


--- Quote ---Edit: I'm too embarrassed to put up yet another post, so I'm going to cheat by adding some stuff to this one!  Another point I want to add: some cleaners have a plastic lid, others a metal one.
--- End quote ---
Mine is metal and I can not sit in the same room..
SteveThackery:

--- Quote from: SolderOcelot on July 08, 2024, 05:05:54 pm ---
The 6L variant has 200W heating power and 180W transducer power. The 10L has 200W heating power and 240W transducer power. Seems like they took this into consideration.


--- End quote ---

Looks like the 6L one should be a bit more punchy, then.  By the way, I'm sure some boffin will tell you that "watts per litre" is not the whole story, but it seems about right to me.
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