Help with ultrasonic cleaning

[gaminn]

Hi,
I have small Chinese ultrasonic cleaner (3l, 100 W of ultrasonic power, 2 transducers) and I used IPA in it to clean my boards. It didn't work well (I had to brush the boards a lot). So I purchased
 Chemtronics ES132 Flux-Off, I use 1:7 solution (deionised water) heated to 50 °C. The results are maybe a little better, but not as expected. I use mainly UV-50/UV-80 chinese flux.

The board in the picture is extremely dirty but the problem exists even with relatively clean PCBs. After 3 minutes in ultrasonic cleaner the flux is not removed at all, but it is soft (second picture). Do you think more ultrasonic power will help? Better ultrasonic cleaner? I try to move my PCBs in the ultrasonic cleaner to avoid void spots of ultrasonic power.

Thanks for any advices.

[David Hess]

You probably need a different solvent.

You might want to test  your ultrasonic cleaner with a small section of aluminum foil.  If it is operating properly, then it should punch holes in the foil.

[JonM]

I have a Crest Powersonic P500H-45 ultrasonic cleaner which is on the high end, but that may not actually matter a lot. For small boards I fill the ultrasonic cleaner with water, raise the basket, and then place the boards in small glass containers with 99% (or 91%) isopropyl alcohol. So far that has done an excellent job of removing flux after about five minutes of ultrasonic power. I do not usually add heat for this application.

[Psi]

Hi,
I have small Chinese ultrasonic cleaner (3l, 100 W of ultrasonic power, 2 transducers) and I used IPA in it to clean my boards. It didn't work well (I had to brush the boards a lot). So I purchased
 Chemtronics ES132 Flux-Off, I use 1:7 solution (deionised water) heated to 50 °C. The results are maybe a little better, but not as expected. I use mainly UV-50/UV-80 chinese flux.

The board in the picture is extremely dirty but the problem exists even with relatively clean PCBs. After 3 minutes in ultrasonic cleaner the flux is not removed at all, but it is soft (second picture). Do you think more ultrasonic power will help? Better ultrasonic cleaner? I try to move my PCBs in the ultrasonic cleaner to avoid void spots of ultrasonic power.

Thanks for any advices.

Louis Rossmann tried quite a few ultrasonic cleaners before he found one that actually works.
Even some of the expensive brands didnt work well.

He uses a Crest Powersonic unit with Branson EC Electronics Cleaner Solution

[German_EE]

The cleaning solution is the key. Once flux has set hard IPA will do a poor job of removing it from a PCB and you need to use specialized flux removers. Also, pay attention to bath temperature, a bath at 50C will be a lot more effective than a bath at room temperature.

[gaminn]

I tested my ultrasonic cleaner with aluminium foil - it got punched after a minute.

I did another test with other quite dirty board and it took 30 min in 60 °C solution to clean the board completely. This time is not acceptable.

Crest is nice, but I would need to see the difference between Crest and some cheaper cleaner to buy it - it is really expensive.

I will probably do some experiments with cleaning solution. Can you recommend some? I already have IPA and Chemtronics ES132.

[sn4k3]

Don't use IPA, you need about 50-60ºc, IPA will evaporate easy so is money to the pit.
You need proper solution, i do 20% of swas safewash super with distilled water at 60ºc. Lately i use only the distilled water (100%) with success
Ultrasonics with sweep function also work better for this kind of aplication.

Your ES132 looks OK for the job, read datasheet, some include the misture recommendation given some cases.

USAGE INSTRUCTIONS:
For industrial use only.
Read MSDS carefully prior to use.
Dilute 1:10 with deionized water for general
cleaning. Can be used in hot or cold
immersion, ultrasonic or aqueous cleaning
systems. For immersion systems, soak as
necessary. For ultrasonic cleaning, add
Flux-Off Aqueous to the ultrasonic
cleaning tank, allow about two minutes for
the mixture to degas, and immerse the part to
be cleaned in the ultrasonic cleaner. After
cleaning, rinse parts thoroughly in deionized water and dry where required

PS: Your boards look like they had a flux bath

[Lord of nothing]

@gaminn where are you from?

[Howardlong]

FWIW I use Elctrolube Safewash Super, SWAS05L.

My main requirement is ionic removal, for ultra low power button cell powered miniature devices.

I don't think I've ever seen anywhere near that amount of residual flux on a board. It almost looks like a badly applied conformal coating! Have you been to the Louis Rossmann school of flux application? ;-)

[Gyro]

I'm surprised nobody mentioned it, but you should never use IPA in a consumer Ultrasonic cleaner. It produces an aerosol (not just vapour) above the surface which is extremely flammable and can travel across the bench to an ignition source.

Some industrial cleaners use IPA or other flammable solvents, but they include an inert gas purge to remove oxygen.

[coppercone2]

when I was a kid I mixed up a buncha crap including soap, alcohol, acetone, cleaners, (nail polish remover) and maybe hydrogen peroxide in the bathroom. In small amounts just messing around. (yes I know fumes are toxic but it looked cool)

It made a foam which I decided to throw a match on. It exploded loud enough with a small lattes worth of foam to almost make my ears ring.

[MilwaukeeMacRepair]

The only thing IPA is good for is final rinse to collect and chase away water. A toaster oven set to 100C. If you want to remove flux: NOTHING beats Acetone, bang for the buck. A large rectangular flat plastic storage bin with a good sealing lid - filled with Acetone will clean many boards. I lay a couple different size bristle brushes and a box of nitrile gloves on top that container. THEN, to the ultrasonic cleaner - so as to save from fouling the solution. IPA is almost USELESS in comparison to acetone for removing flux. Lacquer thinner works great. MEK (methyl ethyl ketone) is AMAZING...but mind the fumes. And the skin contact. Some more whiny / picky people prefer D-Limonene or ZEP low VOC solvent.

[ender4171]

I don't think that is flux.  Looks like conformal coating.

[ogden]

I don't think that is flux.  Looks like conformal coating.

To me it looks like dried-out rosin flux. "Caramelized" flux as conformal coating Choice of flux definitely is main problem here, not cleaning solutions/liquids.

[Psi]

If you want to remove flux: NOTHING beats Acetone, bang for the buck

I would be concerned about all the plastic components dissolving if i used acetone on a PCB.

What I do is two IPA washes with a brush and some gloves.
One in my dirty/used IPA solution and then again in a fresh (or near fresh) IPA solution for a rinse.
The first wash just gets off all the big chunks of flux so that the fresh IPA lasts longer.
The second wash gets rid of any white flux streaks left on the pcb.

I always blow the IPA off the PCB with compressed air while it's wet.
Otherwise you just get dissolved flux reforming on the pcb as it dries.
Obviously i'm careful not to do this near a flame. But i don't do big enough batches to be too worried about flammability.

[Bark]

Hi,
I have small Chinese ultrasonic cleaner (3l, 100 W of ultrasonic power, 2 transducers) and I used IPA in it to clean my boards. It didn't work well (I had to brush the boards a lot). So I purchased
 Chemtronics ES132 Flux-Off, I use 1:7 solution (deionised water) heated to 50 °C. The results are maybe a little better, but not as expected. I use mainly UV-50/UV-80 chinese flux.

The board in the picture is extremely dirty but the problem exists even with relatively clean PCBs. After 3 minutes in ultrasonic cleaner the flux is not removed at all, but it is soft (second picture). Do you think more ultrasonic power will help? Better ultrasonic cleaner? I try to move my PCBs in the ultrasonic cleaner to avoid void spots of ultrasonic power.

Thanks for any advices.

No one has mentioned this yet but I would not use anything with discretes in an ultrasonic cleaner.  You are going to break bond wires or worse, doesn't matter if it is spread spectrum or not.  I'll bet 5 minutes in that cleaner and you'll start seeing failures from the IC's depending on what process and bond wire diameter/material they use.

[coppercone2]

there is a document on this, mtbf is not effected unless your power levels are really high and you are doing it for a long time (>10min). i think it was like less then 5% after 30 minutes for long term reliability on 5x typical home cleaning unit power (i.e. harbor freight).

with good parts. cheap shit made with a bad/non calibrated spot welder and no QC is obviously suspect as usual, so alibaba beware (no one wants to do destructive bond wire yield tests, after all you can sell every part)

a wire bond is not that fragile.. but it requires a good weld setup. bad welds can be pathetically weak/brittle.. and its easy to do (i.e. your first arc weld)

[RiffRaff]

I have observed IC failures from only a few minutes in an ultrasonic cleaner, multiple times!  In every case, it went out into the field working fine and failed quickly.  Ultrasonic cleaning was suspected as the culprit, and subsequent boards were cleaned w/o ultrasonic, this failure mode immediately dissapeared.  Tried two different brand ultrasonic cleaner, both recommended for electrical parts cleaning, still saw the same failures.  I believe all the failures were with surface mount IC's from TI and another manufacturer which I do not recall.  Gave up on the ultrasonic cleaner!