I would like to know why my new ultrasonic cleaner does not clean my circuits

Thread Starter

Joël Huser

Joined Jun 30, 2019
42
Hi everybody,

I've tried my new 22 [L] ultrasonic cleaner some days ago with 4x dirty PCBs, especially stained by rosin from welding wire.

First try : only deionized water, no heating, ultrasonic vibrations during 5 [min]. No result
Second try : only deionized water, heating at 40 [°C], ultrasonic vibrations during 10 [min]. No result
Third try : 3/4 deionized water and 1/4 isopropyl alcohol, heating at 50 [°C], ultrasonic vibrations during 15 [min]. A small result.

The attached user manual is a little bit skinny, and poor in images.

Just one thing : these 4x electronic boards have been soldered a "long time ago", in January 2018. Does this parameter matter ?

Sorry, no pictures available, because my smartphone's camera is out of order. Could someone help me ?

Joël
 

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Wolframore

Joined Jan 21, 2019
1,797
For rosin flux that's basically dried out you will need more time. I suggest leaving them immersed in ethanol for a week. Then try your ultrasonic cleaner to remove any residue.
 

jpanhalt

Joined Jan 18, 2008
10,245
This is the major component in rosin flux:
upload_2019-7-2_16-32-6.png

It is soluble in absolute alcohols, but a little water decreases that solubility a lot. You could try household ammonia and your alcohol mixtures, but I suggest just trying dish detergent in water first. A 3:1 mixture of water and isopropyl alcohol is not much better than water alone.
 

BobaMosfet

Joined Jul 1, 2009
1,208
Hi everybody,

I've tried my new 22 [L] ultrasonic cleaner some days ago with 4x dirty PCBs, especially stained by rosin from welding wire.

First try : only deionized water, no heating, ultrasonic vibrations during 5 [min]. No result
Second try : only deionized water, heating at 40 [°C], ultrasonic vibrations during 10 [min]. No result
Third try : 3/4 deionized water and 1/4 isopropyl alcohol, heating at 50 [°C], ultrasonic vibrations during 15 [min]. A small result.

The attached user manual is a little bit skinny, and poor in images.

Just one thing : these 4x electronic boards have been soldered a "long time ago", in January 2018. Does this parameter matter ?

Sorry, no pictures available, because my smartphone's camera is out of order. Could someone help me ?

Joël
Try rubbing alcohol and a toothbrush. Test on small section first.
 

joeyd999

Joined Jun 6, 2011
4,429
Interesting, made by Alconox. The old Alconox (circa 1960's) would clean our dirtiest glassware, particularly at 60 to 80°C. If it failed, the only alternative was dichromate in sulfuric acid. I have kept some of the old stuff for all these years, but haven't needed it.
I used to use Liquinox for boards requiring ultra low surface leakage current. Liquinox in hot DI ultrasound wash, hot DI rinse, vacuum oven dry. Worked like a charm.
 

Thread Starter

Joël Huser

Joined Jun 30, 2019
42
It's been 4 days that my circuits are bathed in 99 [%] pure alcohol. No more traces of rosin flux ! I am happy !

I would like to try now my ultrasonic cleaner during 10 [min] with only 99 [%] pure alcohol to finish washing ? The device will not be damaged ?

Joël
 
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