isopropyl alcohol leaves residue...

[auato]

Hi all.

I bought from RS Components some specific 99.7% isopropyl alcohol to clean some PCBs
(link) ... but after the cleaning, remains a lot of residual traces (see pic)

I use a generic brush with bristles cutted

 

[OLIVE2222]

A pcb mounting sub-contractor we are working with is using acetone after the soldering process.

 

[shrtrnd]

Are you sure that's not dirt/dust from elsewhere on your board?
That shouldn't have come out of an isopropyl container.
You didn't melt some kind of conformal coating on the board with the alcohol, did you?
I don't know, just doesn't make sense from simple isopropyl.

 

[daddles]

Find out if it's in the IPA: clean a mirror carefully, then put a few drops of the IPA on the mirror and let the thing dry. You shouldn't see any residue. If you do, you might want to get it analyzed at a local chem lab to find out what the impurities are.

 

[auato]

Are you sure that's not dirt/dust from elsewhere on your board?
That shouldn't have come out of an isopropyl container.
You didn't melt some kind of conformal coating on the board with the alcohol, did you?
I don't know, just doesn't make sense from simple isopropyl.

It is very strange Maybe there is a coating that melts or there is dirty that I spread accidentally on the board as you say. But if I use the flux, the cleaning is good on the PCB and there are no residues. I am not aware about that mystery. The isopropyl container doesn't seem dirty.

 

[davelectronic]

The isopropyl alcohol might have dissolved some PCB chemical residue on the PCB, i soldered some new PP3 9 volt battery connections on some gear today, first time i opened it and there are patches of chemical residue on the board, your board looks like dust dirt etc ans the alcohol has spread it around, unless the batch you have is contaminated, best try the mirror test Jackorocko said try, one pass over a clean mirror with a clean applicator, brush or something, as the alcohol evaporates the residue will show, if not, tut tut your board was dirty and you dissolved the dirt, drown it and use a new brush, gently, not sure about acetone, ive worked in the GRP / CF trade molding and acetone is aggressive stuff, not sure on PCB, it might be ok, i don't do PCB production, oh don't drink any of the chemicals. LOL.
Dave.

 

[auato]

I tried to follow the trick of @daddles and @davelectronic by a little mirror. I believe my brush is dirty because if I leave evaporate the isopropyl, then I do not find any trace but if I spread the isopropyl with my brush, after drying, I can see a large opaque stain over the mirror

Thanks for tip

 

[davelectronic]

isoprphyil alcohol

OH, you wandered where that varnish / fence stain brush got to, OOP'S.
Dave.
PS. drown it in alcohol see if that removes it, or pressure washer, or washing machine, not a boil wash, keep look out for the misses, sorry only joking, no, drown it in alcohol, or white spirit then isoprophyil.
Should be ok, or acetone as mentioned, oh and no more staining / varnishing / or french polishing your pcb's.

 

[shrtrnd]

Sounds to me like the problem has been found.
Might be about time to buy a replacement brush.

 

[auato]

Hello mates.

I confirm that my brushes were dirty

Thanks all

 

[davelectronic]

Well its a mistake your not likely to repeat, keep a set of small brushes specifically for electronics cleaning, there not that expensive, ive even got a soft tooth brush in my box, no not for my teeth, but useful for intricate areas.