Quick question about soldering residue cleaner

[eh là bas ma]

Hello,

I've been using some residue cleaner recently, and i notice that pads are much harder to reflow after cleaning the pcb.

When applying heat to reflow and improve some soldering joint, i can see bubbles and strange things going on on the pad, it feels like i should remove the cleaned solder and use some fresh one to be safe.

I guess the cleaner is also removing flux from all the soldering pads ?

So we should only clean the pcb at the end, once we made sure everything works ?

This might be a silly question with an obvious answer, but i'd be glad to know for sure.

Every observations and suggestions are welcome !

 

[JTEX]

What do you use for cleaning residue?

 

[eh là bas ma]

thanks for your reply !

That's what i'm using :

Technoutil | NETTOYANT SOUDURES

NETTOYANT SOUDURES Solvant nettoyant des flux de soudures des circuits imprimés Produit spécial pour dissoudre les flux de soudure des circuits imprimés. L’aérosol est équipé d’un pinceau dur pour bien nettoyer les circuits et éliminer toutes traces de flux. Volatil en quelques minutes, sans...

technoutil.fr

 

[Brett]

I guess the cleaner is also removing flux from all the soldering pads ?

That is precisely what a soldering residue cleaner (flux remover) does, and it sounds like it's doing its job.

 

[JTEX]

If you want nice flow / reflow, you need to add flux to a squeaky clean joint, or it won't flow. Clean it at the very end, if you must. Or leave it on if you don't care that much about aesthetics and it's a no-clean or rosin type. It does no harm. I see 50-year old boards with rosin flux on them that work perfectly fine. And smell good.

 

[eh là bas ma]

That is precisely what a soldering residue cleaner (flux remover) does, and it sounds like it's doing its job.

right, so it's wrong to use it too often ? it should only come into play at the end of the building process ?

I thought flux was burnt while soldering, i didn't know it's still there once the soldering is done. And if there are still flux on the soldering pad, i 'd guess there is still some of it inside the soldering joint, not only on the outside. So if i clean the pad, there should be some flux remaining on the inside of the solder ?

Probably not enough to have a smooth reflowing though ?

 

[eh là bas ma]

you need to add flux to a squeaky clean joint, or it won't flow

makes sense, thanks.

I never used flux on its own before. The friends who taught me how to build stompboxes told me it was toxic and usually not needed.

I guess it is needed if i am going to use some residue cleaner.

 

[chris.knudson]

It's fine to clean the flux off of your board, but if you need to reflow, you'll either need to add flux or fresh solder.

 

[JTEX]

makes sense, thanks.

I never used flux on its own before. The friends who taught me how to build stompboxes told me it was toxic and usually not needed.

I guess it is needed if i am going to use some residue cleaner.

Use rosin flux. It's not toxic (tree sap, basically), smells good, and comes off with regular isopropyl alcohol (use the undiluted, 99% alcohol. The diluted one has water in it). Also, in my decades of experience, no other flux works as well as rosin. Looks messy if left on, though.

 

[Giorfida]

If you want nice flow / reflow, you need to add flux to a squeaky clean joint, or it won't flow. Clean it at the very end, if you must. Or leave it on if you don't care that much about aesthetics and it's a no-clean or rosin type. It does no harm. I see 50-year old boards with rosin flux on them that work perfectly fine. And smell good.

Since my pedals are for my enjoyment and not sale, I never clean the flux.
Im sure it will get me some good natured flack whenever I post something here by y’all, but that don’t bother me

 

[Alan W]

It’s worth it to have some flux on hand. I really didn’t until I started doing surface mount boards, and the method I learned works great, with the first step being wetting all the pads with a fine drop of flux, then placing the part into the tiny puddles. But once I started using it for than, it made sense to also use it for reworking, etc. Even though the desoldering braid I use is “fluxed” I’ll typically add another drop or two—it really increases the thirst of the braid.

 

[darwin999]

The friends who taught me how to build stompboxes told me it was toxic and usually not needed.

Only some fluxes are toxic - and even worse those are also corrosive, so if you don't clean ALL of it then your circuit could fail in the not-so-distant future. The fluxes to NEVER use on electronics are things like zinc chloride, hydrochloric acid, and ammonium chloride - those are more for soldering to large heavy things (and never for water pipes because of toxicity and corrosion).

As @JTEX correctly notes, rosin flux (the stuff inside most electronics solder) is neither toxic or corrosive. It's only issue is that the residue can conduct at a low level, typically 100's kOhms to a few MegaOhm - that's why it makes sense to clean it when done soldering. Most people use isopropyl alcohol to gently remove it.

I'll also note that some flux cleaners also have a preservative in them, which can leave a thin layer that's tough to solder on top of.