Solder, Flux, and Cleaning Discussion

[djQUAN]

Originally posted by Hartono djQUAN

Thinner ??


I don't really know if thinner is safe for the PCB and component or not, It can damage some component ?? no ?? or damage the solder mask surface ?

Thinner is pretty strong stuff. Be careful man

For my "nice" warning,you should send me some :
Kalamansi, Bagoong, and Lechon [/B]

lacquer thinner. yep, the strong stuff that leaves your skin really dry. it basically works like concentrated alcohol. you just need a well ventilated area when working with it. I haven't had any problems with component damage with it (other than some component markings getting erased) but electrical damage, none so far. I used it to clean 41hz Tripath amp kits and no damage. actually, the amps didn't work if I don't use thinner to clean the boards.

lechon is too big to send over. you pay shipping then

[Hartono]

BWRX

In Horowitz book, "art of electronics" they mentioned about cleaning solder flux after soldering, and there's this Ionic Activator inside the flux, and it says that if not removed properly(completely ?) might do more damage than not cleaning the flux. That's why I'm very worried about cleaning fluxes.

As for the damage cause by Ionic Activator, I don't know, I've never left PCB for that long yet ( a few years) to see the damage.


djQUAN

I better forget about the Lechon then

[djQUAN]

I'm actually building a rather big SMPS module right now, a simple unregulated step up supply for a car amp. 1000wrms, two transformers and a lot of caps. I will be using the methods I mentioned above for board cleaning. if I have the time, I could post pictures after everything is done......

[Hartono]

djQUAN

wow 1000 watt In car ??? good luck and post your pics later !!!

[Conrad Hoffman]

There's very fine solder available for SMT rework. Probably good info on Kester's web site (maybe owned by Litton?). Anyway, the two varieties commonly used are "no-clean", which is a minimal rosin flux and doesn't have to be cleaned. (or so they claim) I think it's #242 flux. The other one is #331 water washable. This is great stuff, but you absolutely have to wash the boards. It's corrosive if you don't, but if you wait a day or so, there's no harm done. That lets you build in multiple sessions. If I'm building a board from scratch, I try to use the 331, as it's so easy to wash. I use a bar of Fel's Naphtha soap and a toothbrush, followed by a hot water rinse and a blow off with compressed air. That's the only way to be sure sockets, nooks & crannies are dry. If I use no-clean, or plain old RMA (rosin, mildly activated), I clean with isopropanol and a toothbrush. You have to get the bulk off, then finish with clean solvent so you don't leave tracks. I follow with the naphtha soap, hot water, and compressed air. IMO, the best solder is good old Kester "44" that my dad used on his ham radio stuff. I also like a solder with 2% Ag, as it won't eat into very fine wires and leaves a bit brighter joint.

Hoffman's Rule- "If you solder at my bench, put the darn roll down with the label facing up, so the printing doesn't get worn off and I can tell what it is six months down the road!"

[Hartono]

Hi Conrad,

Did you get any board corroded by the 331 ?
it would be very useful to know if you have any board using the 331 with proper and improper cleaning, and what it does.

how long it takes to corrode the board ?

Horowitz book says the water based one turn out to be tricky to wash, and all flux must be removed thoroughly,or corrosion will occur. He recommend rosin based for DIY.

I also fear that the soap perfume or other chemical sticks to the board.


At least now I know solvent works well for rosin based, I would dip the board in a few separate alcohol bath for now.

Cheers
Hartono

[BWRX]

Originally posted by Hartono
In Horowitz book, "art of electronics" they mentioned about cleaning solder flux after soldering, and there's this Ionic Activator inside the flux, and it says that if not removed properly(completely ?) might do more damage than not cleaning the flux.

I found my copy of that book and read the section you mentioned (on page 840 of the second edition). Generally types of fluxes are described as as active, mildly active, or non-active. The more active a flux is the more aggressive it is at removing oxidation in order for the solder to form a good metal to metal joint.

I use Kester's 186 RMA flux along with their 44 rosin core solder for all of my DIY needs. As is said in the Art of Electronics, the RMA type flux is less active and doesn't necessarily need to be cleaned. I still like to clean my boards as thoroughly as possible though.

You can use organic core solder but most will tell you not to because it can be bad for your health (you think rosin core solder fumes are bad...) and the flux needs to be cleaned well. The advantage is that the organic stuff is water soluble.

In the end, just clean your work the best you can and don't worry about it too much. Poor cleaning of flux residue can cause sensitive and/or high speed circuits to do weird things but circuitry working at audio frequencies is generally much less vulnerable.

[Hartono]

BWRX :

Thanks for the follow up,

I guess I should worry less and do more DIY stuff


............................. for the time being that is

[Conrad Hoffman]

Hartono, I've been pretty casual about instantly washing boards after using 331, and haven't had a problem. We use the same stuff at work, and no problems there. I wouldn't go more than a week though. This stuff isn't like acid core flux- it's nowhere near that corrosive. Mostly it will just dull the surface. The real problem is that it's somewhat conductive, but washing it off is easy. We build high voltage equipment with it, so it's just not an issue. The organics have been pretty well developed at this point, but I do agree they smell bad. You shouldn't breath soldering fumes, smoke, vapors, or whatever the correct term is. I set a small muffin fan behind what I'm soldering to direct the smoke away. The organics will also discolor your expensive diagonal cutters, so if you like to keep your tools very shiny, stick with rosin!

[Hartono]

Thanks Conrad,

I will try the water based one