Rosin, flux, and soldering promoters...

[Externet]

Hello all.

Never seen a label about the ingredients of flux, rosins, liquid or pastes. What is to choose ? Which is better or worse for this or that ?
Solders are usually labeled as 63/37 Sn/Pb Am experimenting with non-cored 89.5%Sn 10% Sb 0.5%Cu solder alloy that melts very well and would like to know which fluxes are more convenient for electronics work. I suspect fluxes are not about favoring melting but proper combining to copper, or some mistery I do not know.
Is there is way to know and choose the proper flux 'recipe' ?
What do you know about ? What are fluxes made of and how are they manufactured ? Were they born from trial-and-error experimentation ?

 

[stenzer]

Hi,

there is for example a labeling according to IPC-J-STD-004x or IEC 61190-1-3, which I have seen already on a couple of soldering-tin, see here. The wikipedia page also explains the individual properties and lists other standards.

BR

 

[Externet]

Thanks, stenzer.
A lot to learn from an often ignored compound of daily use. Not all are simple chemistries.
Remember in the sixties as first steps in soldering, the residue of rosin solder was a brittle glass-like layer with a pleasant aroma. Now such residue after soldering is different.
Will have to experiment which is convenient for my Sn-Sb solder.

 

[dick_freebird]

I worked at a company once which had to recall a
whole lot of boards because the flux was growing a
white "mold" of some sort. Probably shoulda cared
more about cleaning, but MIL systems specify down
in their copious fine print "non-nutritive to fungus",
for reasons. Might check that one with whichever
vendors you're seriously considering. But what to
clean is likely still plain copper or gold wash and
I imagine most fluxes would do (you might make it
easier by some board prep to remove casual oxidation
or return boards too oxidized for "solderability" (a
spec you will also sometimes see on packaging
leads).

I like Kester 44 (60/40 lead bearing) myself.

Flux is for getting through native oxides, primarily.
So what's oxidized and which flux effective, is a
proper question and you hope solder mfrs have
handy answers for what they sell.

 

[D.A.(Tony)Stewart]

If you ever tried a toothpick in water with pine sap on the end, you learned as a kid that very low surface tension produced high acceleration on the toothpick.

The same property pushes molten solder with whatever tree resin they use with a mildly acidic pH to help dissolve oxide.