I really don't know if they're all like this but my limited experience with the "Crystal" or "Kristall" type of solder fluxes are less than stellar. In fact, the worst solder wire i've ever used was "Multicore 5C Crystal 400". The flux in that solderwire smells terrible, it has a nasty poisonous chemical odour, you wouldn't want to use that stuff without fume extraction, that's for sure... But the really bad thing is its obnoxious habit to splatter flux all over the place while soldering, it gets messy really quick. I don't like that at all so i stopped using it and my only use for that roll of solderwire now is as a paper weight. Got that pos a few years ago while attending the ham fest at Lake Constance, bought at the flea market, maybe its a fake, i don't know:
![](http://fs2.directupload.net/images/150614/ljhzqp7r.jpg)
This roll of "Stannol Kristall 505" was delivered from Distrelec Germany, so it should be genuine. Just like the Multicore solder from obove it features 5 flux cores but doesn't splatter nearly as much. Crystal 505 has some halogen content, increasing flux activity, so it spreads really well, even on slightly oxidised surfaces. My main use for this solder is to tin wires, solder them to battery packs and such things. I wouldn't want to use it on delicate circuit boards, at least not without proper cleaning of the residues afterwards. But the smell, the smell... It's even worse than my dreaded "Multicore" branded solder, equally strong poisonous chemical odour, topped with the disgusting note of burned hair. Don't use it if your girlfriend is around or she will give you "the look"...
![Cheesy :D](https://www.eevblog.com/forum/Smileys/default/xcheesy.gif.pagespeed.ic.KPzuH4J-TG.png)
![](http://fs2.directupload.net/images/150614/gps6gqc8.jpg)
After that, I stopped buying the "Crystal" type solder wires and switched to the Felder brand with ( I think) rosin flux cores. These are a real joy to work with, no splattering at all, flows well, produces nice and shiny joints, very little smoke and has a relatively pleasant smell. A friend of mine uses Stannol HS10 solder wire, that's equally good stuff.
![](http://fs2.directupload.net/images/150614/4o3ykz6y.jpg)
60/40 is the usual and widely used alloy in Europe (for leaded hand soldering), you can order some 63/37, of course, but be prepared to pay a huge premium for that. Not because it is so much better (or better at all), just because no one really uses it here in quantity. In my opinion the whole 63/37 vs. 60/40 usage is more a thing of different habits on different sides of the Pond
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif.pagespeed.ce.5xOqKkq0Co.gif)
Bye, Kai.