Update to the whole stuff, a bit delayed due to my broken wrist...
Got myself a good deal on Felder ISO-Core "Clear" solder. Ordered SN100Ni+ (Fuji Patent) and SAc305 (Sn96,5Ag3,0Cu0,5), both in 1mm diameter and with 3,5% Flux. Flux here is some synthetic new stuff, that is deemed on the rather mild side of agressiveness.
I am still soldering with my classic Ersa 30W iron, so regarding temp regulation nothing to write home about. But does the job...
In some short trial to solder header pins into recently bought breadboard carriers, I noticed not much difference in handling in between those two solders, as I had only small holes to fill.
But the main revelation came to me as I realized that this stuff has some big advantages over the old stock of leaded solder I got on ebay for repairs etc.
- 1mm flows way better than 1,5mm (the standard diameter of solder you always get included with everything)
- the amount of flux is very nice, but makes some puddle around the joint. Looks not nice, has to be cleaned off. Flux does not splatter in those two.
- Synthetic flux is smelling way less aggressive than all that classic stuff inside leaded solder of the past. Not exactly roses, but way nicer than everything I had my iron on or in in the past
For me, as SN100Ni+ is about half price of SAC305, I probably will stick with it, unless special requirements ask for SAC305, like repair work or so.