Alloys and fluxes

[zoolu]

Which alloys and fluxes are compatible with lead-free hand-soldering?

[jonathen]

I think the limiting factor with lead-free solders is probably its availability in wire form; some alloys are not easily drawn into wire, as is the case with tin-bismuth solders. At this time the most popular alloys used to make wire are tin-silver-copper and tin-copper based solders. This compliments the industry well at this time where 68% of SMT assemblers and 50%of wave assemblers have chosen tin-silver-copper (SAC) solders. In wave soldering 20% have chosen tin-copper (SnCu) based solders due to the cost of lead-free solder bar. Wire solders for hand-assembly are therefore readily available in these two alloys.
The main differences between SAC and SnCu solders are the melting points; the melting temperatures are approximately 217°:C and 227°:C respectively. From a soldering performance perspective, SAC wets more readily than SnCu based solders, so flow with SAC solders, everything else being equivalent, will be better. Both SAC and SnCu solders are available in no-clean, water washable and rosin based flux formulas. No-clean accounts for over 85% of the total wire usage while water washable is less than 15% and rosin based fewer than 5%. These numbers apply to North America. In other parts of the world no-clean is dominant.

[KBK]

Cardas is now selling a tin/silver/copper fluxed solder roll.

I'm still using the old quad eutectic of theirs, so I've no idea at this point if it sounds any good or not.

Anyone done any 'sonic' comparisons?

Those of us who have to sell into the EU need to know, as Cardas 'quad eutectic' is definitely the preferred solder, for it's sonic qualities.

Maybe I should call them and ask. After all, they do sell both...