lead-free solder

While not using lead-free solder in electronics construction, I'm exposed to it in musical instrument construction and repair, as many insruments now originate in the EU and even some Chinese brands have turned to using it. It has been an interesting experience adapting to using it. I'd usually have two alloys of leaded solder on hand--63/37 "eutectic" solder (it's either liquid or solid, but not "plastic") for most work, and 50/50 for those times when I needed to fill a gap (has a comparatively broad "plastic" range and so can be worked a bit before it sets. Lead-free is different to work with, but not awfully so. Generally, most eutectic alloys melt at a higher temperature than the 63/37 alloy. The type of flux seems to be more critical--but then, I use liquid acid fluxes, so that may not obtain in electronics work. Lead-free is generally harder and stronger than leaded when cool. For non-eutectic solders, the plastic range "feels" different--the solder seems to be a bit more "grainy" (like wet sawdust) than "smooth" (like cake batter), but that's subjective and the plastic phase shouldn't be part of proper electronics work anyway. "Wetting" seems to be somewhat more difficult with lead-free, but good, strong joints can still be made if done with sufficient care (very clean surfaces, sufficient heat and flux). On the plus side, I'm sometimes called on to repair small cracks or splits in silverplated brass. Doing so with leaded solders usually means spot-plating (copper, then silver) over the repaired area because lead stains silver surfaces rather badly. With silver-tin alloy solder, I can make the repair, then simply buff the solder to blend in with the surrounding silver--it's very difficult to see when finished--and I don't need to fuss with the silver cyanide plating solution. I've also been given to understand that it's not a good thing to mix the two types of solder, so I don't. For me, that means cleaning old joints down to the base metal before resoldering. If you're interested, NIST has published a table of properties at: http://www.boulder.nist.gov/div853/lead%20free/props01.html In conclusion, I don't think that lead-free solder should be a barrier to anyone's work, if the effort to learn how to use it well is made. ------ On a side issue, I've been wanting to learn to use the solder-flux paste used in surface-mount work. One thing that's been off-putting is the very low shelf life of the stuff--and the need for refrigeration (raising shipping costs). Does anyone make a two-part solder, where the metal and flux are combined just before use? Cheers, Chuck