I'm trying to solder .020" stainless wire to .009" stainless wire. I can't have a resultant joint larger than .020" diameter. I've been grinding off 1/2 the thickness of the .020" wire and creating a lap joint.
I've used "soft solder" (96% Tin, 4% Silver, 220C or 430F melt) and a standard Weller electronics soldering iron, and have created joints that fail at 8 lbs pull test. The metals pull away from the solder.
I've used "hard solder" (which some folks consider brazing) which is
70% Silver, 20% Copper, 10% Zinc, (melt point 747C or 1390F). I've soldered this with a minute butane torch. These joints fail (also at 8lbs (coincidentally?)) because the .009" wire breaks near the soldered connection; the solder joint itself remains intact.I'm guessing that I'm overheating the .009" stainless wire and it's weakening the metal. It breaks repeatedly in the same place, about 1mm from the solder joint.
Any suggestions?