I found out that it makes a big difference whether you are using silver-bearing solder, which melts at about 430 degrees, or silver brazing solder, which melts at 600 degrees and above. I need to use the low-melting-point silver-bearing solder. By comparison, ordinary electronic solder melts at about 370 degrees, so the silver-bearing solder gives me an extra 60 degrees. The silver-bearing solder comes with its own flux; not sure if it's different from any other flux.
