Eric Bastow recently wrote about using our Indalloy Flux #2 for soldering to Nitinol. He did many tests and wrote an Application Note called Soldering to Nitinol.
Fort Wayne Metals, a leading supplier of medical wire (including Nitinol) also did a test on various fluxes as they relate to break load (maximum load before the joint breaks.
The fluxes tested included:
- Indalloy Flux #2 and Flux #3
- Indalloy Flux #5RMA; #5R; #5RA
- Indalloy Flux #4R
- Flux #400 (no longer commercially available)
The #5 series and the #4R were found to not be strong enough to clean off the tenacious oxides formed on Nitinol. Therefore, they didn't enable the solder to wet the surface properly.
Flux #2 and Flux#3 gave the best results (of the fluxes tested for break load) since they removed more of the oxides and allowed for a stronger solder bond.