A flux for soldering nitinol to nitinol and to stainless steel comes from Johnson Matthey Co.,, San Jose, Calif. Applying Nitinol Flux 400 in a soldering job goes like this: “Remove the brown oxide with sandpaper immediately prior to soldering,” says Johnson Matthey Product Manager Joseph Kain. “Then put the two pieces, usually wire, in contact and apply a bit of the flux to the nitinol. Have a preheated soldering iron set to 315°C with the solder in place. Higher temperatures could damage the nitinol. Then touch the iron to the two wires for a few seconds. When the material reaches temperature, the solder spreads across the contact area. Strength properties are lower than the nitinol, so it's a low strength joint.

Soldering takes no special skill. “But be careful when using the nitinol flux because it's a strong acid base. The pretreatment and postreatment are as important as the operation. And if any flux is spilled, douse it in baking power. Wear gloves, and then rinse properly to get rid of the acid,” he says. Interested designers can request a video that details two ways of soldering nitinol from Kain at kainjb@jmusa.com.