Soldering to Nitinol
Nitinol is a popular material used in the medical industry for products such as stents, catheters, and other implants. This is mostly due to its shape memory and super elastic characteristics. It was developed by the Naval Ordnance Laboratory (NOL) and is composed of nickel (Ni) and titanium (Ti), hence its name.
Bonding to Nitinol is challenging because of the tenacious oxides that form on the surface of the Nitinol. The key to soldering to Nitinol is to use a flux that will effectively reduce both the nickel and titanium surface oxides. Since the devices are used in the human body, it is also important that the selected solder alloy has minimum biological activity and that the flux residue is completely removed after soldering.
Indium Corporation has two fluxes that remove surface oxides to facilitate wetting of the solder to the surface.
Flux #2 is a specialty, acid-based flux formulated specifically for soldering to Nitinol. It also works well on high chromium-containing alloys, including stainless steel. It is compatible with all types of solders. It can be brushed on, dispensed, or sprayed.
Flux #3 is a high viscosity liquid flux also formulated for soldering to Nitinol, as well as aluminum. Flux #3 works best with tin-containing alloys. Because of is higher viscosity, it is best applied by brush or swab.
A Nitinol Soldering Kit can be purchased to test both fluxes with your application. The kit contains:
- Indalloy® #121 96.5Sn 3.5Ag 0.030” solder wire
- Indalloy® Flux #2
- Indalloy® Flux #3
- Nitinol #1 wire 0.017”
Flux Technical Specifications
|Flux #2 (P/N 84002)||Flux #3 (P/N 84003)|
|Specific Gravity||1.53 gm/cc||1.33 gm/cc|
|Chloride Content||No zinc or other heavy metal chlorides||Contains chlorides|
|Appearance||Water white||Yellow to pale green|
|Cleaning||Warm water (<50°C) and mechanical scrubbing||Warm water (<50°C) and mechanical scrubbing|
|Shipping||Transport in accordance with applicable regulations and requirements||Transport in accordance with applicable regulations and requirements|
Nitinol Wire Specifications
|Austenitic Finish Temperature (Af)||10-18°C|
|Chemical Composition||Element||Weight %|
|Nickel||54.5 to 57.0 (Ref.)|
|Carbon||<0.05 (500 PPM max.)|
|Cobalt||<0.05 (500 PPM max.)|
|Copper||<0.01 (100 PPM max.)|
|Chromium||<0.01 (100 PPM max.)|
|Hydrogen||<0.005 (50 PPM max.)|
|Iron||<0.03 (300 PPM max.)|
|Niobium||<0.025 (250 PPM max.)|
|Oxygen||<0.05 (500 PPM max.)|
|Any Single Trace Element||<0.1|
|Total Trace Elements||<0.25|
|Ultimate Tensile Strength||>180,000 psi|
|Appearance||Shiny light brown color|
|Shipping||Transport in accordance with applicable regulations and requirements|
From One Engineer to Another®
All of Indium Corporation’s products and solutions are designed to be commercially available
unless specifically stated otherwise.