Cryogenic wire specifications

Material propertiesPhosphor bronze CopperNichromeManganin
Melting range 1223 K to 1323 K1356 K1673 K1293 K
Coefficient of thermal expansion 1.78 × 10-520 × 10-619 × 10-6
Chemical composition (nominal) 94.8 % copper, 5% tin, 0.2% phosphorus80% nickel, 20% chromium83% copper, 13% manganese, 4% nickel
Electrical resistivity (at 293 K) 11 µΩ•cm1.7 µΩ•cm120 µΩ•cm48 µΩ•cm
Thermal conductivity (W/(m•K))0.1 KNA9NA0.006
0.4 KNA30NA0.02
1 K0.2270NA0.06
4 K1.63000.250.5
10 K4.67000.72
20 K1011002.63.3
80 K25600813
150 K344109.516
300 K484001222
 AWGResistance (Ω/m)Diameter (mm)Fuse current air (A)Fuse current vacuum (A)Number of leadsNameInsulated diameter (mm)Insulation typeInsulation thermal rating (K)Insulation breakdown voltage (VDC)
4.2 K 77 K 305 K
Phosphor bronze323.343.454.020.2034.23.11SL-320.241Polyimide500400
Cryogenic wire

Phosphor bronze wire

Phosphor bronze wires (Quad-Lead™, Quad-Twist™, Duo-Twist™, and nonmagnetic) are suitable for almost all cryogenic applications. The low magnetoresistance of these wires makes them the ideal choice for magnetic field use.

Physical Properties

Melting range:
1,223 K to 1,323 K (950 °C to 1050 °C)

Coefficient of thermal expansion: 1.78 × 10-5

Thermal conductivity: 48 W/(m • K) at 293 K

Electrical resistivity (annealed): 1.15 × 10-7 Ω • m at 293 K

Specific heat: 376.4 J/(kg • K)

Stress relief temperature (1 h): 423 K to 498 K (150 °C to 225 °C)

Chemical composition: nominal 94.8% copper, 5% tin, 0.2% phosphorus

Wire insulation


Polyimide insulation is by far the most versatile insulation option available for cryogenic wiring. It will operate at temperatures in excess of 493 K (220 °C) for intermittent duty and has exceptional resistance to chemical solvents and burnout. Polyimide exhibits excellent resistance to radiation exposure and, as such, is used extensively in spaceflight and high-energy physics applications. Polyimide can be removed mechanically during terminal preparation and is rated to 3525 VAC for 32 AWG and 2525 VAC for 36 AWG.

Polyvinyl Formal (Formvar®)

Formvar® has excellent mechanical properties such as abrasion resistance and flexibility. The film will stand excessive elongation at low temperature without rupture, making it a great choice for wiring applications with tight bend radii at ultra-low temperatures. However, care is advised, as Formvar® has a tendency to craze upon contact with solvents such as toluol, naphtha, and xylol; therefore, it should be given an annealing preheat prior to varnish application. Formvar® can be removed mechanically during terminal preparation and is rated to 3525 VAC for 32 AWG and 2525 VAC for 36 AWG.

Note: At Lake Shore, we strip both Polyimide and Formvar® mechanically using an Eraser Rush Model RT-2 mechanical stripper.