Specifications

 
Abbreviations used in this section:
American Wire Gauge .......AWGNichrome Heater Wire .........NC
Single Lead Wire .............SLHeavy Duty Lead Wire ........HD
Duo-Twist™ Wire ............DTManganin Wire ..................MW
Quad-Twist™ Wire ...........QTCopper Twisted ................CT
Quad-Lead™ Wire ...........QLNonmagnetic ....................NM

 

 

 
Material PropertiesPhosphor bronze CopperNichromeManganin
Melting range 1223 K to 1323 K 1356 K 1673 K 1293 K
Coefficient of thermal expansion 1.78 × 10-5 20 × 10-619 × 10-6
Chemical composition (nominal)
94.8 % copper, 5% tin,
0.2% phosphorus
80% nickel,
20% chromium
83% 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 K NA9NA0.006
0.4 K NA30NA0.02
1 K 0.2270NA0.06
4 K 1.63000.250.5
10 K 4.67000.72
20 K 1011002.63.3
80 K 25600813
150 K 344109.516
300 K 484001222
 
 AWG  Resistance (Ω/m) Diameter (mm) Fuse current air (A) Fuse current vacuum (A)
Number
of leads
Name
Insulated
diameter
(mm)
Insulation
type
Insulation
thermal
rating (K)
Insulation
breakdown
voltage (VDC)
4.2 K 77 K 305 K
Phosphor
bronze
323.343.454.020.2034.23.11SL-320.241Polyimide500400
2DT-320.241Polyimide
4QT-320.241Polyimide
QL-320.241Polyimide
368.568.8310.30.1272.61.41SL-360.152Formvar®378250
2DT-360.152Polyimide500400
4QT-360.152Formvar®378250
QL-360.152Polyimide500400
Nichrome3233.233.4340.2032.51.81NC-320.241Polyimide500400
Copper
300.0030.040.320.25410.28.81HD-300.635Teflon®473250
340.00760.1010.810.1605.14.42CT-340.254Teflon®473100
Manganin308.649.139.690.2544.64.31MW-300.295Formvar®378400
3213.514.315.10.2033.83.51MW-320.241Formvar®400
3634.636.538.80.1272.62.51MW-360.152Formvar®250
 

Phosphor bronze wire

Phosphor bronze wires (QL, QT, DT and NM), are suitable for almost all cryogenic applications. The low magnetoresistance of these wires make 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
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, 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, 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.