enough slack to allow for the thermal contractions that occur during cooling which could fracture a solder joint or lead.
Insulating the soldering joint is recommended. This can be achieved with heat shrink tubing.
NOTE:
Be sure when soldering, or any time during use, the package does not exceed 420 K (146 °C). Exceeding this
temperature may cause a shift in the sensor values.
HEAT SINKING/THERMAL ANCHORING
Since the area being measured is read through the base of the sensor, heat flow through
the connecting leads can create an offset between the sensor chip and the true sample temperature. Thermal anchoring of the
connecting wires is necessary to assure that the sensor and the leads are at the same temperature as the sample.
1. Connecting wires should be thermally anchored at several temperatures between room temperature and cryogenic
temperatures to guarantee that heat is not being conducted through the leads to the sensing element. The leads of the
BO package are thermally anchored to the mounting block with a beryllium oxide heat sink chip.
2. If the sensing leads or connecting wires have a thin insulation such as Formvar™ or Polyimide, a simple thermal anchor
can be made by winding the wires around a copper post, bobbin, or other thermal mass. A minimum of five wraps around
the thermal mass should provide sufficient thermal anchoring. However, if space permits, additional wraps are
recommended for good measure. To maintain good electrical isolation over many thermal cycles, it is good practice to first
varnish a single layer of cigarette paper to the anchored area then wrap the wire around the paper and bond in place with
a thin layer of IMI 7031 varnish. Formvar™ wiring insulation has a tendency to craze with the application of IMI varnish.
Once IMI varnish is applied, the wires cannot be disturbed until all solvents have evaporated and the varnish has fully
cured (typically 12 to 24 h).
3. As a minimum, one of the thermal anchors should be as close as possible to the sample itself to ensure thermal
equilibrium between the sample and temperature sensor.
CRYOGENIC ACCESSORIES
– Recommended for proper installation and use of CX-10XX-BO sensor:
Stycast Epoxy
®
2850FT
(P/N 9003-020, 9003-021): Permanent attachment, excellent low temperature properties, poor
electrical conductor, and low cure shrinkage.
Apiezon
®
N Grease
(P/N 9004-020): Low viscosity, easy to use, solidifies at cryogenic temperatures, excellent lubricant.
IMI 7031 Varnish
(P/N 9009-002): Nonpermanent attachment, excellent thermal conductor, easy to apply and remove.
Indium Solder
(P/N 9007-002-05): 99.99% pure, excellent electroplating material, foil form.
90% Pb 10% Sn Solder
(P/N 9008-001): Greater lead content, for higher temperature applications no greater than 200 °C.
RMA Soldering Flux
(P/N 9008): Variety of types, refer to Lake Shore Product Catalog for details.
Phosphor-bronze Wire
(P/N 9001-00X): Available in single, duo, and quad strands, non-magnetic, low thermal conduction.
Manganin Wire
(P/N 9001-00X): Low thermal conductivity, high resistivity, non-magnetic.
Heat Sink Bobbin
(P/N 9007-900 Large, 9007-901 Small): Gold plated oxygen-free high-conductivity (OFHC) copper bobbins.
Instruments:
Lake Shore sells a complete line of instrumentation used with the CX-10XX-BO sensors, such as current
sources, cryopump monitors, temperature controllers, monitors and thermometers, temperature scanners and transmitters.
For complete product description and detailed specifications on the above accessories and instruments, consult the
Lake Shore Temperature Measurement and Control Catalog, call at (614) 891-2243, E-mail at
,
or visit our website at
www.lakeshore.com
.
Form Number F040-00-00 Revision E — ©2015 Lake Shore Cryotronics, Inc. — 19 August 2015
