ELECTRICAL PROBE SYSTEMS
LIQUID CRYSTAL SYSTEMS
this article is about thermal contact!
ALWAYS BE THINKING ABOUT THERMAL CONTACT!
Thermal contact is an essential factor in the transfer of heat energy between two bodies. When it comes to measuring an objects temperature, good thermal contact is ESSENTIAL for collecting accurate data.
Lets consider the case of measuring the temperature of a fabulous Instec temperature-controlled wafer chuck with a K-Type thermocouple.
Bad thermal contact, ie. just touching the probe to the surface of the plate [Picture #1], could lead to a measurement off by 5 or more degrees C!
Perhaps the easiest (and messiest) way to improve thermal contact is with a dollop of thermal compound [Picture #2]. Most of the time, this will reduce the measurement error down to within a fraction of a degree (depending on the thermal compound, the plate temperature, ambient conditions, etc...)
For the best results however, Instec recommends fixing the sensor directly to the sample area via some metallic tape [Picture #3]. This mechanically secures the sensor so it won't shift around, reduces thermal gradients along the sensor itself, and reduces vertical temperature gradients by trapping radiated heat under the tape.
If you are ever in doubt about your thermal contact, you can always use a dot of thermal compound in ADDITION to metallic tape and ensure ULTIMATE THERMAL CONTACT.