5.6 Thermal Measurements

Measuring the IC’s case temperature is recommended to ensure it is within its operating limits. Although this might seem like a very elementary task, it is easy to get erroneous results. The most common mistake is to use the standard thermocouple that comes with a thermal meter. This thermocouple wire gauge is large, typically 22 gauge, and behaves like a heatsink, resulting in a lower case measurement.

Two methods of temperature measurement are using a smaller thermocouple wire or an infrared thermometer. If a thermocouple wire is used, it must be constructed of 36 gauge wire or higher (smaller wire size) to minimize the wire heat-sinking effect. In addition, the thermocouple tip must be covered in either thermal grease or thermal glue to ensure that the thermocouple junction makes good contact with the case of the IC.

Wherever possible, an infrared thermometer is recommended. An optional stand makes it easy to hold the beam on the IC for long periods of time.