Effect of thermocouple wire size and attachment method on measurement of thermal characteristics of electronic packages

During thermal characterization and testing of electronic equipment, the temperature of electronic components has to be measured. Thermocouples are commonly used for this purpose. The presence of a thermocouple on the surface of the component causes a local distortion of the temperature field and introduces errors in the measured temperature. This paper reviews the effect of thermocouple size and attachment method on the measurement of surface temperature to determine the thermal characteristics of plastic quad flat pack (PQFP) and tape ball grid array (TBGA) packages. Various size ANSI type T thermocouples were used. The methods of attachment included thermally conductive epoxy, nonthermally conductive epoxy, aluminum tape, and polyimide tape. Thermocouple wire size and attachment method can have a significant effect on the measurement of surface temperature and thermal characterization parameters. Small size and low thermal conductivity thermocouple wires are better to minimize errors due to heat losses through the wires. Using tapes and non-thermally conductive epoxy to attach thermocouples results in larger errors.