Data Sheet

Thermal Considerations—Ethernet Controller I210
847
13.7 Component Measurement Methodology
Measurement methodologies for determining the case and junction temperature are outlined in the
sections that follow.
13.7.1 Case Temperature Measurements
Special care is required when measuring the T
case
temperature to ensure an accurate temperature
measurement is produced. Use the following guidelines when measuring T
case
:
• Use 36-gauge (maximum) K-type thermocouples.
• Calibrate the thermocouple before making temperature measurements.
• Measure the surface temperature of the case in the geometric center of the case top.
Note: It is critical that the thermocouple bead be completely in contact with the package surface.
• Use thermally conductive epoxies, as necessary (again, ensuring the thermocouple bead is in
contact with the package surface).
Care must be taken in order to avoid introducing error into the measurements when measuring a
surface temperature. Measurement error might be induced by:
• Poor thermal contact between the thermocouple junction and the surface of the package.
• Contact between the thermocouple cement and the heat-sink base (if used).
• Heat loss through thermocouple leads.
13.7.1.1 Attaching the Thermocouple (No Heat Sink)
Following the guidelines listed, attach the thermocouple at a 0° angle if there is no interference with the
thermocouple attach location or leads (see Figure 2).
Figure 13-29.Technique for Measuring T
case
with 0° Angle Attachment, No Heat Sink