319282-007 Datasheet, PDF (580/586 Pages) Intel Corporation – 10 GbE Controller

Intel^® 82598 10 GbE Controller
8.16.5.5.3 Thermal Resistance of the Material
Thermal resistance describes the ability of the thermal interface material to transfer heat from one
surface to another. The higher the thermal resistance, the less efficient the heat transfer. The thermal
resistance of the interface material has a significant impact on the thermal performance of the overall
thermal solution. The higher the thermal resistance, the larger the temperature drop required across
the interface.
8.16.5.5.4 Wetting/Filling Characteristics of the Material
The wetting/filling characteristic of the thermal interface material is its ability to fill the gap between the
heat spreader top surface and the heatsink. Since air is an extremely poor thermal conductor, the more
completely the interface material fills the gaps, the lower the temperature-drop across the interface,
increasing the efficiency of the thermal solution.
8.16.6 Measurements for Thermal Specifications
Determining the thermal properties of the system requires careful case temperature measurements.
This chapter provides guidelines for doing accurate measurements.
8.16.6.1 Case Temperature Measurements
Special care is required when measuring the Tcase temperature to ensure an accurate temperature
measurement. Use the following guidelines when making Tcase measurements:
• Measure the surface temperature of the case in the geometric center of the case top.
• Calibrate the thermocouples used to measure Tcase before making temperature measurements.
• Use 36-gauge (maximum) K-type thermocouples.
Care must be taken to avoid introducing errors into the measurements when measuring a surface
temperature that is a different temperature from the surrounding local ambient air. Measurement errors
may be due to a poor thermal contact between the thermocouple junction and the surface of the
package, heat loss by radiation, convection, conduction through thermocouple leads, and/or contact
between the thermocouple cement and the heat-sink base (if used).
8.16.6.2 Attaching the Thermocouple (No Heatsink)
The following approach is recommended to minimize measurement errors for attaching the
thermocouple with no heatsink:
• Use 36-gauge or smaller-diameter K-type thermocouples.
• Ensure that the thermocouple has been properly calibrated.
• Attach the thermocouple bead or junction to the top surface of the package (case) in the center of
the heat spreader using high thermal conductivity cements.
It is critical that the entire thermocouple lead be butted tightly to the heat spreader.
Attach the thermocouple at a 0° angle if there is no interference with the thermocouple attach location
or leads (Figure 8-14). This method is recommended for use with packages not having a heat sink.
Intel^® 82598 10 GbE Controller
Datasheet
580
Reference Number: 319282-007
Revision Number: 3.2
October 2010