Guidelines

Intel
®
7500 Chipset Thermal Mechanical Design Guide 19
Thermal Metrology
5 Thermal Metrology
The system designer must make temperature measurements to accurately determine
the thermal performance of the system. Intel has established guidelines for proper
techniques to measure the IOH die temperatures. Section 5.1 provides guidelines on
how to accurately measure the IOH die temperatures. Section 5.1.1 contains
information on running an application program that will emulate anticipated maximum
thermal design power. The flowchart in Figure 5-1 offers useful guidelines for thermal
performance and evaluation.
5.1 Die Temperature Measurements
To ensure functionality and reliability, the T
case
of the IOH must be maintained at or
between the maximum/minimum operating range of the temperature specification as
noted in Table 3-1. The surface temperature at the geometric center of the die
corresponds to T
case
. Measuring T
case
requires special care to ensure an accurate
temperature measurement.
Temperature differences between the temperature of a surface and the surrounding
local ambient air can introduce errors in the measurements. The measurement errors
could be due to a poor thermal contact between the thermocouple junction and the
surface of the package, heat loss by radiation and/or convection, conduction through
thermocouple leads, and/or contact between the thermocouple cement and the
heatsink base (if a heatsink is used). For maximum measurement accuracy, only the 0°
thermocouple attach approach is recommended.
5.1.1 Zero Degree Angle Attach Methodology
1. Mill a 3.3 mm (0.13 in.) diameter and 1.5 mm (0.06 in.) deep hole centered on the
bottom of the heatsink base.
2. Mill a 1.3 mm (0.05 in.) wide and 0.5 mm (0.02 in.) deep slot from the centered
hole to one edge of the heatsink. The slot should be parallel to the heatsink fins
(see Figure 5-2).
3. Attach thermal interface material (TIM) to the bottom of the heatsink base.
4. Cut out portions of the TIM to make room for the thermocouple wire and bead. The
cutouts should match the slot and hole milled into the heatsink base.
5. Attach a 36 gauge or smaller calibrated K-type thermocouple bead or junction to
the center of the top surface of the die using a high thermal conductivity cement.
During this step, ensure no contact is present between the thermocouple cement
and the heatsink base because any contact will affect the thermocouple reading.
It is critical that the thermocouple bead makes contact with the die (see
Figure 5-3).
6. Attach heatsink assembly to the IOH and route thermocouple wires out through the
milled slot.