Intel 320028-001 5.0 Thermal Solution Requirements

Core™ 2 Duo Mobile Processors—Thermal Solution Requirements

Intel® Core™ 2 Duo Mobile Processors on 45-nm process-Thermal Design Guide

TDG June 2008

15 Order Number: 320028-001

5.0 Thermal Solution Requirements

The thermal characterization parameter, Ψ (“psi”), is used to characterize thermal solution

performance, as well as compare thermal solutions in identical situations (i.e., heating source, local

ambient conditions, etc.). It is defined by the following equation:

ΨJA = Junction-to-local ambient thermal characterization parameter (°C/W)

TJUNCTION MAX = Maximum allowed device temperature (°C)

TA = Local ambient temperature near the device (°C) (see Section 7.0, “Thermal Metrology” for

measurement guidelines)

TDP = Thermal Design Power (W)

The thermal characterization parameter assumes that all package power dissipation is through the

thermal solution (heatsink), and is equal to TDP. A small percentage of the die power (< 5%) is

dissipated through the package/socket/motherboard stack to the environment, and should not be

considered to be a means of thermal control.

The junction-to-local ambient thermal characterization parameter, ΨJA, is comprised of ΨJS, which

includes the thermal interface material thermal characterization parameter, and of ΨSA, the sink-to-

local ambient thermal characterization parameter:

Where:

ΨJS = Thermal characterization parameter from junction-to-sink, this also includes thermal resistance

of the thermal interface material (ΨTIM) (°C/W).

ΨSA = Thermal characterization parameter from sink-to-local ambient (°C/W)

ΨSA is a measure of the thermal characterization parameter from the bottom of the heatsink to the

local ambient air. ΨSA is dependent on the heatsink material, thermal conductivity , and geometry. It is

also strongly dependent on the air velocity through the fins of the heatsink. Figure 5 illustrates the

combination of the different thermal characterization parameters.

Equation 1. Junction-to-Local Ambient Thermal Characterization Parameter (ΨJA)

Equation 2. Junction-to-Local Ambient Thermal Characterization Parameter

TT AJ

−