mpc8641 Freescale Semiconductor, Inc, mpc8641 Datasheet - Page 112

• Manufacturer Part Number: mpc8641
• Description: Integrated Host Processor Hardware Specifications
• Manufacturer: Freescale Semiconductor, Inc

Thermal
19.2.2
A thermal interface material is recommended at the package-to-heat sink interface to minimize the thermal
contact resistance.
materials (silicone, graphite/oil, floroether oil), a bare joint, and a joint with thermal grease as a function
of contact pressure. As shown, the performance of these thermal interface materials improves with
increasing contact pressure. The use of thermal grease significantly reduces the interface thermal
resistance. That is, the bare joint results in a thermal resistance approximately seven times greater than the
thermal grease joint.
Often, heat sinks are attached to the package by means of a spring clip to holes in the printed-circuit board
(see
interface pressure, and is recommended due to the high power dissipation of the MPC8641. Of course, the
selection of any thermal interface material depends on many factors—thermal performance requirements,
manufacturability, service temperature, dielectric properties, cost, and so on.
The board designer can choose between several types of thermal interface. Heat sink adhesive materials
should be selected based on high conductivity and mechanical strength to meet equipment shock/vibration
requirements. There are several commercially available thermal interfaces and adhesive materials
provided by the following vendors:
112
Figure
59). Therefore, synthetic grease offers the best thermal performance, considering the low
Thermal Interface Materials
MPC8641 and MPC8641D Integrated Host Processor Hardware Specifications, Rev. 2
1.5
0.5
2
1
0
Figure 61. Thermal Performance of Select Thermal Interface Material
Figure 61
0
10
shows the thermal performance of three thin-sheet thermal-interface
20
Contact Pressure (psi)
30
40
50
Silicone Sheet (0.006 in.)
Bare Joint
Fluoroether Oil Sheet (0.007 in.)
Graphite/Oil Sheet (0.005 in.)
Synthetic Grease
60
70
Freescale Semiconductor
80