PowerPC 750 SCM RISC Microprocessor
PID8p-750
Preliminary Copy
Heat sinks are attached to the package by means of a spring clip to holes in the printed-circuit board (see
Figure 18). Therefore the synthetic grease offers the best thermal performance, considering the low interface
pressure. Of course, the selection of any thermal interface material depends on many factors – thermal per-
formance requirements, manufacturability, service temperature, dielectric properties, cost, etc.
Figure 20. Thermal Performance of Select Thermal Interface Material
Silicone Sheet (0.006 inch)
+
Bare Joint
Floroether Oil Sheet (0.007 inch)
Graphite/Oil Sheet (0.005 inch)
Synthetic Grease
2
+
+
1.5
+
1
0.5
0
0
10
20
30
40
50
60
70
80
Contact Pressure (PSI)
The board designer can choose between several types of thermal interfaces. Heat sink adhesive materials
should be selected based upon high conductivity, yet adequate mechanical strength to meet equipment
shock/vibration requirements. There are several commercially-available thermal interfaces and adhesive
materials provided by the following vendors.
9/30/99
Version 2.0
Datasheet
Page 37
IBM [ IBM ]
