PowerPC 740 and PowerPC 750 Microprocessor
CMOS 0.20 µm Copper Technology, PID-8p, PPC740L and PPC750L, dd3.2
resistance approximately 7 times greater than the thermal grease joint.
Heat sinks are attached to the package by means of a spring clip to holes in the printed-circuit board (see
Figure 21). 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 23. 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)
Heat sink adhesive materials should be selected based upon high conductivity, yet adequate mechanical
strength to meet equipment shock/vibration requirements.
The following section provides a heat sink selection example using one of the commercially available heat
sinks.
Page 47
Version 2.0
9/6/2002
IBM [ IBM ]
