PC8240 datasheet(13/42 Pages) ATMEL

13 / 42 page

PC8240

2149A–HIREL–05/02

Adhesives and Thermal

Interface Materials

A thermal interface material is recommended at the package lid-to-heat sink interface to

minimize the thermal contact resistance. For those applications where the heat sink is

attached by spring clip mechanism, Figure 7 shows the thermal performance of three

thinsheet thermal-interface materials (silicone, graphite/oil, floroether oil), a bare joint,

and a joint with thermal grease as a function of contact pressure. As shown, the perfor-

mance 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 7 times greater than the ther-

mal grease joint.

Heat sinks are attached to the package by means of a spring clip to holes in the printed-

circuit board (see Figure 6). Therefore, the synthetic grease offers the best thermal per-

formance, considering the low interface pressure. Of course, the selection of any

thermal interface material depends on many factors, thermal performance requirements,

manufacturability, service temperature, dielectric properties, cost, etc.

Figure 7. Thermal Performance of Select Thermal Interface Material

1020304050607080

0.5

1.5

Silicone Sheet (0.006 inch)

Bare Joint

Floroether Oil Sheet (0.007 inch)

Graphite/Oil Sheet (0.005 inch)

Synthetic Grease

Contact Pressure (PSI)

PC8240 Datasheet(PDF) 13 Page - ATMEL Corporation