PC7410 datasheet(14/54 Pages) ATMEL

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PC7410

2141D–HIREL–02/04

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 6 shows the thermal performance of three

thin-sheet 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 seven 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 5). This spring force should not exceed 5.5 pounds of force.

Therefore, synthetic grease offers the best thermal performance, considering the low

interface pressure.

The board designer can choose between several types of thermal interface. Heat sink

adhesive materials should be selected based upon high conductivity, yet must have

adequate mechanical strength to meet equipment shock/vibration requirements.

Figure 6. Thermal Performance of Different Thermal Interface Materials

0.5

1.5

010

Silicone Sheet (0.006")

Bare Joint

Floroether Oil Sheet (0.007")

Graphite/Oil Sheet (0.005")

Synthetic Grease

Contact Pressure (psi)

PC7410 Datasheet(PDF) 14 Page - ATMEL Corporation