PC7447AMGH1000LB datasheet(13/44 Pages) ATMEL

13 / 44 page

5387B–HIREL–07/05

PC7447A [Preliminary]

Figure 6-3.

Package Exploded Cross-sectional View with Several Heat Sink Options

6.4.4

Thermal Interface Materials

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

mize the thermal contact resistance. For those applications where the heat sink is attached by

spring clip mechanism, Figure 6-4 on page 14 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 performance of these thermal interface materials improves with increasing con-

tact 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 Figure 6-3 on page 13). Therefore, synthetic grease offers the best thermal

performance, considering the low interface pressure, and is recommended due to the high

power dissipation of the PC7447A. Of course, the selection of any thermal interface material

depends on many factors – thermal performance requirements, manufacturability, service tem-

perature, dielectric properties, cost, and so on.

Printed-Circuit Board

Thermal Interface

Material

Heat Sink

Clip

Heat Sink

HCTE Package

PC7447AMGH1000LB Datasheet(PDF) 13 Page - ATMEL Corporation