Thermal Considerations and Package Mounting

The rated power dissipation is only available when the package mounting surface is at 25 °C and the junction

temperature is 175 °C. The thermal resistance between junctions and case mounting surface is 0.16 °C/W. When

installed, an additional thermal impedance of 0.15 °C/W between the package base and the mounting surface is

typical. Ensure that the mounting surface is smooth and flat. Thermal joint compound must be used to reduce the

effects of small surface irregularities. Use the minimum amount necessary to coat the surface. The heat sink should

incorporate a copper heat spreader to obtain best results.

The package design clamps the ceramic base to the heat sink. A clamped joint maintains the required mounting

pressure while allowing for thermal expansion of both the base and the heat sink. Four 4-40 (M3) screws provide the

required mounting force. T = 3-4 in-lb (0.34 - 0.45 N-m).

ARF476FL

Package Specification

and its subsidiaries

Datasheet

DS00004436A-page 9