Thermal Management Calculations for RF Amplifiers in LFCSP and Flange Packages

Radio frequency (RF) amplifiers are available in lead frame chip scale packages (LFCSPs) and flange packages attached to printed circuit boards (PCBs) using mature reflow soldering processes. The PCB must function not only as the electrical interconnect between devices, but as the primary path to conduct heat away from the amplifier using the metal slug on the underside of the package.

This application note describes the concepts of thermal impedance and provides a technique for modeling the heat flow from the die to the heat sink of a typical RF amplifier in a LFCSP or flange package.