Browse Prior Art Database

RF POWER MODULE UTILIZING SURFACE MOUNT TECHNOLOGY

IP.com Disclosure Number: IPCOM000007348D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-18
Document File: 2 page(s) / 101K

Publishing Venue

Motorola

Related People

Robert A. Richter Jr.: AUTHOR

Abstract

There have always been performance and man- ufacturing trade offs with RF power amplifier mod- ules. Older module designs have power devices with heat spreading flanges that require direct mounting to the heat sink. These modules also have horizon- tal blade like leads extruding from the side of the device as the electrical interconnects to the module. These devices are known as standard packages.

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MOTOROLA Technical Developments Volume 24 March 1995

RF POWER MODULE UTILIZING SURFACE MOUNT TECHNOLOGY

by Robert A. Richter Jr.

on top of the circuit substrate, the substrate is inca- pable of providing the adequate thermal path for proper device dissipation.

  In addition, the device and the substrate medium must be cost effective in order to be able to provide a high quality, cost effective module. Therefore, the need for this process is to be able to manufacture a cost effective surface mount high power RF ampli- fier module.

BACKGROUND:

  There have always been performance and man- ufacturing trade offs with RF power amplifier mod- ules. Older module designs have power devices with heat spreading flanges that require direct mounting to the heat sink. These modules also have horizon- tal blade like leads extruding from the side of the device as the electrical interconnects to the module. These devices are known as standard packages.

  The leads of these devices present enough induct- ance in the RF path requiring the usage of imped- ance matching capacitors placed on the leads of the device. The usage of these matching capacitors dic- tated that fixturing be required for both alignment and hold-down of various parts of the module in order to achieve a quality assembly. The fixturing is costly in material, development, maintenance and build cycle time, plus it does not eliminate all of the quality issues.

  The thickness difference between the circuit sub- strate and the device height between the bottom of the leads and package bottom also becomes an issue. This stack-up tolerance adversely affects the manufacturability of the module and could compro- mise the RF performance of the module. While the thermal dissipation capability was there, the manu- facturing issues present will always prevent these mod- ules from being six sigma in the module manufac- turing environment.

  An alternative to this form factor was to use a surface mount device placed directly on the circuit substrate. While this improves manufacturing, the overall dissipation capability of the module is dra- matically reduced, thus eliminating the potential of a high power module.

  While...