Browse Prior Art Database

LOAD BEARING SOLDER SURFACE FOR COPPER PLATED GRAPHITE CARRIERS

IP.com Disclosure Number: IPCOM000007128D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2002-Feb-27
Document File: 1 page(s) / 67K

Publishing Venue

Motorola

Related People

Clark Fischbach: AUTHOR [+3]

Abstract

Recent RF Power Amplifier designs employ cop- per plated graphite plates as carriers for the RF power transistors and their matching circumy. This tech- nology allows ceramic substrates to be soldered directly to the copper plated graphite carrier, pro- viding a electrical and thermal interface superior to historical non-soldered approaches. What makes this possible is the fact that graphite can be affordably manufactured with a similar CTE to ceramic.

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Technical Developments Volume 21 February 1994

LOAD BEARING SOLDER SURFACE FOR COPPER PLATED GRAPHITE CARRIERS

by Clark Fischbach, John Lubbe and Alan Grimshaw

age becomes increasingly severe with multiple inser- tions of the screw. This damage is detrimental both in appearance and in electrical continuity of the contact.

For the above reasons, a method to protect the plating in the area ofthescrew head was sought.

BACKGROUND

  Recent RF Power Amplifier designs employ cop- per plated graphite plates as carriers for the RF power transistors and their matching circumy. This tech- nology allows ceramic substrates to be soldered directly to the copper plated graphite carrier, pro- viding a electrical and thermal interface superior to historical non-soldered approaches. What makes this possible is the fact that graphite can be affordably manufactured with a similar CTE to ceramic.

  Carrier and ceramic modules are ohen mounted to a heat sink by screws. Unfortunately, any contact of a screw with a ceramic surface usually results in cracking of the ceramic. Consequently, the ceramic is relieved around the screw holes so that the screw head may come in contact with the less brittle graph- ite. This is where another problem occurs. As the screw head comes in contact with the copper plat- ing, damage to the plating ohen occurs. Plating dam-

  To provide protection to the plating, a layer of solder is applied in an annular ring around the mounting hole on the carrier. (...