Accession Number : ADD014112

Title :   LED Soldering Method Utilizing a PT Migration Barrier.

Descriptive Note : Patent, Filed 22 Dec 87, patented 4 Apr 89,

Corporate Author : DEPARTMENT OF THE AIR FORCE WASHINGTON DC

Personal Author(s) : Tihanyi, Peter L ; Vollmer, Hubert J ; Mott, Jeffrey S

Report Date : 04 Apr 1989

Pagination or Media Count : 4

Abstract : Method of bonding a chip to a Cu heat sink comprises depositing a layer of Ni upon the sink, depositing a layer of Pt over the NI, and thereafter annealing the sink in a partial vacuum containing a reducing gas. After the annealing step, a metallic wetting layer of Au and a layer of In are sequentially deposited upon the Pt, and the chip is soldered to the heat sink by means of a flux free soldering process. The pure Pt is very dense and stable, does not have microholes therein which would otherwise allow the Cu ions to penetrate the Pt. For a BeO heat sink, a Ti layer is deposited over the sink rather than Ni, and a layer of Pt is thereafter deposited over the Ti layer. The Ti, Pt and BeO interact to form a good bond of high thermal conductivity, which also blocks ion migration upwardly toward the solder and the electronic chip. PAT-CL-228-124. (jes)

Descriptors :   *PLATINUM, *SOLDERING, ANNEALING, BARRIERS, CHIPS(ELECTRONICS), FLUX(RATE), HEAT SINKS, HIGH RATE, IONS, LAYERS, METALS, THERMAL CONDUCTIVITY, VACUUM, WETTING

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE