Fluxless die bonding of high power laser bars using the AuSn-metallurgy

Abstract

This paper presents a new concept for a fluxless package design for commercial high power laser bars. The laser bars are soldered on CuW heatsinks using Au(80)Sn(20) solder. Then a Cu lead is bonded with the FPC method (Fiber-Push-Connection) as a cap and electrical contact. Finally, the heatsink is mounted on a Cu microchannel cooler with Pb(37)Sn(63). We describe the mounting processes in detail, showing the large bonding window for soldering with Au(80)Sn(20), which is necessary for industrial production. The metallurgy of the Au(80)Sn(20) bonding interface is not dependent on the bond parameters in the area of the bonding window. Electro-optical characterizations show excellent performance of the laser bars. An accelerated aging test gives a first indicator of the high reliability of this package concept.