W. Pittroff, G. Erbert, G. Beister, F. Bugge, A. Klein, A. Knauer, J. Maege, P. Ressel, J. Sebastian, R. Staske, and G. Tränkle

Published in:

IEEE Trans. Adv. Packag., vol. 24, no. 4, pp. 434-441 (2001).

Abstract:

High power diode lasers become more and more important to industrial and medical applications. In contrast to low power applications, long cavity lasers or laser bars are used in this field and mounting quality influences considerably laser performance and life time. In this paper we focus on the solder metallurgy and stress-induced laser behavior after mounting.
The laser chips have been bonded fluxless epi-side down on translucent cubic boron nitride (T-cBN) using Au/Sn solder. The laser behavior has been tested with different chip metallizations preserving the eutectic solder composition or forming the Au rich ζ-phase during reflow. The resulting additional stress in the lasing region has been independently indicated by polarization measurements of the emitted light.
A metallization scheme has been developed which forms the highly melting ζ-phase during soldering within a wide process window. This procedure yields better results then using eutectic Au/Sn which has a higher hardness than the ζ-phase. Laser diodes up to a cavity length of 2000 µm and an aperture of 200 µm have successfully been mounted on T-cBN. State of the art laser data, excellent thermal stability, high yield and reliability have been obtained.

Index Terms:
Gold/tin solder, heat dissipation, laser diodes, soldering, stress control.

© Copyright 2001 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Full version in pdf-format.