Hard-Solder Packaging of High Power Diode Bars for High Temperature Applications

摘要

In this paper, we describe cohductively-cooled single and multi-bar diode packages utilizing a telecom-grade solder technology to achieve high performance and reliability at elevated temperatures (50 to 75° C). Historically, high power diode bar packages have used a soft solder material, such as indium, for the critical bar attachment onto the heatsink/submount due to inherent low stress attributes. However, it is not uncommon for field-deployable laser-based systems to require laser diodes to operate under high temperature conditions (>50° C). At such operating temperatures, laser diode failure will be accelerated due to a number of well-known mechanisms, e.g. indium migration. By replacing the soft solder used for P-side attachment with a telecom grade (Au-Sn) or hard solder, it is possible to greatly reduce or eliminate these failure modes, thereby increasing not only the life of the part but the operating conditions/environments under which it can be used as well. We have implemented this telecom grade solder packaging technology into both single and multi-bar device configurations. We will present results of a conductively-cooled single bar package capable of reliable QCW operation at temperatures greater than 75° C. We will show extensive lifetest data of multi-bar QCW stacks at 80 Watts per bar, exhibiting lifetimes over a billion shots at 50° C. We have power-scaled and tested multi-bar stacks to 200 W/bar, enabling higher brightness pumping applications. To demonstrate robustness of these single and multi- bar packages, we will also present temperature cycling as well as mechanical shock and vibration testing. In addition, time dependent chirp measurements and FEA modeling have been performed to further characterize and verify these package designs.