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Proceedings Paper

Expansion-matched passively cooled heatsinks with low thermal resistance for high-power diode laser bars
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Paper Abstract

The lifetime of high-power diode lasers, which are cooled by standard copper heatsinks, is limited. The reasons are the aging of the indium solder normally employed as well as the mechanical stress caused by the mismatch between the copper heatsink (16 - 17ppm/K) and the GaAs diode laser bars (6 - 7.5 ppm/K). For micro - channel heatsinks corrosion and erosion of the micro channels limit the lifetime additionally. The different thermal behavior and the resulting stress cannot be compensated totally by the solder. Expansion matched heatsink materials like tungsten-copper or aluminum nitride reduce this stress. A further possible solution is a combination of copper and molybdenum layers, but all these materials have a high thermal resistance in common. For high-power electronic or low cost medical applications novel materials like copper/carbon compound, compound diamond or high-conductivity ceramics were developed during recent years. Based on these novel materials, passively cooled heatsinks are designed, and thermal and mechanical simulations are performed to check their properties. The expansion of the heatsink and the induced mechanical stress between laser bar and heatsink are the main tasks for the simulations. A comparison of the simulation with experimental results for different material combinations illustrates the advantages and disadvantages of the different approaches. Together with the boundary conditions the ideal applications for packaging with these materials are defined. The goal of the development of passively-cooled expansion-matched heatsinks has to be a long-term reliability of several 10.000h and a thermal resistance below 1 K/W.

Paper Details

Date Published: 15 February 2006
PDF: 10 pages
Proc. SPIE 6104, High-Power Diode Laser Technology and Applications IV, 610403 (15 February 2006); doi: 10.1117/12.645934
Show Author Affiliations
Michael Leers, Fraunhofer Institute for Laser Technology (Germany)
Christian Scholz, Fraunhofer Institute for Laser Technology (Germany)
Konstantin Boucke, Fraunhofer Institute for Laser Technology (Germany)
Reinhart Poprawe, Fraunhofer Institute for Laser Technology (Germany)


Published in SPIE Proceedings Vol. 6104:
High-Power Diode Laser Technology and Applications IV
Mark S. Zediker, Editor(s)

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