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Alternative cooling solutions for high power optoelectronic

: Leers, M.; Schmidt, H.; Imgrund, P.

International Microelectronics and Packaging Society -IMAPS-:
41st International Symposium on Microelectronics 2008 : November 2-6, 2008, Rhode Island Convention Center, Providence, Rhode Island, USA
Reston, Va.: IMAPS, 2008
ISBN: 0-930815-86-6
8 pp.
International Symposium on Microelectronics <41, 2008, Providence/RI>
Conference Paper
Fraunhofer ILT ()

The market for high power diode lasers is still growing very fast (more than 10% a year). New applications are developed permanent and the range besides telecommunication, automobile and medical industries is rising rapidly Because of the bright facilities of high power diode lasers plenty of niche applications also benefit from the high efficiency of the semiconductors.
The interests in the R&D departments of diode laser industries have changed in the last years. Not the maximum of the emitted optical power out of the array is the main focus of the investigations anymore. The lifetime of the package is the critical value of the high power diode laser bars. A lot of R&D projects are focused on this issue. Common packages use a copper heat sink and Indium soft solder for mounting the laser bar. In the field of thigh power applications (> 100 W optical output power) water cooled heat sinks are necessary. In combination with the needed deionized water and high flow rates (0.5 l/min) corrosion is hard to prevent. Therefore, new cooling techniques are needed. In the last 12 months a lot of new solutions to increase the lifetime of the high power diode laser packages have been developed.
Basically the new solutions are divided into two groups. One is using new high performance materials, especially diamond composites. Their thermal conductivity is announced with up to 600 W/mK depending on the suppliers. This heat spreading material has a thermal conductivity which is up to 50% better than pure copper and will replace water cooled heat sinks.
The other is using new materials combinations for their active cooled heat sink instead of copper. New heat sink designs are possible because of new fabrication techniques like selected laser melting or µ-metal injection molding.