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tEchnology cooling


velocity, creating a boundary layer that impedes the removal of heat. SLT’s solution is to turn the channels 90°


and make them perpendicular to the die attach surface. ‘The effect is essentially an array of fi re hoses spraying water on the hot surface,’ says Aland Chin, CEO of SLT. ‘The large number of nozzles allows greater removal of heat compared to standard microchannel coolers.’ Using an EPIC heat sink, researchers from


A stack of three Epic heat sinks, each with a standard 10mm laser diode bar attached. Image courtesy of SLT ➤


but has so far not seen common use in the laser diode industry. HTCC has also been widely used in microfl uidic applications, including many applications where harsh chemicals fl ow through the device. CEO has leveraged the conventional thick fi lm processing and bonding techniques of the HTCC industry to create multi-layer devices with water channels similar in nature to copper microchannel coolers. One big difference between ceramic and


copper versions is that the ceramic design uses an electrically-isolating, thermally conductive heat sink in the thermal path between the bar and the cooling water. This heat sink is called a thermal window and is typically made of aluminium nitride, beryllium oxide, or diamond. The thermal window is attached to the cooler during the manufacturing process and causes the diode bar to be electrically isolated from the coolant path. This eliminates the need for deionised coolants and enables the use of standard fi ltered water, along with a number of other exotic coolants.


‘While the HTCC process is an established


manufacturing technique, making a product that was suitable for high-volume manufacture and that meets the requirements of the laser industry was very challenging,’ says Feeler. ‘We started development in 2006, hoping it was a two-year process, but we are only now ready to go to market. Our aim is to steer all our customers towards using ceramic coolers and eventually replace copper coolers completely.’ Other companies are not ready to give up


 


on copper and are looking at new designs of microchannels in order to improve the cooling effi ciency and hence the lifetime and power of the laser diode bar. US company Sommerville Laser Technology (SLT) has developed what it calls the enhanced performance impingement cooler (EPIC). In conventional coolers, the cooling channels run parallel to the die-attach surface. This presents two problems: the pressure required to force water through the channels can be large; and water immediately adjacent to the microchannel wall has zero fl ow


SLT and Science Research Laboratory were able to achieve record 250W continuous- wave output power from a single, 20 per cent fi ll-factor, 1cm diode bar at 20°C. ‘This record brightness was made possible, because the EPIC heatsink has a heat removal capacity exceeding 3kW/cm2


shift in internal architecture provides high coolant contact area with low pressure loss.’ As with all the above technologies, SLT’s


EPIC heat sink is just emerging onto the market and the company is in the process of determining the lifetime of its product. If EPIC and all the other technologies mentioned above are able to exceed the 20,000hrs of operation that are required for industrial applications the future looks even brighter for laser diode applications. l


For further information curamik www.curamik.de


cutting Edge optronics www.as.northropgrumman.com Fraunhofer ilt www.ilt.fraunhofer.de Jenoptik laser www.jenoptik.com sommerville laser technology www.slt-lasers.com Versarien www.versarien.co.uk


7 innovations from Lasermet


The New Laser Safety Interlock Controller


ICS15XM. Numerous advanced features including network and internet connectivity


• New Safety Logic Plus - virtually obsolescent- free interlock management system


• New Laser Jailer - Active Laser Guarding Enclosure


• New Optoblock - Optical Table Guarding System


• New Slim JimJi Sign - 11mm deep,


contractor friendly LED sign (no PSU)


• New version of Lasersafe PC Software with LB nos. and more…


• New Flatfoot Laser Blocking Screens


,’ says Chin. ‘This paradigm


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