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Thermal management substrate handles high-power UV LED applications

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By Graham Prophet

Ultraviolet (UV) light has key applications for curing resins and inks (UVA) and for disinfection and sterilisation (UVC). LED technology has transformed the industry by enabling smaller, more cost-effective and robust devices that have opened up previously inaccessible applications.

 

UVA LEDs are rapidly displacing traditional UV lamps in the industrial printing industry, speeding up print times and reducing cost, while UVC LEDs open up applications such as portable sterilisation units that can provide clean drinking water. Market analysts Yole Développement are quoted as forecasting the market for UVC LEDs to grow from $7 million in 2015 to $610 million in 2021.

 

UV LEDs present a significant thermal challenge; in terms of UV light output, they are around 5% efficient, and high Uvflux implies a heat-sinking burden. As shorter wave lengths of UV light degrade organic material the choice of PCB is often limited to inorganic materials, discounting cost-effective metal-clad PCBs (MCPCBs) that rely on an organic epoxy based dielectric layer. Ceramics such as aluminium oxide (Al2O3) or aluminium nitride (AIN) are used, but they present a conundrum to LED designers — low-performance but cost-effective alumina (25 W/mK), or high-performance but expensive aluminium nitride (140-170 W/mK).

 

Ceramic is also brittle and prone to cracking, far from ideal for the new wave of portable applications and equally an issue for industrial applications.

 

Cambridge Nanotherm presents Nanotherm DMS as a solution to these issues. It combines the robustness and manufacturability of aluminium with the high thermal performance of AIN and as it undergoes thin-film processing, it’s entirely inorganic.

 

Nanotherm’s direct metallised single-sided PCB (Nanotherm DMS) uses an electro-chemical oxidation (ECO) process to convert the surface of aluminium into an alumina dielectric layer. [the illustration is of the related, but prior, Nanotherm DM product]. This nanoceramic alumina has a thermal conductivity of 7.2 W/mK which, coupled with being just tens of microns thick and using a direct metallisation process, gives a composite thermal performance of 152 W/mK. While this is slightly inferior to the very best and most expensive AIN substrates, the mechanical robustness of the Nanotherm metal board permits better approaches to mounting so measured system performance exceeds that of aluminium nitride.

 

Cambridge Nanotherm; www.camnano.com

 

 


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