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14 The PCB Magazine • March 2014 THERMALLY CONDUCTIVE SUBSTRATES & THERMAL MANAGEMENT continues The need to dissipate heat from electronic modules and assemblies has, over the years, be- come increasingly important; this is not only as a consequence of the inevitable "smaller, faster, cheaper" trend for microelectronics to operate at higher frequencies and higher-performance levels. In the field of automotive engineering, an increasing number of functions, previously accomplished mechanically, are now solved electronically: braking and power steering are two examples. Elsewhere in power electronics, thermal management becomes a critical con- sideration in the design of DC power supplies, inverters, power controllers and motor drivers. But it is the global and exponential growth in general, and automotive, LED lighting tech- nologies that is creating huge market demand for efficient, reliable, low-cost thermal manage- ment, IMS solutions. Keeping heat generating components (LEDs/embedded components) cooler—in- creases component life, which in turn increases product life and long term reliability. The move to increased usage of IMS is primarily driven by the need to reduce system costs through, in the main, reduction in size of or elimination of costly, and bulky cooling fans and heat-sinks. LED key applications: • Back light units, typically • Notebooks and desktop computers • High-end televisions • High-end monitors for medical and industrial uses • General lighting • Street safety • Automotive Recent advances in high-brightness (HB) LED technology have alleviated concerns about excessive costs and have led to an increasing number of local authorities across the world installing eco-friendly LED lighting, and its adoption in domestic, industrial and automo- tive applications is rapidly, and exponentially, accelerating. Putting things into perspective, a standard FR-4 laminate has a thermal conductivity coef- ficient of around 0.25W/mK, thermally conduc- tive prepregs, laminates and insulated metal sub- strates offer thermal conductivity coefficients of up to 8W/mK, and development continues. Global regulation is becoming more strin- gent, fuelling the increasing demand and pen- etration of more energy efficient lighting, and with a global energy gap looming, is this a sur- prise? Earlier estimates suggested that LED tech- nology would capture over 46% of the Global lighting market by 2020, more recent estimates suggest that this will exceed 70%, this alone provides a huge market potential for thermally conductive printed circuits. Considering LEDs: Good thermal man- agement is required to achieve a bright light, whilst maintaining the colour spectrum, with- out overheating the junction or the LED unit itself. The life expectancy of an LED is closely related to operating temperature. For example 10°C reductions in temperature will approxi- mately double the life expectancy of the LED. How to disperse the heat? Conduction, con- vection or radiation cooling? Probably the most efficient mode of heat transfer is conduction through the substrate. Many power-electronics Figure 1: ims construction.