As mentioned before, LEDs generate both light and heat that must be removed. For LED power <0.25 W, a package with power supply is sufficient to disperse the required heat. An improved cooling system is required for mid-power LEDs, e.g. Duris E5, usually including a large copper surface on a printed circuit board (PCB) directly below the LED. High density mid-power LEDs or PowerLEDs require a special base and a package with heat sinks to disperse generated heat. The base is called a Metal Core Printed Circuit Board (MCPCB) and is made mostly of aluminium, less often of copper.
The main parameter describing the efficiency of heat removal is a thermal resistance of material used expressed in kelvin per one watt of power emitted (K/W), defining an increase in component temperature at specific emitted power. All manufacturers specify this parameter, and it must be considered when designing PCBs, MCPCBs, packages and heat sinks. Standard PCB features a high thermal resistance compared to even the most simple MCPCB, and may be used in LEDs with <0.5 W power and large copper surface removing the heat. Modified PCB surfaces also allow use of PowerLEDs in certain applications. MCPCBs give the best results in all LED types (in some cases, the MCPCB alone will be sufficient to remove the heat generated by the LEDs - similar to a heat sink). The drawback is a high price and complex production process.
When designing our luminaires, we have to consider the heat distribution from LED surface (in case the entire luminaire is a heat sink) or the lowest thermal resistance path to the external heat sinks. Most of our products have aluminium enclosures, which besides heat dissipation also direct the outlet light beam and feature high aesthetic qualities.