Improved design of cup-shaped copper heat spreaders for high-power InGaN/sapphire LEDs

We have developed and designed copper heat spreader to improve light extraction efficiency and heat dissipation of sapphire-based light-emitting diodes (LEDs) that were electroformed in close contact with sapphire. The junction temperature of a LED with copper substrate is lower than that of the original LED without copper based on simulation results. In addition, copper-surrounding the LED with protruded bottom surface exhibits similar thermal performance as a flat bottom surface. For practical fabrication, all LED samples with copper show significant reductions in junction temperatures from 56.4°C for the original LED to less than 50°C at of 350 mA (~1 W/mm ²) injection current. The LEDs with flat bottom Cu substrate at the 350 mA driven current yield a thermal resistance of 6.3 K/W. This is lower than the original LED without copper substrate (12.5 K/W).