Thermal Management Design from Chip to Package for High Power InGaN/Sapphire LED Applications

Abstract

Device performances were investigated for InGaN/sapphire light-emitting diodes ͑LEDs͒ with advanced heat dissipation design from chip to package. By directly contacting a copper heat spreader with sapphire, the maximum junction temperature of the LED chip was reduced from 62.9°C of a conventional LED to 48.3°C at an injection current of 350 mA. Further temperature reduction to 37.3°C could be achieved by packaging the copper-surrounded LED chip on the heat sink coated with a diamond-like layer which acts as the second heat spreader. The reduced junction temperature was attributed to good heat dissipation from both the copper and the diamond-like layer due to their low thermal resistance. The copper heat spreader not only extracts heat efficiently, but also enhances the light extraction of the LED, as the copper was designed with a proper geometry such as cup-shaped profile. The improved LED performance suggests that the proposed thermal management from chip to package is an efficient alternative for high power applications. High power GaN-based light-emitting diodes ͑LEDs͒ are essential for next-generation lighting applications. To achieve higher light output performance, it is necessary to drive a GaN-based LED to a high current density level. However, under such a high current injection, the LED typically exhibits the performance deterioration of power saturation.

Impact of Die Carrier on Reliability of Power LEDs

“…To promote the efficient removal of the heat from the die, researchers and manufacturers have proposed different solutions that minimize the thermal resistance of the package. As an example, the integration of a copper (Cu) heat spreader increases the power efficiency by 3% when compared to a conventional package [3]. The use of flip-chip architecture provides an efficient means to decrease the thermal resistance of the package, especially if combined with carriers with large thermal conductivity (κ).…”

“…Diamond has also been used to improve the thermal management of power LEDs at different levels. Horng et al [3] mounted the LED die on a diamond-coated copper heat sink and obtained an 11°C reduction in T J in comparison to mounting the LED on a conventional MCPCB. Chen et al [24] reported a 20°C reduction in T J at 1 A when the LED chips were bonded on Si substrates coated with 20 µm of diamond.…”

Junction temperature estimation for multiple light emitting diodes based on surface point measurement

“…For single LED chip packaging, the junction temperature is easy to measure. Both the electrical method [9][10][11] and optical method [12][13][14][15][16] can be adopted. However, the optical flux of a single LED chip is too low to satisfy the lumen demand of LED applications, such as LED street lamp, LED vehicle lamp and so on, so it is usual to package multiple LED chips on one board.…”

Improved Design of Cup-Shaped Copper Heat Spreaders for High-Power InGaN/Sapphire LEDs

“…Recently, we reported on a novel design of cup-shaped copper heat spreader for high-power sapphire-based LEDs that demonstrated the cup-shaped copper design is capable of enhancing light extraction and offers heat dissipation as an inherent ability. 8,9 However, optimization of cup-shaped copper needs to be conducted in detail to maximize its thermal and optical performance enhancements. In this paper, we report on detailed geometric design of copper using ANSYS and TracePro software to optimize heat dissipation and light extraction efficiency, respectively.…”