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In this study, composite electroplating technique is used to fabricate the diamond-added copper (DAC) heat spreader for UV LED applications. Thermal dissipation characteristic and optical performance are improved as the composite DAC heat spreader adoption. The low thermal resistance of 18.4 K/W with UV LED using DAC heat spreader was measured. Surface temperature of UV LED using the DAC heat spreader is 45.32◦C (at 350 mA injecting current), which is lower than those of LEDs using pure copper heat spreader (50.11oC) and only sapphire substrate (62.49◦C). The thermal diffusivity of the DAC is 0.7179 cm2/s measurement by laser flash method. Output power and power efficiency of UV LEDs are also enhanced to 71.81 mW and 4.32%, respectively, at 350 mA injection current. The optimal structure design and materials fabrication will be discussed

In this study, cup-shaped copper sheets were developed to improve heat dispassion for high-power light emitting diodes (LEDs) array module (3 × 3, 4 × 4, and 5 × 5) using an electroplating technique. The cup-shaped copper sheets were directly contacted with sapphire to enhance the heat dissipation of the chip itself. The lateral emitting light extraction and heat dissipation of high-power LEDs were enhanced and efficient. The surface temperature was not only decreasing but also uniform for each LED chip with the cup-shaped copper heat spreader adoption. The high thermal transmitting performance of cup-shaped copper heat spreader allows thermal resistance reducing 0.7, 0.6, and 0.7 K/W of 3 × 3, 4 × 4, and 5 × 5 LED array module, respectively. In addition, the light output power was increased of 14, 13, and 12% with 3 × 3, 4 × 4, and 5 × 5 LEDs array module using cup-shaped copper sheet at high current injection. High heat dissipation performance and light extraction were obtained by cup-shaped copper sheet with copper bulk and silver mirror.

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/mm2) 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).

Device performances of GaN-based flip-chip light-emitting diodes (FC LEDs) with planar and patterned sapphire substrates (PSS) were compared in this study. It was found that for the FC LED with planar sapphire, enhancement factor of luminous intensity can be raised to 107.5% after the processes of substrate removal and surface roughening. By contrast, for the FC LED with PSS, the intensity enhancement factor is already up to 169.5% without any post-processes as compared with the intensity of an as-fabricated conventional FC LED. Further intensity improvement to 205.1% can be achieved for the FC LED with PSS by employing subsequent processes such as substrate removal and surface roughening. These results indicate that the PSS approach is useful in improving light extraction of a nitride-based FC LED.

In this study, composite electroplating technique is used to fabricate the diamond-added copper heat spreader for UV LED applications. Thermal dissipation characteristic and optical performance are improved as the composite diamond-added copper heat spreader adoption. The low thermal resistance of 18.4 K/W with UV LED using diamond-added copper heat spreader was measured. Surface temperature of UV LED using the diamond-added copper heat spreader is 50.42 o C at 500 mA injecting current lower than pure copper heat spreader of 59.9 o C and original heat spreader of 90.4 o C. The thermal diffusivity of the diamond-added copper is 0.7179 cm 2 /s measurement by laser flash method. Output power and power efficiency of UV LEDs are also enhanced to 71.81 mW and 4.32 %, respectively, at 400 mA injection current. The optimal structure design and materials fabrication will be discussed.

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