Packaging of High Power UV-LED Modules on Ceramic and Aluminum Substrates

Abstract

An LED module consisting of 98 UV-LEDs with an emission wavelength of 395 nm placed on a ceramic substrate of 211 mm2 is presented. The module is cooled by a forced air heat sink as well as a high performance microstructured water cooler to lower the thermal resistance. For high thermal conductance a liquid metal as the thermal interface material between substrate and heat sink is used. With the forced air heat sink a maximum irradiance of 27.3 W/cm2 at a forward current of 700 mA and 220 W electrical input power was achieved. The microstructured water cooler enabled an almost doubling of the electrical input power (430 W) while maintaining the chip's maximum temperature. For a reduction of the module's thermal resistance a thick film process for aluminum sheet metal substrates was developed. A prototype LED module with 25 UV-LED chips on an area of 54 mm2 achieved a maximum optical power density of 31.6 W/cm2 at a forward current of 900 mA using a forced air heat sink. For an improved cooling of the LED chips a chip-on-heat sink-technology with embedded water cooling channels is developed to eliminate the thermal interface between substrate and heat sink.

Very high power density LED modules on aluminum substrates with embedded water cooling

“…Insulation and conduction layers were fabricated on the aluminum plate by thick film processes. A thick film paste system (Celcion) from Heraeus Precious Metals consisting of a dielectric for aluminum substrates (IP6075) and compatible silver conductor paste (C8829D) was used as a further development of the technique described in [4]. The dielectric is a low temperature melting glass and was fired at a peak temperature of 580 °C, which is also the temperature where the used aluminum alloy may start to soften.…”