Thermal improvements for high power UV LED clusters

We present a high power density UV LED module for a wavelength of 395 nm with an optical power density of 27.3 W/cm². The module consists of 98 densely packed LED chips soldered onto an Al₂O₃ ceramic board. Thermal and optical measurements were conducted. The module was cooled by a forced air heat sink for the characterization experiments. A room temperature liquid gallium alloy was used as thermal interface material between substrate and heat sink with a TiN barrier layer to prevent corrosion. Further a technology to replace Al₂O₃ ceramics by aluminum as substrate is presented. An initial characterization shows that aluminum with a dielectric layer for electrical insulation is a competitive substrate material for efficient heat removal.