Mounting of Light-Emitting Diodes for the UV Spectral Range
LEDs in the ultra violet (UV) spectral range are assembled within a Joint Lab with the TU Berlin. The mounting of UV LEDs can differ by a lot, depending on the application and wavelength as well as the different technologies used during epitaxy / processing.
UV-A-LEDs emitting around 365 nm and above can emit via a semi-transparent p-contact on top of the chip. They are mounted p-side up (epi-up), and the heat removal is accomplished via the substrate, e.g., the back side.
On the other hand, UV-B as well as UV-C-LEDs (320 - 230 nm), which are currently in the research focus, emit only through the sapphire substrate on the back side of the chip. They are assembled p-side down (epi down), and the excess heat is extracted via the bonded surfaces on the front side of the chip. Currently, the chips are mainly mounted onto patterned AlN substrates or SMD packaged on solder-coated ceramic mounts. Further mounting technologies, such as thermo compression bonding via Au-bumps or coating the chips with structured solder layers, are currently being developed. Here you can find further parameters regarding LEDs.