Improved performance of far-UVC LEDs by mounting on a thermally optimized Al-core PCB
Fig. 1: Temperature dependence of optical power in UVC LEDs at different wavelengths
Fig. 2: Increased optical performance through circuit board design optimization
Fig. 3: UV LED planar AlN submount with NGK elliptical quartz lens on PCB
Far-UVC LEDs (UVC LEDs with a wavelength below 240 nm) are becoming increasingly important for disinfection and sterilisation applications. Their short emission wavelengths not only enable the detection of certain flue gases [1], but also only minimally penetrate the skin, thus posing a potentially lowered risk of skin damage. The short emission wavelength of far-UVC LEDs is capable of inactivating germs, thus making them suitable for inactivating multi-resistant pathogens and fungi directly on human skin [2]. Furthermore, far-UVC LEDs are compact, offer low power consumption, and are immediately operationally ready. They are an alternative to discharge lamps, which are conventionally used as far-UVC light sources.
However, compared to UVC LEDs with longer wavelengths in the range of 260 nm to 285 nm, the light emission efficiencies of far-UVC LEDs are typically lower by one order of magnitude. When optimizing far-UVC LEDs, increasing the emission power by a few milliwatts is currently very challenging. Additionally, the emission power of far-UVC LEDs is significantly more temperature-dependent compared to their longer wavelength counterparts (see Fig. 1). Their emission power therefore decreases even further due to self-heating.
Appropriate heat dissipation during the operation of far-UVC LEDs is therefore necessary. Heat dissipation, specifically the thermal resistance, can be influenced through mounting and assembly. In our investigations, we analyzed the influence of the PCB design on the emission performance of far-UVC LEDs at a constant heatsink temperature of 20 °C. By using a thicker copper layer, we achieved a larger heat spread, reducing the thermal resistance. As a result, we observed an increased emission power of 20% at an operating current of 200 mA (see Fig. 2). With the results obtained using the improved PCBs, we also expect to increase the emission power of our far-UVC irradiation systems developed at FBH.
Publications
[1] F. Mehnke, M. Guttman, J. Enslin , C. Kuhn, C. Reich, J. Jordan, S. Kapanke, A. Knauer and S. Eindfelt, “Gas Sensing of Nitrogen Oxide Utilizing Spectrally Pure Deep UV LEDs,” in IEEE Journal of Selected Topics in Quantum Electronics, vol. 23, no. 2, pp. 29-36, 2017.
[2] J. Glaab, N. Lobo Ploch, H. K. Cho, T. Filler, H. Gundlach, . M. Guttmann, S. Hagedorn, S. B. Lohan, . F. Mehnke, J. Schleusene, C. Sicher, L. Sulmoni, T. Werneke, L. Wittenbecher, U. Woggon , P. Zwicker, A. Kramer, M. C. Meinke, M. Kneissl, M. Weyers, U. Winterwerber and S. Einfeldt, “Skin tolerant inactivation of multiresistant pathogens using far-UVC LEDs,” Scientific Reports, vol. 11, no. 1, p. 14647, 2021.