Calogero Sciascia received a PhD in Physics from Politecnico of Milan. His academic activity continued with a position as post-doc at Italian Institute of Technology where his activity was equally divided among spectroscopy, microscopy and material science. Finally he moved to SAES Group S.p.A., initially as Senior Researcher and now as Head of the Light Sources Laboratory. He participated in several research projects, involving major players of industry and academia, for the development of elements for discharge and solid state light sources. He presented more than 20 papers in scientific journals and international conferences and is author/co-author of several pending patents.
An Optimized Gas Filling for Gas Cooled LED Bulbs
One of the main barriers for a broad adoption of LED retrofit bulbs is the higher cost of SSL products with respect to conventional lamps. For this reason engineers efforts are devoted to reduce costs by trying to qualify cheaper materials and to simplify lamp design, but this can have an impact on the final products quality and performances.
One important technological trend is the reduction or even elimination of heat sinks, intermediate assemblies and thermal management materials but such reduction may be detrimental to the effective heat removal from the SSL emitters, resulting in a degradation in efficiency, lifetime and color stability of LED bulbs. An effective and elegant solution to combine simple and potentially low-cost structures assuring optimum heat dissipation is used in the Gas Cooled LED lamps: they consist of glass sealed LED bulbs (based on LED filaments or on LEDs mounted on PCBs) that are filled with low molecular weight gases to assure a suitable heat dissipation without the need for additional thermal sinks. Pure helium or helium-based gas mixtures at pressures just below 1Atm are currently used as main filling gas in sealed LED lamps. Helium, despite of its high cost and its limited availability, is the preferred option because it is inert and safe and has a high thermal conductivity. However this work will show that it is possible to further improve the thermal management characteristics in the Gas Cooled Lamps by means of a special gas dosing solutions able to provide an optimal alternative gas filling with safe and reproducible features. In particular, collecting a large set of experimental and computational data, we demonstrate that a solution based on hydrogen gas provides benefits in terms of heat sink, lowering the LED operation temperature for a given power input. Moreover, a solid state dispenser-getter technology, specifically developed for this purpose, allows high-purity and precise dosing. The proposed approach also circumvents safety issues related to pure hydrogen handling.