Alessio Corazza graduated in Physics and specialized in Material Science at Milano University. In 1995 he joined SAES Group and worked in the Metallurgical Laboratory for five years; then he headed the SAES Lighting Applications and Materials Laboratory, coordinating R&D projects for the development of innovative solutions and components for light sources. Since 2014 he is Business Development Manager for Lighting, Photonics, and Opto-electronics Applications. He is author of more than 25 scientific papers and more than 20 international patents.
Advanced Materials to Protect LED Systems from Degradation Caused by Sulphur and Halogens Based Contaminants
Nowadays LED packages and LED based products are adopted in a wide variety of applications. Generally their robustness and durability are well appreciated features, but it is known that if they are exposed to aggressive gaseous contaminants or to harsh environmental conditions a premature degradation of their performances can occur. Typical problems are experienced in outdoor applications, such as street lighting, tunnel lighting, automotive lighting and industrial lighting applications, when relatively high concentrations of Sulphur-compounds or Halogens-compounds can be detrimental to LED systems and LED luminaires. In some polluted areas the concentration of H2S, SO2, COS and other contaminants can be much higher than 100ppb and accelerated corrosion, tarnishing and blackening on the silver parts and silver coatings in the LED packages. The formation of silver sulphide or of silver chloride may cause a significant reduction of the light reflected and extracted from the systems, leading to evident luminous flux decrease and colour shift. Eventual catastrophic electrical failures can be also expected if silver contacts are employed. The presence of moisture and of heat tends to enhance the sulfidation mechanisms.
Sometimes these problems are observed even in indoor modules and luminaires due to unexpected high levels of pollutants or to specific undesired sources. In some cases materials or components used inside the LED modules and fixtures, such as solder paste, PCBs, O-rings, gaskets can be sources of significant amounts of these contaminants. However, most of the issues described above are known to be caused by the permeation of Sulphur-compounds through the sealant, the venting membranes, the gasket or the O-ring. These materials are easily permeable to S-compounds such as H2S and SO2 and their concentration in the inner volume increases during the lifetime of the system.
Moreover, Sulphur contaminants can be generated from materials used for the storage and the shipping (cardboard, corrugated cartoon boxes and duct tape) of LEDs chips and LEDs modules.
In our work we present a recently developed advanced materials solution suitable to be applied in sealed or partially sealed LED systems and to prevent the degradation of the luminous performances. The solution is based on active getter materials able to react with sulphur, halogens and their compounds. The getter is designed in such a way that when mounted in the inner volume of the system is capable to quickly sorb the dangerous contaminants for all the expected lifetime.