Analysis of degradation effects on LEDs according to the production processes

Abstract

More and more Light Emitting Diodes (LEDs) become more important in lightening system, for instance in cars, street lights, flashlights and individual lightening solutions. With the increasing use of LEDs an effect becomes visible: after short operating times some LEDs lose their brightness or become ohmic. What is the reason for this effect? How does the production process influence the appearance of this effect and how do we investigate the aging of LEDs? These questions will be discussed in this paper. MotivationThe implementation of lead-free processes brought not only advantages. A lot of components have lead-free interfaces but they are not allowed for the standard lead-free reflow soldering process because of the high peak temperatures during the soldering process. They have to be processed by special soldering processes like selective soldering or hand soldering or with low melting solder pastes which are quite expensive and time-consuming processes. Affected components are inductors, capacitors, blue tooth antennas, relays, active components like older microprocessors and high brightness LEDs. Supported by leading members of the German organization ZVEI, we set up together with nine industrial partners and two Fraunhofer Institutes the publicly funded project TDMA -Thermal induced Damage Mechanisms on electronic assemblies and Deduction of operational alternatives. Fig. 1 shows the logos of the project partners.