An approach to “Design for Reliability” in solid state lighting systems at high temperatures

Abstract

Providing correct reliability information is critical for all manufacturers for both their customers and also their in-house departments intended for product improvements. Solid state lighting (SSL) technology as the novel lighting technology is not an exception. Due to the fact that SSL is a relatively new technology, research on its reliability issues and also systematic methods for design improvement is lacking.In this paper, we introduce an approach for “Design for Reliability” in SSL. Our approach includes three major steps. The first step is the design phase where the physics of failure of the device and virtual assessment of the reliability of the device is investigated. Based on these results, their failure’s causes; and their relationship with reliability and lifetime of the SSL device is defined. Sensors are then assigned to the critical failure causes at the proper positions of the system. The second step of our approach is processing the data from sensors while device is functional. In this phase, gathered data from the sensors, are processed in order to calculate the lifetime of the device. The system should have a processing capability for accomplishing this task and also report the status to the maintenance system. The third step of our reliability approach is to have built-in self-maintenance capabilities. Therefore, the system can predict its failure and be functional for longer time.At the second part of this paper, we introduced a SSL device which has been designed in our group which can fulfill the criteria for our “Design for Reliability approach”. This SSL device can provide around 200lumen and has the capability of sensing and monitoring the high temperature in system. High junction temperature is one of the major failure causes in SSL devices. Due to the additional flexibility that smart controller of this device gives us, self-maintenance solution can be implemented in this device.