Robust Reliability for Light Emitting Diodes Using Degradation Measurements

Taguchi's robust design provides an important paradigm for producing robust products. There are many successful applications of this paradigm, but few have dealt with reliability, i.e. when the quality characteristic is lifetime. In this paper, an actual experiment is presented which was performed to achieve robust reliability of light emitting diodes. Three major factors chosen from many potentially important manufacturing factors and one noise factor were investigated. For light emitting diodes, failure occurs when their luminosity or light intensity fall below a specified level. An interesting feature of this experiment is the periodic monitoring of the luminosity. The paper shows how the luminosity's degradation over time provides a practical way to achieve robust reliability of light emitting diodes which are already highly reliable.