Direct correlation between reliability and pH changes of phosphors for white light-emitting diodes

The reactivity of phosphor with water was investigated by measuring pH change, and the results are compared with long-term reliability test results as well as scanning electron microscope (SEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES) results. We found that the slope of pH change strongly depends on phosphor composition and represents a long-term reliability test result induced by phosphor in an LED package.