The Development of a System for Measuring the Junction Temperatures of Multiple LEDs on a Package Simultaneously by Using Pulsed-laser Raman Scattering

Abstract

This paper details a novel method consisting of employing a pulsed-laser Raman scattering technique to estimate junction temperatures of several LED chips arranged in a straight line on a phosphor-less blue-LED package and a phosphor-resin coated blue-LED package. By using a sheet-shaped irradiation pattern, each of the GaN-E₂^H Raman spectra from several chips mounted straight on a phosphor-less blue LED package was observed at the same time and the junction temperature of each chip was estimated successfully by means of each Raman shift during operation despite the existence of strong LED emission. In addition, the GaN-E₂^H Raman signal from the phosphor-resin coated blue-LED was observed for the first time by using 633 nm laser to reduce the negative influence from the phosphor and light diffusing substances in the resin. It is concluded that this technique would be a useful method for a remote and standard system for 2D mapping of the junction temperatures of blue-LED packages.