Thermal, Photometric and Radiometric Properties of Multi-Color LEDs Situated on the Common PCB

This paper presents the results of experimental investigations illustrating the influence of the spectra of the light emitted by power LEDs on their thermal, photometric and radiometric parameters. The investigations were performed for six diodes emitting white or monochromatic light of different spectra. Each of these diodes was produced by the same manufacturer, mounted in the same package and the tested devices were soldered to the common PCB. In the paper, the manner and set-ups making possible measurements of self and transfer transient thermal impedances, illuminance and the surface power density of the light emitted by the tested devices are described. Selected results of measurements are shown and discussed. These results prove that the spectra of the emitted light influence self-transient thermal impedances of the considered devices and transfer transient thermal impedances between some pairs of these devices. Additionally, it is proved that thermal couplings between the tested diodes strongly influence their junction temperature and the surface power density of the emitted radiation.