Spectroradiometer Requirements for LED Binning

Need for LED Binning

Despite the most sophisticated manufacturing technologies employed by the semiconductor industry, light output and colour temperature of LEDs varies from chip to chip. Therefore, binning is employed to maximise yields and to categorise products. Standards such as ANSI C78.377-2017 [1] define tolerance bands or ‘bins’ with respect to chromaticity boundaries.

Therefore, without exception, LED binning requires the absolute spectral power distribution of devices to be measured in order to precisely determine the light output and the correlated colour temperature (CCT) of each individual LED. Light output is most commonly measured in terms of luminous flux (lm) although Averaged LED Intensity [2] is also sometimes specified.

LEDs are mass produced necessitating the shortest possible measuring times for binning purposes.

High Speed Testing Binning Measurement Systems

Manufacturers test their devices using a single pulse with typical durations of around 20 ms or less. This high speed testing places great demands on the spectroradiometer requiring high light throughput of the input optics, high sensitivity and the smallest possible dark signal as well as fast data processing and data transmission. Additionally, the software must provide for easy integration of the measuring device into complete automated systems. With the BTS2048-VL spectroradiometer and its measurement accessories for luminous flux and Averaged LED Intensity, Gigahertz-Optik GmbH offers a high-performance measuring device for LED binning.

References

[1] Specifications for the Chromaticity of Solid State Lighting Products, ANSI C78.377-2017

[2] CIE 127:2007 Measurement of LEDs