It’s always been a pain – the binning of LEDs whether by colour or lumens just made life awkward. If we imagine the wafer from which the LED dies are made as a Pizza, the edges of the Pizza are usually cooked more than the centre; and it’s just the same with the LED wafers. The dies made from the edge will be slightly different from those in the middle.
To categorise them, they have to be illuminated and then flicked into one of many bins – hence binning. There could be many different bins from a single wafer. This leads to a complex and expensive selection process for the purchaser and design engineer who want to ensure a uniformity of supply and performance from one batch of LEDs to the next.
Now, coming up to date with the increase in control of the wafer growing process “epitaxy”, the difference between the outer edge of the wafer and the centre has become more refined and hence we now have fewer bins.
In an effort to bring the ‘wild world’ of LEDs into a somewhat more ordered system, the American National Standards Institute (ANSI) have established a bin standard (ANSI C78 377A), which has become a minimum requirement for Energy Star certification – the international standard for energy efficient consumer products.
Most of the major manufacturers now supply ANSI binned products therefore ensuring uniformity from one supplier to another.
One further advance is from Phillips Lumileds who are now marketing ‘Freedom from Binning’ with their Luxeon; S’ LEDs meaning that there are no colour bin selections to be made. With a correlated colour temperature of 3000K and a CRI >80, uniformity and consistency within the light beam and between emitters is guaranteed from one batch to another.
This could be the first stage of binning hitting the bin!
Paul Ward, Opto Product Manager, Farnell