What is LED bead color separation (Bin)? Why are there color differences in the same batch of LED beads?
The same batch of goods, loaded on the same panel, have two obvious yellow lights and one obvious dark light out of ten green lights - a problem that almost every equipment factory that uses light beads has encountered. The root cause is not your welding process, but whether the lamp beads were made before leaving the factorySpectral Separation (Bin Sorting)And how finely to divide it.
This article explains from an internal perspective of the packaging factory what spectral separation is and what data should be requested from the manufacturer when purchasing.
1、 Why are there inherent differences in light bulbs
LED chips are grown on a wafer, and chips at different positions on the same wafer naturally have discrete wavelengths, brightness, and voltage. After being packaged into light beads, the dispersion is further amplified:
- wavelengthThe main wavelength of the same batch of red light beads may be distributed between 615-630nm, with a difference of 5nm that can be distinguished by the naked eye
- Brightness (IV)The same batch of 0805 green lights may have a luminous intensity that spans from 200mcd to 500mcd
- Forward voltage (VF)The same batch may have both 1.9-2.3V
Directly mixing and shipping without sorting is what you see as a "colorful board of lights".
2、 How is spectral separation done
The spectrophotometer is powered on to each lamp bead and measures in millisecondsBrightness, main wavelength, voltageThree sets of data are automatically sorted into different bins according to preset gears. Each gear is oneBin.
Taking our Hongcheng Optoelectronics 0805 pure green light bead as an example:
| parameter | Classification method | Typical Bin Width |
|---|---|---|
| Brightness IV | 1:1.2-1:1.4 per level | Such as 300-360mcd, 360-430mcd |
| Main wavelength | 1-2.5nm per level | Such as 520-522.5nm, 522.5-525nm |
| Voltage VF | 0.05-0.1V per gear | Such as 3.0-3.1V, 3.1-3.2V |
The narrower the bin width, the better the consistency within the same batch, and the greater the sorting loss and cost.That's why the consistency of LED beads purchased through different channels with the same model and brand varies greatly - what you buy may be a wide bin, or it may be a leftover bin from someone else's selection.
3、 How narrow should the bin be for different applications
- Multiple lights arranged side by side on the same panel(Charging pile, energy storage cabinet, instrument): wavelength Bin ≤ 2.5nm, brightness ratio ≤ 1:1.2, parallel without color difference
- Single light status indicatorThe wavelength Bin can be relaxed to 5nm, and a brightness ratio of 1:1.4 is sufficient
- Backlight/LightingFocus on color temperature Bin (white light SDCM ≤ 3 steps, high-end requirement ≤ 2)
- Traffic signals and vehicle regulationsLock the wavelength range according to industry standards, usually with the strictest requirements
Procurement writing example: "0805 pure green, main wavelength 520-525nm, single bin width ≤ 2.5nm, brightness 300-400mcd, single level shipment" - Write this sentence into the procurement specification document, and consistency will be guaranteed at the contract level.
4、 The Relationship between Spectral Separation, Light Attenuation, and Reliability
Sorting solves the problem of "factory consistency", while light decay solves the problem of "time consistency", but the two are strongly correlated:
- The testing station of the spectrophotometer can simultaneously removeDark spot, leakage, VF abnormalityThe hidden danger particles are equivalent to an additional full inspection
- The formal sorting process will be matchedaging test(Light up at room temperature for 8-24 hours for sampling/full testing), screen out early failure particles before leaving the factory
- Manufacturers that skip aging and only focus on spectral analysis have beautiful factory data, but still have dead lights after three months of installation
So when choosing a manufacturer, asking for two pieces of data is enough:What is the width of the spectral bin? How long does it age before shipment?Those who dare to give specific numbers are generally not inferior.
5、 Reference standards for light attenuation
Industry standard judgment criteria (20mA rated drive, 25 ℃ environment):
| time | High quality products with light decay | Qualified line | Poor quality product performance |
|---|---|---|---|
| 1000 hours | ≤3% | ≤5% | >10% or dead lights occur |
| 5000 hours | ≤8% | ≤15% | >30%, significantly darkened |
| 10000 hours | ≤12% | ≤20% | Extensive yellowing and blackening |
Requesting manufacturers to provide LM-80 reports or long-term testing data of their own aging rooms is more credible than any promotional slogan.
VI FAQ
Q: How much is the unit price of sorted light beads?
According to the Bin width requirement, it is usually 10% -30% higher than the pre selection unified goods. But overall, the labor cost of reworking a panel far exceeds the price difference of the LED chips.
Q: Can I buy standardized goods and sort them on my own machine?
Theory is feasible, but in practice it is not cost-effective - manual sorting is far less consistent than machine sorting, and without spectral data, you can only distinguish by naked eye.
Q: Can the same Bin of LED beads be used in different batches of orders to ensure consistency across batches?
Sure, provided that the manufacturer locks in the same chip supplier and defines the same bin. This is also the reason why we create a "project specific Bin file" for our clients - the renewal order is shipped directly according to the file.
7、 Summary
The root cause of color difference is the natural dispersion of chips, and the antidote isNarrow Bin Sorting+Aging ScreeningWhen purchasing, include the four indicators of "wavelength bin width, brightness grading, aging time, and light attenuation data" in the specification sheet to ensure consistency.
Hongcheng Optoelectronics' full range of lamp beads are shipped by narrow Bin spectral separation (with a wavelength Bin as narrow as 1nm), and undergo a full aging test 24 hours before shipment, supporting project specific Bin file management. Samples and grading data sheets are welcome to be requested: 139 2571 4318 (same WeChat account), sales@led-hc.com .
