LED Binning

Understanding LED Binning

Binning is a fundamental quality control process that determines the visual consistency of LED displays. The practice emerged from the inherent variability in LED semiconductor manufacturing.

Manufacturing Variation

LED chips are created through semiconductor fabrication processes that introduce natural variation:

Material Variation: Slight differences in gallium, indium, and phosphor concentrations

Process Variation: Temperature, timing, and deposition thickness fluctuations

Crystal Structure: Microscopic defects and grain boundaries

These variations result in LEDs with measurably different characteristics, even from the same wafer.

Binning Parameters

**Luminous Intensity (Brightness)** LEDs are sorted into brightness bins measured in millicandelas (mcd). A typical red LED might have bins ranging from 400mcd to 800mcd. Using LEDs from different brightness bins would create visible brightness variation.

**Dominant Wavelength (Color)** Color is sorted by wavelength in nanometers. For example:

• Red: 620nm to 630nm range, with 2-3nm bins
• Green: 520nm to 535nm range
• Blue: 465nm to 475nm range

Mixing LEDs from different wavelength bins causes color inconsistency.

**Forward Voltage** Voltage bins ensure consistent electrical characteristics for driver circuit design. This is less visually critical but affects power consumption and heat generation.

Binning Steps

The industry uses "step" terminology for binning tolerance:

3-Step Binning: Tightest tolerance, highest consistency, highest cost

5-Step Binning: Standard for professional displays

7-Step Binning: Looser tolerance, visible variation may occur

9+ Step Binning: Budget applications only

Binning and Display Assembly

Quality display manufacturers enforce binning consistency:

Single-Bin Policy: All LEDs in one panel from same bin

Matched Bins: Adjacent panels use compatible bins

Inventory Management: Bins tracked through production

Poor binning management results in the "patchwork" appearance where some panels appear different colors or brightness than others.

Calibration Relationship

Even with perfect binning, some variation exists. Calibration compensates:

Factory Calibration: Measures actual output and adjusts driving parameters

Field Calibration: Corrects for aging and environmental factors

Binning + Calibration: Together achieve the best uniformity

Well-binned displays require less aggressive calibration, preserving dynamic range.

Industry Best Practices

For professional installations:

• Specify 3-step or 5-step binning maximum in purchase specifications
• Require bin documentation from manufacturer
• Ensure replacement panels match original bin ranges
• Include calibration in maintenance schedules
• Track panel serial numbers to bin information