Comprehensive Guide to LED Bin Selection in TFT Displays
LED (Light Emitting Diodes) have revolutionized the display industry with their compact size, energy efficiency, environmental friendliness, high luminous efficiency, fast response times, vibration resistance, and long lifespan. In TFT (Thin-Film Transistor) displays, the choice of LEDs is crucial to achieve the desired color and brightness. This guide delves deeper into the intricacies of LED bin selection, highlighting the importance of this process in the manufacturing of TFT displays.
The Role of Phosphor and Blue LED Substrates:
Before we delve into LED bin selection, it’s essential to understand the fundamental elements at play. In the TFT display industry, white LEDs are the standard choice. These white LEDs are created by exciting phosphor, typically cerium-doped yttrium-aluminum-garnet (Ce:YAG), using blue LED substrates emitting light at approximately 460nm. When the phosphor is excited, it emits yellow light at around 550nm. This yellow light, when combined with the blue light, creates the white light that illuminates the TFT display.
Why LED Bin Selection Matters:
The human eye is incredibly sensitive to variations in color and brightness. Even minor discrepancies in LED characteristics, such as lumens, voltage, and color temperature, can result in noticeable differences in the displayed image. This is where LED binning comes into pla
Understanding LED Binning:
LED binning is the process by which LEDs are categorized into groups or “bins” based on their similarity in specific parameters. The key factors for binning include:
Lumens (Brightness): Binning LEDs based on lumens is a relatively straightforward process. LEDs are sorted into groups depending on their luminous output.
Voltage: LEDs can also be categorized based on their drive voltage. This classification helps match LEDs with similar electrical characteristics.
Color Coordinates: The most complex aspect of LED binning is categorizing LEDs based on their color coordinates. This process involves determining the precise chromaticity of the emitted light. Chromaticity coordinates are represented on color spaces like the CIE 1931 Chromaticity Diagram. the CIE 1931 Chromaticity Diagram is a fundamental tool in LED binning. It represents colors perceptible to the human eye in a two-dimensional space. This diagram helps manufacturers define regions where colors are indistinguishable to the human eye, known as “just noticeable differences” (JND).
Color Series in LED Binning:
LEDs are divided into different color series based on chromaticity coordinates. Each series represents a specific color temperature range. Below we take a white light LED as an example to facilitate your understanding. The color series of this LED are:
A-Series (x: 0.2374, y: 0.2014 to x: 0.2597, y: 0.2356)
B-Series (x: 0.2520, y: 0.2206 to x: 0.2836, y: 0.2728)
H-Series (x: 0.2584, y: 0.2287 to x: 0.2948, y: 0.2899)
C-Series (x: 0.2508, y: 0.2098 to x: 0.2966, y: 0.2890)
D-Series (x: 0.2607, y: 0.2200 to x: 0.3017, y: 0.2902)
P-Series (x: 0.2625, y: 0.2191 to x: 0.3035, y: 0.2893)
R-Series (x: 0.2574, y: 0.2179 to x: 0.2937, y: 0.2791)
S-Series (x: 0.2661, y: 0.2173 to x: 0.3009, y: 0.2755)
Each color series is further divided into 6-10 gradations, resulting in a wide range of classifications for white LED chips. During the initial stages of a project, LEDs are chosen based on the required color coordinates, ensuring stability in the product’s color performance.
Practical Application of LED Binning:
In real-world applications, the selection of LEDs based on color coordinates is crucial for maintaining consistent and accurate color representation on TFT displays. Project teams evaluate the requirements and choose LEDs from the appropriate series and gradations to achieve the desired color temperature and performance.
Considerations in LED Binning:
It’s important to note that LED binning primarily focuses on color coordinate control, with data typically gathered under a standard condition of 20mA current supply. However, when higher currents are employed, there may be slight deviations in the color coordinates of the emitted light.
Conclusion:
In the TFT display industry, the meticulous process of LED bin selection ensures that displays meet stringent color requirements and deliver consistent and high-quality visual experiences. Understanding the nuances of LED binning, from lumens to color coordinates, is essential for display manufacturers striving to produce displays that meet the exacting standards of diverse applications. The precision achieved through LED binning plays a pivotal role in the success of TFT displays across a range of industries, from consumer electronics to medical imaging and beyond.
