LTST-B32JEGBK-AT SMD LED Datasheet - Full Color RGB - 0.65mm Height - 25mA/20mA Forward Current - English Technical Document

1. Product Overview

The LTST-B32JEGBK-AT is a compact, full-color surface-mount LED designed for modern electronic applications requiring vibrant color indication or backlighting in a minimal footprint. This device integrates three distinct semiconductor chips within a single package: an AlInGaP chip for red emission and two InGaN chips for green and blue emission. This combination enables the generation of a wide spectrum of colors through individual or combined control of the three primary light sources. Its defining characteristic is an exceptionally low profile of 0.65mm, making it suitable for applications where vertical space is severely constrained, such as ultra-thin consumer electronics, wearable devices, or sophisticated control panels.

The LED is packaged on 8mm tape and supplied on 7-inch diameter reels, conforming to EIA standards, which ensures compatibility with high-speed, automated pick-and-place assembly equipment commonly used in volume manufacturing. Furthermore, it is qualified for lead-free infrared (IR) reflow soldering processes, aligning with contemporary environmental regulations and manufacturing practices.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Extra-thin package profile with a height of only 0.65mm.
• Utilizes high-efficiency AlInGaP technology for red light and InGaN technology for green and blue light, resulting in high luminous intensity.
• Packaged in 8mm tape on 7-inch reels for automated handling.
• Standard EIA-compliant package outline.
• Designed for compatibility with integrated circuit (IC) drive levels.
• Suitable for use with automatic placement equipment.
• Withstands standard infrared reflow soldering profiles.

1.2 Applications

• Status and power indicators in telecommunications equipment, office automation devices, home appliances, and industrial control systems.
• Backlighting for keypads, keyboards, and control buttons.
• Illumination for micro-displays and symbolic luminaries.
• General-purpose signal lighting where multi-color capability is required.

2. Technical Parameters: In-Depth Objective Interpretation

The performance of the LTST-B32JEGBK-AT is defined by a comprehensive set of electrical, optical, and thermal parameters. Understanding these specifications is crucial for reliable circuit design and achieving the desired visual performance.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed.

• Power Dissipation (Pd): Red: 62.5 mW, Green/Blue: 76 mW. This parameter, combined with thermal resistance, determines the maximum allowable power to prevent overheating.
• Peak Forward Current (I_F(PEAK)): Red: 60 mA, Green/Blue: 100 mA. This is the maximum permissible pulsed current, typically specified at a low duty cycle (1/10) and short pulse width (0.1ms), useful for multiplexing or brief high-brightness pulses.
• DC Forward Current (I_F): Red: 25 mA, Green/Blue: 20 mA. This is the maximum continuous current recommended for reliable long-term operation.
• Electrostatic Discharge (ESD) Withstand: Red: 2000V (HBM), Green/Blue: 1000V (HBM). The green and blue InGaN chips are generally more sensitive to ESD than the AlInGaP red chip, necessitating stricter handling precautions.
• Operating & Storage Temperature: -40°C to +85°C (operating), -40°C to +90°C (storage). This defines the environmental conditions the device can endure.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, which is a standard condition for lead-free reflow processes.

2.2 Electrical & Optical Characteristics

These are the typical and guaranteed performance parameters measured under standard test conditions (Ta=25°C, I_F=5mA unless noted).

• Luminous Intensity (I_V): Measured in millicandelas (mcd). Minimum values are: Red: 26.0 mcd, Green: 122.0 mcd, Blue: 22.0 mcd. The green chip exhibits significantly higher output due to the high efficiency of the InGaN material at this wavelength and the human eye's peak sensitivity in the green region.
• Viewing Angle (2θ_1/2): Typically 120 degrees. This wide viewing angle indicates a Lambertian or near-Lambertian emission pattern, providing uniform brightness over a broad area.
• Peak Emission Wavelength (λ_P): Typical values: Red: 632 nm, Green: 518 nm, Blue: 468 nm. This is the wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): The single wavelength perceived by the human eye that defines the color. The specified ranges are: Red: 616-628 nm, Green: 519-537 nm, Blue: 464-479 nm.
• Spectral Line Half-Width (Δλ): Typical values: Red: 12 nm, Green: 27 nm, Blue: 20 nm. This indicates the spectral purity; a smaller value means a more monochromatic light. Red light from AlInGaP tends to have a narrower spectrum than green/blue from InGaN.
• Forward Voltage (V_F): At 5mA: Red: 1.50-2.15V, Green: 2.00-3.20V, Blue: 2.00-3.20V. The lower V_F of the red chip is characteristic of AlInGaP technology compared to InGaN.
• Reverse Current (I_R): Maximum 10 μA at V_R=5V. LEDs are not designed for reverse bias operation; this parameter is for quality test purposes only.

3. Binning System Explanation

To ensure color consistency and brightness matching in production, the LEDs are sorted into bins based on key optical parameters.

3.1 Luminous Intensity (Brightness) Binning

Each color is binned into several ranks (e.g., A, B, C...). The luminous intensity is measured at a standard drive current of 5mA. For example, Red bin 'A' covers 26.0-31.0 mcd, while bin 'E' covers 54.0-65.0 mcd. Green and blue have their own distinct binning tables. A tolerance of +/-10% is applied within each bin. Designers must specify the required bin code to guarantee brightness uniformity across multiple units in an assembly.

3.2 Hue (Dominant Wavelength) Binning

This binning ensures color consistency. LEDs are sorted based on their dominant wavelength. For instance, Red is binned from 616-628 nm in 1 nm steps (bins 1-4). Green is binned from 519-537 nm (bins 1-6), and Blue from 464-479 nm (bins 1-5). Each bin has a +/-1 nm tolerance. Specifying a hue bin is critical for applications where precise color matching is required, such in multi-LED displays or status indicators where all red LEDs must appear identical.

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet (Fig.1, Fig.5), their implications are standard.

• I-V Curve: The forward voltage (V_F) increases with current (I_F) in a non-linear, exponential manner typical of a diode. The curve will differ for each chip color due to different semiconductor materials and bandgaps.
• Luminous Intensity vs. Current: Light output is generally proportional to forward current in the normal operating range, but efficiency may drop at very high currents due to thermal effects and droop.
• Spectral Distribution: The output spectrum for the red chip is guaranteed to be single-peaked. The graphs would show the relative radiant power versus wavelength, illustrating the peak wavelength (λ_P) and spectral half-width (Δλ).
• Viewing Angle Pattern: A polar diagram (Fig.5) illustrates the angular distribution of light intensity, confirming the 120-degree viewing angle where intensity falls to half of its on-axis value.

5. Mechanical & Package Information

5.1 Package Dimensions and Pin Assignment

The device follows a standard SMD footprint. The pin assignment is clearly defined: Pin 2 is the cathode for the Red chip, Pin 3 for the Green chip, and Pin 4 for the Blue chip. The common anode is likely Pin 1 (implied by standard RGB LED configuration). All dimensions are provided in millimeters with a standard tolerance of ±0.1mm. The ultra-thin 0.65mm height is a key mechanical feature.

5.2 Recommended PCB Attachment Pad Layout

A land pattern design is provided to ensure proper soldering and mechanical stability. Adhering to this recommended footprint is essential for achieving reliable solder joints, preventing tombstoning, and ensuring correct alignment during the reflow process.

6. Soldering & Assembly Guidelines

6.1 IR Reflow Soldering Conditions (Pb-Free Process)

A detailed reflow profile is recommended. Key parameters include a pre-heat stage, a defined time above liquidus, and a peak temperature not exceeding 260°C for a maximum of 10 seconds. The device is rated to withstand this profile twice maximum. For manual rework with a soldering iron, the tip temperature should not exceed 300°C, and contact time should be limited to 3 seconds per joint, for one time only.

6.2 Storage and Handling

• ESD Precautions: Mandatory use of wrist straps, anti-static mats, and properly grounded equipment is required, especially for the ESD-sensitive green and blue chips.
• Moisture Sensitivity Level (MSL): The device is rated MSL 3. When the original moisture-barrier bag is opened, the components must be subjected to reflow soldering within one week when stored at conditions ≤ 30°C/60% RH. For longer storage outside the original bag, baking at approximately 60°C for at least 20 hours is required before soldering to prevent popcorning during reflow.
• Cleaning: If post-solder cleaning is necessary, only alcohol-based solvents like isopropyl alcohol or ethyl alcohol should be used. Immersion should be at normal temperature for less than one minute. Unspecified chemicals may damage the LED package or lens.

7. Packaging and Ordering Information

The LEDs are supplied on embossed carrier tape, 8mm in width, wound onto standard 7-inch (178mm) diameter reels. Each reel contains 4,000 pieces. The tape has a cover tape to protect the components. Reels are typically packed three per inner carton. The packaging conforms to ANSI/EIA-481 specifications. The part number LTST-B32JEGBK-AT uniquely identifies this specific full-color, water-clear lens variant.

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

Each color channel (Red, Green, Blue) must be driven independently. A series current-limiting resistor is essential for each anode pin to set the desired forward current and protect the LED. The resistor value is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Since V_F differs per color, three different resistor values will typically be needed even if driven from the same supply voltage and at the same current. For precise current control or multiplexing many LEDs, dedicated LED driver ICs or constant-current sources are recommended.

8.2 Thermal Management

Although power dissipation is low, proper thermal design on the PCB is important for longevity and maintaining stable optical output. Ensure adequate copper area connected to the thermal pad (if any) or the LED's solder pads to act as a heat sink, especially when operating near maximum ratings or in high ambient temperatures.

8.3 Optical Design

The water-clear lens provides a wide, diffuse light pattern. For applications requiring focused light or specific beam patterns, secondary optics (such as light pipes, lenses, or diffusers) must be designed considering the LED's 120-degree viewing angle and spatial separation of the three color chips within the package, which can affect color mixing at close distances.

9. Technical Comparison and Differentiation

The primary differentiating factor of the LTST-B32JEGBK-AT is its combination of a full RGB color gamut within an extra-thin 0.65mm package height. Compared to older technology using discrete single-color LEDs or larger RGB packages, this device enables sleeker product designs. The use of AlInGaP for red offers higher efficiency and better temperature stability compared to some other red LED technologies. Its compatibility with automated assembly and standard reflow processes reduces manufacturing complexity and cost compared to devices requiring manual soldering or special handling.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Why is the maximum DC current different for red (25mA) vs. green/blue (20mA)?

This difference stems from the inherent material properties and chip design. The AlInGaP red chip can typically handle slightly higher current densities within the same package thermal constraints compared to the InGaN green and blue chips, leading to a higher rated continuous current.

10.2 Can I drive all three colors with a single resistor on the common anode?

No. Due to the significantly different forward voltages (V_F) of the red, green, and blue chips, connecting them in parallel with a single current-limiting resistor would result in severely unbalanced currents. The color with the lowest V_F (red) would draw most of the current, potentially exceeding its rating, while the others might be dim or not light at all. Each color channel must have its own independent current-limiting mechanism.

10.3 What does "Bin Code" mean, and why is it important to specify?

Due to manufacturing variations, LEDs are not identical. They are sorted (binned) after production based on measured luminous intensity and dominant wavelength. Specifying a bin code when ordering ensures you receive LEDs with nearly identical brightness and color. This is critical for applications using multiple LEDs where visual uniformity is required (e.g., a backlight panel or multi-segment display). Using LEDs from different bins can result in noticeable brightness or color differences.

11. Practical Design and Usage Case

Case: Designing a Multi-Color Status Indicator for a Network Router
A designer needs three status LEDs (Power, Internet, Wi-Fi) but has space for only one LED footprint on the PCB. The LTST-B32JEGBK-AT is selected. The microcontroller drives each color independently: Red for "Power Off/Error," Green for "Normal Operation," Blue for "Wi-Fi Active," and combinations like Cyan (Green+Blue) for other states. The 0.65mm height fits within the slim router casing. The designer specifies a tight hue bin (e.g., Green Bin 2: 522-525nm) and a mid-range intensity bin to ensure consistent color and brightness across all manufactured units. The recommended reflow profile is used in assembly, and the device passes all reliability tests.

12. Principle Introduction

Light emission in LEDs is based on electroluminescence in semiconductor materials. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. This recombination releases energy in the form of photons (light). The color (wavelength) of the emitted light is determined by the bandgap energy of the semiconductor material. AlInGaP (Aluminum Indium Gallium Phosphide) has a bandgap corresponding to red and amber-orange light. InGaN (Indium Gallium Nitride) has a wider, tunable bandgap capable of emitting light from ultraviolet through blue and green spectra. By integrating chips of these different materials into one package, full-color capability is achieved.

13. Development Trends

The trend in SMD LEDs for indicators and backlights continues toward higher efficiency (more light output per watt), smaller package sizes, and lower profiles to enable thinner end products. There is also a drive toward improved color rendering and consistency. Furthermore, integration of control electronics (like drivers or pulse-width modulation circuits) within the LED package itself is an ongoing development to simplify system design. The use of advanced materials and chip-scale packaging (CSP) technologies will likely push the limits of miniaturization and performance further.