SMD LED LTST-S43FBEGW Datasheet - Dimensions 4.0x3.0x0.4mm - Voltage 1.7-3.1V - Power 30-35mW - Full Color RGB - English Technical Document

1. Product Overview

The LTST-S43FBEGW is a compact, side-looking Surface Mount Device (SMD) LED designed for space-constrained applications requiring full-color indication or backlighting. This component integrates three distinct semiconductor chips within a single, ultra-thin 0.4mm profile package: an InGaN (Indium Gallium Nitride) chip for blue emission, an AlInGaP (Aluminum Indium Gallium Phosphide) chip for red emission, and a second InGaN chip for green emission. The combination of these primary colors (RGB) enables the creation of a wide gamut of colors through individual or combined control. The white diffused lens ensures a uniform light distribution, making it suitable for status indicators and backlighting where a consistent, wide-angle glow is desired.

Its core advantages include RoHS compliance, compatibility with automated pick-and-place assembly systems, and suitability for standard infrared (IR) reflow soldering processes. The primary target markets are consumer electronics, telecommunications equipment, office automation devices, home appliances, and industrial control panels where reliable, multi-color indication in a minimal footprint is critical.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Extremely low profile design with a thickness of only 0.4mm.
• Side-viewing form factor with a white diffused lens.
• Incorporates high-efficiency InGaN (Blue/Green) and AlInGaP (Red) semiconductor chips.
• Terminations feature tin plating for improved solderability.
• Packaged in 8mm tape on 7-inch diameter reels for automated assembly.
• Compatible with standard EIA (Electronic Industries Alliance) package outlines.
• Designed for use with automatic placement equipment.
• Suitable for infrared reflow soldering processes.

1.2 Applications

• Backlighting for keypads and keyboards in mobile devices and computers.
• Multi-color status and power indicators in networking equipment and home appliances.
• Illumination for micro-displays and symbolic luminaries.
• General-purpose indicator lights in telecommunications and industrial equipment.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed, objective analysis of the LED's key performance characteristics as defined in the datasheet. All values are specified at an ambient temperature (Ta) of 25°C unless otherwise noted.

2.1 Absolute Maximum Ratings

The Absolute Maximum Ratings define the stress limits beyond which permanent damage to the device may occur. These are not conditions for normal operation.

• Power Dissipation (Pd): 35 mW for Blue and Green chips; 30 mW for the Red chip. This parameter limits the total electrical power that can be converted into heat within the LED package.
• Peak Forward Current (I_F(PEAK)): 50 mA for Blue/Green, 40 mA for Red. This is the maximum allowable instantaneous current under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). Exceeding this can cause catastrophic failure.
• DC Forward Current (I_F): 10 mA for Blue/Green, 20 mA for Red. This is the maximum continuous forward current recommended for reliable long-term operation.
• Operating & Storage Temperature: The device is rated for an ambient operating range of -20°C to +80°C. The storage temperature range is wider, from -30°C to +100°C.
• Infrared Soldering Condition: The package can withstand a peak temperature of 260°C for a maximum of 10 seconds during reflow soldering.

2.2 Electrical & Optical Characteristics

These parameters define the typical performance of the LED under normal operating conditions (I_F = 5mA).

• Luminous Intensity (I_V): Measured in millicandelas (mcd). The minimum and maximum values vary by color: Blue (11.2-45.0 mcd), Red (11.2-45.0 mcd), Green (45.0-180.0 mcd). The green chip exhibits significantly higher output for the same drive current.
• Viewing Angle (2θ_1/2): A typical value of 130 degrees, indicating a very wide emission pattern characteristic of side-view LEDs with diffused lenses.
• Peak Wavelength (λ_P): The wavelength at which the spectral power output is highest. Typical values are 468 nm (Blue), 631 nm (Red), and 518 nm (Green).
• Dominant Wavelength (λ_d): The single wavelength perceived by the human eye that defines the color. Ranges are: Blue (465-475 nm), Red (619-629 nm), Green (525-540 nm).
• Spectral Line Half-Width (Δλ): The bandwidth of the emitted light at half its maximum intensity. Typical values are 25 nm (Blue), 17 nm (Red), and 35 nm (Green). A narrower half-width indicates a more spectrally pure color.
• Forward Voltage (V_F): The voltage drop across the LED when driven at 5mA. Ranges are: Blue (2.60-3.10V), Red (1.70-2.30V), Green (2.60-3.10V). The red chip typically has a lower forward voltage due to its different semiconductor material (AlInGaP vs. InGaN).
• Reverse Current (I_R): Maximum of 10 µA for all colors when a reverse bias of 5V is applied. The datasheet explicitly cautions that the device is not designed for reverse operation; this test is for informational/quality purposes only.

3. Binning System Explanation

The LED's luminous intensity is sorted into bins to ensure consistency within a production lot. The bin code defines a minimum and maximum intensity range.

3.1 Luminous Intensity Binning

Each color has its own set of bin codes with a tolerance of +/-15% within each bin.

• Blue & Red Intensity Bins:
  • Bin Code L: 11.2 mcd (Min) to 18.0 mcd (Max)
  • Bin Code M: 18.0 mcd to 28.0 mcd
  • Bin Code N: 28.0 mcd to 45.0 mcd
• Green Intensity Bins:
  • Bin Code P: 45.0 mcd to 71.0 mcd
  • Bin Code Q: 71.0 mcd to 112.0 mcd
  • Bin Code R: 112.0 mcd to 180.0 mcd

This binning allows designers to select LEDs with predictable brightness levels for applications requiring color mixing or specific luminance requirements.

4. Mechanical and Packaging Information

4.1 Package Dimensions

The LTST-S43FBEGW conforms to a standard SMD footprint. Key dimensions include a body length of approximately 4.0mm, a width of 3.0mm, and the defining ultra-thin height of 0.4mm. All dimensional tolerances are ±0.1mm unless otherwise specified. The pin assignment is clearly defined: Pin 1 for the Green chip anode, Pin 3 for the Red chip anode, and Pin 4 for the Blue chip anode. A detailed dimensioned drawing is essential for accurate PCB land pattern design.

4.2 Recommended PCB Pad Design & Polarity

The datasheet includes a suggested printed circuit board (PCB) attachment pad layout. Following this recommendation is crucial for achieving proper solder fillets, ensuring mechanical stability, and facilitating reliable electrical connection during the reflow process. The pad design accounts for the component's thermal mass and helps prevent tombstoning (component standing on end). The polarity marking on the LED package must be aligned with the corresponding polarity marking on the PCB silkscreen.

4.3 Tape and Reel Packaging

The components are supplied in industry-standard embossed carrier tape with a width of 8mm, wound onto 7-inch (178mm) diameter reels. Each reel contains 4000 pieces. The tape is sealed with a top cover to protect the components from contamination and moisture. The packaging conforms to ANSI/EIA-481 specifications, ensuring compatibility with automated feeders. For quantities less than a full reel, a minimum packing quantity of 500 pieces is available.

5. Soldering and Assembly Guidelines

5.1 IR Reflow Soldering Profile

The datasheet provides a suggested reflow profile compliant with IPC J-STD-020D.1 for Pb-free processes. Key parameters include:

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum of 120 seconds to gradually raise temperature and activate flux.
• Peak Temperature: Maximum of 260°C.
• Time Above Liquidus (TAL): The component should be exposed to the peak temperature for a maximum of 10 seconds. Reflow should be performed a maximum of two times.

It is emphasized that the optimal profile depends on the specific PCB design, solder paste, and oven characteristics. Board-level characterization is recommended.

5.2 Hand Soldering

If hand soldering is necessary, extreme care must be taken. The recommended maximum soldering iron tip temperature is 300°C, with a maximum contact time of 3 seconds per solder joint. Hand soldering should be limited to a single repair cycle to prevent excessive thermal stress on the plastic package and the internal wire bonds.

5.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used. The recommended method is to immerse the assembled board in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. The use of unspecified or aggressive chemical cleaners can damage the LED's plastic lens and package material.

6. Storage and Handling Precautions

6.1 Electrostatic Discharge (ESD) Sensitivity

Like most semiconductor devices, these LEDs are sensitive to electrostatic discharge. Proper ESD controls must be in place during handling and assembly. This includes the use of grounded wrist straps, anti-static mats, and ensuring all equipment is properly grounded. ESD can cause immediate failure or latent damage that reduces long-term reliability.

6.2 Moisture Sensitivity and Storage

The LEDs are packaged in a moisture-barrier bag with desiccant. In this sealed state, they should be stored at 30°C or less and 90% relative humidity (RH) or less, with a recommended shelf life of one year from the date code.

Once the original packaging is opened, the components are rated at Moisture Sensitivity Level (MSL) 3. This means they must be subjected to IR reflow soldering within 168 hours (7 days) of exposure to an environment not exceeding 30°C / 60% RH. For storage beyond this period outside the original bag, they should be placed in a sealed container with desiccant. Components exposed for more than 168 hours require a baking process (approximately 60°C for at least 20 hours) to remove absorbed moisture before soldering to prevent "popcorning" or package cracking during reflow.

7. Application Suggestions and Design Considerations

7.1 Current Limiting

A fundamental requirement for driving LEDs is the use of a current-limiting resistor or a constant-current driver. The forward voltage (V_F) of an LED has a tolerance and varies with temperature. Connecting an LED directly to a voltage source will result in uncontrolled current, likely exceeding the Absolute Maximum Rating and destroying the device. The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet to ensure sufficient current limiting under all conditions.

7.2 Thermal Management

Although the power dissipation is low (30-35 mW), effective thermal management on the PCB is still important for longevity and stable performance. Excessive junction temperature leads to reduced light output (lumen depreciation), a shift in dominant wavelength (color shift), and accelerated aging. Ensure the PCB pads have adequate thermal relief and, if possible, connect to copper pour areas to act as a heat sink.

7.3 Color Mixing and Control

To achieve specific colors (e.g., white, yellow, cyan, magenta) or dynamic color effects, the three chips must be driven independently. This typically requires three separate control channels, often implemented via pulse-width modulation (PWM) from a microcontroller. The different luminous intensities and forward voltages of each color must be accounted for in the circuit design and control software to achieve balanced color output.

8. Frequently Asked Questions (Based on Technical Parameters)

8.1 Can I drive the LED at its peak current (50mA) continuously?

No. The Peak Forward Current rating (50mA for Blue/Green) is for pulsed operation only (1/10 duty cycle, 0.1ms pulses). The maximum recommended continuous current (DC Forward Current) is 10mA for these colors. Exceeding the DC rating will cause excessive heating, leading to rapid degradation and failure.

8.2 Why is the forward voltage different for the red chip?

The forward voltage is a fundamental property of the semiconductor material's bandgap energy. The red chip uses AlInGaP, which has a lower bandgap energy (~1.9-2.0 eV) compared to the InGaN used for blue and green (~2.5-3.4 eV). A lower bandgap requires less energy for electrons to cross, resulting in a lower forward voltage drop.

8.3 What does "Dominant Wavelength" mean compared to "Peak Wavelength"?

Peak Wavelength (λ_P): The physical wavelength where the LED emits the most optical power. It is measured directly by a spectrometer.
Dominant Wavelength (λ_d): The perceptual wavelength. It is derived from the CIE chromaticity diagram and represents the single wavelength of pure spectral light that the human eye would perceive as matching the LED's color most closely. For LEDs with a broad spectrum, λ_d and λ_P can differ.

8.4 How do I interpret the bin code when ordering?

When specifying this component for production, you should request the desired luminous intensity bin code for each color (e.g., Blue: N, Red: M, Green: Q). This ensures you receive LEDs with brightness levels within a predictable, narrow range, which is critical for applications requiring uniform appearance or precise color mixing. If no bin is specified, you may receive components from any production bin.