SMD LED LTST-C950KGKT-5A Datasheet - Green AlInGaP - 5V Reverse Voltage - 75mW Power - English Technical Document

1. Product Overview

This document details the specifications for a high-performance, surface-mount LED designed for modern electronic applications. The device utilizes an advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a bright green light output. It is housed in a compact, industry-standard package suitable for automated assembly processes, including pick-and-place machines and infrared (IR) reflow soldering. The LED is classified as a green product and complies with relevant environmental directives.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its ultra-high luminous intensity, achieved through the AlInGaP chip technology, and its robust construction suitable for high-volume manufacturing. Key features contributing to its reliability are compatibility with automatic placement equipment and infrared reflow solder processes. This makes it an ideal component for applications in consumer electronics, industrial indicators, automotive interior lighting, and general-purpose status or backlighting where consistent, bright green illumination is required.

2. In-Depth Technical Parameter Analysis

The electrical and optical characteristics define the operational boundaries and performance of the LED. Understanding these parameters is crucial for proper circuit design and ensuring long-term reliability.

2.1 Absolute Maximum Ratings

These ratings specify the limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED package can dissipate as heat at an ambient temperature (Ta) of 25°C.
• Peak Forward Current (I_FP): 80 mA. This current can be applied under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) but must not be exceeded.
• DC Forward Current (I_F): 30 mA. This is the maximum continuous forward current recommended for reliable operation.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage higher than this can break down the LED's PN junction.
• Operating Temperature Range: -30°C to +85°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +85°C.

2.2 Electro-Optical Characteristics

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

• Luminous Intensity (I_V): 112.0 - 450.0 mcd (millicandela). The light output is binned, with minimum and typical values provided. The actual value depends on the specific bin code.
• Viewing Angle (2θ_1/2): 25 degrees. This is the full angle at which the luminous intensity is half of the intensity measured on-axis (0 degrees). A 25-degree angle indicates a relatively focused beam.
• Peak Emission Wavelength (λ_P): 574.0 nm. This is the wavelength at which the spectral power distribution of the emitted light is at its maximum.
• Dominant Wavelength (λ_d): 564.5 - 573.5 nm. This is the single wavelength perceived by the human eye that defines the color (green) of the LED. It is derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 15 nm. This parameter indicates the spectral purity of the light; a smaller value means a more monochromatic output.
• Forward Voltage (V_F): 1.6 - 2.2 V. The voltage drop across the LED when a 5mA current is flowing through it. This value is also binned.
• Reverse Current (I_R): 10 μA (max). The small leakage current that flows when the maximum reverse voltage (5V) is applied.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into bins based on key parameters. This allows designers to select parts that meet specific application requirements for color and electrical characteristics.

3.1 Forward Voltage Binning

Bins are defined from Code 1 to Code 6, each covering a 0.1V range from 1.60V to 2.20V at 5mA. The tolerance within each bin is ±0.1V. Selecting LEDs from the same voltage bin helps maintain uniform brightness in parallel circuits or when using a constant-voltage driver.

3.2 Luminous Intensity Binning

Intensity is binned into three categories: R (112.0-180.0 mcd), S (180.0-280.0 mcd), and T (280.0-450.0 mcd). The tolerance on each bin is ±15%. This binning is critical for applications requiring specific brightness levels or uniformity across multiple LEDs.

3.3 Dominant Wavelength Binning

The color (green hue) is controlled by binning the dominant wavelength into three ranges: B (564.5-567.5 nm), C (567.5-570.5 nm), and D (570.5-573.5 nm). The tolerance is ±1 nm. This ensures a consistent perceived color, which is vital for aesthetic and signaling applications.

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet (e.g., Fig.1, Fig.5), their implications are standard. The forward current vs. forward voltage (I-V) curve will show the exponential relationship typical of a diode. The luminous intensity is directly proportional to the forward current within the safe operating area. The viewing angle diagram (Fig.5) illustrates the 25-degree half-angle beam pattern. The spectral distribution graph (Fig.1) would show a peak at approximately 574nm with a 15nm half-width, confirming the narrow-band green emission characteristic of AlInGaP technology. Performance will degrade at temperature extremes; luminous intensity typically decreases as junction temperature increases.

5. Mechanical and Package Information

The LED conforms to EIA standard package dimensions, though specific measurements are contained in the referenced package drawing. The device uses a dome lens which helps shape the light output and provides mechanical protection for the chip. The product is supplied in 8mm tape on 7-inch diameter reels, which is the standard for automated SMD assembly lines. The tape and reel specifications comply with ANSI/EIA 481 standards. A suggested soldering pad layout diagram is provided to ensure proper solder joint formation and mechanical stability during and after the reflow process.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

The LED is compatible with infrared reflow soldering processes. A suggested profile for lead-free (Pb-free) solder is provided. Key parameters include a pre-heat zone up to 150-200°C, a peak temperature not exceeding 260°C, and a time above 260°C limited to a maximum of 10 seconds. The profile should be characterized for the specific PCB design, solder paste, and oven used. The datasheet references JEDEC standard profiles as a reliable baseline.

6.2 Handling and Storage

The LED is sensitive to Electrostatic Discharge (ESD). Proper ESD precautions, such as using grounded wrist straps and workstations, are mandatory during handling. For storage, unopened moisture-proof bags should be kept at ≤30°C and ≤90% RH, with a shelf life of one year. Once opened, LEDs should be stored at ≤30°C and ≤60% RH and used within one week. If stored longer out of the original bag, a bake-out at 60°C for 20 hours is recommended before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

6.3 Cleaning

If cleaning after soldering is necessary, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. Unspecified chemicals may damage the package material or lens.

7. Packaging and Ordering Information

The standard packaging is 2000 pieces per 7-inch reel. A minimum order quantity of 500 pieces may apply for remainder quantities. The tape is designed with a cover tape sealing empty pockets, and the maximum number of consecutive missing components in the tape is two, as per industry standards. The part number LTST-C950KGKT-5A encodes specific attributes, though the exact naming convention logic is proprietary.

8. Application Recommendations

8.1 Typical Application Scenarios

This LED is suited for general illumination and indication purposes where high brightness and reliability are needed. Common applications include status indicators on consumer electronics (routers, chargers, appliances), backlighting for small displays or buttons, panel lighting in automotive dashboards, and signage.

8.2 Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to 30mA DC or less. Operating at or near the maximum rating will reduce lifespan.
• Thermal Management: While the power dissipation is low, ensuring adequate PCB copper area or thermal vias can help manage junction temperature, especially in high ambient temperature environments or when driven at higher currents.
• Reverse Voltage Protection: In circuits where reverse voltage transients are possible, consider adding a protection diode in parallel with the LED (cathode to anode) to clamp the reverse voltage below 5V.
• Optical Design: The 25-degree viewing angle provides a focused beam. For wider illumination, secondary optics (diffusers, lenses) may be required.

9. Technical Comparison and Differentiation

Compared to older GaP (Gallium Phosphide) green LEDs, AlInGaP technology offers significantly higher luminous efficiency and brightness. Compared to some InGaN (Indium Gallium Nitride) based green LEDs, AlInGaP typically offers superior color purity (narrower spectral width) and stability over temperature and current variations. The water-clear lens, as opposed to a diffused lens, maximizes light output and is ideal for applications requiring a sharp, well-defined beam or when external diffusers are used.

10. Frequently Asked Questions (FAQs)

Q: Can I drive this LED directly from a 5V supply?

A: No. The typical forward voltage is around 2.0V at 5mA. Connecting it directly to 5V would cause excessive current to flow, destroying the LED. A current-limiting resistor must be used. For example, with a 5V supply and a target current of 5mA, the resistor value would be R = (5V - 2.0V) / 0.005A = 600Ω.

Q: What is the difference between peak wavelength and dominant wavelength?

A: Peak wavelength is the physical peak of the light spectrum emitted. Dominant wavelength is the perceived color point on the CIE chart. For a monochromatic source like this green LED, they are close but not identical. Dominant wavelength is more relevant for color specification.

Q: How do I interpret the bin codes when ordering?

A: The full part number may include or imply specific bin codes for voltage (1-6), intensity (R, S, T), and wavelength (B, C, D). For consistent results in a production run, specify the required bin codes to your distributor or manufacturer.

11. Practical Design and Usage Case

Scenario: Designing a multi-LED status panel. A designer needs 10 uniformly bright green indicators on a control panel. They should:

1. Specify LEDs from the same Luminous Intensity bin (e.g., all from Bin T) and the same Dominant Wavelength bin (e.g., all from Bin C) to ensure visual consistency.

2. Design the driver circuit. If using a constant 3.3V rail, calculate the current-limiting resistor for each LED. Assuming a V_F from Bin 4 (1.9V-2.0V) and a target I_F of 10mA: R = (3.3V - 2.0V) / 0.01A = 130Ω. A 130Ω or 150Ω resistor would be suitable.

3. Follow the suggested pad layout on the PCB for reliable soldering.

4. Program the pick-and-place machine using the provided tape and reel dimensions.

5. Validate the assembly using the recommended IR reflow profile, ensuring peak temperature and time limits are not exceeded.

12. Technology Principle Introduction

This LED is based on AlInGaP semiconductor material grown on a substrate. When a forward voltage is applied, electrons and holes recombine in the active region of the PN junction, releasing energy in the form of photons (light). The specific composition of the Aluminum, Indium, Gallium, and Phosphide atoms determines the bandgap energy of the semiconductor, which directly dictates the wavelength (color) of the emitted light. In this case, the composition is tuned to produce photons in the green region of the visible spectrum (around 570nm). The dome-shaped epoxy lens serves to protect the delicate semiconductor chip, enhance light extraction from the material, and shape the radiation pattern.

13. Technology Development Trends

The general trend in LED technology is toward higher efficiency (more lumens per watt), increased power density, and better color rendering. For indicator-type SMD LEDs like this one, trends include further miniaturization (smaller package sizes), higher brightness within the same footprint, and improved reliability under harsh conditions (higher temperature, humidity). There is also a growing emphasis on precise color binning and tighter tolerances to meet the demands of applications like full-color displays and automotive lighting, where color consistency is paramount. The underlying AlInGaP material technology continues to be refined for efficiency and stability, though for pure green and blue colors, InGaN-based LEDs are also prevalent and competing in different performance segments.