SMD LED LTST-C950TGKT Datasheet - Ultra Bright Green InGaN - 20mA - 76mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-performance, surface-mount LED designed for modern electronic applications. The device utilizes an advanced InGaN semiconductor chip to produce a brilliant green light output. Its miniature form factor and standardized package make it ideal for automated assembly processes and space-constrained designs.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its exceptional luminous intensity, compliance with environmental regulations, and robust construction suitable for high-volume manufacturing. It is engineered to meet the demands of automated pick-and-place equipment and withstand standard infrared (IR) reflow soldering profiles, which are critical for efficient PCB assembly.

The target market encompasses a wide range of consumer and industrial electronics. Key application areas include telecommunications devices such as cellular and cordless phones, portable computing equipment like notebook computers, network infrastructure systems, various home appliances, and indoor signage or display applications. Its reliability and brightness also make it suitable for status indication, keypad or keyboard backlighting, and integration into micro-displays.

2. Technical Parameters: In-Depth Objective Interpretation

This section details the absolute limits and operational characteristics of the LED. All parameters are specified at an ambient temperature (Ta) of 25°C unless otherwise stated.

2.1 Absolute Maximum Ratings

The Absolute Maximum Ratings define the stress limits beyond which permanent damage to the device may occur. Continuous operation at or near these limits is not advised. The ratings are as follows:

• Power Dissipation (Pd): 76 mW. This is the maximum amount of power the device can dissipate as heat.
• Peak Forward Current (I_FP): 100 mA. This current is permissible only under pulsed conditions with a 1/10 duty cycle and a pulse width of 0.1ms.
• Continuous Forward Current (I_F): 20 mA. This is the recommended maximum current for DC operation.
• Operating Temperature Range: -20°C to +80°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -30°C to +100°C.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, which is standard for Pb-free (lead-free) assembly processes.

2.2 Electrical and Optical Characteristics

The following table lists the typical and guaranteed performance parameters under normal operating conditions (I_F = 20mA, Ta=25°C).

• Luminous Intensity (I_V): Ranges from a minimum of 1120 mcd to a maximum of 7100 mcd, with typical values falling within this broad range. Intensity is measured using a sensor filtered to match the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): 25 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on the central axis. It indicates a relatively focused beam pattern.
• Peak Emission Wavelength (λ_P): 530 nm. This is the wavelength at which the spectral output is strongest.
• Dominant Wavelength (λ_d): 520 nm to 535 nm. This parameter, derived from the CIE chromaticity diagram, defines the perceived color of the light and is more relevant for color specification than the peak wavelength.
• Spectral Line Half-Width (Δλ): 35 nm. This indicates the spectral purity or bandwidth of the emitted light.
• Forward Voltage (V_F): 2.8 V to 3.8 V at 20mA. The voltage drop across the LED when operating.
• Reverse Current (I_R): Maximum 10 μA at a Reverse Voltage (V_R) of 5V. The device is not designed for reverse bias operation; this test is for quality verification only.

3. Bin Ranking System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins based on key parameters. This allows designers to select parts that meet specific circuit requirements.

3.1 Forward Voltage (V_F) Rank

LEDs are categorized by their forward voltage drop at 20mA. The bin codes (D7 to D11) represent increasing voltage ranges from 2.8V-3.0V up to 3.6V-3.8V, with a tolerance of ±0.1V per bin. This is critical for designing current-limiting circuitry and ensuring uniform brightness in parallel arrays.

3.2 Luminous Intensity (I_V) Rank

This is the primary brightness binning. Codes W, X, Y, and Z represent ascending minimum/maximum intensity ranges from 1120-1800 mcd up to 4500-7100 mcd, with a ±15% tolerance per bin. Selection depends on the required brightness level for the application.

3.3 Hue (Dominant Wavelength) Rank

LEDs are binned by color point using dominant wavelength. Codes AP (520-525 nm), AQ (525-530 nm), and AR (530-535 nm) allow selection for specific green color requirements, with a tight tolerance of ±1 nm per bin. This ensures color consistency in applications where multiple LEDs are used side-by-side.

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet, the typical relationships between key parameters are described below.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

The LED exhibits a non-linear I-V characteristic typical of diodes. The forward voltage (V_F) increases with current but remains within the specified bin ranges at the nominal 20mA drive current. Operating above the absolute maximum current will cause V_F to rise more sharply and generate excessive heat.

4.2 Luminous Intensity vs. Forward Current

The light output (luminous intensity) is approximately proportional to the forward current in its normal operating range. However, efficiency may decrease at very high currents due to increased thermal effects. Driving the LED at its rated 20mA ensures optimal performance and longevity.

4.3 Temperature Characteristics

Like all semiconductors, LED performance is temperature-dependent. The forward voltage (V_F) typically has a negative temperature coefficient, meaning it decreases slightly as the junction temperature rises. More significantly, luminous intensity decreases as temperature increases. Proper thermal management in the application is essential to maintain consistent brightness and device reliability over the specified operating temperature range.

5. Mechanical and Package Information

5.1 Package Dimensions and Polarity Identification

The device conforms to a standard industry SMD package outline. Key dimensions include the body size, lead spacing, and overall height. The cathode is typically identified by a visual marker on the package, such as a notch, a dot, or a green tint on the corresponding lens area. Correct polarity orientation during assembly is mandatory for proper function.

5.2 Recommended PCB Land Pattern

A suggested printed circuit board (PCB) pad layout is provided to ensure reliable soldering and mechanical stability. This pattern accounts for the component's footprint and facilitates good solder fillet formation during reflow. Adhering to this recommendation helps prevent tombstoning (component standing up on one end) and ensures proper alignment.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

The device is compatible with lead-free (Pb-free) infrared reflow soldering processes. A recommended profile is provided, which generally includes:

• Pre-heat: 150-200°C for up to 120 seconds maximum to gradually heat the board and activate the flux.
• Peak Temperature: 260°C maximum. The component body must not exceed this temperature.
• Time Above Liquidus (TAL): The time within 5°C of the peak temperature should be limited to 10 seconds maximum.
• Number of Cycles: The device can withstand a maximum of two reflow cycles under these conditions.

It is critical to note that the optimal profile depends on the specific PCB design, solder paste, and oven used. The provided values are guidelines that should be validated for the actual production setup.

6.2 Hand Soldering

If hand soldering is necessary, extreme care must be taken. The soldering iron tip temperature should not exceed 300°C, and contact time with the LED lead should be limited to 3 seconds maximum. Apply heat to the PCB pad, not directly to the LED body, to prevent thermal damage.

6.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used. Recommended agents include ethyl alcohol or isopropyl alcohol (IPA). The LED should be immersed at normal temperature for less than one minute. Harsh or unspecified chemicals can damage the epoxy lens or package material.

6.4 Storage and Handling Conditions

Electrostatic Discharge (ESD): The device is sensitive to ESD. Proper handling procedures must be followed, including the use of grounded wrist straps, anti-static mats, and ESD-safe packaging and equipment.

Moisture Sensitivity: The package has a Moisture Sensitivity Level (MSL) rating. As indicated, if the original sealed moisture-proof bag is opened, the components should be subjected to IR reflow within one week (MSL 3). For longer storage outside the original bag, they must be stored in a dry cabinet or sealed container with desiccant. Components stored beyond one week may require a baking process (e.g., 60°C for 20 hours) to remove absorbed moisture before soldering to prevent \"popcorning\" damage during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied packaged for automated assembly. They are mounted in embossed carrier tape with a protective cover tape sealed over the top. The tape is wound onto a standard 7-inch (178 mm) diameter reel.

Key packaging details include:

• Quantity per Reel: 2000 pieces.
• Minimum Order Quantity (MOQ): For remainder quantities, a minimum of 500 pieces is specified.
• Pocket Coverage: Empty component pockets in the tape are sealed with cover tape.
• Missing Components: A maximum of two consecutive missing lamps is allowed per the packaging standard.
• The packaging conforms to ANSI/EIA-481 specifications, ensuring compatibility with standard automated equipment.

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

The most common drive method is a constant current source or a simple current-limiting resistor in series with a voltage supply. The resistor value (R_limit) can be calculated using Ohm's Law: R_limit = (V_supply - V_F) / I_F. Using the maximum V_F from the bin (e.g., 3.8V) in this calculation ensures the current does not exceed 20mA even with a low V_F part. For applications requiring stable brightness, a dedicated LED driver IC is recommended, especially when operating from a variable voltage source like a battery.

8.2 Thermal Management Design

Although power dissipation is relatively low (76mW max), effective heat sinking is important for maintaining performance and lifespan, especially in high ambient temperatures or enclosed spaces. The PCB copper pads act as the primary heat sink. Increasing the copper area connected to the cathode and anode pads, using thermal vias to connect to inner or bottom copper layers, and ensuring adequate airflow will help manage junction temperature.

8.3 Optical Design Considerations

The 25-degree viewing angle provides a focused beam. For wider illumination, secondary optics such as diffusers or light guides may be required. The choice of bin for luminous intensity and dominant wavelength should be made based on the final application's brightness and color uniformity requirements. Mixing bins within a single product is not recommended if visual consistency is important.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED with a 5V supply and a resistor?
A: Yes. For example, using a typical V_F of 3.2V at 20mA: R = (5V - 3.2V) / 0.02A = 90 Ohms. A standard 91 Ohm resistor would be suitable. Always verify the current using the actual V_F of your specific bin.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P) is the literal peak of the spectral output curve. Dominant Wavelength (λ_d) is a calculated value that represents the single wavelength of a pure monochromatic light that would appear to have the same color as the LED to the human eye. λ_d is more relevant for color matching.

Q: How do I interpret the luminous intensity bin code (e.g., \"Y\")?
A: The bin code defines a guaranteed range. A \"Y\" bin part will have a luminous intensity between 2800 mcd and 4500 mcd when measured under standard conditions (20mA, Ta=25°C).

Q: Is this LED suitable for outdoor use?
A: The datasheet specifies an operating temperature range of -20°C to +80°C and typical indoor applications. For outdoor use, consider the potential for exposure to moisture, UV radiation, and temperatures outside the specified range, which may require additional protective measures or a different product grade.

10. Technology Introduction and Trends

10.1 InGaN Semiconductor Technology

This LED is based on Indium Gallium Nitride (InGaN) semiconductor material. InGaN allows for the efficient production of light in the blue, green, and white (when combined with a phosphor) spectral regions. The efficiency and brightness of InGaN LEDs have improved significantly over earlier technologies like Gallium Phosphide (GaP), making them the standard for high-performance green and blue LEDs.

10.2 Industry Trends

The general trend in SMD LED technology continues toward higher luminous efficacy (more light output per watt of electrical input), improved color rendering, and smaller package sizes enabling higher density designs. There is also a strong focus on enhanced reliability and longevity under various environmental stresses. The compatibility with lead-free, high-temperature reflow processes, as seen in this device, is now a fundamental requirement driven by global environmental regulations (e.g., RoHS).