SMD LED LTST-C216TGKT Datasheet - 3.2x1.6x1.2mm - 3.2V Typ - 76mW - Water Clear Lens Green Light - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C216TGKT, a surface-mount device (SMD) LED lamp. This component is designed for automated printed circuit board (PCB) assembly and is suitable for applications where space is a critical constraint. The LED utilizes an ultra-bright Indium Gallium Nitride (InGaN) semiconductor chip to produce green light, housed within a water-clear lens package.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its compliance with the Restriction of Hazardous Substances (RoHS) directive, its high luminous intensity, and its design compatibility with standard industrial assembly processes. It is packaged on 8mm tape wound onto 7-inch diameter reels, conforming to Electronic Industries Alliance (EIA) standards, making it ideal for high-volume, automated pick-and-place manufacturing.

The target applications span a broad range of consumer and industrial electronics. Key markets include telecommunications equipment (e.g., cordless and cellular phones), portable computing devices (e.g., notebook computers), network infrastructure systems, various home appliances, and indoor signage or display applications. Its primary functions within these systems are status indication, keypad or keyboard backlighting, integration into micro-displays, and general signal or symbol illumination.

2. In-Depth Technical Parameter Analysis

The performance of the LTST-C216TGKT is defined under specific environmental and electrical conditions, primarily at an ambient temperature (Ta) of 25°C.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed and should be avoided.

• Power Dissipation (Pd): 76 mW. This is the maximum amount of power the device can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 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 continuous DC operation.
• Operating Temperature Range: -20°C to +80°C. The device is designed to function within this ambient temperature range.
• Storage Temperature Range: -30°C to +100°C.
• Infrared Reflow Soldering Condition: Withstands a peak temperature of 260°C for a maximum of 10 seconds, which is critical for lead-free (Pb-free) assembly processes.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under standard test conditions (I_F = 20mA, Ta=25°C unless noted).

• Luminous Intensity (I_V): Ranges from a minimum of 71.0 millicandelas (mcd) to a maximum of 450.0 mcd. The intensity is measured using a sensor and filter combination that approximates the CIE standard photopic (human eye) response curve.
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on the central axis (0 degrees). This indicates a wide viewing pattern.
• Peak Emission Wavelength (λ_P): 530 nanometers (nm). This is the wavelength at which the spectral power output is highest.
• Dominant Wavelength (λ_d): 525 nm. Derived from the CIE chromaticity diagram, this single wavelength best represents the perceived color (green) of the LED.
• Spectral Line Half-Width (Δλ): 35 nm. This parameter indicates the spectral purity or bandwidth of the emitted light, measured as the width at half the maximum intensity.
• Forward Voltage (V_F): Typically 3.2V, with a range from 2.80V to 3.60V when driven at 20mA. This is the voltage drop across the LED when it is conducting.
• Reverse Current (I_R): Maximum of 10 microamperes (μA) when a reverse voltage (V_R) of 5V is applied. The device is not designed for operation under reverse bias.

3. Bin Ranking System Explanation

To ensure consistency in mass production, LEDs are sorted into performance categories or "bins" based on key parameters. The LTST-C216TGKT uses a three-dimensional binning system.

3.1 Forward Voltage (V_F) Binning

LEDs are categorized by their forward voltage drop at 20mA. This is crucial for designing current-limiting circuits and ensuring uniform brightness in parallel arrays.

• Bin Code D7: V_F = 2.80V to 3.00V
• Bin Code D8: V_F = 3.00V to 3.20V
• Bin Code D9: V_F = 3.20V to 3.40V
• Bin Code D10: V_F = 3.40V to 3.60V

Tolerance within each bin is ±0.1V.

3.2 Luminous Intensity (I_V) Binning

This binning sorts LEDs based on their light output power, measured in millicandelas.

• Bin Code Q: I_V = 71.0 mcd to 112.0 mcd
• Bin Code R: I_V = 112.0 mcd to 180.0 mcd
• Bin Code S: I_V = 180.0 mcd to 280.0 mcd
• Bin Code T: I_V = 280.0 mcd to 450.0 mcd

Tolerance within each bin is ±15%.

3.3 Hue (Dominant Wavelength) Binning

This classification ensures color consistency by grouping LEDs with similar dominant wavelengths.

• Bin Code AP: λ_d = 520.0 nm to 525.0 nm
• Bin Code AQ: λ_d = 525.0 nm to 530.0 nm
• Bin Code AR: λ_d = 530.0 nm to 535.0 nm

Tolerance within each bin is ±1 nm.

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet, typical performance curves for such LEDs provide critical insights for design engineers.

4.1 Current vs. Voltage (I-V) Characteristic

The I-V curve is non-linear, similar to a standard diode. The forward voltage (V_F) exhibits a positive temperature coefficient, meaning it decreases slightly as the junction temperature increases for a given current. The curve shows a sharp turn-on characteristic above the threshold voltage.

4.2 Relative Luminous Intensity vs. Forward Current

This curve typically shows a near-linear relationship between forward current (I_F) and light output (I_V) within the recommended operating range (up to 20mA). Driving the LED beyond its absolute maximum ratings can lead to super-linear efficiency roll-off and accelerated degradation.

4.3 Relative Luminous Intensity vs. Ambient Temperature

The light output of an InGaN LED generally decreases as the ambient (and consequently, junction) temperature increases. This derating curve is essential for applications operating at high ambient temperatures to ensure sufficient brightness is maintained.

4.4 Spectral Distribution

The spectral output curve centers around the peak wavelength of 530 nm with a characteristic half-width of 35 nm, defining the green color emission. The shape is typically Gaussian.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED conforms to a standard SMD package outline. All dimensions are in millimeters with a general tolerance of ±0.1 mm unless otherwise specified. The package features a water-clear lens. The cathode is typically identified by a visual marker such as a notch, a green dot, or a cut corner on the package, which must be cross-referenced with the recommended PCB footprint.

5.2 Recommended PCB Attachment Pad Layout

A land pattern diagram is provided to ensure proper solder joint formation and mechanical stability. Adhering to this recommended footprint is critical for successful reflow soldering and to prevent tombstoning (component standing on end). The design typically includes thermal relief connections to manage heat dissipation during soldering.

6. Soldering and Assembly Guidelines

6.1 Infrared Reflow Soldering Profile

The device is fully compatible with infrared (IR) reflow soldering processes, which is the standard for surface-mount assembly. A specific temperature profile is recommended for lead-free solder pastes:

• Pre-heat Zone: Ramp to 150-200°C.
• Soak/Pre-heat Time: Maximum of 120 seconds to activate flux and equalize board temperature.
• Peak Temperature: Maximum of 260°C.
• Time Above Liquidus (TAL): The component body should be exposed to the peak temperature for a maximum of 10 seconds. The LED can withstand this reflow cycle a maximum of two times.

These parameters align with common JEDEC industry standards for surface-mount devices.

6.2 Hand Soldering

If hand soldering is necessary, extreme care must be taken:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per solder joint.
• Limit: Hand soldering should be performed only once to avoid thermal damage to the epoxy package and the semiconductor die.

6.3 Cleaning

Post-solder cleaning must be performed with care. Only specified alcohol-based solvents should be used, such as ethyl alcohol or isopropyl alcohol (IPA). The LED should be immersed at normal room temperature for less than one minute. Harsh or unspecified chemical cleaners can damage the plastic lens and package material.

6.4 Storage and Handling Conditions

Electrostatic Discharge (ESD) Sensitivity: The LED is sensitive to ESD and surge currents. Proper ESD precautions are mandatory during handling. This includes the use of grounded wrist straps, anti-static gloves, and ensuring all workstations and equipment are properly grounded.

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 soldering within one week (MSL 3). For storage beyond one week outside the original packaging, components must be stored in a sealed container with desiccant or in a nitrogen ambient. Components stored under these conditions for more than a week require a bake-out at approximately 60°C for at least 20 hours before assembly to remove absorbed moisture and prevent "popcorning" (package cracking) during reflow.

General Storage: For unopened packages, store at ≤30°C and ≤90% Relative Humidity (RH), with a recommended shelf life of one year from the date code. For opened packages, the environment should not exceed 30°C and 60% RH.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in industry-standard embossed carrier tape for automated assembly.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches (178 mm).
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Pocket Sealing: Empty pockets are sealed with a top cover tape.
• Missing Components: A maximum of two consecutive missing LEDs is allowed per the tape specification.

These specifications comply with ANSI/EIA-481 standards.

8. Application Notes and Design Considerations

8.1 Typical Application Circuits

The LED must be driven with a constant current source or, more commonly, a current-limiting resistor in series with a voltage source. The series resistor value (R_S) can be calculated using Ohm's Law: R_S = (V_SUPPLY - V_F) / I_F. Using the typical V_F of 3.2V and a desired I_F of 20mA with a 5V supply, R_S = (5V - 3.2V) / 0.02A = 90 Ohms. A standard 91 Ohm or 100 Ohm resistor would be suitable, also dissipating (5V-3.2V)*0.02A = 36mW of power.

8.2 Thermal Management

While the power dissipation is low (76mW max), effective thermal management via the PCB is still important for long-term reliability and maintaining consistent light output. The recommended PCB pad design aids in transferring heat away from the LED junction. In applications with high ambient temperatures or where multiple LEDs are densely packed, additional thermal design considerations for the PCB may be necessary.

8.3 Optical Design Considerations

The wide 130-degree viewing angle makes this LED suitable for applications requiring broad area illumination or visibility from wide angles, such as status indicators. For applications requiring a more focused beam, secondary optics (e.g., lenses, light guides) would need to be designed and placed over the LED.

8.4 Application Limitations and Warnings

This component is intended for use in standard commercial and industrial electronic equipment. It is not designed or qualified for safety-critical applications where failure could directly jeopardize life or health. Such applications include, but are not limited to, aviation systems, transportation controls, medical life-support devices, and critical safety equipment. For these applications, components with appropriate safety certifications must be selected.

9. Technical Comparison and Differentiation

The LTST-C216TGKT positions itself within the market of standard SMD green LEDs. Its key differentiators are its combination of high typical luminous intensity (up to 450 mcd) with a standard package size, RoHS compliance for global market access, and proven compatibility with high-temperature, lead-free reflow processes. The three-dimensional binning (V_F, I_V, λ_d) offers designers the ability to select components for applications requiring tight parameter matching, such as in multi-LED arrays or displays where color and brightness uniformity are paramount.

10. Frequently Asked Questions (FAQ)

10.1 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak Wavelength (λ_P) is the physical wavelength at which the LED emits the most optical power. Dominant Wavelength (λ_d) is a calculated value from colorimetry that represents the single wavelength of monochromatic light that would appear to have the same color as the LED's output to the human eye. For green LEDs, λ_d is often slightly shorter ("bluer") than λ_P due to the shape of the eye's sensitivity curve.

10.2 Can I drive this LED with a constant voltage source?

No, it is not recommended. An LED is a current-driven device. Its forward voltage has a tolerance and varies with temperature. Connecting it directly to a voltage source, even at its typical V_F, would result in an uncontrolled current that could easily exceed the maximum rating and destroy the device. Always use a series current-limiting resistor or a dedicated constant-current driver circuit.

10.3 Why is the storage and handling moisture sensitivity important?

SMD plastic packages can absorb moisture from the atmosphere. During the high-temperature reflow soldering process, this trapped moisture rapidly turns to steam, creating high internal pressure. This can cause delamination inside the package or catastrophic failure like cracking ("popcorning"), leading to immediate or latent reliability issues. Following the MSL guidelines prevents this.

10.4 How do I interpret the bin codes when ordering?

When specifying this LED for purchase, you can request specific bin codes for V_F, I_V, and λ_d to ensure the performance characteristics match your design requirements. For example, requesting bins D8 (V_F), T (I_V), and AQ (λ_d) would select LEDs with a forward voltage around 3.1V, very high brightness, and a dominant wavelength centered at 527.5 nm.

11. Design and Usage Case Study

11.1 Case Study: Multi-LED Status Indicator Panel

Consider designing a panel with 20 green LEDs to indicate the operational status of various subsystems in a network router. Uniform brightness and color are critical for user experience.

Design Steps:

1. Current Setting: Choose I_F = 15 mA (below the 20mA max) to ensure long life and provide a safety margin. This also reduces power consumption and heat generation.
2. Driver Circuit: Use a common 3.3V rail. Calculate the series resistor: R_S = (3.3V - 3.2V) / 0.015A ≈ 6.7 Ohms. Use a standard 6.8 Ohm resistor. Verify resistor power: P = I²R = (0.015)²*6.8 ≈ 1.5 mW.
3. Ensuring Uniformity: To achieve uniform appearance, specify tight binning when ordering. Request all LEDs from a single luminous intensity bin (e.g., Bin S) and a single hue bin (e.g., Bin AQ). Forward voltage bin is less critical for visual uniformity when using individual series resistors.
4. PCB Layout: Follow the recommended land pattern. Route traces to provide equal current paths to each LED. Include a sufficient ground plane for thermal dissipation.
5. Assembly: Follow the IR reflow profile precisely. If the panels are assembled in batches, ensure components from opened reels are used within the one-week window or are properly baked.

This approach results in a reliable, professional-looking indicator panel with consistent performance across all units.

12. Operating Principle Introduction

The LTST-C216TGKT is a semiconductor light source based on the principle of electroluminescence in a direct bandgap material. The active region uses an Indium Gallium Nitride (InGaN) compound semiconductor. When a forward bias voltage is applied across the p-n junction, electrons from the n-type region and holes from the p-type region are injected into the active region. Here, they recombine, releasing energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the InGaN material, which is engineered to be approximately 2.34 eV, corresponding to green light around 530 nm. The water-clear epoxy lens encapsulates the semiconductor die, provides mechanical protection, and shapes the light output pattern.

13. Technology Trends and Context

This component represents a mature and widely adopted technology within the broader field of solid-state lighting. InGaN-based LEDs are the standard for producing blue and green light. Key ongoing trends in the industry that provide context for this device include:

• Increased Efficiency: Continuous R&D aims to improve the internal quantum efficiency (IQE) and light extraction efficiency (LEE) of InGaN LEDs, leading to higher luminous efficacy (more light output per electrical watt input).
• Miniaturization: The drive for smaller, denser electronics pushes for LEDs in even smaller package footprints while maintaining or improving optical power.
• Enhanced Reliability: Improvements in packaging materials, die attach techniques, and phosphor technology (for white LEDs) focus on extending operational lifetime and stability under harsh conditions.
• Smart Integration: A growing trend is the integration of control circuitry, sensors, or communication interfaces directly with LED packages, moving beyond simple discrete components.

The LTST-C216TGKT, with its RoHS compliance, reflow compatibility, and detailed binning, is a product designed to meet the current demands of efficient, reliable, and high-volume electronic manufacturing.