SMD LED LTST-C170KGKT Datasheet - 3.2x1.6x1.4mm - 2.0V - Green - 0.06W - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) LED lamp. Designed for automated printed circuit board (PCB) assembly, this component is ideal for space-constrained applications across a broad spectrum of electronic equipment.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Utilizes an Ultra Bright Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor chip for green light emission.
• Packaged on 8mm tape wound onto 7-inch diameter reels for efficient automated pick-and-place assembly.
• Standardized EIA (Electronic Industries Alliance) package footprint ensures compatibility with industry designs.
• Input/output characteristics are compatible with standard integrated circuit (IC) logic levels.
• Designed for compatibility with automated surface-mount technology (SMT) placement equipment.
• Withstands standard infrared (IR) reflow soldering processes used in high-volume PCB manufacturing.

1.2 Applications

This LED is suitable for a wide range of applications, including but not limited to:

• Telecommunication devices, office automation equipment, home appliances, and industrial control systems.
• Backlighting for keypads and keyboards.
• Status and power indicators.
• Micro-displays and panel indicators.
• Signal lighting and symbolic luminaries.

2. Technical Parameters Deep Objective Interpretation

2.1 Absolute Maximum Ratings

The following ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Power Dissipation (Pd): 75 mW. This is the maximum total power the package can dissipate as heat.
• Peak Forward Current (I_FP): 80 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• DC Forward Current (I_F): 30 mA. This is the maximum continuous forward current for reliable long-term operation.
• Reverse Voltage (V_R): 5 V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Operating & Storage Temperature Range: -55°C to +85°C. The device can function and be stored within this ambient temperature range.
• Infrared Soldering Condition: 260°C for 10 seconds maximum. This defines the peak temperature and time tolerance for reflow soldering processes.

2.2 Electrical & Optical Characteristics

These parameters are measured at an ambient temperature (T_a) of 25°C and define the typical performance of the device.

• Luminous Intensity (I_V): 18.0 - 71.0 mcd (Typical: 35.0 mcd) at I_F = 20 mA. This measures the perceived brightness of the LED to the human eye. The wide range is managed through binning (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity is half the value measured on-axis (0°). A wide viewing angle like this provides a more diffuse light pattern suitable for indicator applications.
• Peak Emission Wavelength (λ_P): 574.0 nm (Typical). This is the wavelength at which the spectral power output is maximum.
• Dominant Wavelength (λ_d): 567.5 - 576.5 nm (Typical: 571.0 nm) at I_F = 20 mA. This is the single wavelength perceived by the human eye that defines the color (green). It is derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 15.0 nm. This indicates the spectral purity, defining the range of wavelengths around the peak that contain significant optical power.
• Forward Voltage (V_F): 1.90 - 2.40 V (Typical) at I_F = 20 mA. This is the voltage drop across the LED when conducting the specified current.
• Reverse Current (I_R): 10 μA (Maximum) at V_R = 5 V. This is the small leakage current that flows when the diode is reverse-biased.

3. Binning System Explanation

To ensure consistent performance in production, LEDs are sorted into bins based on key parameters. This allows designers to select parts that meet specific application requirements for color and brightness uniformity.

3.1 Forward Voltage (V_F) Rank

Binned at I_F = 20 mA. Tolerance per bin is ±0.1V.

• Bin 4: 1.9V - 2.0V
• Bin 5: 2.0V - 2.1V
• Bin 6: 2.1V - 2.2V
• Bin 7: 2.2V - 2.3V
• Bin 8: 2.3V - 2.4V

3.2 Luminous Intensity (I_V) Rank

Binned at I_F = 20 mA. Tolerance per bin is ±15%.

• Bin M: 18.0 mcd - 28.0 mcd
• Bin N: 28.0 mcd - 45.0 mcd
• Bin P: 45.0 mcd - 71.0 mcd

3.3 Hue (Dominant Wavelength, λ_d) Rank

Binned at I_F = 20 mA. Tolerance per bin is ±1 nm.

• Bin C: 567.5 nm - 570.5 nm
• Bin D: 570.5 nm - 573.5 nm
• Bin E: 573.5 nm - 576.5 nm

4. Performance Curve Analysis

Typical performance curves illustrate the relationship between key parameters under varying conditions. These are essential for robust circuit design.

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

The I-V curve shows the exponential relationship typical of a diode. For this AlInGaP green LED, the forward voltage (V_F) has a typical value around 2.0V at 20mA. Designers must ensure the current-limiting resistor or driver circuit provides the correct voltage to achieve the desired current, as small changes in voltage can cause large changes in current.

4.2 Luminous Intensity vs. Forward Current

This curve is generally linear within the recommended operating current range (up to 30mA DC). Increasing the forward current increases the light output proportionally. However, operating above the absolute maximum ratings will lead to efficiency droop, increased heat, and reduced lifespan.

4.3 Spectral Distribution

The spectral output curve centers around the peak wavelength of 574 nm (green) with a typical half-width of 15 nm. The dominant wavelength (λ_d), which defines the perceived color, falls within the 571 nm ± 5 nm range depending on the bin. This narrow spectrum is characteristic of AlInGaP technology, offering saturated color purity.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The LED is housed in a standard SMD package. Key dimensions (in millimeters) are: Length: 3.2 mm, Width: 1.6 mm, Height: 1.4 mm. Tolerances are typically ±0.1 mm unless otherwise noted. The lens is water clear.

5.2 Polarity Identification & PCB Pad Design

The component has a marked cathode (typically indicated by a green dot, a notch, or a shorter lead on the tape). A recommended PCB land pattern (footprint) is provided to ensure proper solder joint formation, reliable electrical connection, and correct alignment during reflow. Following this guideline prevents tombstoning and other soldering defects.

5.3 Tape and Reel Packaging

The LEDs are supplied on embossed carrier tape with a width of 8 mm, wound onto 7-inch (178 mm) diameter reels. Standard reel quantity is 3000 pieces. The packaging includes a top cover tape to protect components. The orientation and pocket spacing comply with ANSI/EIA-481 standards for automated handling.

6. Soldering & Assembly Guidelines

6.1 IR Reflow Soldering Profile (Pb-Free Process)

A recommended reflow profile is provided for lead-free (Pb-free) solder assembly. Key parameters include:

• Pre-heat: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds to allow for flux activation and temperature stabilization.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus (at peak): Maximum 10 seconds. The device can withstand a maximum of two reflow cycles under these conditions.

Profiles should be developed based on JEDEC standards and validated with the specific PCB design, solder paste, and oven used in production.

6.2 Hand Soldering

If hand soldering is necessary, use a temperature-controlled iron. The soldering iron tip temperature should not exceed 300°C, and contact time should be limited to a maximum of 3 seconds per pad. Hand soldering should be performed only once.

6.3 Cleaning

If post-solder cleaning is required, use only approved alcohol-based solvents such as ethyl alcohol or isopropyl alcohol at room temperature. Immersion time should be less than one minute. Avoid unspecified chemical cleaners which may damage the LED package or lens.

6.4 Storage & Handling

• ESD Precautions: This device is sensitive to electrostatic discharge (ESD). Handle using appropriate ESD controls such as grounded wrist straps, anti-static mats, and containers.
• Moisture Sensitivity: The package is moisture-sensitive. When stored in its original sealed moisture-barrier bag with desiccant, the shelf life is one year at ≤30°C and ≤90% RH. Once the bag is opened, components should be stored at ≤30°C and ≤70% RH and should undergo IR reflow within 672 hours (28 days, MSL 2a). For storage beyond this period or in non-controlled environments, a bake-out at approximately 60°C for at least 20 hours is recommended before soldering.

7. Application Notes & Design Considerations

7.1 Current Limiting

An LED is a current-driven device. A series current-limiting resistor is mandatory when driving from a voltage source. The resistor value (R) can be calculated using Ohm's Law: R = (V_source - V_F) / I_F. Use the maximum V_F from the datasheet (2.4V) for a conservative design to ensure the current does not exceed the desired value. For example, driving from a 5V supply at 20mA: R = (5V - 2.4V) / 0.02A = 130 Ω. A standard 130 Ω or 150 Ω resistor would be suitable.

7.2 Thermal Management

While the power dissipation is low (75 mW max), proper thermal design extends lifespan and maintains stable optical output. Ensure adequate copper area around the PCB pads to act as a heat sink. Avoid operating at the absolute maximum current and temperature limits continuously.

7.3 Optical Design

The 130-degree viewing angle produces a wide, diffuse beam. For applications requiring a more focused beam, secondary optics (lenses or light guides) would be necessary. The water-clear lens is optimal for true color emission without tinting.

8. Technical Comparison & Differentiation

This AlInGaP green LED offers specific advantages:

• vs. Traditional GaP Green LEDs: AlInGaP technology provides significantly higher luminous efficiency and brightness (luminous intensity) for the same drive current, along with better color saturation and stability over temperature.
• vs. InGaN Blue/Green LEDs: While InGaN LEDs can achieve very high brightness, this AlInGaP green LED in this package format offers a proven, cost-effective solution for standard brightness indicator applications with a stable forward voltage characteristic.
• Key Differentiators: The combination of a wide 130-degree viewing angle, RoHS compliance, compatibility with IR reflow, and detailed binning for color and brightness consistency makes this component a reliable choice for automated, high-volume manufacturing.

9. Frequently Asked Questions (FAQ)

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

Peak Wavelength (λ_P) is the physical wavelength where the LED emits the most optical power, measured by a spectrometer. Dominant Wavelength (λ_d) is the perceptual single wavelength that matches the color the human eye sees, calculated from the CIE chromaticity coordinates. For monochromatic LEDs like this green one, they are typically close in value.

9.2 Can I drive this LED without a current-limiting resistor?

No. An LED's forward voltage has a negative temperature coefficient and varies from unit to unit. Connecting it directly to a voltage source will cause an uncontrolled surge in current, likely exceeding the Absolute Maximum Rating and destroying the device instantly. Always use a series resistor or a constant-current driver.

9.3 Why is there such a wide range in Luminous Intensity (18-71 mcd)?

This range reflects natural variations in semiconductor manufacturing. The binning system (M, N, P ranks) sorts LEDs into groups with much tighter intensity ranges. For applications requiring uniform brightness, specify and use LEDs from the same intensity bin.

9.4 How do I interpret the \"Viewing Angle\" of 130 degrees?

This is the full angle at which the light intensity drops to 50% of its on-axis (center) intensity. So, at 65 degrees off-axis to the left and 65 degrees off-axis to the right (total 130 degrees), the brightness is half of what you see when looking straight at the LED. This defines the beam spread.

10. Practical Application Examples

10.1 Status Indicator Panel

In a network router or industrial control panel, multiple LEDs of this type can be used to indicate power, network activity, system errors, or operational modes. The wide viewing angle ensures visibility from various angles. By selecting LEDs from the same V_F and I_V bin, uniform brightness and color can be achieved across the panel. A simple circuit with a 5V supply, a microcontroller GPIO pin, a 150Ω current-limiting resistor, and the LED in series is typical.

10.2 Keyboard Backlighting

For illuminating keys on a membrane or mechanical keyboard, these SMD LEDs can be placed on a PCB beneath translucent keycaps. Their small size (3.2x1.6mm) allows placement between switch footprints. The AlInGaP green chip provides a clear, distinct color. Design considerations include managing current for multiple LEDs in parallel (preferably with individual resistors or a constant-current array driver) and ensuring even light diffusion through the keycap material.

11. Technology Introduction

This LED is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology. This material system is grown epitaxially on a substrate and is particularly efficient in the red, orange, amber, and green regions of the visible spectrum. When a forward voltage is applied, electrons and holes recombine in the active region of the semiconductor junction, releasing energy in the form of photons (light). The specific composition of the AlInGaP layers determines the bandgap energy and thus the wavelength (color) of the emitted light. The water-clear epoxy lens encapsulates the chip, provides mechanical protection, and shapes the light output pattern.

12. Industry Trends

The general trend in SMD indicator LEDs continues toward increased efficiency (more light output per unit of electrical power), smaller package sizes for higher density boards, and enhanced reliability. There is also a growing emphasis on precise color tuning and tighter binning to meet the demands of applications requiring high color consistency, such as full-color displays and automotive interior lighting. Furthermore, integration with intelligent drivers for dimming and color control is becoming more common. The component described in this datasheet represents a mature, reliable technology well-suited for its target applications in consumer and industrial electronics.