SMD LED LTST-C170KSKT Datasheet - Package Dimensions - Forward Voltage 1.8-2.4V - Luminous Intensity 28-112mcd - Yellow Color - 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 to produce yellow light.
• Packaged on 8mm tape wound onto 7-inch diameter reels for efficient automated handling.
• Conforms to standard EIA (Electronic Industries Alliance) package outlines.
• Electrically compatible with integrated circuit (IC) logic levels.
• Designed for compatibility with standard automatic pick-and-place assembly equipment.
• Withstands standard infrared (IR) reflow soldering processes used in surface-mount technology (SMT).

1.2 Applications

This LED is suitable for a wide range of indication and illumination purposes, including but not limited to:

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

2. Package Dimensions and Mechanical Information

The device features a standard SMD package. The lens is water clear, while the light source emits a yellow color via the AlInGaP chip. All critical dimensions are provided in technical drawings within the datasheet, with standard tolerances of ±0.1 mm unless otherwise specified. This includes the body length, width, height, and the placement of the cathode/anode terminals.

3. Technical Parameters and Characteristics

All ratings and characteristics are specified at an ambient temperature (Ta) of 25°C unless noted otherwise.

3.1 Absolute Maximum Ratings

Stresses beyond these limits may cause permanent damage to the device.

• Power Dissipation (Pd): 75 mW
• Peak Forward Current (IFP): 80 mA (at 1/10 duty cycle, 0.1ms pulse width)
• Continuous Forward Current (IF): 30 mA DC
• Reverse Voltage (VR): 5 V
• Operating Temperature Range: -55°C to +85°C
• Storage Temperature Range: -55°C to +85°C
• Infrared Reflow Soldering Condition: 260°C peak temperature for a maximum of 10 seconds.

3.2 Electrical and Optical Characteristics

Typical performance parameters measured under standard test conditions (IF = 20mA, Ta=25°C).

• Luminous Intensity (Iv): 28.0 - 112.0 mcd (millicandela). The actual value is binned.
• Viewing Angle (2θ1/2): 130 degrees. This is the full angle at which intensity is half the peak axial value.
• Peak Emission Wavelength (λP): 588.0 nm (typical).
• Dominant Wavelength (λd): 587.0 - 594.5 nm. This defines the perceived color and is binned.
• Spectral Line Half-Width (Δλ): 15 nm (typical).
• Forward Voltage (VF): 1.80 - 2.40 V. The actual value is binned.
• Reverse Current (IR): 10 μA maximum at VR = 5V.

3.3 Caution on Electrostatic Discharge (ESD)

This device is sensitive to electrostatic discharge and electrical surges. Proper ESD control measures must be implemented during handling, including the use of grounded wrist straps, anti-static gloves, and ensuring all equipment is properly grounded. The specified reverse voltage rating is for testing purposes only; the LED is not designed for operation under reverse bias.

4. Bin Rank System

To ensure consistency in application, devices are sorted into bins based on key parameters. This allows designers to select LEDs with tightly grouped characteristics.

4.1 Forward Voltage (Vf) Rank

Binned at a test current of 20mA. Tolerance per bin is ±0.1V.

• Bin 3: 1.80V - 1.90V
• Bin 4: 1.90V - 2.00V
• Bin 5: 2.00V - 2.10V
• Bin 6: 2.10V - 2.20V
• Bin 7: 2.20V - 2.30V
• Bin 8: 2.30V - 2.40V

4.2 Luminous Intensity (Iv) Rank

Binned at a test current of 20mA. Tolerance per bin is ±15%.

• Bin N: 28.0 mcd - 45.0 mcd
• Bin P: 45.0 mcd - 71.0 mcd
• Bin Q: 71.0 mcd - 112.0 mcd

4.3 Hue (Dominant Wavelength λd) Rank

Binned at a test current of 20mA. Tolerance per bin is ±1 nm.

• Bin J: 587.0 nm - 589.5 nm
• Bin K: 589.5 nm - 592.0 nm
• Bin L: 592.0 nm - 594.5 nm

5. Typical Performance Curves Analysis

The datasheet includes graphical representations of key relationships, which are crucial for circuit design and thermal management.

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship, critical for determining the required current-limiting resistor value and power dissipation.
• Luminous Intensity vs. Forward Current: Illustrates how light output increases with current, up to the maximum rating.
• Luminous Intensity vs. Ambient Temperature: Demonstrates the decrease in light output as junction temperature rises, which is vital for applications in high-temperature environments.
• Relative Spectral Power Distribution: Depicts the emission spectrum, centered around the peak wavelength of ~588 nm, confirming the yellow color output.
• Viewing Angle Pattern: A polar diagram showing the angular distribution of light intensity, confirming the wide 130-degree viewing angle.

6. Assembly and Handling Guidelines

6.1 Cleaning

Only specified cleaning agents should be used. Unspecified chemicals may damage the LED package. If cleaning is necessary, immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute.

6.2 Recommended PCB Attachment Pad Layout

A detailed land pattern (footprint) is provided to ensure proper solder joint formation, component alignment, and thermal relief during reflow soldering. Adhering to this pattern is essential for manufacturing yield and reliability.

6.3 Soldering Process

Reflow Soldering (Pb-Free Process Recommended):

• Pre-heat Temperature: 150°C - 200°C
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus (at peak): Maximum 10 seconds. The reflow process should not be repeated more than twice.

Hand Soldering (Soldering Iron):

• Iron Tip Temperature: Maximum 300°C.
• Contact Time: Maximum 3 seconds per joint. This should be performed only once.

The provided temperature profile is based on JEDEC standards. The actual profile must be characterized for the specific PCB design, solder paste, and oven used.

6.4 Storage Conditions

Sealed Moisture-Barrier Bag (MBP): Store at ≤30°C and ≤90% Relative Humidity (RH). The shelf life within the sealed bag with desiccant is one year.

After Bag Opening: Store at ≤30°C and ≤60% RH. Components should be subjected to IR reflow within 672 hours (28 days) of exposure. For storage beyond this period, bake at approximately 60°C for at least 20 hours before assembly to remove absorbed moisture and prevent "popcorning" during reflow.

7. Packaging Information

The LEDs are supplied on embossed carrier tape with a protective cover tape.

• Reel Size: 7 inches (178 mm) in diameter.
• Tape Width: 8 mm.
• Quantity per Reel: 3000 pieces.
• Minimum Packing Quantity: 500 pieces for remainder lots.
• The packaging conforms to ANSI/EIA-481 specifications. A maximum of two consecutive missing components (pockets) is allowed per reel.

8. Application Notes and Cautions

8.1 Intended Use

This LED is designed for general-purpose electronic equipment (e.g., consumer electronics, office equipment, communications devices). It is not rated for safety-critical applications where failure could lead to direct risk to life or health (e.g., aviation, medical life-support, transportation control). For such applications, consultation with the component manufacturer is mandatory to assess suitability and reliability requirements.

8.2 Design Considerations

• Current Limiting: An external series resistor is always required to limit the forward current to the desired value (≤30 mA DC). The resistor value is calculated using Ohm's Law: R = (Vsupply - VF) / IF, where VF is the forward voltage from the appropriate bin.
• Thermal Management: The power dissipation (Pd = VF * IF) must not exceed 75 mW. Adequate PCB copper area (using the recommended pad layout) helps dissipate heat and maintain lower junction temperature, preserving luminous output and longevity.
• Reverse Voltage Protection: If the circuit exposes the LED to potential reverse bias (e.g., in AC or multiplexed circuits), a protection diode in parallel (cathode to cathode) is recommended.

9. Technical Comparison and Differentiation

Key advantages of this component in its class include:

• Material Technology: The use of AlInGaP provides higher efficiency and better temperature stability for red, orange, and yellow colors compared to older technologies like GaAsP.
• Wide Viewing Angle: The 130-degree viewing angle offers broad, even illumination suitable for status indicators that need to be visible from various angles.
• Robust Packaging: Compatibility with IR reflow soldering and standard SMT processes ensures high reliability in volume manufacturing.
• Comprehensive Binning: The three-parameter binning (Vf, Iv, Wavelength) allows for precise color and brightness matching in applications requiring multiple LEDs.

10. Frequently Asked Questions (FAQs)

Q: What is the typical forward voltage for calculating my current-limiting resistor?
A: Use the maximum Vf from your specified bin (e.g., 2.40V for Bin 8) for a conservative design that ensures current never exceeds the desired limit, even with component variation.

Q: Can I drive this LED with a 3.3V or 5V logic supply?
A: Yes. For a 3.3V supply and a target current of 20mA, using a typical Vf of 2.0V, the series resistor would be approximately (3.3V - 2.0V) / 0.020A = 65 Ohms. A standard 68 Ohm resistor would be suitable. For a 5V supply, the resistor would be approximately (5V - 2.0V) / 0.020A = 150 Ohms.

Q: How does temperature affect brightness?
A: Luminous intensity decreases as the ambient (and thus junction) temperature increases. Refer to the "Luminous Intensity vs. Ambient Temperature" curve in the datasheet. For high-temperature environments, derating the operating current or improving heat sinking may be necessary.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λP) is the single wavelength at which the emission spectrum is strongest. Dominant Wavelength (λd) is derived from the color coordinates and represents the single wavelength of a pure monochromatic light that would appear to have the same color to the human eye. λd is more relevant for color specification.

11. Design and Usage Case Example

Scenario: Designing a multi-LED status panel for a network router.

1. Requirement: Four yellow status indicators for "Power," "Internet," "Wi-Fi," and "Ethernet." They must be uniformly bright and visually matched in color.
2. Selection: Specify LEDs from the same Intensity Bin (e.g., Bin Q for high brightness) and the same Hue Bin (e.g., Bin K) to ensure consistency. The Forward Voltage bin is less critical for matching but affects power supply design.
3. Circuit Design: Using a 5V system rail. Assuming a chosen Vf of 2.2V (mid-range) and a target current of 20mA for good brightness and longevity. Calculate resistor: R = (5V - 2.2V) / 0.020A = 140 Ohms. Use a 150 Ohm standard resistor for a slight derating (~19mA).
4. Layout: Place LEDs on the PCB using the recommended land pattern. Ensure adequate spacing for airflow and to prevent thermal coupling. Connect each LED in parallel with its own current-limiting resistor to the 5V supply, controlled by individual microcontroller GPIO pins set to sink current.
5. Manufacturing: Follow the recommended IR reflow profile. After assembly, verify light output and color consistency.

12. Operating Principle Introduction

This LED is a semiconductor photonic device. Its core is a chip made of AlInGaP materials, forming a p-n junction. When a forward voltage exceeding the junction's built-in potential is applied, electrons and holes are injected across the junction. When these charge carriers recombine, they release energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, in the yellow region (~587-595 nm). The water-clear epoxy lens encapsulates the chip, provides mechanical protection, and shapes the light output beam.

13. Technology Trends

The development of SMD LEDs like this one is driven by several ongoing trends in electronics:

• Miniaturization: Continuous reduction in package size to enable higher-density PCB designs and smaller end products.
• Increased Efficiency: Advancements in epitaxial growth and chip design yield higher luminous efficacy (more light output per electrical watt), reducing power consumption and thermal load.
• Improved Color Rendering and Gamut: While this is a monochrome LED, broader trends involve developing narrow-band emitters for display backlights and specialty lighting to achieve wider color gamuts.
• Enhanced Reliability and Robustness: Improvements in packaging materials and processes lead to longer operational lifetimes and better resistance to thermal cycling, humidity, and other environmental stresses.
• Integration: A trend towards integrating multiple LED chips (e.g., RGB), control circuitry, and even drivers into single, smarter package modules.