SMD LED LTST-B680VEKT Datasheet - AlInGaP Red - 20mA - 710-1400mcd - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) LED. This component is designed for automated printed circuit board (PCB) assembly, featuring a miniature form factor suitable for space-constrained applications. The LED utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a red light output. Its design is compatible with standard infrared reflow soldering processes, making it ideal for high-volume manufacturing.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged in 8mm tape on 7-inch diameter reels for automated pick-and-place equipment.
• Standard EIA (Electronic Industries Alliance) package outline.
• Input compatible with integrated circuit (IC) logic levels.
• Designed for compatibility with infrared reflow soldering profiles.
• Preconditioned to JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3.

1.2 Applications

This LED is suitable for a broad range of electronic equipment, including but not limited to:

• Telecommunication devices (e.g., cordless phones, cellular phones).
• Office automation equipment (e.g., notebook computers, network systems).
• Home appliances and consumer electronics.
• Industrial control and instrumentation panels.
• Indoor signage and display applications.

2. Package Dimensions and Mechanical Data

The LED features a standard SMD package. The lens is water clear. Critical dimensions include length, width, and height, with a general tolerance of ±0.2 mm unless otherwise specified on the detailed dimensional drawing. The polarity is indicated by a cathode mark on the package. The recommended PCB attachment pad layout for infrared or vapor phase reflow soldering is provided to ensure proper solder joint formation and thermal management.

3. Technical Specifications Deep Dive

3.1 Absolute Maximum Ratings

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

• Power Dissipation (Pd): 130 mW at Ta=25°C.
• Peak Forward Current (I_F(peak)): 100 mA (pulsed at 1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current (I_F): 50 mA DC.
• Reverse Voltage (V_R): 5 V. Note: The device is not designed for operation under reverse bias; this rating is primarily for test conditions.
• Operating Temperature Range (T_opr): -40°C to +100°C.
• Storage Temperature Range (T_stg): -40°C to +100°C.

3.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (T_a) of 25°C and a forward current (I_F) of 20 mA, unless stated otherwise.

• Luminous Intensity (I_V): Ranges from a minimum of 710 mcd to a maximum of 1400 mcd. Measured using a sensor filtered to approximate the CIE photopic eye response curve.
• Viewing Angle (2θ_1/2): 120 degrees (typical). This is the full angle at which the luminous intensity is half the value measured on the central axis.
• Dominant Wavelength (λ_d): Between 617.0 nm and 630.0 nm, defining the perceived red color. Tolerance is ±1 nm.
• Spectral Line Half-Width (Δλ): Approximately 15 nm (typical), indicating the spectral purity of the emitted light.
• Forward Voltage (V_F): Between 1.8 V and 2.6 V at 20 mA.
• Reverse Current (I_R): Maximum of 10 μA when a reverse voltage of 5 V is applied.

4. Bin Rank System Explanation

To ensure consistency in application, LEDs are sorted (binned) based on key parameters. This allows designers to select parts that meet specific voltage or brightness requirements for their circuit.

4.1 Forward Voltage (V_F) Binning

Binned at I_F = 20 mA. Each bin has a tolerance of ±0.1V.

• Bin D2: V_F = 1.8V to 2.0V
• Bin D3: V_F = 2.0V to 2.2V
• Bin D4: V_F = 2.2V to 2.4V
• Bin D5: V_F = 2.4V to 2.6V

4.2 Luminous Intensity (I_V) Binning

Binned at I_F = 20 mA. Each bin has a tolerance of ±11%.

• Bin V1: I_V = 710 mcd to 900 mcd
• Bin V2: I_V = 900 mcd to 1120 mcd
• Bin W1: I_V = 1120 mcd to 1400 mcd

5. Performance Curve Analysis

Typical performance curves illustrate the relationship between various parameters. These are essential for understanding device behavior under different operating conditions.

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship, crucial for designing current-limiting circuits.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, typically in a near-linear relationship within the operating range.
• Luminous Intensity vs. Ambient Temperature: Shows the derating of light output as junction temperature increases, which is critical for thermal management in high-power or high-ambient-temperature applications.
• Spectral Distribution: A plot of relative radiant power versus wavelength, centered around the dominant wavelength with a characteristic half-width.

6. Soldering and Assembly Guidelines

6.1 Recommended Reflow Soldering Profile

For lead-free (Pb-free) solder processes, follow a profile compliant with J-STD-020. Key parameters include:

• Pre-heat: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus: As per solder paste specifications, but typically 10 seconds maximum.
• Maximum number of reflow cycles: Two.

Note: The actual profile must be characterized for the specific PCB design, components, and solder paste used.

6.2 Hand Soldering

If hand soldering is necessary:

• Soldering Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per lead.
• Maximum number of soldering attempts: One time only.

6.3 Cleaning

Use only approved cleaning solvents. Immersion in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable if cleaning is required. Avoid unspecified chemical liquids.

7. Storage and Handling

7.1 Moisture Sensitivity

This device is rated MSL 3. When the original moisture-proof bag is sealed with desiccant:

• Store at ≤30°C and ≤70% RH.
• The shelf life is one year from the bag seal date.

Once the original bag is opened:

• Store at ≤30°C and ≤60% RH.
• It is recommended to complete IR reflow soldering within 168 hours (7 days).
• For storage beyond 168 hours, store in a sealed container with desiccant or in a nitrogen desiccator.
• Devices exposed beyond 168 hours should be baked at approximately 60°C for at least 48 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

7.2 Electrostatic Discharge (ESD)

Although not explicitly rated as an ESD-sensitive device in this datasheet, it is a standard industry practice to handle all semiconductor components, including LEDs, with appropriate ESD precautions (e.g., grounded workstations, wrist straps) to prevent damage from static electricity or power surges.

8. Application Design Considerations

8.1 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness and prevent current hogging, especially when connecting multiple LEDs in parallel, a series current-limiting resistor should be used for each LED. Driving LEDs directly from a voltage source without current regulation is not recommended, as small variations in forward voltage (V_F) can lead to large differences in current and, consequently, brightness between devices.

8.2 Thermal Management

The maximum power dissipation is 130 mW. Operating at or near the maximum continuous forward current (50 mA) will generate heat. Proper PCB layout, including adequate copper area for the attachment pads to act as a heat sink, is important to maintain the junction temperature within safe limits, ensuring long-term reliability and stable light output.

8.3 Optical Design

The wide 120-degree viewing angle makes this LED suitable for applications requiring broad area illumination or visibility from wide angles. For applications requiring a more focused beam, secondary optics (e.g., lenses) would be necessary.

9. Packaging and Ordering

The standard packaging is 8mm wide embossed carrier tape on 7-inch (178mm) diameter reels. Each reel contains 2000 pieces. The tape pockets are sealed with a top cover tape. Packaging follows ANSI/EIA-481 specifications. A minimum order quantity of 500 pieces may apply for remainder quantities.

10. Technical Comparison and Selection Guidance

When selecting this LED, key differentiators include its AlInGaP technology, which typically offers higher efficiency and better temperature stability for red/orange/amber colors compared to older technologies like GaAsP. The combination of a relatively high luminous intensity (up to 1400 mcd) with a wide viewing angle is notable. Designers should compare the V_F binning and I_V binning against their circuit's voltage headroom and required brightness consistency. The compatibility with standard SMD assembly processes (reflow soldering, tape-and-reel) is a significant advantage for automated production.

11. Frequently Asked Questions (FAQ)

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

Answer: It is strongly discouraged. The forward voltage has a negative temperature coefficient and can vary between units. Driving directly from a voltage source can lead to thermal runaway, where increasing current causes more heat, which lowers V_F, allowing even more current to flow, potentially destroying the LED. Always use a series resistor or a constant-current driver.

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

Answer: Dominant wavelength (λ_d) is derived from the CIE chromaticity diagram and represents the single wavelength of a monochromatic light that would appear to have the same color as the LED's output to the human eye. Peak wavelength is the wavelength at which the spectral power distribution is maximum. For LEDs, the dominant wavelength is the more relevant parameter for color specification.

11.3 Why is the storage condition after bag opening so strict?

Answer: SMD packages can absorb moisture from the atmosphere. During the high-temperature reflow soldering process, this trapped moisture can vaporize rapidly, creating internal pressure that may delaminate the package or crack the die ("popcorning"). The 168-hour floor life and baking requirements are standardized (JEDEC MSL) methods to manage this risk.

12. Practical Design Example

Scenario: Designing a status indicator panel with 5 red LEDs in parallel, powered by a 5V DC supply. Target forward current per LED is 20 mA.

1. Calculate Series Resistor: Using typical V_F = 2.2V (Bin D3). R = (V_supply - V_F) / I_F = (5V - 2.2V) / 0.02A = 140 Ω. The nearest standard value of 150 Ω would result in I_F ≈ 18.7 mA.
2. Resistor Power Rating: P = I² * R = (0.0187)² * 150 ≈ 0.052 W. A standard 1/8W (0.125W) or 1/10W resistor is sufficient.
3. Circuit Layout: Place one 150 Ω resistor in series with each of the 5 LEDs. Do not share a single resistor among multiple parallel LEDs, as V_F variations would cause uneven brightness.
4. PCB Thermal Design: Ensure the LED pads have sufficient copper area connected to dissipate heat, especially if the ambient temperature is high or if the enclosure restricts airflow.

13. Operating Principle

This LED is based on a semiconductor p-n junction fabricated from AlInGaP materials. When a forward bias voltage exceeding the junction's potential barrier is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, energy is released in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly defines the dominant wavelength of the emitted light—in this case, in the red spectrum (617-630 nm). The water-clear epoxy lens encapsulates the semiconductor die, provides mechanical protection, and shapes the light output pattern.

14. Technology Trends

SMD LEDs continue to evolve towards higher efficiency (more lumens per watt), improved color consistency through tighter binning, and increased reliability. There is a trend for miniaturization while maintaining or increasing light output. Furthermore, advancements in packaging materials aim to enhance thermal performance, allowing for higher drive currents and power densities. The widespread adoption of AlInGaP technology for red, orange, and amber colors has largely superseded older, less efficient materials, offering better performance over temperature and longer operational lifetimes. The integration of LEDs with onboard control circuitry (e.g., constant current drivers, addressable RGB LEDs) is another significant trend, simplifying system design for the end user.