SMD LED LTST-B680QEKT Datasheet - AlInGaP Red - 120mW - 2.6V - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) light-emitting diode (LED). This component is designed for automated printed circuit board (PCB) assembly processes and is suitable for applications where space is a critical constraint. The LED utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material to produce red light, offering a balance of performance and reliability for modern electronic designs.

1.1 Features and Core Advantages

The LED is engineered to meet several key industry standards and manufacturing requirements, providing distinct advantages for designers and manufacturers.

• Environmental Compliance: The device is compliant with the Restriction of Hazardous Substances (RoHS) directive.
• Manufacturing Compatibility: It is supplied in industry-standard 8mm tape on 7-inch reels, making it fully compatible with high-speed automated pick-and-place assembly equipment.
• Process Compatibility: The package is designed to withstand standard infrared (IR) reflow soldering processes commonly used in surface-mount technology (SMT) assembly lines.
• Reliability: The component undergoes preconditioning testing accelerated to JEDEC Moisture Sensitivity Level 3, indicating a robust package construction suitable for typical handling and storage conditions before soldering.
• Electrical Interface: It is I.C. (Integrated Circuit) compatible, allowing for straightforward integration into digital control circuits.

1.2 Target Applications and Markets

Due to its compact size, reliability, and performance characteristics, this LED is targeted at a broad spectrum of electronic equipment. Primary application areas include:

• Telecommunications Equipment: Status indicators on routers, modems, and network switches.
• Office Automation: Indicator lights on printers, scanners, and multifunction devices.
• Consumer Electronics: Backlighting for front panels, power status indicators, and functional symbols in appliances and audio/video equipment.
• Industrial Equipment: Machine status, fault indication, and operational feedback panels.
• General Purpose: Any application requiring a compact, bright, and reliable red status indicator or symbolic luminary.

2. Technical Parameter Deep-Dive

This section provides a detailed, objective analysis of the LED's electrical, optical, and thermal specifications. Understanding these parameters is crucial for proper circuit design and ensuring long-term performance.

2.1 Absolute Maximum Ratings

The Absolute Maximum Ratings define the stress limits beyond which permanent damage to the device may occur. These are not conditions for normal operation.

• Power Dissipation (Pd): 120 mW. This is the maximum amount of power the device can dissipate as heat without damage. Exceeding this limit risks overheating the semiconductor junction.
• 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 excessive heating.
• Continuous Forward Current (I_F): 50 mA. This is the maximum DC current that can be applied continuously under specified ambient temperature conditions.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage greater than this value can cause breakdown and catastrophic failure of the LED junction. The datasheet explicitly notes the device is not designed for reverse operation.
• Operating & Storage Temperature Range: -40°C to +100°C. This defines the environmental temperature limits for both active operation and inactive storage, ensuring the material integrity of the package and die.

2.2 Electro-Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C, I_F=20mA) and define the device's performance.

• Luminous Intensity (I_V): 450 - 1120 mcd (millicandela). This is the perceived brightness of the LED as measured by a sensor filtered to match the human eye's photopic response. The wide range is managed through a binning system (see Section 3).
• Viewing Angle (2θ_1/2): 120 degrees (typical). This is the full angle at which the luminous intensity drops to half of its peak (on-axis) value. A 120° angle indicates a wide, diffuse emission pattern suitable for status indicators.
• Peak Emission Wavelength (λ_P): 631 nm (typical). This is the wavelength at which the spectral power output is highest. It is a physical property of the AlInGaP material.
• Dominant Wavelength (λ_d): 624 nm (typical). This is the single wavelength perceived by the human eye that best matches the LED's color. It is derived from the CIE chromaticity coordinates. The tolerance is +/- 1nm.
• Spectral Line Half-Width (Δλ): 15 nm (typical). This measures the spectral purity, indicating the range of wavelengths emitted. A narrower half-width indicates a more monochromatic (pure) color.
• Forward Voltage (V_F): 1.8V (Min) to 2.6V (Max) at 20mA. This is the voltage drop across the LED when operating. Circuit design must account for this variation to ensure consistent current.
• Reverse Current (I_R): 10 μA (Max) at V_R=5V. This is the small leakage current that flows when a reverse voltage is applied, relevant for testing purposes only.

3. Binning System Explanation

To manage natural variations in semiconductor manufacturing, LEDs are sorted into performance bins. This allows designers to select components that meet specific brightness requirements.

3.1 Luminous Intensity Binning

The luminous intensity is categorized into distinct bins, each with a minimum and maximum value. The tolerance within each bin is +/-11%.

• Bin U1: 450.0 mcd (Min) to 560.0 mcd (Max)
• Bin U2: 560.0 mcd (Min) to 680.0 mcd (Max)
• Bin V1: 680.0 mcd (Min) to 900.0 mcd (Max)
• Bin V2: 900.0 mcd (Min) to 1120.0 mcd (Max)

Designers should specify the required bin code when ordering to ensure brightness consistency across multiple units in an assembly. For applications where absolute brightness is less critical, a wider bin or no specific bin may be acceptable.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1, Figure 5), their implications are critical for design.

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

The relationship between forward current (I_F) and forward voltage (V_F) is non-linear, similar to a standard diode. The specified V_F range (1.8V-2.6V) at 20mA is the key design point. Driving the LED with a constant current, rather than a constant voltage, is essential to maintain stable light output and prevent thermal runaway, as V_F decreases with increasing temperature.

4.2 Luminous Intensity vs. Forward Current

The light output (I_V) is approximately proportional to the forward current within the operating range. However, efficiency may drop at very high currents due to increased heat. Operating at or below the recommended 20mA test condition ensures optimal performance and longevity.

4.3 Spectral Distribution

The spectral output curve centers around the peak wavelength of 631 nm with a typical half-width of 15 nm. This defines the specific shade of red. The dominant wavelength (624 nm) is the key parameter for color matching in applications where multiple LEDs must appear identical.

4.4 Temperature Dependence

LED performance is temperature-sensitive. Typically, luminous intensity decreases as the junction temperature increases. The wide operating temperature range (-40°C to +100°C) indicates the device is rated to function across extreme environments, though output will vary. Proper thermal management on the PCB is necessary for high-current or high-ambient-temperature applications to maintain brightness and lifespan.

5. Mechanical and Package Information

5.1 Physical Dimensions and Polarity

The LED conforms to an EIA standard SMD package footprint. Detailed dimensioned drawings are provided in the datasheet, including length, width, height, and lead spacing. All dimensions are in millimeters with a standard tolerance of ±0.2 mm. The package features a water-clear lens, which does not diffuse the light, allowing the native AlInGaP red color to be seen. The polarity (anode and cathode) is indicated by physical markings on the component body, which must be observed during placement to ensure correct operation.

5.2 Recommended PCB Land Pattern

A suggested printed circuit board attachment pad layout is provided for infrared or vapor phase reflow soldering. Following this land pattern is crucial for achieving reliable solder joints, proper self-alignment during reflow, and effective heat dissipation away from the LED junction.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

The device is compatible with lead-free (Pb-free) IR reflow soldering processes. The recommended profile is based on the J-STD-020B standard. Key parameters include:

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Body Temperature: Maximum 260°C.
• Time Above Liquidus: Recommended to be within standard JEDEC limits (typically 60-150 seconds).
• Maximum Soldering Cycles: Two times.

It is emphasized that the optimal profile depends on the specific PCB design, solder paste, and oven. The JEDEC-based profile should be used as a target, with final tuning based on solder paste manufacturer recommendations and board-level characterization.

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 lead.
• Number of Times: One time only. Repeated heating can damage the package and the internal die bond.

6.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used. The datasheet recommends immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Unspecified or aggressive chemical cleaners can damage the plastic lens and package material.

7. Storage and Handling Cautions

7.1 Moisture Sensitivity and Storage

The LED package is moisture-sensitive. Prolonged exposure to ambient humidity can lead to popcorn cracking during the high-temperature reflow soldering process.

• Sealed Package: Devices should be stored at ≤30°C and ≤70% Relative Humidity (RH). The shelf life in the original moisture-proof bag with desiccant is one year.
• Opened Package: Once the sealed bag is opened, the storage environment must not exceed 30°C and 60% RH.
• Floor Life: Components removed from their original packaging should be subjected to IR reflow soldering within 168 hours (7 days).
• Extended Storage: For storage beyond 168 hours, LEDs should be kept in a sealed container with desiccant or in a nitrogen desiccator.
• Baking: Components exposed beyond the 168-hour floor life require a bake-out at approximately 60°C for at least 48 hours before assembly to remove absorbed moisture.

7.2 Drive Circuit Design

An LED is a current-driven device. To ensure uniform brightness and prevent current hogging, especially when driving multiple LEDs in parallel, a current-limiting resistor must be used in series with each LED. The datasheet strongly recommends this configuration (Circuit A) over directly connecting LEDs in parallel without individual resistors (Circuit B), which can lead to uneven brightness and potential failure due to uneven current distribution caused by minor V_F variations between units.

8. Packaging and Ordering Information

8.1 Tape and Reel Specifications

The component is supplied for automated assembly in embossed carrier tape wound on 7-inch (178 mm) diameter reels.

• Pocket Pitch: 8 mm.
• Quantity per Reel: 2000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Cover Tape: Empty component pockets are sealed with a top cover tape.
• Missing Components: A maximum of two consecutive missing lamps (empty pockets) is allowed per the packing specification.
• Standard: Packaging conforms to ANSI/EIA-481 specifications.

9. Application Notes and Design Considerations

9.1 Typical Application Scenarios

This LED is intended for use in ordinary electronic equipment, including office automation, telecommunications, home appliances, and general industrial controls. It is suitable for status indication, backlighting of symbols on front panels, and general-purpose luminous signaling.

9.2 Design Considerations

• Current Control: Always use a series resistor or a dedicated constant-current driver to set the forward current. Do not connect directly to a voltage source.
• Thermal Management: While the package is small, ensure adequate copper area on the PCB pads to act as a heat sink, especially when operating near the maximum continuous current (50mA).
• ESD Protection: Although not explicitly stated as sensitive, handling LEDs with standard ESD (Electrostatic Discharge) precautions is considered good practice.
• Optical Design: The water-clear lens produces a focused beam with a 120° viewing angle. For wider or more diffused illumination, external lenses or light guides may be necessary.

10. Technical Comparison and Differentiation

While a direct comparison to other part numbers is not provided in this standalone datasheet, the key differentiating features of this component can be inferred:

• Material (AlInGaP): Offers high efficiency and good color stability for red LEDs compared to older technologies like GaAsP.
• Wide Viewing Angle (120°): Provides broad visibility, making it excellent for panel-mounted status indicators.
• JEDEC Level 3 Preconditioning: Indicates a good level of moisture resistance suitable for most commercial applications without requiring ultra-dry storage, simplifying logistics.
• Standardized Packaging: Compliance with EIA package standards and ANSI/EIA-481 reel specs ensures seamless integration into automated assembly lines.

11. Frequently Asked Questions (FAQ)

Q: Can I drive this LED without a current-limiting resistor?
A: No. An LED must be driven with a controlled current. Connecting it directly to a voltage source will cause excessive current to flow, potentially destroying the device instantly. Always use a series resistor or constant-current circuit.

Q: What does the "Bin Code" mean when ordering?
A: The bin code (e.g., V1, U2) specifies the guaranteed minimum and maximum luminous intensity of the LEDs in that batch. Specifying a bin ensures brightness consistency across all the LEDs in your product. If color consistency is critical, you may also need to specify wavelength bins.

Q: How long can I store these LEDs after opening the bag?
A: For reliable soldering, you should use them within 168 hours (7 days) if stored in an environment ≤30°C/60% RH. If stored longer, they must be baked at 60°C for 48 hours before use.

Q: Is this LED suitable for automotive or medical applications?
A: The datasheet states it is intended for ordinary electronic equipment. For applications requiring exceptional reliability or where failure could jeopardize safety (aviation, automotive, medical, life support), consultation with the manufacturer is required to assess suitability and potentially qualify the component for that specific use.

Q: Can I use wave soldering for this SMD LED?
A: The datasheet only provides guidelines for IR reflow and hand soldering. SMD components of this type are generally not recommended for wave soldering due to the thermal shock and potential for contamination. Reflow soldering is the intended and recommended assembly process.

12. Practical Design Example

Scenario: Designing a power "ON" indicator for a device powered by a 5V DC rail. The goal is to achieve good visibility with a forward current of approximately 15mA (below the 20mA test point for longer life).

Calculation:
Assume a typical forward voltage (V_F) of 2.2V.
The required voltage drop across the series resistor (R_S) is: V_supply - V_F = 5V - 2.2V = 2.8V.
Using Ohm's Law: R_S = V / I = 2.8V / 0.015A = 186.67 Ω.
The nearest standard resistor value is 180 Ω or 200 Ω.

Selection: Choose a 180 Ω resistor. Recalculating the current: I = (5V - 2.2V) / 180Ω ≈ 15.6mA. This is safe and within limits.
Power in Resistor: P = I²R = (0.0156)² * 180 ≈ 0.044W. A standard 1/8W (0.125W) or 1/10W resistor is sufficient.

PCB Layout: Place the 180Ω resistor in series with the LED's anode. Follow the recommended land pattern from the datasheet for the LED pads, ensuring sufficient copper area for heat dissipation. Include polarity marking (e.g., "+" for anode) on the PCB silkscreen.

13. Operating Principle

Light-emitting diodes are semiconductor devices that convert electrical energy directly into light through a process called electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type material recombine with holes from the p-type material in the active region. In an AlInGaP LED, this recombination event releases energy in the form of photons (light particles). The specific wavelength (color) of the emitted light, in this case red at ~624-631 nm, is determined by the bandgap energy of the Aluminum Indium Gallium Phosphide semiconductor material used in the construction of the chip. The water-clear epoxy package encapsulates and protects the semiconductor die, forms the lens to shape the light output, and contains the metal lead frame which provides the electrical connections and mechanical support.

14. Technology Trends

The development of SMD LEDs like this one is part of broader trends in optoelectronics and electronics manufacturing. Key trends influencing such components include:

• Miniaturization: Continuous demand for smaller package sizes to enable denser PCB layouts and more compact end products.
• Increased Efficiency: Ongoing material science research aims to improve the luminous efficacy (lumens per watt) of colored LEDs, reducing power consumption for a given light output.
• Enhanced Reliability: Improvements in package materials (epoxy, silicone) and die-attach techniques lead to longer operational lifetimes and better performance under high-temperature and high-humidity conditions.
• Standardization: The adoption of industry-standard footprints, reel sizes, and performance metrics (like JEDEC MSL ratings) streamlines the supply chain and simplifies design-in for engineers.
• Integration: While this is a discrete component, a trend exists towards integrating control electronics (like current regulators or drivers) directly into LED packages, creating "smart" LED modules.