SMD LED LTST-C19DKFKT-NB Datasheet - Orange AlInGaP - 20mA - 50mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) Light Emitting Diode (LED). The device utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor chip to produce orange light. Designed for automated printed circuit board (PCB) assembly, this LED is packaged in industry-standard 8mm tape on 7-inch reels, making it suitable for high-volume production environments. Its miniature footprint and robust construction cater to space-constrained and reliability-focused applications across various electronic sectors.

1.1 Features

• Compliant with Restriction of Hazardous Substances (RoHS) directives.
• Utilizes an ultra-bright AlInGaP semiconductor chip for high luminous efficiency.
• Packaged on 8mm tape wound onto 7-inch diameter reels for automated pick-and-place machinery.
• Conforms to Electronic Industries Alliance (EIA) standard package outlines.
• Input logic levels are compatible with standard integrated circuit (IC) outputs.
• Designed for compatibility with automated surface-mount technology (SMT) placement equipment.
• Withstands standard infrared (IR) reflow soldering profiles used in lead-free (Pb-free) assembly processes.

1.2 Applications

The LED is designed for a broad spectrum of electronic equipment where reliable, compact indication or backlighting is required. Primary application areas include:

• Telecommunication Equipment: Status indicators in routers, modems, and handsets.
• Office Automation: Backlighting for keypads, keyboards, and status lights in printers and scanners.
• Consumer Appliances: Power, mode, or function indicators in household devices.
• Industrial Equipment: Panel indicators for machinery and control systems.
• Microdisplays & Signage: Low-level illumination for symbolic indicators or small informational displays.

2. Technical Parameters: In-Depth Objective Interpretation

The following sections provide a detailed analysis of the device's operational limits and performance characteristics under defined conditions. All ratings and characteristics are specified at an ambient temperature (Ta) of 25°C unless otherwise stated.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed and should be avoided in circuit design.

• Power Dissipation (Pd): 50 mW. This is the maximum total power (current * forward voltage) the package can dissipate as heat without exceeding its maximum junction temperature.
• Peak Forward Current (I_FP): 40 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to manage thermal rise.
• Continuous Forward Current (I_F): 20 mA. This is the maximum recommended DC current for continuous operation, ensuring long-term reliability and stable light output.
• Reverse Voltage (V_R): 5 V. Applying a reverse bias voltage exceeding this value can cause junction breakdown and device failure.
• Operating Temperature Range: -30°C to +85°C. The ambient temperature range over which the device is designed to function correctly.
• Storage Temperature Range: -40°C to +85°C. The temperature range for non-operational storage without degradation.
• Soldering Temperature: Withstands 260°C for 10 seconds, defining its compatibility with lead-free reflow soldering processes.

2.2 Electro-Optical Characteristics

These parameters define the typical performance of the device under normal operating conditions (I_F = 5mA, Ta=25°C).

• Luminous Intensity (I_V): 8.2 to 28.0 millicandelas (mcd). Measured on-axis using a sensor filtered to match the photopic (human eye) response curve. The wide range is managed through a binning system.
• Viewing Angle (2θ_1/2): 50 degrees. This is the full angle at which the luminous intensity drops to half of its on-axis (0°) value, defining the beam spread.
• Peak Emission Wavelength (λ_P): Approximately 611 nm. The wavelength at which the spectral power distribution of the emitted light is at its maximum.
• Dominant Wavelength (λ_d): 595 to 610 nm. This is the single wavelength perceived by the human eye to represent the color of the light, derived from the CIE chromaticity coordinates. It is the key parameter for color specification.
• Spectral Line Half-Width (Δλ): Approximately 17 nm. The width of the emission spectrum at half of its maximum power, indicating the color purity.
• Forward Voltage (V_F): 1.70 to 2.30 V. The voltage drop across the LED when driven with 5mA of current. This range is also managed through binning.
• Reverse Current (I_R): 10 μA maximum. The small leakage current that flows when the maximum reverse voltage (5V) is applied.

3. Binning System Explanation

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

3.1 Forward Voltage (V_F) Binning

Bins define the forward voltage range at a test current of 5mA. This is critical for designing current-limiting circuits, especially when multiple LEDs are connected in parallel, to ensure uniform current sharing.

• Bin D1: V_F = 1.7V to 1.9V
• Bin D2: V_F = 1.9V to 2.1V
• Bin D3: V_F = 2.1V to 2.3V
• Tolerance per bin: ±0.1V

3.2 Luminous Intensity (I_V) Binning

Bins categorize the minimum and maximum luminous output, allowing selection based on brightness needs.

• Bin K: I_V = 8.2 mcd to 11.0 mcd
• Bin L: I_V = 11.0 mcd to 18.0 mcd
• Bin M: I_V = 18.0 mcd to 28.0 mcd
• Tolerance per bin: ±15%

3.3 Dominant Wavelength (λ_d) Binning

This binning ensures color consistency across different production lots, which is vital for applications requiring matched colors.

• Bin N: λ_d = 595 nm to 600 nm
• Bin P: λ_d = 600 nm to 605 nm
• Bin Q: λ_d = 605 nm to 610 nm
• Tolerance per bin: ±1 nm

4. Performance Curve Analysis

Graphical data provides insight into device behavior under varying conditions. While specific curves are referenced in the datasheet, typical relationships are described below.

4.1 Current vs. Voltage (I-V) Characteristic

The forward voltage (V_F) exhibits a logarithmic relationship with forward current (I_F). It increases non-linearly, with a sharper rise at very low currents (near the turn-on voltage) and a more linear increase at higher currents due to series resistance within the chip and package. Operating the LED within the specified current range ensures stable V_F and optimal efficiency.

4.2 Luminous Intensity vs. Forward Current

The light output (luminous intensity) is approximately proportional to the forward current over a significant range. However, efficiency (lumens per watt) may decrease at very high currents due to increased thermal effects and droop. The datasheet's typical operating condition of 5mA is chosen for a balance of brightness, efficiency, and longevity.

4.3 Temperature Dependence

LED performance is temperature-sensitive. As the junction temperature increases:
- The forward voltage (V_F) typically decreases.
- The luminous intensity decreases for a given current.
- The dominant wavelength may shift slightly (usually towards longer wavelengths for AlInGaP). Proper thermal management in the PCB design is essential to maintain consistent optical performance over the operating temperature range.

5. Mechanical and Package Information

5.1 Package Dimensions

The device conforms to a standard SMD package outline. Key dimensional tolerances are ±0.1mm unless otherwise specified. The lens is water-clear with a black cap, which enhances contrast by reducing stray light reflection and improving the perceived brightness of the orange emission.

5.2 Recommended PCB Land Pattern

A suggested solder pad layout is provided to ensure reliable solder joint formation during reflow. This pattern is designed to facilitate good solder wetting, proper alignment, and sufficient mechanical strength while minimizing solder bridging. Adhering to this recommendation is crucial for assembly yield.

5.3 Polarity Identification

The cathode is typically marked on the device body, often indicated by a green tint on the lens, a notch, or a dot. Correct polarity must be observed during placement to ensure proper circuit operation.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters (Pb-Free Process)

The device is qualified for lead-free soldering. A critical parameter is the peak body temperature not exceeding 260°C for a maximum of 10 seconds. A complete reflow profile includes:
- Pre-heat/Ramp: A controlled ramp to activate flux and minimize thermal shock.
- Soak Zone: Typically 150-200°C for up to 120 seconds to equalize board temperature.
- Reflow Zone: Peak temperature of 260°C max, with time above liquidus (TAL) controlled.
- Cooling Zone: Controlled ramp-down to solidify solder joints.
Profiles should be developed based on the specific PCB assembly, following JEDEC standards and solder paste manufacturer recommendations.

6.2 Hand Soldering

If manual soldering is necessary, use a temperature-controlled iron set to a maximum of 300°C. Contact time with the solder pad should be limited to 3 seconds or less per joint, and should be performed only once to prevent thermal damage to the LED package or wire bonds.

6.3 Storage and Handling

- ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Handle using grounded wrist straps, anti-static mats, and in controlled environments.
- Moisture Sensitivity: The package is rated at Moisture Sensitivity Level (MSL) 3. If the original sealed moisture-barrier bag is opened, components must be subjected to IR reflow within one week (168 hours) of factory conditions (≤30°C/60% RH). For storage beyond this period, bake at 60°C for at least 20 hours before soldering.
- Long-Term Storage: Unopened bags should be stored at ≤30°C and ≤90% RH, with a recommended shelf life of one year from the date code.

6.4 Cleaning

Post-solder cleaning, if required, should use mild, alcohol-based solvents such as isopropyl alcohol (IPA) or ethyl alcohol. Immersion should be at room temperature for less than one minute. Harsh or unspecified chemicals can damage the plastic lens and package.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The device is supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178mm) diameter reels. Standard packaging contains 4000 pieces per reel. For quantities less than a full reel, a minimum pack quantity of 500 pieces is available. The tape and reel dimensions conform to ANSI/EIA-481 standards to ensure compatibility with automated feeders.

7.2 Part Number Interpretation

The part number LTST-C19DKFKT-NB encodes specific attributes:
- LTST: Product family/Series identifier.
- C19DKFKT: Internal code defining package type, color, and performance characteristics.
- NB: Suffix often indicating specific bin combinations or special options (e.g., specific V_F/I_V/λ_d bins). The exact bin codes for this suffix should be confirmed with the supplier.

8. Application Suggestions and Design Considerations

8.1 Current Limiting

An LED is a current-driven device. Always use a series current-limiting resistor or a constant-current driver circuit. The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (or the selected bin) to ensure the current does not exceed the maximum rating even with supply voltage variations and component tolerances.

8.2 Thermal Management

While the power dissipation is low, effective heat sinking through the PCB copper pads improves longevity and maintains stable light output. Use adequate copper area connected to the thermal pads, and consider thermal vias to inner or bottom layers for improved heat spreading, especially in high ambient temperature environments or when driving near maximum current.

8.3 Optical Design

The 50-degree viewing angle provides a wide beam. For applications requiring a more focused beam, secondary optics (lenses) can be used. The black cap reduces side glare, making the LED suitable for front-panel indicators where off-axis visibility needs to be minimized.

9. Technical Comparison and Differentiation

This AlInGaP orange LED offers distinct advantages compared to other technologies:
- vs. Traditional GaAsP/GaP: AlInGaP provides significantly higher luminous efficiency and brightness for the same drive current, resulting in lower power consumption for a given light output or greater visibility.
- vs. Phosphor-Converted LEDs: Direct-emitting AlInGaP LEDs typically have a narrower spectral bandwidth (≈17nm), offering more saturated and pure orange color compared to broader spectra from phosphor-converted white LEDs filtered to appear orange.
- vs. Other Package Sizes: The standardized EIA package ensures broad compatibility with industry-standard PCB footprints and pick-and-place nozzles, reducing design and assembly complexity.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this LED directly from a 3.3V or 5V logic output?
A: Not directly without a current-limiting resistor. The forward voltage is ~1.8V, so connecting it directly to 3.3V or 5V would cause excessive current flow, destroying the LED. Always calculate and use an appropriate series resistor.

Q2: Why is there such a wide range in luminous intensity (8.2 to 28.0 mcd)?
A: This is due to natural variations in semiconductor manufacturing. The binning system (K, L, M) allows you to select the brightness grade required for your application, ensuring consistency within a production run.

Q3: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P) is the physical peak of the light spectrum. Dominant Wavelength (λ_d) is calculated from the CIE color coordinates and represents the single wavelength the human eye perceives the color to be. λ_d is the more relevant parameter for color specification and matching.

Q4: How many times can I reflow this LED?
A: The datasheet specifies the soldering condition (260°C for 10 sec) can be applied a maximum of two times. This accounts for potential rework. It is best practice to minimize reflow cycles.

11. Practical Application Example

Scenario: Designing a status indicator for a network switch.
The LED will indicate "Link Active" on each port. The design uses a 3.3V supply rail.
1. Current Selection: Choose I_F = 5mA for adequate brightness and long life.
2. Resistor Calculation: Assuming a conservative V_F of 2.3V (Max from datasheet), R = (3.3V - 2.3V) / 0.005A = 200Ω. A standard 220Ω resistor would provide I_F ≈ (3.3-1.8)/220 ≈ 6.8mA, which is still safe and provides good brightness.
3. Binning: For uniform appearance across all ports on a panel, specify a tight Dominant Wavelength bin (e.g., Bin P: 600-605nm) and a consistent Luminous Intensity bin (e.g., Bin L: 11-18mcd).
4. PCB Layout: Use the recommended land pattern. Connect the cathode pad to a slightly larger copper pour for minor heat sinking.
5. Assembly: Follow the IR reflow profile guidelines. Ensure the board is baked if the LEDs have been exposed beyond the MSL 3 floor life.

12. Operating Principle

This LED operates on the principle of electroluminescence in a semiconductor p-n junction. The active region is composed of Aluminum Indium Gallium Phosphide (AlInGaP). When a forward bias voltage exceeding the junction's turn-on voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. Here, they recombine radiatively, releasing energy in the form of photons. The specific bandgap energy of the AlInGaP alloy determines the wavelength (color) of the emitted light, which in this case is in the orange spectrum (≈605nm dominant wavelength). The epoxy lens package serves to protect the semiconductor chip, provide mechanical stability, and shape the emitted light pattern.

13. Technology Trends

The development of SMD LEDs like this one is part of broader trends in optoelectronics:
- Increased Efficiency: Ongoing material science research aims to improve the internal quantum efficiency and light extraction efficiency of AlInGaP and other compound semiconductors, leading to higher lumens per watt.
- Miniaturization: The drive for smaller, denser electronics continues to push package sizes down (e.g., from 0603 to 0402 metric footprints), while maintaining or improving optical performance.
- Integration: Trends include integrating multiple LED chips (RGB) into a single package for color mixing, or combining control ICs with LEDs for "smart" lighting solutions.
- Reliability and Standardization: Emphasis on stringent quality standards, longer operational lifetimes, and standardized testing/performance metrics (e.g., TM-21 for lifetime projection) to meet the demands of automotive, industrial, and professional lighting applications.