LTST-C281KFKT Orange LED Datasheet - 0.35mm Height - 2.4V Forward Voltage - 75mW Power Dissipation - English Technical Document

1. Product Overview

The LTST-C281KFKT is a surface-mount device (SMD) light-emitting diode (LED) designed for modern electronic applications requiring compact, high-brightness indicators. This component belongs to the category of chip LEDs, characterized by their minimal profile and compatibility with automated assembly processes.

Core Advantages: The primary advantages of this LED include its exceptionally thin package height of 0.35 mm, which facilitates use in space-constrained designs. It utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material, known for producing high luminous efficiency and stable orange light output. The device is compliant with RoHS (Restriction of Hazardous Substances) directives, classifying it as a green product. Its packaging on 8mm tape within 7-inch diameter reels makes it fully compatible with high-speed automatic pick-and-place equipment, streamlining volume manufacturing.

Target Market: This LED is targeted at applications within consumer electronics, office automation equipment, communication devices, and general household appliances where reliable, bright status indication is required. Its design parameters make it suitable for integration into PCBs (Printed Circuit Boards) using standard infrared reflow soldering techniques.

2. Technical Parameter Deep-Dive

2.1 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): 75 mW. This is the maximum amount of power the LED package can dissipate as heat under specified ambient conditions (Ta=25°C). Exceeding this limit risks thermal degradation.
• Peak Forward Current (I_FP): 80 mA. This is the maximum allowable instantaneous forward current, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). It is significantly higher than the DC rating to accommodate brief current surges.
• DC Forward Current (I_F): 30 mA. This is the maximum continuous forward current recommended for reliable long-term operation. The typical operating condition for testing optical characteristics is 20 mA.
• Reverse Voltage (V_R): 5 V. Applying a reverse bias voltage exceeding this value can cause junction breakdown.
• Operating & Storage Temperature: The device can operate within an ambient temperature range of -30°C to +85°C. For non-operational storage, the range extends from -40°C to +85°C.
• Soldering Condition: The LED can withstand infrared reflow soldering with a peak temperature of 260°C for a duration of 10 seconds, which aligns with common lead-free (Pb-free) solder process profiles.

2.2 Electro-Optical Characteristics

These parameters are measured at a standard ambient temperature of 25°C and a forward current (I_F) of 20 mA, unless otherwise noted. They define the device's performance under normal operating conditions.

• Luminous Intensity (I_V): Ranges from a minimum of 45.0 mcd to a typical value of 90.0 mcd. Intensity is measured using a sensor-filter combination that approximates the photopic (CIE) human eye response curve. Actual intensity is subject to a binning system (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on the central axis (0°). A wide viewing angle like this is typical for chip LEDs with a non-lensed (water-clear) package, providing broad, diffuse illumination.
• Peak Emission Wavelength (λ_P): 611 nm. This is the wavelength at which the spectral power distribution of the emitted light reaches its maximum. It defines the perceived hue of the orange light.
• Dominant Wavelength (λ_d): 605 nm. Derived from the CIE chromaticity diagram, this is the single wavelength that best represents the perceived color of the LED's output, which is a standard orange.
• Spectral Line Half-Width (Δλ): 17 nm. This parameter indicates the spectral purity or bandwidth of the emitted light. It is the width of the spectral distribution at half of its maximum power. A value of 17 nm is characteristic of AlInGaP materials, offering good color saturation.
• Forward Voltage (V_F): Typically 2.40 V, with a maximum of 2.40 V at I_F=20mA. The minimum is specified as 2.0 V. This is the voltage drop across the LED when conducting the specified current.
• Reverse Current (I_R): Maximum 10 μA when a reverse voltage (V_R) of 5V is applied. This indicates the leakage current in the off-state.

3. Binning System Explanation

To ensure consistency in brightness across production batches, the luminous intensity of the LTST-C281KFKT is categorized into bins. Each bin represents a specific range of intensity values measured at the standard test condition of 20 mA forward current.

The bin code list is as follows:

• Bin Code P: 45.0 mcd (Min) to 71.0 mcd (Max)
• Bin Code Q: 71.0 mcd to 112.0 mcd
• Bin Code R: 112.0 mcd to 180.0 mcd
• Bin Code S: 180.0 mcd to 280.0 mcd

A tolerance of +/-15% is applied to each intensity bin. This means that any individual LED within a specific bin, for example Bin Q, is guaranteed to have an intensity between 71.0 mcd and 112.0 mcd, but the actual distribution may have a spread of ±15% around the nominal bin range. Designers should select the appropriate bin based on the required brightness level for their application, considering this tolerance.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1, Fig.6), their typical behavior can be described based on the technology.

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

For an AlInGaP LED like the LTST-C281KFKT, the I-V relationship is exponential, similar to a standard diode. The forward voltage (V_F) has a relatively low temperature coefficient compared to some other LED types, but it will still decrease slightly as junction temperature increases for a given current. The specified V_F of 2.4V (typ) at 20mA is a key parameter for driving circuit design.

4.2 Luminous Intensity vs. Forward Current

The light output (luminous intensity) is approximately proportional to the forward current in the normal operating range (up to the DC maximum of 30mA). However, efficiency may decrease at very high currents due to increased thermal effects and droop. Operating at the typical 20mA provides a good balance of brightness and longevity.

4.3 Temperature Characteristics

Like all LEDs, the performance of the LTST-C281KFKT is temperature-dependent. As the junction temperature rises, the luminous intensity typically decreases. The dominant wavelength (λ_d) may also experience a slight redshift (increase in wavelength) with increasing temperature, which can cause a subtle shift in perceived color. Proper thermal management in the application is crucial to maintain consistent optical performance.

4.4 Spectral Distribution

The spectral output is centered around 611 nm (peak) with a half-width of 17 nm. This results in a monochromatic orange light with high color purity. The spectrum does not contain the broad white light components found in phosphor-converted white LEDs.

5. Mechanical & Package Information

5.1 Package Dimensions

The LED features an EIA (Electronic Industries Alliance) standard package footprint. The defining characteristic is its ultra-thin profile with a height (H) of 0.35 mm. All dimensional drawings specify measurements in millimeters, with a standard tolerance of ±0.10 mm unless otherwise noted. The package is "water clear," meaning the encapsulant is transparent without a diffusing lens, contributing to the wide 130-degree viewing angle.

5.2 Polarity Identification

The datasheet includes a diagram showing the recommended solder pad layout on the PCB. This layout typically indicates the anode and cathode connections. Correct polarity is essential for the LED to function. Applying reverse voltage exceeding the 5V rating can cause immediate damage.

5.3 Tape and Reel Packaging

The components are supplied on 8mm wide embossed carrier tape, wound onto 7-inch (178 mm) diameter reels. This is standard packaging for automated SMD assembly. Each reel contains 5000 pieces. The tape has a cover seal to protect the components from contamination. Specifications note that a maximum of two consecutive component pockets may be empty, and the minimum order quantity for remnants is 500 pieces. This packaging conforms to ANSI/EIA-481 standards.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile for lead-free processes is provided. Key parameters include:

• Pre-heat: Ramp-up to a temperature between 150°C and 200°C.
• Pre-heat Time: Maximum of 120 seconds to allow for uniform heating and solvent evaporation from solder paste.
• Peak Temperature: Maximum of 260°C.
• Time Above Liquidus: The LED should be subjected to the peak temperature for a maximum of 10 seconds. The profile is designed to be compliant with JEDEC standards to ensure reliable solder joint formation without damaging the LED package. It is critical to follow solder paste manufacturer recommendations and perform board-specific characterization, as different PCB designs and materials affect the thermal profile.

6.2 Hand Soldering

If hand soldering is necessary, use a soldering iron with a temperature not exceeding 300°C. The contact time for each solder joint should be limited to a maximum of 3 seconds, and this should be performed only once per pad to prevent thermal stress on the LED.

6.3 Storage Conditions

Proper storage is vital to maintain solderability and prevent moisture-induced damage (popcorning) during reflow.

• Sealed Package: LEDs in their original moisture-proof bag with desiccant should be stored at ≤30°C and ≤90% Relative Humidity (RH). The recommended shelf life under these conditions is one year.
• Opened Package: Once the moisture barrier bag is opened, components should be stored at ≤30°C and ≤60% RH. It is recommended to complete the IR reflow process within 672 hours (28 days) of exposure.
• Extended Open Storage: For storage beyond 672 hours, components should be placed in a sealed container with desiccant or in a nitrogen desiccator. If stored open for more than 672 hours, a bake-out at approximately 60°C for at least 20 hours is required prior to soldering to remove absorbed moisture.

6.4 Cleaning

If post-solder cleaning is required, only specified alcohol-based solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. The use of unspecified chemical cleaners can damage the LED package material.

7. Application Suggestions

7.1 Typical Application Scenarios

This LED is suitable for status indication, backlighting for small icons or symbols, and panel illumination in a wide range of consumer and industrial electronics. Examples include power-on indicators on routers/modems, backlighting for buttons on remote controls or appliances, and status lights on computer peripherals. Its thin profile makes it ideal for ultra-slim devices like modern smartphones, tablets, and laptops where internal space is at a premium.

7.2 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness, especially when multiple LEDs are connected in parallel, it is strongly recommended to use a current-limiting resistor in series with each LED. A simple drive circuit consists of a voltage source (V_CC), a series resistor (R_S), and the LED. The resistor value can be calculated using Ohm's Law: R_S = (V_CC - V_F) / I_F, where V_F is the forward voltage of the LED (use 2.4V for design margin) and I_F is the desired operating current (e.g., 20mA). This configuration provides stable current regulation and protects the LED from current spikes.

7.3 Design Considerations

• ESD Protection: AlInGaP LEDs are sensitive to electrostatic discharge (ESD). Handling procedures must include proper ESD precautions: use of wrist straps, anti-static mats, and grounded equipment. The LED itself may not have integrated ESD protection, so circuit-level protection (e.g., transient voltage suppression diodes) may be necessary in ESD-prone environments.
• Thermal Management: Although power dissipation is low (75 mW max), ensuring adequate heat sinking through the PCB copper pads is important for maintaining long-term reliability and consistent light output, especially in high ambient temperature conditions or when operating near maximum current.
• Optical Design: The wide viewing angle and water-clear package mean light is emitted diffusely. For applications requiring a more directed beam, external lenses or light guides may be necessary.

8. Technical Comparison & Differentiation

The LTST-C281KFKT differentiates itself primarily through its ultra-thin 0.35mm height, which is thinner than many standard chip LEDs (e.g., 0603 or 0402 packages which are often 0.55-0.65mm tall). This is a critical advantage for modern portable and wearable electronics. The use of AlInGaP technology provides higher luminous efficiency and better temperature stability for orange/red colors compared to older technologies like GaAsP. Its compatibility with standard IR reflow for Pb-free processes and tape-and-reel packaging aligns it with high-volume, automated manufacturing, offering a cost-effective solution for mass production.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this LED directly from a 3.3V or 5V logic output?
A: No. You must use a series current-limiting resistor. For example, with a 3.3V supply and a target current of 20mA, the resistor value would be approximately (3.3V - 2.4V) / 0.02A = 45 Ohms. Driving it directly would likely exceed the maximum current and destroy the LED.

Q2: What is the difference between Peak Wavelength (611nm) and Dominant Wavelength (605nm)?
A: Peak wavelength is the literal highest point on the spectral output curve. Dominant wavelength is a calculated value from color science that represents the perceived color as a single wavelength. For this orange LED, both values are close, confirming a saturated color.

Q3: The bin code is "Q". What exact brightness can I expect?
A: You can expect a luminous intensity between 71.0 mcd and 112.0 mcd when measured at 20mA. Due to the +/-15% tolerance on the bin, the actual value for any single LED could be anywhere within that range. For critical brightness-matching applications, testing and sorting may be required.

Q4: How do I interpret the "130 deg" viewing angle?
A: This means if you look at the LED from directly above (0°), you see maximum brightness. As you move off-axis, the brightness decreases. At an angle of 65° from the center (130°/2), the brightness will be half of the on-axis value. Light is still visible at angles beyond this.

10. Practical Design & Usage Case

Case: Designing a Status Indicator for a Portable Bluetooth Speaker
A designer needs a low-power, bright orange LED to indicate "charging" status. The speaker's main PCB has a thickness constraint, and the LED must be placed behind a thin plastic diffuser.

Implementation: The LTST-C281KFKT is selected for its 0.35mm height, fitting within the mechanical stack-up. The drive circuit uses the existing 3.3V system rail. A 47 Ohm (standard value) series resistor is calculated: (3.3V - 2.4V) / 0.02A ≈ 45 Ohms, providing ~19mA. The wide 130° viewing angle ensures the charging light is visible from various angles of the speaker. The LED is placed on tape-and-reel for automated assembly during mass production. The designer specifies Bin Code R or higher from the supplier to guarantee high brightness visible even in well-lit rooms.

11. Technology Principle Introduction

The LTST-C281KFKT is based on AlInGaP semiconductor technology. This material is a compound semiconductor from the III-V group. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region. Their recombination releases energy in the form of photons (light). The specific composition of Aluminum, Indium, Gallium, and Phosphide in the crystal lattice determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light. For this LED, the bandgap is engineered to produce photons in the orange spectrum (~605-611 nm). The water-clear epoxy encapsulant protects the semiconductor chip, provides mechanical stability, and acts as a primary optical element, shaping the light output pattern.

12. Technology Trends

The trend in indicator LEDs like the LTST-C281KFKT continues toward miniaturization (smaller footprints and thinner profiles) to enable sleeker product designs. Increased efficiency (more light output per mA of current) is a constant driver, reducing power consumption in battery-operated devices. There is also a focus on improved color consistency and tighter binning to meet the demands of applications where multiple LEDs must match perfectly. Furthermore, integration with advanced packaging and driver ICs in multi-chip modules is an emerging trend for smart lighting applications, though for simple indicators, discrete components like this LED remain highly cost-effective and versatile.