LTST-C281KGKT-5A SMD LED Datasheet - 0.35mm Height - 1.7-2.3V Forward Voltage - Green Color - 75mW Power - English Technical Document

1. Product Overview

The LTST-C281KGKT-5A is a surface-mount device (SMD) LED designed for modern, compact electronic applications. It belongs to the category of ultra-thin chip LEDs, featuring a remarkably low profile of just 0.35mm in height. This makes it an ideal choice for applications where space constraints are critical, such as in ultra-slim displays, mobile devices, and wearable technology.

The LED utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for its light-emitting chip. This technology is known for producing high-efficiency light output, particularly in the green, yellow, and red portions of the spectrum. The specific model, LTST-C281KGKT-5A, emits a green light with a water-clear lens, which does not diffuse the light, resulting in a more focused and intense beam suitable for status indicators, backlighting, and panel illumination.

Its core advantages include compliance with RoHS (Restriction of Hazardous Substances) directives, making it an environmentally friendly \"green product.\" It is packaged in industry-standard 8mm tape on 7-inch diameter reels, ensuring compatibility with high-speed automated pick-and-place assembly equipment commonly used in mass production. Furthermore, it is designed to be compatible with infrared (IR) reflow soldering processes, which is the standard for surface-mount technology (SMT) assembly lines.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operating the LED under these conditions is not recommended for reliable performance.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED package can dissipate as heat without exceeding its maximum junction temperature. Exceeding this limit risks thermal degradation.
• Peak Forward Current (I_FP): 80 mA. This is the maximum instantaneous forward current, permissible only under pulsed conditions (specified at a 1/10 duty cycle and 0.1ms pulse width). It is used for brief, high-intensity flashes.
• Continuous Forward Current (I_F): 30 mA. This is the maximum DC current that can be applied continuously. For most standard indicator applications, a drive current of 5-20mA is typical.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage greater than this can cause breakdown and failure of the LED junction.
• Operating & Storage Temperature: -30°C to +85°C and -40°C to +85°C, respectively. These ranges define the environmental conditions for reliable operation and non-operational storage.

2.2 Electro-Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C) and define the LED's performance.

• Luminous Intensity (I_V): 4.5 - 28.0 mcd (Typical). Measured at a forward current (I_F) of 5mA. The wide range is due to the binning system (explained in Section 3). Intensity is measured with a filter approximating the photopic (human eye) response curve.
• Viewing Angle (2θ_1/2): 130 degrees (Typical). This is the full angle at which the luminous intensity drops to half of its peak (on-axis) value. A 130° angle indicates a very wide viewing pattern.
• Peak Wavelength (λ_P): 574 nm (Typical). The wavelength at which the spectral power distribution is at its maximum.
• Dominant Wavelength (λ_d): 567.5 - 576.5 nm. This is the single wavelength perceived by the human eye that defines the color. It is derived from the CIE chromaticity diagram and is the key parameter for color specification.
• Spectral Half-Width (Δλ): 15 nm (Typical). The width of the emission spectrum at half its maximum intensity. A narrower width indicates a more spectrally pure color.
• Forward Voltage (V_F): 1.7 - 2.3 V at I_F=5mA. The voltage drop across the LED when conducting current. This range is also subject to binning.
• Reverse Current (I_R): 10 μA (Max) at V_R=5V. A small leakage current that flows when the LED is reverse-biased within its maximum rating.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The LTST-C281KGKT-5A uses a three-dimensional binning system for key parameters.

3.1 Forward Voltage Binning (Unit: V @5mA)

LEDs are sorted based on their forward voltage drop to ensure uniform brightness when driven by a constant voltage source or in parallel configurations.

• Bin E2: 1.70V (Min) - 1.90V (Max)
• Bin E3: 1.90V (Min) - 2.10V (Max)
• Bin E4: 2.10V (Min) - 2.30V (Max)
• Tolerance per bin: ±0.1V

3.2 Luminous Intensity Binning (Unit: mcd @5mA)

This binning ensures a predictable minimum light output for a given drive current.

• Bin J: 4.50 mcd (Min) - 7.10 mcd (Max)
• Bin K: 7.10 mcd (Min) - 11.20 mcd (Max)
• Bin L: 11.20 mcd (Min) - 18.00 mcd (Max)
• Bin M: 18.00 mcd (Min) - 28.00 mcd (Max)
• Tolerance per bin: ±15%

3.3 Dominant Wavelength Binning (Unit: nm @5mA)

This critical binning controls the precise shade of green color emitted.

• Bin C: 567.50 nm (Min) - 570.50 nm (Max)
• Bin D: 570.50 nm (Min) - 573.50 nm (Max)
• Bin E: 573.50 nm (Min) - 576.50 nm (Max)
• Tolerance per bin: ±1 nm

The full part number may include codes specifying which bins are supplied for a particular order.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (Fig.1, Fig.6), their implications are standard for LED technology.

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

The relationship is exponential. A small increase in voltage leads to a large increase in current. This is why LEDs must be driven with a current-limiting mechanism (resistor or constant-current driver) to prevent thermal runaway.

4.2 Luminous Intensity vs. Forward Current

Light output is approximately proportional to forward current, but efficiency (lumens per watt) typically decreases at very high currents due to increased heat.

4.3 Spectral Distribution

The referenced Fig.1 would show a Gaussian-like curve centered around 574 nm (peak) with a half-width of 15 nm, confirming the monochromatic green output of the AlInGaP chip.

4.4 Temperature Dependence

LED performance is temperature-sensitive. Forward voltage typically decreases with increasing temperature (~2mV/°C), while luminous intensity also decreases. Operating within the specified temperature range is crucial for maintaining performance and longevity.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The LED conforms to an EIA (Electronic Industries Alliance) standard package outline. Key dimensions include the overall height of 0.35mm, length, and width as defined in the detailed mechanical drawing. All tolerances are ±0.10mm unless otherwise specified.

5.2 Polarity Identification

The cathode (negative) terminal is typically indicated by a marking on the package, such as a notch, dot, or green marking, as shown in the dimension diagram. Correct polarity is essential for operation.

5.3 Suggested Solder Pad Layout

A recommended land pattern (solder pad footprint) is provided to ensure proper soldering and mechanical stability during and after the reflow process. Adhering to this layout prevents tombstoning (component standing up) and ensures good solder fillets.

6. Soldering & Assembly Guidelines

6.1 Infrared Reflow Soldering Profile

The LED is qualified for lead-free (Pb-free) soldering processes. The suggested profile includes:

• Preheat: Ramp to 120-150°C.
• Soak/Preheat Time: Maximum 120 seconds to allow for temperature stabilization across the board.
• Peak Temperature: Maximum 260°C. The component body must not exceed this temperature.
• Time Above Liquidus (TAL): Suggested to be 5 seconds maximum at peak temperature. The LED can withstand this reflow cycle a maximum of two times.

6.2 Hand Soldering

If manual soldering is necessary:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per lead.
• Limit: One soldering cycle only.

6.3 Storage & Handling

• Storage Conditions: Recommended at ≤30°C and ≤60% relative humidity.
• Moisture Sensitivity: LEDs removed from their original, dry packaging should be reflow-soldered within 672 hours (28 days). If stored longer, a bake at 60°C for at least 20 hours is required before soldering to prevent \"popcorning\" (package cracking due to vaporized moisture).
• Cleaning: Only use specified solvents like ethyl alcohol or isopropyl alcohol at room temperature for less than one minute if cleaning is required. Other chemicals may damage the plastic lens.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The product is supplied in embossed carrier tape:

• Tape Width: 8mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 5000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging Standard: Conforms to ANSI/EIA-481.
• Empty pockets are sealed with cover tape. A maximum of two consecutive missing components is allowed.

8. Application Recommendations

8.1 Typical Application Scenarios

• Status Indicators: Power, connectivity, or function status lights in consumer electronics, appliances, and industrial control panels.
• Backlighting: For keypads, icons, or small LCD displays in mobile devices and instrumentation.
• Panel Illumination: In thin-profile automotive dashboards, control interfaces, or medical devices.
• Decorative Lighting: In compact signage or accent lighting where a thin form factor is needed.

8.2 Circuit Design Considerations

Critical: LEDs are current-driven devices.

• Recommended Drive Circuit (Circuit A): Use a series current-limiting resistor for each LED, even when multiple LEDs are connected in parallel to a voltage source. This compensates for the natural variation in forward voltage (V_F) between individual LEDs, ensuring uniform brightness. The resistor value is calculated as R = (V_supply - V_F) / I_F.
• Not Recommended (Circuit B): Connecting multiple LEDs directly in parallel without individual current limiting is discouraged. Slight differences in V_F will cause current to unevenly distribute, leading to significant differences in brightness and potential over-current in the LED with the lowest V_F.
• Constant Current Drivers: For highest precision and efficiency, especially in display or lighting applications, a dedicated constant-current LED driver IC is recommended.

9. Electrostatic Discharge (ESD) Protection

The AlInGaP semiconductor structure is sensitive to electrostatic discharge. ESD can cause immediate failure or latent damage that shortens lifespan.

Mandatory ESD Precautions:

• Operators must wear a grounded wrist strap or anti-static gloves when handling LEDs.
• All workstations, tools, and equipment must be properly grounded.
• Store and transport LEDs in anti-static packaging.
• Use an ionizer to neutralize static charges that may accumulate on the plastic lens during handling.

10. Technical Comparison & Differentiation

The LTST-C281KGKT-5A's primary differentiator is its 0.35mm ultra-thin profile. Compared to standard SMD LEDs (e.g., 0603 or 0805 packages which are often 0.6-0.8mm tall), this represents a reduction in height of over 50%. This is a critical advantage for applications pushing the limits of device thinness.

Its use of AlInGaP technology for green light offers higher efficiency and better color stability over time and temperature compared to older technologies like traditional GaP (Gallium Phosphide) green LEDs, which are typically less bright and can have a more yellowish-green hue.

11. Frequently Asked Questions (FAQs)

11.1 Can I drive this LED directly from a 3.3V or 5V logic output?

No, not directly. You must always use a series current-limiting resistor. For example, with a 5V supply, a V_F of 2.0V, and a desired I_F of 5mA: R = (5V - 2.0V) / 0.005A = 600Ω. A 560Ω or 620Ω standard resistor would be suitable.

11.2 Why is there such a wide range in luminous intensity (4.5 to 28 mcd)?

This is due to the production spread and the binning system. When ordering, you can specify the intensity bin (J, K, L, M) required for your application to guarantee a minimum brightness level.

11.3 What does \"water clear\" lens mean?

It means the lens material is transparent and non-diffused. The light emitted appears as a distinct, bright point. For a wider, more scattered beam, a diffused (milky) lens type would be used, but it typically reduces the on-axis luminous intensity.

11.4 How do I interpret the part number LTST-C281KGKT-5A?

While the full naming convention is proprietary, typical elements include: \"LTST\" (product family), \"C281\" (package size/style), \"K\" (likely intensity bin), \"GK\" (likely color/wavelength bin), \"T\" (tape and reel packaging), and \"5A\" (revision or variant).

12. Design-in Case Study

Scenario: Designing a status indicator for a new smartwatch. The main board has a thickness constraint of 1.0mm, and the indicator must be visible under various lighting conditions.

Selection Rationale: The 0.35mm height of the LTST-C281KGKT-5A allows it to fit comfortably within the stacked layers of the watch assembly (PCB, LED, light guide, outer lens). The high efficiency of the AlInGaP chip ensures sufficient brightness (selecting Bin L or M) to be seen outdoors while maintaining low power consumption, which is critical for battery life. The wide 130° viewing angle ensures the indicator is visible from different angles when glancing at the wrist. The compatibility with IR reflow allows it to be soldered simultaneously with all other SMD components on the main board, simplifying assembly.

13. Operating Principle

Light is generated through a process called electroluminescence within the AlInGaP semiconductor chip. When a forward voltage exceeding the diode's turn-on threshold is applied, electrons from the n-type region and holes from the p-type region are injected into the active region (the \"quantum well\"). When an electron recombines with a hole, energy is released in the form of a photon (light particle). The specific composition of the Aluminum, Indium, Gallium, and Phosphide atoms in the crystal lattice determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light. For the LTST-C281KGKT-5A, this composition is tuned to produce photons in the green spectrum (~574 nm).

14. Technology Trends

The trend in indicator and backlight LEDs continues toward miniaturization and increased efficiency. The 0.35mm height of this device represents the ongoing push for thinner components. Future developments may focus on even thinner packages, higher luminous efficacy (more light output per watt of electrical input), and improved color rendering or the development of new saturated colors. Integration with driver circuitry or the creation of multi-color, addressable micro-LED arrays in ultra-thin formats are also active areas of research and development, driven by demands from consumer electronics, automotive lighting, and advanced display technologies.