LTST-S270KFKT Orange SMD LED Datasheet - Side View - 2.0-2.4V - 30mA - 75mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-brightness, side-looking surface-mount LED. The device utilizes an advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor chip to produce a vibrant orange light output. Designed for automated assembly processes, it is packaged on 8mm tape and supplied on 7-inch reels, making it suitable for high-volume manufacturing. The product is compliant with RoHS directives and is classified as a green product.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its ultra-bright output from the AlInGaP technology, compatibility with infrared reflow soldering processes, and its side-emitting design which is ideal for applications requiring illumination from the side of the component. Its EIA-standard package ensures broad compatibility. This LED is targeted at applications in consumer electronics, industrial indicators, automotive interior lighting, and backlighting where a compact, reliable, and bright orange indicator is required.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device's operational limits are defined under an ambient temperature (Ta) of 25°C. Exceeding these ratings may cause permanent damage.

• Power Dissipation (Pd): 75 mW. This is the maximum power the package can dissipate as heat.
• Peak Forward Current (I_F(peak)): 80 mA. This is permissible only under pulsed conditions with a 1/10 duty cycle and a 0.1ms pulse width.
• Continuous Forward Current (I_F): 30 mA DC. This is the recommended maximum current for continuous operation.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage beyond this limit can break down the LED junction.
• Operating Temperature Range (T_opr): -30°C to +85°C.
• Storage Temperature Range (T_stg): -40°C to +85°C.
• Infrared Soldering Condition: Withstands 260°C for 10 seconds, which is typical for lead-free (Pb-free) reflow processes.

2.2 Electrical and Optical Characteristics

Key performance parameters are measured at Ta=25°C and a forward current (I_F) of 20 mA, unless otherwise specified.

• Luminous Intensity (I_V): 45.0 - 90.0 mcd (typical). The actual intensity is binned (see Section 3). Measured with a sensor/filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): 130 degrees (typical). This wide viewing angle is characteristic of the side-looking lens design.
• Peak Emission Wavelength (λ_P): 611 nm (typical). The wavelength at which the spectral output is maximum.
• Dominant Wavelength (λ_d): 605 nm (typical at I_F=20mA). This is the single wavelength perceived by the human eye, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 17 nm (typical). A measure of the spectral purity of the emitted light.
• Forward Voltage (V_F): 2.0 - 2.4 V (typical at I_F=20mA). The voltage drop across the LED when conducting.
• Reverse Current (I_R): 10 μA (maximum at V_R=5V). The small leakage current when the LED is reverse-biased.

ESD Caution: The device is sensitive to electrostatic discharge (ESD). Proper handling procedures, including the use of grounded wrist straps and anti-static equipment, are mandatory to prevent damage.

3. Binning System Explanation

The luminous intensity of the LEDs is sorted into bins to ensure consistency within a production lot. The bin code defines the minimum and maximum intensity range.

• Bin Code P: 45.0 - 71.0 mcd
• Bin Code Q: 71.0 - 112.0 mcd
• Bin Code R: 112.0 - 180.0 mcd
• Bin Code S: 180.0 - 280.0 mcd

A tolerance of +/-15% is applied to each intensity bin. This system allows designers to select the appropriate brightness grade for their application, balancing cost and performance.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral output, Figure 6 for viewing angle), the typical relationships can be described:

• I-V (Current-Voltage) Curve: The forward voltage (V_F) exhibits a logarithmic relationship with forward current (I_F). It is relatively constant in the normal operating range but increases with current.
• Luminous Intensity vs. Current: The light output is approximately proportional to the forward current up to the maximum rated current. Operating above the rated current leads to super-linear increase in heat and potential efficiency drop (droop).
• Temperature Dependence: The forward voltage typically decreases with increasing junction temperature (negative temperature coefficient). Luminous intensity generally decreases as temperature rises, which is a key consideration for thermal management in high-power or high-ambient-temperature applications.
• Spectral Distribution: The emitted light spectrum is centered around 611 nm (peak) with a relatively narrow half-width of 17 nm, indicating a saturated orange color.

5. Mechanical and Package Information

5.1 Package Dimensions and Polarity

The LED features a side-looking package with a water-clear lens. Detailed dimensional drawings are provided in the datasheet, with all units in millimeters (tolerance ±0.10mm unless noted). The package is designed to EIA standards for compatibility. The cathode is typically identified by a visual marker such as a notch, a green dot, or a cut corner on the package. The suggested soldering pad layout and orientation are provided to ensure proper alignment and soldering during PCB assembly.

5.2 Tape and Reel Specifications

The components are supplied on embossed carrier tape with a protective cover tape, wound onto 7-inch (178mm) diameter reels.

• Pieces per Reel: 4000
• Minimum Order Quantity (MOQ) for Remainders: 500 pieces
• Consecutive Missing Lamps: Maximum of two allowed per reel.
• The packaging conforms to ANSI/EIA-481 specifications.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

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

• Pre-heat: 150–200°C
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus: 10 seconds maximum (recommended profile on page 3).
• The profile should be characterized for the specific PCB design, solder paste, and oven used.

6.2 Hand Soldering

If hand soldering is necessary:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per joint.
• Limit to one soldering cycle to prevent thermal damage to the plastic package.

6.3 Cleaning

Only specified cleaning agents should be used. Recommended solvents are ethyl alcohol or isopropyl alcohol at room temperature. The LED should be immersed for less than one minute. Unspecified chemicals may damage the epoxy lens or package.

6.4 Storage Conditions

Proper storage is critical to maintain solderability and prevent moisture absorption (which can cause "popcorning" during reflow).

• Sealed Moisture-Barrier Bag (MBB): Store at ≤30°C and ≤90% RH. Use within one year of bag seal date.
• After Bag Opening: Store at ≤30°C and ≤60% RH. It is recommended to complete IR reflow within one week of exposure.
• Extended Storage (Opened): Store in a sealed container with desiccant or in a nitrogen desiccator.
• Baking: If exposed for more than one week, bake at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture.

7. Application Notes and Design Considerations

7.1 Typical Application Scenarios

This side-looking orange LED is ideal for:

• Status Indicators: On consumer electronics, appliances, and networking equipment where a wide viewing angle is needed.
• Backlighting: For edge-lit panels, membrane switches, or symbols where side emission is advantageous.
• Automotive Interior Lighting: For dashboard or console illumination.
• Industrial Control Panels: As alert or status lights on machinery.

7.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a constant-current driver. Calculate the resistor value using R = (V_supply - V_F) / I_F. For a 5V supply and targeting I_F=20mA with V_F=2.4V, R = (5 - 2.4) / 0.02 = 130 Ω.
• Thermal Management: Although power dissipation is low (75mW), ensure adequate PCB copper area or thermal vias if operating at high ambient temperatures or near maximum current to maintain LED longevity and stable light output.
• ESD Protection: Incorporate ESD protection diodes on sensitive input lines if the LED is in an exposed location, and follow strict ESD handling protocols during assembly.
• Optical Design: The side-emitting nature means the primary light output is parallel to the PCB surface. Consider light pipes, reflectors, or diffusers to direct light as needed.

8. Technical Comparison and Differentiation

Compared to standard top-emitting LEDs or those using older technologies like GaAsP, this AlInGaP side-looking LED offers distinct advantages:

• Higher Efficiency (AlInGaP vs. GaAsP): AlInGaP technology provides significantly higher luminous efficacy, resulting in brighter output at the same current.
• Superior Color Saturation: The narrow spectral half-width (17nm) produces a more pure and saturated orange color compared to broader-spectrum alternatives.
• Design Flexibility (Side-Looking): The package enables unique optical designs not possible with top-emitters, saving vertical space and enabling edge-lighting solutions.
• Modern Process Compatibility: Full compatibility with infrared reflow soldering and automatic pick-and-place equipment streamlines modern SMT assembly lines.

9. Frequently Asked Questions (FAQs)

Q1: What is the difference between peak wavelength and dominant wavelength?
A1: Peak wavelength (λ_P=611nm) is the physical point of maximum energy in the spectrum. Dominant wavelength (λ_d=605nm) is the perceptual color point on the CIE chart. λ_d is more relevant for color specification.

Q2: Can I drive this LED with a 3.3V supply without a resistor?
A2: No. The forward voltage is ~2.4V. Connecting it directly to 3.3V would cause excessive current, potentially exceeding the 30mA limit and damaging the LED. A current-limiting resistor is always required.

Q3: Why is there a binning system for luminous intensity?
A3: Manufacturing variations cause slight differences in output. Binning sorts LEDs into consistent brightness groups, allowing designers to choose a suitable grade and ensuring predictable performance within a batch.

Q4: How do I interpret the viewing angle of 130 degrees?
A4: The viewing angle (2θ_1/2) is the full angle where the intensity drops to half of its peak value. A 130° angle means light is emitted over a very wide cone, making it visible from many side angles.

Q5: Is baking always required before soldering?
A5: Baking is required only if the LEDs have been exposed to ambient conditions outside their original sealed bag for more than the specified time (e.g., one week at ≤60% RH). This prevents moisture-induced package cracking during reflow.

10. Practical Design and Usage Examples

Example 1: Panel-Mount Status Indicator
In a control panel, the LED can be mounted at the edge of a cutout, with its side emission directed through a light pipe or a frosted window. The wide viewing angle ensures the indicator is visible to an operator from various positions. A simple circuit with a 150Ω resistor from a 5V microcontroller GPIO pin provides adequate drive at ~17mA.

Example 2: Sequential Lighting in a Consumer Device
Multiple LEDs can be placed side-by-side along the edge of a device housing. By controlling them sequentially via a microcontroller, a "Knight Rider"-style scanning effect or a progress bar can be created, utilizing their side emission to create a seamless line of light.

11. Technology Principle Introduction

This LED is based on AlInGaP semiconductor material grown on a substrate. When a forward voltage is applied, electrons and holes recombine in the active region of the PN junction, releasing energy in the form of photons. The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, orange (~605-611 nm). The side-looking package incorporates a molded epoxy lens that shapes the light output pattern, extracting it from the side of the chip rather than the top. This design often involves reflective cavities within the package to redirect the light.

12. Industry Trends and Developments

The trend in SMD indicator LEDs continues towards higher efficiency, smaller packages, and greater integration. While AlInGaP remains the dominant technology for high-efficacy red, orange, and yellow LEDs, ongoing research focuses on improving extraction efficiency and thermal stability. There is also a move towards more precise binning and tighter tolerances to meet the demands of applications like automotive lighting and high-end displays. The compatibility with lead-free, high-temperature reflow processes is now a standard requirement, driven by global environmental regulations. Furthermore, the demand for reliable performance in harsh environments (wider temperature ranges, higher humidity) continues to push advancements in package sealing and materials science.