LTST-S270KSKT SMD LED Datasheet - Yellow - 20mA - 2.4V - English Technical Document

1. Product Overview

This document provides comprehensive technical data for a high-brightness, side-looking surface-mount device (SMD) LED. The component utilizes an advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor chip to produce a yellow light output. It is designed for compatibility with modern automated assembly processes, including pick-and-place equipment and infrared reflow soldering, making it suitable for high-volume manufacturing. The device is packaged on 8mm tape wound onto 7-inch diameter reels, adhering to EIA standard packaging for efficient handling.

2. Technical Specifications

2.1 Absolute Maximum Ratings

The device must not be operated beyond the following limits to prevent permanent damage. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 75 mW
• Peak Forward Current (IFP): 80 mA (under pulsed conditions: 1/10 duty cycle, 0.1ms pulse width)
• Continuous Forward Current (IF): 30 mA DC
• Reverse Voltage (VR): 5 V
• Operating Temperature Range: -30°C to +85°C
• Storage Temperature Range: -40°C to +85°C
• Infrared Reflow Soldering Condition: Maximum peak temperature of 260°C for 10 seconds.

2.2 Electrical & Optical Characteristics

The following parameters define the typical performance of the LED under standard test conditions (Ta=25°C, IF=20mA unless noted).

• Luminous Intensity (Iv): 28.0 mcd (Minimum), 80.0 mcd (Typical). Measured using a sensor/filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its axial (on-center) value.
• Peak Emission Wavelength (λP): 588 nm.
• Dominant Wavelength (λd): 587 nm. This is the single wavelength perceived by the human eye that defines the color, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 15 nm. This indicates the spectral purity of the emitted light.
• Forward Voltage (VF): 2.0 V (Minimum), 2.4 V (Typical).
• Reverse Current (IR): 10 μA (Maximum) at VR = 5V.

3. Binning System

The luminous intensity of the LEDs is sorted into specific bins to ensure consistency. The bin code is part of the product identification. The tolerance for each intensity bin is +/- 15%.

• Bin Code N: 28.0 mcd (Min) to 45.0 mcd (Max)
• Bin Code P: 45.0 mcd (Min) to 71.0 mcd (Max)
• Bin Code Q: 71.0 mcd (Min) to 112.0 mcd (Max)
• Bin Code R: 112.0 mcd (Min) to 180.0 mcd (Max)

4. Mechanical & Packaging Information

4.1 Package Dimensions

The LED features a side-looking package design. Detailed mechanical drawings are provided in the datasheet, with all dimensions specified in millimeters. Tolerances are typically ±0.10 mm unless otherwise noted. The lens is water clear.

4.2 Suggested Soldering Pad Layout and Orientation

The datasheet includes a recommended land pattern (solder pad dimensions) for PCB design to ensure reliable solder joints and proper alignment. A clear indication of the suggested soldering direction is provided to aid in automated assembly and polarity identification.

4.3 Tape and Reel Specifications

The components are supplied on embossed carrier tape sealed with cover tape.

• Carrier Tape Width: 8 mm
• Reel Diameter: 7 inches
• Quantity per Reel: 4000 pieces
• Minimum Order Quantity (for remainders): 500 pieces
• The packaging conforms to ANSI/EIA-481 specifications.

5. Assembly & Handling Guidelines

5.1 Soldering Process

The LED is compatible with infrared (IR) reflow soldering processes, which is critical for lead-free (Pb-free) assembly. A suggested reflow profile is provided, which generally follows JEDEC standards.

• Reflow Soldering:
  • Pre-heat Temperature: 150–200°C
  • Pre-heat Time: Maximum 120 seconds
  • Peak Temperature: Maximum 260°C
  • Time at Peak: Maximum 10 seconds (maximum of two reflow cycles allowed).
• Hand Soldering (if necessary):
  • Iron Temperature: Maximum 300°C
  • Soldering Time: Maximum 3 seconds (one time only).

Note: The optimal temperature profile depends on the specific PCB design, solder paste, and oven. It is recommended to characterize the process for the specific application.

5.2 Cleaning

If cleaning is required after soldering, only specified solvents should be used to avoid damaging the LED package. Acceptable methods include:

• Immersion in ethyl alcohol or isopropyl alcohol at normal room temperature.
• Immersion time should be less than one minute.
• Unspecified chemical liquids must not be used.

5.3 Storage Conditions

Proper storage is essential to maintain solderability and device reliability.

• Sealed Original Package: Store at ≤30°C and ≤90% Relative Humidity (RH). Components should be used within one year when the moisture-proof bag with desiccant is intact.
• Opened Package / Loose Components: Store at ≤30°C and ≤60% RH. It is recommended to complete the IR reflow process within one week of opening.
• Extended Storage (out of original bag): Store in a sealed container with desiccant or in a nitrogen desiccator.
• Baking: If components have been exposed to ambient conditions for more than one week, they should be baked at approximately 60°C for at least 20 hours before assembly to remove moisture and prevent "popcorning" during reflow.

5.4 Electrostatic Discharge (ESD) Precautions

LEDs are sensitive to static electricity and voltage surges. To prevent ESD damage:

• Use a grounded wrist strap or anti-static gloves when handling.
• Ensure all workstations, tools, and equipment are properly grounded.

6. Application Information

6.1 Intended Use

This LED is designed for use in standard electronic equipment, including office automation devices, communication equipment, and household appliances. Its side-emitting profile makes it suitable for applications requiring edge-lighting or status indication on the side of a PCB.

6.2 Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to the recommended 20mA (or lower) for continuous operation. Exceeding the absolute maximum ratings will degrade performance and shorten lifespan.
• Thermal Management: While the power dissipation is low, ensuring adequate PCB copper area or thermal vias can help manage heat, especially in high ambient temperature environments or when driven near maximum ratings.
• Polarity: Observe the correct anode/cathode orientation as indicated in the mechanical drawings to ensure proper operation.

7. Technical Deep Dive

7.1 AlInGaP Technology

The use of an AlInGaP chip is a key factor in this LED's performance. AlInGaP materials are known for their high efficiency in the red, orange, amber, and yellow wavelength regions compared to older technologies like GaAsP. This results in higher luminous intensity and better color stability over drive current and temperature variations.

7.2 Performance Curve Analysis

Typical performance curves (not fully detailed in the provided excerpt but standard for such datasheets) would include:

• Relative Luminous Intensity vs. Forward Current (I_F): Shows how light output increases with current, typically in a sub-linear fashion, highlighting the importance of current regulation.
• Forward Voltage vs. Forward Current (V_F-I_F): Demonstrates the diode's exponential I-V characteristic.
• Relative Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as junction temperature rises, a critical consideration for thermal design.
• Spectral Distribution: A graph showing the relative radiant power across wavelengths, centered around the 588 nm peak with a 15 nm half-width.

8. Frequently Asked Questions (FAQs)

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the wavelength at which the emitted optical power is maximum. Dominant wavelength (λd) is the single wavelength perceived by the human eye that matches the color of the LED, calculated from the CIE chromaticity coordinates. For a monochromatic source like this yellow LED, they are often very close, as seen here (588 nm vs. 587 nm).

Q: Can I drive this LED without a current-limiting resistor?
A: No. An LED is a current-driven device. Connecting it directly to a voltage source will cause excessive current to flow, potentially exceeding the maximum ratings and destroying the device. Always use an appropriate series resistor or constant-current driver.

Q: Why is the storage condition for opened packages stricter (60% RH vs. 90% RH)?
A> Once the moisture-barrier bag is opened, the components are exposed to ambient humidity. The stricter limit (60% RH) helps prevent the absorption of excessive moisture, which can cause internal delamination or cracking during the high-temperature reflow soldering process (known as "popcorning").

Q: What does "side-looking" mean?
A> Unlike top-emitting LEDs where light exits perpendicular to the PCB, a side-looking LED emits light parallel to the PCB surface. This is useful for lighting edges, slots, or providing status indicators on the side of a device.