SMD LED LTST-E143EGSW Datasheet - SMD Package - Red/Green/Yellow - 20mA - English Technical Document

1. Product Overview

The LTST-E143EGSW is a surface-mount device (SMD) LED designed for automated printed circuit board (PCB) assembly. Its miniature size makes it suitable for space-constrained applications across a broad spectrum of electronic equipment.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged in 8mm tape on 7-inch diameter reels for automated pick-and-place processes.
• Standard EIA (Electronic Industries Alliance) package footprint.
• IC (Integrated Circuit) compatible drive levels.
• Designed for compatibility with automatic placement equipment.
• Suitable for infrared (IR) reflow soldering processes.
• Preconditioned to accelerate to JEDEC (Joint Electron Device Engineering Council) moisture sensitivity Level 3.

1.2 Applications

This LED is intended for use as a status indicator, signal luminary, symbol illumination, and front panel backlighting in various sectors, including:

• Telecommunication equipment
• Office automation devices
• Home appliances
• Industrial equipment

2. Package Dimensions and Configuration

The device features a standard SMD package. All dimensions are provided in millimeters, with a general tolerance of ±0.2 mm unless otherwise specified. The LED utilizes a diffused lens.

The pin assignment and corresponding light source colors are as follows:

• Red (AlInGaP): Pins 2 (Anode) and 1 (Cathode)
• Green (InGaN): Pins 2 (Anode) and 4 (Cathode)
• Yellow (AlInGaP): Pins 2 (Anode) and 3 (Cathode)

Pin 2 is the common anode for all color variants.

3. Ratings and Characteristics

All specifications are defined at an ambient temperature (Ta) of 25°C.

3.1 Absolute Maximum Ratings

Stresses beyond these limits may cause permanent damage.

• Power Dissipation (Pd): Red: 75 mW, Green: 76 mW, Yellow: 72 mW
• Peak Forward Current (I_F(peak)): 80 mA (for all colors, at 1/10 duty cycle, 0.1ms pulse width)
• DC Forward Current (I_F): Red: 30 mA, Green: 20 mA, Yellow: 30 mA
• Operating Temperature Range: -40°C to +100°C
• Storage Temperature Range: -40°C to +100°C

3.2 Thermal Characteristics

• Maximum Junction Temperature (T_j): 125°C
• Typical Thermal Resistance, Junction to Ambient (R_θJA): 100 °C/W (Note: Measured on FR4 substrate, 1.6mm thick, with 16mm² copper pad).
• Typical Thermal Resistance, Junction to Solder Pad (R_θJT): 60 °C/W

3.3 Suggested IR Reflow Profile

A lead-free soldering profile compliant with J-STD-020B is recommended. The profile typically includes preheat, soak, reflow (with peak temperature), and cooling stages to ensure reliable solder joints without damaging the LED package.

3.4 Electrical and Optical Characteristics

Measured at I_F = 20mA and Ta=25°C.

• Luminous Intensity (I_v):
  • Red: 140-350 mcd (min-max)
  • Green: 710-1540 mcd (min-max)
  • Yellow: 140-390 mcd (min-max)
• Viewing Angle (2θ_1/2): 120 degrees (typical). This is the full angle at which intensity is half the on-axis value.
• Dominant Wavelength (λ_d):
  • Red: 615-630 nm
  • Green: 518-528 nm
  • Yellow: 586-596 nm
• Forward Voltage (V_F):
  • Red: 1.7-2.5 V
  • Green: 2.8-3.8 V
  • Yellow: 1.7-2.5 V
• Spectral Line Half-Width (Δλ): Red/Yellow: 15 nm (typ), Green: 25 nm (typ).
• Reverse Current (I_R): 10 μA (max) at V_R = 5V. Note: The device is not designed for reverse bias operation; this parameter is for test purposes only.

4. Binning System

The LEDs are sorted (binned) based on key optical parameters to ensure consistency within a production lot.

4.1 Luminous Intensity (I_v) Binning

Intensity is measured in millicandelas (mcd) at 20mA. Tolerance within each bin is ±11%.

• Red: R1 (140-190 mcd), R2 (190-260 mcd), R3 (260-350 mcd)
• Green: G1 (710-910 mcd), G2 (910-1185 mcd), G3 (1185-1540 mcd)
• Yellow: Y1 (140-180 mcd), Y2 (180-230 mcd), Y3 (230-300 mcd), Y4 (300-390 mcd)

4.2 Dominant Wavelength (λ_d) Binning

Wavelength is measured in nanometers (nm) at 20mA. Tolerance within each bin is ±1 nm.

• Red: RA (615-630 nm)
• Green: GA (518-523 nm), GB (523-528 nm)
• Yellow: YA (586-591 nm), YB (591-596 nm)

4.3 Combined Bin Code on Product Tag

A single alphanumeric code on the product tag combines the intensity and wavelength bins. For example, code "A1" corresponds to Red=R1, Green=G1, Yellow=Y1. Codes D1-D4 represent the wavelength bins (Wd Rank) independently. This system allows precise identification of the LED's optical performance.

5. Typical Performance Curves

The datasheet includes graphical representations of key relationships (at 25°C unless noted):

• Relative Luminous Intensity vs. Forward Current: Shows how light output increases with current, typically in a non-linear fashion, highlighting the importance of constant current drive.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic, crucial for designing the current-limiting circuitry.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal quenching effect, where light output decreases as junction temperature rises. This is critical for thermal management in high-power or high-ambient-temperature applications.
• Spectral Distribution: Shows the relative power emitted across wavelengths, defining the color purity and helping in applications requiring specific spectral characteristics.

6. User Guide and Assembly Information

6.1 Cleaning

If cleaning is necessary post-solder or during rework, immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. Avoid using unspecified chemical cleaners as they may damage the epoxy lens or package.

6.2 Recommended PCB Pad Layout

A recommended land pattern (footprint) is provided to ensure proper soldering, mechanical stability, and optimal thermal performance. Adhering to this layout helps prevent tombstoning and ensures good solder fillets.

6.3 Tape and Reel Packaging

The LEDs are supplied in embossed carrier tape (8mm width) wound onto 7-inch (178mm) diameter reels. The tape pocket dimensions and reel specifications (hub diameter, flange diameter, etc.) are detailed, conforming to ANSI/EIA-481 standards. This packaging is essential for automated assembly lines.

• Standard reel contains 4000 pieces.
• Minimum order quantity for remnants is 500 pieces.
• A maximum of two consecutive missing components (empty pockets) is allowed per reel.

7. Application Cautions and Design Considerations

7.1 Intended Use and Reliability

These LEDs are designed for general-purpose electronic equipment. For applications where exceptional reliability is paramount, or where failure could risk safety (e.g., aviation, medical life-support, transportation control), a specific reliability assessment and consultation with the manufacturer is strongly advised prior to design-in.

7.2 Electrical Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to the specified maximum DC value (20mA for Green, 30mA for Red/Yellow). Exceeding this will reduce lifespan and can cause catastrophic failure.
• Reverse Voltage Protection: The LED has a very low reverse breakdown voltage (5V test condition). Circuits should be designed to prevent the application of any reverse bias, potentially using a protection diode in parallel if the LED is connected to a bipolar signal.
• Thermal Management: While power dissipation is low, the junction temperature must be kept below 125°C. Ensure adequate copper area on the PCB (as per the recommended pad) to act as a heat sink, especially in high ambient temperature environments or when driving at higher currents.

7.3 Optical Design Considerations

• Viewing Angle: The 120-degree viewing angle provides a wide, diffuse illumination pattern suitable for status indicators. For more focused light, secondary optics (lenses) would be required.
• Binning for Color Consistency: For applications requiring uniform color appearance across multiple LEDs (e.g., backlighting an array), specifying tight wavelength bins (e.g., GA or GB for green) is necessary.
• Intensity Matching: Similarly, specifying a narrow intensity bin ensures consistent brightness across all indicators in a product.

8. Technical Comparison and Selection Guidance

The LTST-E143EGSW offers a combination of features common in modern SMD LEDs: RoHS compliance, IR reflow compatibility, and tape-and-reel packaging. Its key differentiators lie in its specific binning structure for green and yellow, offering finer granularity in wavelength and intensity selection compared to some generic parts. The separate cathode pins for each color in a 4-pin package allow for individual control in a multi-color module, unlike some common anode RGB packages. When selecting an LED, engineers must cross-reference the forward voltage (especially the higher V_F of the green InGaN die), viewing angle, and luminous intensity against the application's power budget, optical layout, and required brightness.

9. Frequently Asked Questions (FAQ)

Q: Can I drive the Green LED at 30mA like the Red and Yellow ones?

A: No. The Absolute Maximum Rating for DC forward current on the Green variant is 20mA. Exceeding this rating may cause permanent damage and void warranties.

Q: What does "JEDEC Level 3" preconditioning mean?

A: It means the components have been baked and/or stored under controlled conditions to reduce moisture absorption in the package, making them suitable for a floor life of 168 hours (7 days) at factory conditions (<30°C/60%RH) before they require rebaking for reflow soldering.

Q: Why is the forward voltage range for the Green LED (2.8-3.8V) higher than for Red/Yellow (1.7-2.5V)?

A> This is due to the fundamental semiconductor material. Green LEDs typically use Indium Gallium Nitride (InGaN), which has a wider bandgap than the Aluminum Indium Gallium Phosphide (AlInGaP) used for Red and Yellow LEDs. A wider bandgap requires a higher voltage to energize electrons across it.

Q: How do I interpret the bin code "B5" from the tag?

A: According to the cross-table, "B5" indicates: Red Intensity Bin = R2 (190-260 mcd), Green Intensity Bin = G2 (910-1185 mcd), and Yellow Intensity Bin = Y1 (140-180 mcd). The wavelength bin would be indicated by a separate "D" code (e.g., D1, D2, etc.).

10. Design-in Example: Status Indicator Panel

Scenario: Designing a control panel with three status LEDs: Red (Fault), Green (Ready), Yellow (Standby). Uniform high brightness is required.

Design Steps:

1. Selection: Choose the LTST-E143EGSW for its common package and availability in all three colors.
2. Binning: Specify intensity bin R3 for Red, G3 for Green, and Y4 for Yellow to get the highest brightness from each. Specify wavelength bin RA for Red, GB for Green, and YB for Yellow for consistent, saturated colors.
3. Circuit Design:
   • Supply Voltage (V_cc): 5V.
   • Calculate series resistors for I_F = 20mA (use 20mA for Green, can use 20-30mA for Red/Yellow based on desired brightness).
     • Red Resistor (using typical V_F=2.1V): R = (5V - 2.1V) / 0.020A = 145 Ω. Use 150 Ω standard value.
     • Green Resistor (using typical V_F=3.3V): R = (5V - 3.3V) / 0.020A = 85 Ω. Use 82 Ω or 91 Ω standard value.
     • Yellow Resistor (using typical V_F=2.1V): Same as Red, 150 Ω.
   • Power per LED: P = V_F * I_F. For Green: ~66mW, which is within the 76mW maximum.
4. PCB Layout: Use the recommended pad layout. Connect Pin 2 (common anode) to V_cc via the resistors. Connect Pins 1, 4, and 3 (cathodes for Red, Green, Yellow respectively) to ground via microcontroller pins or switches for individual control.
5. Thermal Check: With power dissipation under 75mW per LED and a 16mm² pad, junction temperature rise will be minimal in a typical indoor environment, ensuring long-term reliability.