SMD LED LTST-E682TBTGWT Datasheet - Dual Color (Green/Blue) - 20mA - 76mW - English Technical Document

1. Product Overview

This document details the specifications for a dual-color Surface-Mount Device (SMD) LED. The component is designed for automated printed circuit board (PCB) assembly and is suitable for space-constrained applications. It features a diffused lens and contains two distinct LED chips within a single package: one emitting blue light and the other emitting green light.

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 assembly.
• Standard EIA (Electronic Industries Alliance) package outline.
• Integrated Circuit (IC) compatible drive levels.
• Fully compatible with standard automatic placement equipment.
• Suitable for use with infrared (IR) reflow soldering processes.
• Preconditioned to JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3.

1.2 Applications

This LED is intended for a broad range of electronic equipment where compact size and reliable performance are required. Typical application areas include:

• Telecommunication devices (e.g., cordless phones, cellular phones).
• Office automation equipment (e.g., notebook computers, network systems).
• Home appliances and consumer electronics.
• Industrial control and instrumentation panels.
• Status and power indicators.
• Signal and symbol illumination (e.g., backlit buttons, icons).
• Front panel backlighting.

2. Package Dimensions and Pin Assignment

The LED is housed in a compact SMD package. Detailed mechanical drawings with dimensions in millimeters (and inches) are provided in the source document. The tolerance for most dimensions is ±0.2 mm (±0.008").

Pin Assignment:

• Blue LED Chip: Connected to pins 1 and 2.
• Green LED Chip: Connected to pins 3 and 4.

This independent pin configuration allows for separate control of the two colors, enabling static or dynamic color indication.

3. Ratings and Characteristics

3.1 Absolute Maximum Ratings

Ratings are specified at an ambient temperature (Ta) of 25°C. Exceeding these values may cause permanent damage.

• Power Dissipation (Pd): 76 mW (for both Blue and Green).
• Peak Forward Current (I_F(peak)): 80 mA (at 1/10 duty cycle, 0.1ms pulse width).
• Continuous DC Forward Current (I_F): 20 mA.
• Operating Temperature Range: -40°C to +100°C.
• Storage Temperature Range: -40°C to +100°C.

3.2 Electrical and Optical Characteristics

Typical performance parameters are measured at Ta=25°C with a forward current (I_F) of 20mA, unless otherwise noted.

Optical Characteristics:

• Luminous Intensity (I_V):
  • Blue: Minimum 210 mcd, Typical, Maximum 475 mcd.
  • Green: Minimum 850 mcd, Typical, Maximum 1860 mcd.
• Viewing Angle (2θ_1/2): Typically 120 degrees for both colors. This wide viewing angle is characteristic of a diffused lens, providing a more uniform light distribution.
• Peak Emission Wavelength (λ_P):
  • Blue: Typically 468 nm.
  • Green: Typically 518 nm.
• Dominant Wavelength (λ_d):
  • Blue: Range from 460 nm to 475 nm.
  • Green: Range from 515 nm to 530 nm.
• Spectral Line Half-Width (Δλ):
  • Blue: Typically 25 nm.
  • Green: Typically 35 nm.

Electrical Characteristics:

• Forward Voltage (V_F):
  • Blue: Range from 2.8 V to 3.8 V.
  • Green: Range from 2.8 V to 3.8 V.
• Reverse Current (I_R): Maximum 10 μA at a reverse voltage (V_R) of 5V. Note: The device is not designed for operation in reverse bias; this parameter is for test purposes only.

4. Binning System

To ensure consistency in production, LEDs are sorted into bins based on key optical parameters. This allows designers to select parts that meet specific color and brightness requirements for their application.

4.1 Luminous Intensity (I_V) Binning

LEDs are categorized by their measured luminous intensity at 20mA.

Blue LED Bins:

• S2: 210 - 275 mcd
• T1: 275 - 360 mcd
• T2: 360 - 475 mcd

Green LED Bins:

• V1: 850 - 1100 mcd
• V2: 1100 - 1430 mcd
• W1: 1430 - 1860 mcd

Tolerance for each intensity bin is ±11%.

4.2 Dominant Wavelength (λ_d) Binning

LEDs are also sorted by their dominant wavelength, which defines the perceived color.

Blue LED Wavelength Bins:

• AB1: 460 - 465 nm
• AB2: 465 - 470 nm
• AB3: 470 - 475 nm

Green LED Wavelength Bins:

• AG1: 515 - 520 nm
• AG2: 520 - 525 nm
• AG3: 525 - 530 nm

Tolerance for each wavelength bin is ±1 nm.

4.3 Combined Bin Code

A cross-reference table is provided that combines both intensity and wavelength bins into a single alphanumeric code (e.g., A1, C4). This code is typically marked on the product packaging or reel tag, allowing for precise identification of the LED's performance characteristics.

5. Soldering and Assembly Guidelines

5.1 Reflow Soldering Profile

A recommended infrared (IR) reflow soldering profile is provided for lead-free (Pb-free) solder processes, in accordance with the J-STD-020B standard. Key parameters of this profile include:

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus: As per the provided profile curve.
• Total Soldering Time: Maximum 10 seconds at peak temperature. Reflow should be performed a maximum of two times.

For hand soldering with an iron, the tip temperature should not exceed 300°C, and contact time should be limited to a maximum of 3 seconds, for one time only.

5.2 Recommended PCB Pad Layout

A suggested land pattern (footprint) for the PCB is illustrated to ensure proper solder joint formation and mechanical stability during and after the reflow process. Adhering to this recommended layout helps prevent tombstoning and ensures good thermal and electrical connection.

5.3 Cleaning

If cleaning after soldering is necessary, only specified solvents should be used. The LED can be immersed in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. The use of unspecified chemicals may damage the LED package or lens.

6. Packaging Information

The LEDs are supplied in a tape-and-reel format compatible with high-speed automated assembly equipment.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 2000 pieces.
• Minimum Order Quantity (MOQ) for Remainders: 500 pieces.
• The packaging conforms to ANSI/EIA-481 specifications. Empty pockets in the tape are sealed with a cover tape.

7. Handling and Storage Cautions

7.1 Moisture Sensitivity

This LED is rated at Moisture Sensitivity Level (MSL) 3. As a moisture-sensitive device, proper handling is critical to prevent "popcorning" or delamination during reflow soldering.

• Sealed Package: LEDs in the original, unopened moisture-barrier bag (with desiccant) should be stored at ≤30°C and ≤70% Relative Humidity (RH). The recommended "floor life" from the bag seal date is one year.
• Opened Package: Once the bag is opened, the LEDs must be used within 168 hours (7 days) if the ambient storage conditions do not exceed 30°C / 60% RH.
• Extended Storage (Out of Bag): For storage beyond 168 hours, LEDs should be kept in a sealed container with desiccant or in a nitrogen desiccator.
• Rebaking: Components that have been exposed beyond the 168-hour limit must be baked at approximately 60°C for at least 48 hours before being subjected to reflow soldering to remove absorbed moisture.

7.2 Application Notes

This product is designed for use in standard commercial and industrial electronic equipment. For applications requiring exceptional reliability or where failure could risk safety (e.g., aviation, medical life-support, transportation controls), specific qualification and consultation with the manufacturer are necessary prior to design-in.

8. Design Considerations and Typical Performance Curves

The source document includes several characteristic curves that are essential for circuit design and understanding performance under varying conditions. These typically include:

• Forward Current vs. Forward Voltage (I_F-V_F): Shows the relationship between drive current and the voltage drop across the LED. This is crucial for designing the current-limiting circuitry.
• Luminous Intensity vs. Forward Current (I_V-I_F): Illustrates how light output increases with drive current. It helps determine the operating point for desired brightness.
• Luminous Intensity vs. Ambient Temperature (I_V-T_a): Demonstrates the derating of light output as the ambient temperature rises. This is important for applications operating in high-temperature environments.
• Spectral Distribution: A graph showing the relative light intensity across different wavelengths, centered around the peak wavelength. This defines the color purity of the LED.

When designing a driver circuit, the forward voltage (V_F) range and the recommended 20mA DC forward current must be considered. A constant-current driver is generally preferred over a constant-voltage driver with a series resistor for better stability and longevity, especially when operating over a wide temperature range or when precise brightness control is needed. The independent pins for the blue and green chips allow for flexible control schemes, such as alternating blinking, mixed colors (if driven simultaneously at different intensities), or individual status indications.

9. Comparison and Selection Guidance

The key differentiator of this component is the integration of two distinct LED colors (blue and green) in one compact SMD package. This offers significant space savings on the PCB compared to using two separate single-color LEDs. The wide 120-degree viewing angle provided by the diffused lens makes it suitable for applications where the indicator needs to be visible from a broad range of perspectives.

When selecting a bin code, designers must balance cost and performance. Tighter bins (e.g., specific wavelength and high brightness) may command a premium but ensure visual consistency in end products, which is critical for multi-unit displays or status panels. The provided binning system allows for precise selection to match application requirements for both color and luminous intensity.

10. Common Questions Based on Technical Parameters

Q: Can I drive the blue and green LEDs simultaneously?
A: Yes, since they have independent pins (1,2 for blue; 3,4 for green), you can drive them independently or simultaneously. Ensure the total power dissipation for the package is not exceeded if both are on at full current.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P) is the wavelength at which the emitted optical power is maximum. Dominant Wavelength (λ_d) is the single wavelength perceived by the human eye that matches the color of the LED. λ_d is more relevant for color specification in visual applications.

Q: Why is the reverse current (I_R) specified if the device is not for reverse operation?
A: The I_R specification is a quality and leakage test parameter. It ensures the LED chip and package have proper isolation. In circuit design, precautions (like a parallel protection diode) should be taken to avoid exposing the LED to reverse voltage.

Q: How critical is it to follow the 168-hour floor life after opening the bag?
A: It is very important for reliability. Moisture absorbed by the plastic package can vaporize rapidly during the high-temperature reflow soldering process, causing internal cracks or delamination ("popcorning"). Following the MSL 3 handling guidelines is essential to prevent solder joint failures.