SMD LED LTST-M140TGKT Datasheet - 3.2x1.6x1.2mm - 3.8V Max - 80mW - Green Water Clear Lens - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-M140TGKT, a surface-mount device (SMD) light-emitting diode (LED). This component is designed for automated printed circuit board (PCB) assembly processes and is suitable for applications where space is a critical constraint. The LED features a water-clear lens encapsulating an InGaN (Indium Gallium Nitride) semiconductor chip that emits green light.

The primary design goals for this LED family include compatibility with high-volume manufacturing, reliability under standard operating conditions, and consistent optical performance. These LEDs are engineered to meet the requirements of modern electronic equipment, offering a balance of size, performance, and cost-effectiveness for indicator and lighting functions.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged in industry-standard 12mm tape on 7-inch diameter reels for automated pick-and-place equipment.
• EIA (Electronic Industries Alliance) standard package outline.
• Input/output characteristics are compatible with standard integrated circuit (IC) logic levels.
• Designed for compatibility with automatic placement and assembly systems.
• Withstands infrared (IR) reflow soldering processes commonly used in surface-mount technology (SMT).
• Preconditioned to JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3, indicating a floor life of 168 hours at <30°C/60% RH after the bag is opened.

1.2 Applications

This LED is intended for use as a status indicator, backlight, or signal source in a wide range of electronic products. Typical application areas include:

• Telecommunication equipment (e.g., routers, switches, phones).
• Office automation devices (e.g., printers, scanners, multifunction devices).
• Home appliances and consumer electronics.
• Industrial control panels and equipment.
• Front panel backlighting for displays and buttons.
• Symbolic or informational luminaires in indoor settings.

2. Package Dimensions and Mechanical Information

The LTST-M140TGKT utilizes a standard SMD LED package. The lens color is specified as \"Water Clear,\" and the light source color is Green, produced by the InGaN chip.

Key Mechanical Notes:

• All linear dimensions provided in the package drawing are in millimeters (mm).
• The default dimensional tolerance is ±0.2 mm (±0.008 inches) unless a specific note on the drawing indicates otherwise.
• The package is designed for stability during the reflow soldering process and for reliable optical performance over the product's lifetime.

3. Ratings and Characteristics

All specifications are defined at an ambient temperature (Ta) of 25°C unless otherwise stated. Exceeding Absolute Maximum Ratings may cause permanent damage to the device.

3.1 Absolute Maximum Ratings

• Power Dissipation (Pd): 80 mW
• Peak Forward Current (I_F(PEAK)): 100 mA (Maximum permissible under pulsed conditions with a 1/10 duty cycle and 0.1ms pulse width).
• Continuous Forward Current (I_F): 20 mA (DC).
• Operating Temperature Range (T_opr): -40°C to +85°C.
• Storage Temperature Range (T_stg): -40°C to +100°C.

3.2 Suggested IR Reflow Profile for Lead-Free Process

The component is qualified for lead-free soldering processes. The recommended reflow profile conforms to the J-STD-020B standard. Key parameters of this profile include controlled pre-heat, a defined time above liquidus, and a peak temperature not exceeding 260°C. The specific ramp rates, soak times, and cooling rates must be optimized for the specific PCB assembly, but the profile ensures the LED package integrity is maintained during soldering.

3.3 Electrical and Optical Characteristics

Typical performance is measured at I_F = 20 mA, Ta = 25°C.

• Luminous Flux (Φ_v): 0.84 lm (Min), 2.70 lm (Max). Measured with a sensor/filter approximating the CIE photopic eye-response curve.
• Luminous Intensity (I_v): 280 mcd (Min), 900 mcd (Max). This is a derived value from luminous flux for reference; the primary optical specification is luminous flux.
• Viewing Angle (2θ_1/2): 120 degrees (Typical). Defined as the full angle at which intensity is half the peak axial intensity.
• Peak Emission Wavelength (λ_P): 518 nm (Typical). The wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): 520 nm to 535 nm. The single wavelength perceived by the human eye that defines the color. Tolerance is ±1 nm within its bin.
• Spectral Line Half-Width (Δλ): 35 nm (Typical). The spectral width at 50% of the peak intensity.
• Forward Voltage (V_F): 2.8 V (Min), 3.8 V (Max) at 20mA. Tolerance for a specific bin is ±0.1V.
• Reverse Current (I_R): 10 μA (Max) at V_R = 5V. The device is not designed for operation in reverse bias; this test is for quality verification only.

Important Measurement Notes:

1. Luminous flux is the primary photometric quantity. Luminous intensity (mcd) is provided for reference based on standard measurement conditions.
2. The viewing angle is defined by the half-intensity points.
3. Dominant wavelength is derived from CIE chromaticity coordinates.
4. Reverse voltage testing is for internal quality assurance; the LED should not be subjected to reverse bias in application circuits.

4. Bin Rank System

To ensure color and brightness consistency in production, LEDs are sorted into bins based on key parameters. This allows designers to select the appropriate bin for their application's requirements.

4.1 Forward Voltage (V_F) Rank

Binning at I_F = 20 mA for Green color.
Bin Code D7: 2.8V - 3.0V
Bin Code D8: 3.0V - 3.2V
Bin Code D9: 3.2V - 3.4V
Bin Code D10: 3.4V - 3.6V
Bin Code D11: 3.6V - 3.8V
Tolerance within each bin: ±0.1V.

4.2 Luminous Flux / Intensity Rank

Binning at I_F = 20 mA for Green color. Luminous Intensity is for reference.
Bin Code E1: 0.84 lm - 1.07 lm (280 mcd - 355 mcd)
Bin Code E2: 1.07 lm - 1.35 lm (355 mcd - 450 mcd)
Bin Code F1: 1.35 lm - 1.68 lm (450 mcd - 560 mcd)
Bin Code F2: 1.68 lm - 2.13 lm (560 mcd - 710 mcd)
Bin Code G1: 2.13 lm - 2.70 lm (710 mcd - 900 mcd)
Tolerance on each luminous intensity bin: ±11%.

4.3 Hue (Dominant Wavelength) Rank

Binning at I_F = 20 mA for Green color.
Bin Code AP: 520.0 nm - 525.0 nm
Bin Code AQ: 525.0 nm - 530.0 nm
Bin Code AR: 530.0 nm - 535.0 nm
Tolerance within each bin: ±1 nm.

5. Typical Performance Curves

Graphical representations of key characteristics are provided to aid in design. These curves are typical and based on testing at 25°C ambient temperature.

• Relative Luminous Intensity vs. Forward Current: Shows the non-linear relationship between drive current and light output.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the decrease in light output as junction temperature increases.
• Spectral Power Distribution: Depicts the relative radiant power as a function of wavelength, centered around 518 nm.
• Viewing Angle Pattern: A polar plot showing the angular distribution of luminous intensity.

These curves are essential for designing appropriate drive circuitry, managing thermal effects, and understanding the spatial light distribution for optical system design.

6. User Guide and Handling Instructions

6.1 Cleaning

Unspecified chemical cleaners should not be used as they may damage the LED package material (epoxy lens). If cleaning after soldering is necessary, the recommended method is to immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for a duration not exceeding one minute. Agitation should be gentle to avoid mechanical stress.

6.2 Recommended PCB Land Pattern

A suggested solder pad layout for infrared or vapor phase reflow soldering is provided. This pattern is designed to ensure reliable solder joint formation, proper self-alignment during reflow due to surface tension, and sufficient thermal relief. The dimensions balance solder volume, joint strength, and prevention of solder bridging.

6.3 Tape and Reel Packaging Specifications

The LEDs are supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178 mm) diameter reels. Detailed dimensions for the pocket size, tape width, pitch, and reel hub are specified to ensure compatibility with automated SMT equipment feeders. Standard reel quantity is 3000 pieces.

6.4 Reel and Packing Notes

• Empty pockets in the tape are sealed with the cover tape.
• Standard packing: 3000 pieces per 7-inch reel.
• A minimum order quantity (MOQ) of 500 pieces is available for remainder quantities.
• The packaging conforms to ANSI/EIA-481 specifications.
• A maximum of two consecutive missing components (empty pockets) is allowed per the tape specification.

7. Cautions and Application Notes

7.1 Intended Application

This LED is designed for use in standard commercial and industrial electronic equipment, including office automation, telecommunications, home appliances, and general indicator applications. It is not specifically designed or tested for applications where failure could lead to direct risk to life, health, or safety (e.g., aviation control, medical life-support, transportation safety systems). For such high-reliability applications, consultation with the component manufacturer for suitability assessment is mandatory.

7.2 Storage Conditions

Sealed Moisture Barrier Bag (MBB): Store at ≤30°C and ≤70% Relative Humidity (RH). The components have a shelf life of one year from the date code when stored in the original bag with desiccant.

After Bag Opening: The \"floor life\" at ≤30°C / ≤60% RH is 168 hours (JEDEC MSL 3). Components exposed beyond this time may absorb moisture, leading to potential \"popcorning\" or delamination during reflow soldering.

Extended Storage (Out of Bag): For storage beyond 168 hours, place components in a sealed container with fresh desiccant or in a nitrogen-purged desiccator.

Rebaking: Components that have exceeded the 168-hour floor life must be baked at approximately 60°C for at least 48 hours prior to soldering to remove absorbed moisture.

7.3 Soldering Recommendations

Reflow Soldering (Primary Method):
- Pre-heat Temperature: 150-200°C.
- Time Above Liquidus (Pre-heat time): 120 seconds maximum.
- Peak Body Temperature: 260°C maximum.
- Time at Peak Temperature: 10 seconds maximum.
- Maximum number of reflow cycles: Two.

Hand Soldering (Iron): Use only for repair or rework.
- Iron Tip Temperature: 300°C maximum.
- Soldering Time per lead: 3 seconds maximum.
- Maximum number of hand-soldering cycles: One.

Important Note: The optimal reflow profile depends on the specific PCB design, number of components, solder paste, and oven characteristics. The provided guidelines and JEDEC-based profile are starting points that must be validated for the actual production assembly line.

8. Design Considerations and Technical Analysis

8.1 Drive Circuit Design

The forward voltage (V_F) range of 2.8V to 3.8V at 20mA necessitates a constant-current drive circuit for stable light output, especially when multiple LEDs are used in series or when brightness consistency is critical. A simple series resistor can be used for single-LED, low-cost applications, but the current will vary with the specific V_F of the LED and the supply voltage. For example, with a 5V supply and a target of 20mA, the series resistor (R_S) would be calculated as R_S = (V_supply - V_F) / I_F. Using the maximum V_F of 3.8V gives R_S = (5 - 3.8) / 0.02 = 60Ω. Using the minimum V_F of 2.8V with the same resistor results in I_F = (5 - 2.8) / 60 ≈ 36.7mA, which exceeds the absolute maximum continuous current. Therefore, a regulated current source or careful resistor selection based on the worst-case V_F bin is advised.

8.2 Thermal Management

With a maximum power dissipation of 80mW (at 20mA and up to 3.8V), thermal management is important for maintaining longevity and stable light output. The luminous intensity decreases as the junction temperature rises, as shown in the characteristic curves. To minimize temperature rise:
1. Use the recommended PCB land pattern to provide adequate thermal conduction from the LED package to the board.
2. Consider using thermal vias in the PCB under the LED's thermal pad (if applicable) to conduct heat to inner layers or the opposite side of the board.
3. Avoid operating at the absolute maximum current for extended periods.
4. Ensure adequate airflow in the end-product enclosure if power dissipation is a concern in high-density layouts.

8.3 Optical Design Considerations

The 120-degree viewing angle and water-clear lens produce a wide, diffuse emission pattern suitable for status indicators that need to be visible from a broad range of angles. For applications requiring a more focused beam, secondary optics (e.g., lenses, light pipes) would be necessary. The dominant wavelength bins (AP, AQ, AR) allow for selection based on the desired shade of green, which can be important for color-coded indicators or aesthetic matching in backlighting arrays.

8.4 Comparison with Alternative Technologies

The use of InGaN technology for green LEDs offers advantages in efficiency and brightness compared to older technologies like Gallium Phosphide (GaP). InGaN LEDs typically have a narrower spectral bandwidth, resulting in a more saturated green color. The 120-degree viewing angle is a common standard, offering a good balance between wide visibility and forward intensity. For applications requiring an even wider field of view, diffused lens types or side-view packages might be considered.

8.5 Reliability and Lifespan Factors

LED lifespan is primarily affected by operating junction temperature and drive current. Operating well within the specified limits—for example, at 15-18mA instead of 20mA—can significantly extend operational life. Proper adherence to the soldering profile prevents thermal shock and package stress. Following the moisture sensitivity handling procedures (MSL 3) is critical to prevent latent failures caused by moisture-induced package cracking during reflow.