SMD LED LTST-S320KGKT Datasheet - Dimensions 3.2x1.6x1.2mm - Voltage 1.9-2.4V - Green Color - English Technical Document

1. Product Overview

This document details the specifications for a surface-mount device (SMD) LED lamp. This component is designed for automated printed circuit board (PCB) assembly and is suitable for applications where space is a critical constraint. The LED utilizes an ultra-bright AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor chip to produce green light, encapsulated in a water-clear lens package.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Features an ultra-bright AlInGaP green chip with tin-plated leads for improved solderability.
• Packaged in 8mm tape on 7-inch diameter reels, compatible with EIA (Electronic Industries Alliance) standard packaging.
• Integrated circuit (IC) compatible drive characteristics.
• Designed for compatibility with automated pick-and-place assembly equipment.
• Suitable for use with infrared (IR) reflow soldering processes.

1.2 Target Applications

This LED is intended for a broad range of electronic equipment, including but not limited to:

• Telecommunication devices (e.g., cordless and cellular phones).
• Office automation equipment and notebook computers.
• Home appliances and industrial control equipment.
• Network systems and indoor signboards.
• Specific functions include keypad/keyboard backlighting, status indicators, microdisplays, and signal/symbol illumination.

2. Package Dimensions

The LED is housed in a standard SMD package. The lens color is water clear, and the light source is an AlInGaP green chip. All dimensional tolerances are \u00b10.1 mm unless otherwise specified. The specific length, width, and height dimensions are provided in the detailed mechanical drawing within the original datasheet.

3. Ratings and Characteristics

3.1 Absolute Maximum Ratings

Ratings are specified at an ambient temperature (Ta) of 25\u00b0C. Exceeding these values may cause permanent damage.

• Power Dissipation (Pd): 62.5 mW
• Peak Forward Current (I_F(PEAK)): 60 mA (at 1/10 duty cycle, 0.1ms pulse width)
• DC Forward Current (I_F): 25 mA
• Reverse Voltage (V_R): 5 V
• Operating Temperature Range (T_opr): -30\u00b0C to +85\u00b0C
• Storage Temperature Range (T_stg): -40\u00b0C to +85\u00b0C
• Infrared Soldering Condition: 260\u00b0C peak temperature for a maximum of 10 seconds.

3.2 Suggested IR Reflow Profile (Pb-Free Process)

A recommended temperature profile for lead-free reflow soldering is provided, typically adhering to JEDEC standards. This profile includes pre-heat, soak, reflow, and cooling stages, with a critical peak temperature limit of 260\u00b0C.

3.3 Electrical and Optical Characteristics

Typical performance parameters are measured at Ta=25\u00b0C and I_F=20mA, unless noted.

• Luminous Intensity (I_V): 18.0 - 71.0 mcd (millicandela). Measured with a filter approximating the CIE photopic eye response.
• Viewing Angle (2\u03b8_1/2): 130 degrees. Defined as the full angle where intensity drops to half its axial value.
• Peak Emission Wavelength (\u03bb_P): 574 nm (typical).
• Dominant Wavelength (\u03bb_d): 567.5 - 576.5 nm. Derived from CIE chromaticity coordinates.
• Spectral Line Half-Width (\u0394\u03bb): 15 nm (typical).
• Forward Voltage (V_F): 1.90 - 2.40 V.
• Reverse Current (I_R): 10 \u03bcA (maximum) at V_R=5V.

Measurement Notes: Caution against Electrostatic Discharge (ESD) is emphasized. Proper grounding of personnel and equipment via wrist straps or anti-static gloves is recommended when handling the device.

4. Bin Rank System

The LEDs are sorted into bins based on key parameters to ensure consistency in application. Tolerances are applied to each bin.

4.1 Forward Voltage (V_F) Rank

Binned at I_F=20mA. Tolerance per bin is \u00b10.1V.

• Bin 4: 1.90V - 2.00V
• Bin 5: 2.00V - 2.10V
• Bin 6: 2.10V - 2.20V
• Bin 7: 2.20V - 2.30V
• Bin 8: 2.30V - 2.40V

4.2 Luminous Intensity (I_V) Rank

Binned at I_F=20mA. Tolerance per bin is \u00b115%.

• Bin M: 18.0 - 28.0 mcd
• Bin N: 28.0 - 45.0 mcd
• Bin P: 45.0 - 71.0 mcd

4.3 Dominant Wavelength (\u03bb_d) Rank

Binned at I_F=20mA. Tolerance per bin is \u00b11 nm.

• Bin C: 567.5 - 570.5 nm
• Bin D: 570.5 - 573.5 nm
• Bin E: 573.5 - 576.5 nm

5. Typical Performance Curves

The datasheet includes graphical representations of key characteristics to aid in design. These curves, typically plotted against forward current or ambient temperature, illustrate the relationships and trends for parameters such as:

• Relative Luminous Intensity vs. Forward Current (I_F)
• Forward Voltage (V_F) vs. Forward Current (I_F)
• Relative Luminous Intensity vs. Ambient Temperature (T_a)
• Peak Wavelength vs. Ambient Temperature (T_a)
• Spectral Radiation Distribution (showing the emission peak and half-width)

These curves are essential for understanding the device's behavior under different operating conditions and for performing accurate circuit design and thermal management.

6. User Guide for Assembly and Handling

6.1 Cleaning

Unspecified chemical cleaners should be avoided as they may damage the LED package. If cleaning is necessary, immersion in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is recommended.

6.2 Recommended PCB Pad Layout and Soldering Orientation

A suggested land pattern (footprint) for the PCB is provided to ensure proper solder joint formation and mechanical stability. The diagram also indicates the correct orientation of the LED (typically marked by a cathode indicator on the device) relative to the PCB pads.

6.3 Tape and Reel Packaging Specifications

The LEDs are supplied in embossed carrier tape wound onto 7-inch (178mm) diameter reels. Key specifications include:

• Tape width: 8 mm.
• Pocket pitch and dimensions for component housing.
• Cover tape sealing the pockets.
• Reel hub diameter, flange diameter, and overall dimensions.
• Standard packing quantity: 3000 pieces per reel.
• Minimum order quantity for remainder reels: 500 pieces.
• Compliance with ANSI/EIA-481 specifications.

7. Important Cautions and Application Notes

7.1 Intended Application Scope

This LED is designed for use in ordinary electronic equipment (e.g., office, communication, household). It is not intended for applications where failure could directly jeopardize life or health (e.g., aviation, medical life-support, critical safety systems) without prior consultation and specific qualification.

7.2 Storage Conditions

• Sealed Package: Store at \u2264 30\u00b0C and \u2264 90% Relative Humidity (RH). Use within one year when packed with desiccant.
• Opened Package: Store at \u2264 30\u00b0C and \u2264 60% RH. Components should be IR-reflowed within one week of opening (Moisture Sensitivity Level 3, MSL 3).
• Extended Storage (Opened): Store in a sealed container with desiccant or in a nitrogen desiccator.
• Rebaking: LEDs stored out of original packaging for >1 week should be baked at approximately 60\u00b0C for at least 20 hours before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

7.3 Soldering Process Guidelines

Detailed soldering parameters are provided to ensure reliable assembly:

Reflow Soldering (Recommended for Pb-Free):

• Pre-heat Temperature: 150\u00b0C \u2013 200\u00b0C
• Pre-heat Time: Maximum 120 seconds
• Peak Temperature: Maximum 260\u00b0C
• Time at Peak: Maximum 10 seconds (maximum two reflow cycles allowed)

Hand Soldering (Soldering Iron):

• Iron Tip Temperature: Maximum 300\u00b0C
• Soldering Time: Maximum 3 seconds per pad (one-time only)

Critical Note: The optimal reflow profile depends on the specific PCB design, components, solder paste, and oven. The provided profile is a JEDEC-compliant example. Board-level characterization is essential for a robust process. Component and board-level reliability testing should be conducted to validate the assembly process.

8. Design Considerations and Technical Analysis

8.1 Current Limiting and Drive Circuit

The forward voltage (V_F) range of 1.9V to 2.4V at 20mA must be considered when designing the drive circuit. A constant current source or a current-limiting resistor in series with a voltage source is mandatory to prevent exceeding the absolute maximum DC forward current of 25mA. The value of the current-limiting resistor (R_limit) can be calculated using Ohm's Law: R_limit = (V_supply - V_F) / I_F. Using the maximum V_F from the bin ensures the current does not exceed the desired level even with unit-to-unit variation.

8.2 Thermal Management

While the power dissipation is relatively low at 62.5 mW, proper thermal design is still important for longevity and stable light output. The derating of luminous intensity with increasing ambient temperature (as shown in the performance curves) must be factored into the application's brightness requirements. Ensuring adequate PCB copper area around the LED pads can help dissipate heat and maintain a lower junction temperature.

8.3 Optical Design for Uniform Illumination

The wide 130-degree viewing angle makes this LED suitable for applications requiring broad, diffuse illumination rather than a focused beam. For backlighting panels or indicators requiring more directional light, secondary optics (such as light guides or lenses) may be necessary. The water-clear lens provides minimal light diffusion from the package itself.

8.4 Wavelength Selection and Binning Impact

The dominant wavelength binning (C, D, E) allows designers to select LEDs for specific color requirements. For example, applications requiring a precise green hue for color matching or signaling would benefit from specifying a tighter wavelength bin. The typical peak at 574 nm and spectral width of 15 nm define the color purity of the emitted green light.

8.5 Comparison with Other LED Technologies

The use of AlInGaP material for green light offers advantages in certain aspects compared to other technologies like InGaN (used for blue and some green LEDs). AlInGaP LEDs traditionally exhibit high efficiency in the red to yellow-green spectrum and can offer good stability over temperature. The specific choice depends on the required wavelength, efficiency, cost, and application environment.

9. Application-Specific Guidance and Troubleshooting

9.1 Typical Application Circuit for Status Indication

A simple implementation involves connecting the LED in series with a current-limiting resistor to a microcontroller GPIO pin or a system voltage rail (e.g., 3.3V or 5V). The microcontroller can then toggle the pin to turn the indicator on or off. For 5V supply and a target I_F of 20mA, using a conservative V_F of 2.4V, the resistor value would be R = (5V - 2.4V) / 0.02A = 130 Ohms. A standard 130 or 150 Ohm resistor would be suitable.

9.2 Common Issues and Solutions

• Dim or No Light: Check polarity (reverse connection). Verify forward voltage of the specific LED bin matches the driving circuit calculation. Measure actual current flow with a multimeter.
• Inconsistent Brightness Across Multiple LEDs: This is often due to forward voltage (V_F) variation when LEDs are connected in parallel without individual current limiting. Use separate resistors for each LED or implement a constant current driver array.
• LED Failure After Soldering: Likely caused by excessive heat during hand soldering (>300\u00b0C or >3s) or improper reflow profile (exceeding 260\u00b0C peak). Verify process parameters and ensure MSL handling rules were followed if the package was exposed to humidity.
• ESD Damage: Failure may occur immediately or manifest as degraded performance over time. Always follow ESD precautions during handling and assembly.

10. Operational Principles and Technology Trends

10.1 Basic Operating Principle

Light is produced through electroluminescence in the AlInGaP semiconductor chip. When a forward voltage exceeding the diode's junction potential is applied, electrons and holes are injected into the active region where they recombine. The energy released during this recombination is emitted as photons (light). The specific composition of the Aluminum, Indium, Gallium, and Phosphide layers determines the bandgap energy and thus the wavelength (color) of the emitted light, in this case, green.

10.2 Industry Trends

The general trend in SMD LEDs is toward higher luminous efficacy (more light output per watt of electrical input), improved color consistency through tighter binning, and increased reliability under higher temperature and current conditions. Packaging continues to evolve for better thermal performance and optical control. Furthermore, there is a continuous drive for miniaturization while maintaining or increasing light output, as well as integration with driver electronics for \"smart\" lighting solutions. The use of robust, lead-free soldering compatible materials and processes remains a standard requirement globally.