SMD LED LTST-010KGKT Datasheet - 3.0x1.5x1.1mm - 2.4V Max - 72mW - Water Clear AlInGaP Green - English Technical Document

1. Product Overview

The LTST-010KGKT is a surface-mount device (SMD) light-emitting diode (LED) designed for automated printed circuit board (PCB) assembly. Its miniature footprint makes it suitable for space-constrained applications across a wide range of consumer and industrial electronics.

1.1 Core Advantages

• Miniature Size: The compact package allows for high-density PCB layouts.
• Automation Compatibility: Packaged in 12mm tape on 7-inch reels, it is fully compatible with standard pick-and-place and automated assembly equipment.
• Process Compatibility: Designed to withstand infrared (IR) reflow soldering processes, aligning with modern lead-free (Pb-free) manufacturing standards.
• Material Compliance: The product meets RoHS (Restriction of Hazardous Substances) directives.
• Wide Viewing Angle: Features a typical 110-degree viewing angle (2θ1/2), providing broad light distribution.

1.2 Target Market & Applications

This LED is intended for use as a status indicator, backlighting element, or signal luminary in various electronic equipment. Primary application areas include:

• Telecommunication devices (e.g., cordless/cellular phones)
• Portable computing (e.g., notebook computers)
• Network systems and home appliances
• Industrial control panels and indoor signage
• Office automation equipment

2. In-Depth Technical Parameter Analysis

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

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Power Dissipation (Pd): 72 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
• Operating Temperature Range: -40°C to +85°C
• Storage Temperature Range: -40°C to +100°C

2.2 Electro-Optical Characteristics

These are the typical performance parameters under standard test conditions (IF = 20mA).

• Luminous Intensity (Iv): Minimum 56 mcd, typical values vary by bin, maximum 180 mcd. Measured using a sensor filtered to the CIE photopic eye-response curve.
• Forward Voltage (VF): Ranges from 1.8V (Min) to 2.4V (Max). Typical value depends on the forward voltage bin (D2, D3, D4).
• Peak Wavelength (λP): Approximately 570 nm.
• Dominant Wavelength (λd): Typically 571 nm, with specific bins defined from 564.5 nm to 576.5 nm.
• Spectral Bandwidth (Δλ): Approximately 15 nm (half-width).
• Reverse Current (IR): Maximum 10 μA at a reverse voltage (VR) of 5V. Note: This LED is not designed for reverse bias operation; this parameter is for test purposes only.

3. Bin Ranking System Explanation

The product is sorted into performance bins to ensure consistency in applications. Designers can specify bins to match their requirements for brightness, color, and voltage drop.

3.1 Luminous Intensity (Iv) Rank

Binning ensures a predictable minimum brightness. Units are millicandelas (mcd) at 20mA.

• P2: 56 – 71 mcd
• Q1: 71 – 90 mcd
• Q2: 90 – 112 mcd
• R1: 112 – 140 mcd
• R2: 140 – 180 mcd

Tolerance within each bin is ±11%.

3.2 Forward Voltage (VF) Rank

Voltage binning aids in designing current-limiting circuits and predicting power consumption. Units are Volts (V) at 20mA.

• D2: 1.8 – 2.0 V
• D3: 2.0 – 2.2 V
• D4: 2.2 – 2.4 V

Tolerance within each bin is ±0.1V.

3.3 Hue / Dominant Wavelength (λd) Rank

This binning controls the perceived color of the green light. Units are nanometers (nm) at 20mA.

• B: 564.5 – 567.5 nm
• C: 567.5 – 570.5 nm
• D: 570.5 – 573.5 nm
• E: 573.5 – 576.5 nm

Tolerance within each bin is ±1 nm.

4. Performance Curve Analysis

Typical characteristic curves provide insight into device behavior under varying conditions. These are essential for robust circuit design.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

The I-V curve exhibits the typical exponential relationship of a diode. The forward voltage (VF) increases with current (IF) and is also temperature-dependent. Designers must use this curve to select appropriate current-limiting resistors to ensure the LED operates within its specified current range, especially considering the variation across the voltage bins (D2-D4).

4.2 Luminous Intensity vs. Forward Current

This curve shows that luminous intensity is approximately proportional to forward current in the typical operating range (up to 30mA DC). However, efficiency may decrease at very high currents due to increased thermal effects. Operating at or below the recommended 20mA test condition ensures stable performance and longevity.

4.3 Spectral Distribution

The spectral output curve centers around the peak wavelength of 570 nm with a typical half-width of 15 nm. This relatively narrow bandwidth is characteristic of AlInGaP (Aluminum Indium Gallium Phosphide) technology, which produces a saturated green color compared to older technologies like phosphor-converted LEDs.

5. Mechanical & Package Information

5.1 Package Dimensions

The LTST-010KGKT conforms to an industry-standard SMD package outline. Key dimensions (in millimeters) include a typical body size of approximately 3.0mm in length, 1.5mm in width, and 1.1mm in height. Tolerances are typically ±0.1mm unless otherwise noted. The package features a water-clear lens over an AlInGaP green light source.

5.2 Recommended PCB Land Pattern

A suggested solder pad layout is provided to ensure reliable solder joint formation during reflow soldering. This pattern is designed to facilitate proper solder wetting and mechanical stability while minimizing the risk of tombstoning (component standing up on one end). The pad design is optimized for both infrared and vapor phase reflow processes.

5.3 Polarity Identification

The cathode is typically indicated by a visual marker on the LED package, such as a notch, a green dot, or a cut corner on the lens. The datasheet diagram must be consulted to confirm the exact polarity marking for this specific part. Correct polarity is critical during assembly to ensure the device functions.

6. Soldering & Assembly Guidelines

6.1 IR Reflow Soldering Profile

For lead-free (Pb-free) soldering processes, a J-STD-020B compliant profile is recommended. Key parameters include:

• Preheat: 150-200°C for a maximum of 120 seconds to gradually heat the board and components.
• Peak Temperature: Should not exceed 260°C.
• Time Above Liquidus (TAL): The duration within which the solder is molten should be controlled according to the solder paste manufacturer's specifications, typically within the limits shown in the provided profile graph.

The profile is critical to prevent thermal shock, which can damage the LED's internal structure or epoxy lens.

6.2 Hand Soldering (If Necessary)

If manual soldering is required, extreme caution is needed:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per solder joint.
• Limit: Soldering should be performed only once. Avoid reheating existing joints.

6.3 Cleaning

If post-solder cleaning is necessary, only specified solvents should be used. Recommended agents include ethyl alcohol or isopropyl alcohol. The LED should be immersed at normal temperature for less than one minute. Unspecified chemical cleaners may damage the epoxy lens or package markings.

6.4 Storage & Moisture Sensitivity

The LEDs are moisture-sensitive. When the sealed moisture-proof bag (with desiccant) is unopened, they should be stored at ≤30°C and ≤70% RH and used within one year. Once the original bag is opened:

• Storage conditions should not exceed 30°C and 60% RH.
• It is recommended to complete the IR reflow process within 168 hours (7 days) of exposure.
• For storage beyond 168 hours, the LEDs should be re-baked at approximately 60°C for at least 48 hours before soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking during reflow).

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The product is supplied in embossed carrier tape for automated handling.

• Tape Width: 12 mm.
• Reel Diameter: 7 inches (178 mm).
• Quantity per Reel: 4000 pieces (full reel).
• Minimum Order Quantity (MOQ): 500 pieces for partial/reel remnants.
• The packaging conforms to ANSI/EIA-481 specifications. The tape is sealed with a cover tape to protect components.

8. Application Design Considerations

8.1 Drive Circuit Design

LEDs are current-driven devices. To ensure consistent brightness and longevity, a constant current source or a current-limiting resistor must be used. The resistor value (R) can be calculated using Ohm's Law: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the forward voltage from the chosen bin (use max value for worst-case current calculation), and IF is the desired forward current (e.g., 20mA). Driving multiple LEDs in parallel without individual current limiting is not recommended due to VF variation, which can lead to significant brightness mismatch.

8.2 Thermal Management

While the power dissipation is low (72mW max), effective thermal management on the PCB is still important, especially in high ambient temperature environments or when operating near maximum ratings. Excessive junction temperature will reduce luminous output and accelerate degradation. Ensuring adequate copper area around the solder pads can help dissipate heat.

8.3 Optical Design

The 110-degree viewing angle makes this LED suitable for wide-area illumination. For applications requiring a more focused beam, secondary optics (e.g., lenses, light guides) would be necessary. The water-clear lens provides the true color of the AlInGaP chip, which is a saturated green.

9. Technology Introduction & Comparison

9.1 AlInGaP Technology

The LTST-010KGKT utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material for its light-emitting region. This technology is known for producing high-efficiency light in the amber, orange, red, and green-yellow parts of the spectrum. Compared to older technologies like Gallium Phosphide (GaP), AlInGaP LEDs offer significantly higher luminous efficiency and more saturated color purity. The green emission achieved here is in the 570nm region, which is highly visible to the human eye.

9.2 Differentiation from Other Green LEDs

Green LEDs can also be made using Indium Gallium Nitride (InGaN) technology, which typically produces a bluish-green or pure green color at shorter wavelengths (around 520-530nm). The AlInGaP-based green (around 570nm) often appears more yellowish-green or \"lime\" green. The choice depends on the specific color coordinate required by the application. AlInGaP greens in this wavelength range generally have very stable color over drive current and temperature compared to some InGaN greens.

10. Frequently Asked Questions (FAQs)

10.1 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak Wavelength (λP) is the wavelength at which the spectral power distribution is maximum. Dominant Wavelength (λd) is the single wavelength of monochromatic light that matches the perceived color of the LED when compared to a reference white light. For LEDs with a relatively symmetrical spectrum, they are often close. Dominant wavelength is more directly related to the human perception of color.

10.2 Can I drive this LED with a 3.3V supply without a resistor?

No, this is not recommended and is likely to destroy the LED. With a typical VF of 2.0-2.4V, connecting it directly to 3.3V would cause excessive current to flow, far exceeding the absolute maximum rating of 30mA DC. A series current-limiting resistor is always required when using a voltage source.

10.3 How do I interpret the bin codes when ordering?

You can specify a combination of bins to get LEDs with tightly grouped characteristics. For example, requesting \"Iv=R1, VF=D3, λd=C\" would give you LEDs with luminous intensity between 112-140 mcd, forward voltage between 2.0-2.2V, and dominant wavelength between 567.5-570.5 nm. If no bin is specified, you will receive product from the standard production mix.

10.4 Is this LED suitable for outdoor use?

The datasheet specifies an operating temperature range of -40°C to +85°C, which covers many outdoor conditions. However, prolonged exposure to direct sunlight, UV radiation, and moisture could degrade the epoxy lens over time. For harsh outdoor environments, LEDs specifically rated and packaged for such conditions (e.g., with silicone encapsulation) should be considered.

11. Design-in Case Study Example

11.1 Front Panel Status Indicator for a Network Switch

Requirement: Provide a clear, green link/activity status indicator visible from various angles on a rack-mounted unit.

Design Choice: The LTST-010KGKT is selected for its 110° viewing angle, ensuring visibility even when viewed off-axis. The AlInGaP green provides a distinct, attention-grabbing color.

Implementation: A bank of 8 LEDs is used, one per port. To ensure uniform brightness, all LEDs are specified from the same luminous intensity bin (e.g., R1). They are driven from a 5V rail via individual 150Ω current-limiting resistors (calculated for a VF of 2.2V typ. and IF=20mA: R = (5V - 2.2V) / 0.02A = 140Ω; 150Ω is the nearest standard value). The PCB layout uses the recommended land pattern with a small thermal relief connection to a ground plane for heat dissipation.

12. Technology Trends

12.1 Efficiency and Miniaturization

The general trend in SMD LEDs continues toward higher luminous efficacy (more light output per electrical watt) and further miniaturization. While this part represents a mature package size, newer packages like chip-scale LEDs (CSLED) are emerging, offering even smaller footprints. The drive for energy efficiency across all electronics pushes for LEDs that deliver required brightness at lower currents.

12.2 Color Stability and Consistency

Advancements in epitaxial growth and packaging materials aim to improve color consistency (reducing the spread within a bin) and stability over the device's lifetime and across temperature variations. This is particularly important for applications where multiple LEDs are used adjacent to each other, such as in full-color displays or backlighting arrays.

12.3 Integration

There is a growing trend toward integrating the LED driver circuitry (constant current source, PWM dimming control) directly into modules or even onto the LED package itself, simplifying design for end-users and improving overall system reliability.