LTST-S326KGJRKT Dual Color SMD LED Datasheet - Side View - AlInGaP Green & Red - 30mA - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-S326KGJRKT, a surface-mount device (SMD) LED lamp. This component is a side-looking, dual-color LED featuring separate AlInGaP (Aluminum Indium Gallium Phosphide) chips for green and red emission within a single, compact package. Designed for automated printed circuit board (PCB) assembly, it is ideal for space-constrained applications across a broad spectrum of consumer and industrial electronics.

1.1 Core Features and Advantages

The LTST-S326KGJRKT offers several key advantages for modern electronic design:

• Dual Color Source: Integrates independent ultra-bright AlInGaP chips for green and red light emission, controlled via separate pins (C1 for Red, C2 for Green).
• Side-Viewing Package: The primary light emission is from the side of the component, making it suitable for edge-lighting, status indication in tight spaces, and backlighting applications where top-down mounting is not feasible.
• Manufacturing Compatibility: The package conforms to EIA standards and is supplied on 8mm tape on 7-inch reels, making it fully compatible with high-speed automatic pick-and-place equipment.
• Robust Assembly Process: Designed to withstand standard infrared (IR) reflow soldering processes, facilitating reliable surface-mount assembly.
• Environmental Compliance: The device is compliant with RoHS (Restriction of Hazardous Substances) directives.
• Electrical Compatibility: The device is IC-compatible, allowing for direct drive from microcontroller or logic outputs in many cases.

1.2 Target Applications and Markets

This LED is engineered for versatility in electronic equipment where reliable, compact indicators are required. Primary application areas include:

• Telecommunications Equipment: Status indicators in cordless phones, cellular phones, and network system hardware.
• Computing and Office Automation: Backlighting for keypads and keyboards in notebook computers and other portable devices; status lights on peripherals.
• Consumer and Home Appliances: Power, mode, or function indicators in a wide range of household devices.
• Industrial Equipment: Panel indicators, machine status lights, and control system feedback.
• Specialized Displays: Suitable for micro-displays and as a luminous source for small-scale signal and symbol illumination.

2. In-Depth Technical Parameter Analysis

The following sections provide a detailed, objective interpretation of the key electrical, optical, and reliability parameters defined in the datasheet.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or near these limits is not recommended for normal use. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 75 mW per chip. This is the maximum amount of power that can be dissipated as heat by each LED chip. Exceeding this can lead to excessive junction temperature and accelerated degradation or failure.
• Peak Forward Current (I_FP): 80 mA, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This allows for brief periods of high-intensity flashing without overheating.
• Continuous Forward Current (I_F): 30 mA DC. This is the recommended maximum current for continuous operation, balancing brightness and long-term reliability.
• Reverse Voltage (V_R): 5 V. Applying a reverse bias voltage higher than this can cause breakdown and damage the semiconductor junction.
• Operating & Storage Temperature: The device can operate from -30°C to +85°C and be stored from -40°C to +85°C. These ranges ensure functionality in most commercial and industrial environments.
• Soldering Thermal Limit: The package can withstand a peak temperature of 260°C for up to 10 seconds during IR reflow, which is standard for Pb-free (lead-free) assembly processes.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under standard test conditions (Ta=25°C, I_F=20mA unless noted). They define the expected behavior of the device in a circuit.

• Luminous Intensity (I_V): A key measure of perceived brightness. For the Green chip, the typical value is 35.0 mcd (millicandelas), with a range from 18.0 mcd (Min) to 112.0 mcd (Max). For the Red chip, the typical value is higher at 45.0 mcd, with the same min/max range. The wide range necessitates the binning system described later.
• Viewing Angle (2θ_1/2): 130 degrees (typical). This is the full angle at which the luminous intensity drops to half of its peak (on-axis) value. The wide 130° angle is characteristic of a side-view LED with a diffused lens, providing a broad emission pattern suitable for area illumination or wide-angle visibility.
• Forward Voltage (V_F): Typically 2.0 V for both colors at 20mA, with a maximum of 2.4 V. This is relatively low compared to some blue or white LEDs, simplifying drive circuit design. The consistent V_F between colors allows for similar current-limiting resistor values if driven separately.
• Peak Wavelength (λ_P) & Dominant Wavelength (λ_d):
  • Green: Peak at 574 nm (Typ), Dominant at 571 nm (Typ). This places it in the pure green region of the spectrum.
  • Red: Peak at 639 nm (Typ), Dominant at 631 nm (Typ). This is a standard red, distinct from deep red or orange-red.
  Dominant wavelength is the single-wavelength perception of the color, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): Approximately 15 nm for Green and 20 nm for Red. This indicates the spectral purity; a smaller value means a more monochromatic (pure color) output.
• Reverse Current (I_R): Maximum of 10 µA at a reverse bias of 5V, indicating a high-quality junction with low leakage.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted (binned) based on key optical parameters. The LTST-S326KGJRKT uses a two-dimensional binning system.

3.1 Luminous Intensity (Brightness) Binning

Both the Green and Red chips are binned identically for luminous intensity at 20mA. The bin code defines a minimum and maximum brightness range. Tolerance within each bin is +/-15%.

• Bin Code M: 18.0 – 28.0 mcd
• Bin Code N: 28.0 – 45.0 mcd (Covers the typical values)
• Bin Code P: 45.0 – 71.0 mcd
• Bin Code Q: 71.0 – 112.0 mcd

Designers must select the appropriate bin based on the required brightness for their application. Using a higher bin (e.g., P or Q) ensures a minimum higher brightness but may come at a cost premium.

3.2 Hue (Dominant Wavelength) Binning for Green

Only the Green chip has a specified hue (wavelength) binning to control color consistency. The tolerance for each bin is +/- 1 nm.

• Bin Code C: 567.5 – 570.5 nm
• Bin Code D: 570.5 – 573.5 nm (Contains the typical 571 nm)
• Bin Code E: 573.5 – 576.5 nm

The Red chip's dominant wavelength is specified as a typical value (631 nm) without a formal binning table in this datasheet, implying tighter process control or less sensitivity to color shift in the application.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1, Fig.5), their general implications are critical for design.

4.1 Current vs. Voltage (I-V) Characteristic

The forward voltage (V_F) has a positive temperature coefficient and also increases slightly with current. The typical V_F of 2.0V at 20mA is a crucial parameter for designing the current-limiting circuit. A simple series resistor is often sufficient: R = (V_supply - V_F) / I_F. Designers should use the maximum V_F (2.4V) for worst-case current calculation to avoid overdriving the LED.

4.2 Luminous Intensity vs. Forward Current

The light output (I_V) is approximately proportional to the forward current (I_F) in the normal operating range. Driving the LED at less than 20mA will reduce brightness proportionally. Operating above 20mA up to the 30mA maximum will increase brightness but also increase power dissipation and junction temperature, which can affect longevity and cause a slight shift in wavelength.

4.3 Temperature Dependence

Like all LEDs, the performance of the AlInGaP chips is temperature-sensitive. As junction temperature increases:

• Luminous Intensity Decreases: The light output drops. The datasheet likely shows a derating curve.
• Forward Voltage Decreases: Slightly, due to changes in the semiconductor bandgap.
• Wavelength Shifts: Typically, the dominant wavelength increases (shifts to longer wavelengths) with temperature. This is more pronounced in AlInGaP LEDs than in some other types. Proper thermal management on the PCB is essential for color stability in critical applications.

5. Mechanical and Package Information

5.1 Package Dimensions and Polarity

The device uses a standard SMD footprint. The pin assignment is clearly defined: Cathode 1 (C1) is for the Red chip, and Cathode 2 (C2) is for the Green chip. The anodes are likely common or internally connected as per the package drawing, which must be consulted for the exact layout. All critical dimensions are provided in millimeters with a standard tolerance of ±0.1 mm, ensuring reliable placement and soldering.

5.2 Recommended PCB Pad Design

The datasheet includes a suggested land pattern (solder pad layout) for the PCB. Adhering to this design is crucial for achieving a reliable solder joint, proper alignment, and managing heat dissipation during reflow. The pad design accounts for solder fillet formation and prevents tombstoning (one end lifting during reflow).

6. Soldering, Assembly, and Handling Guide

6.1 IR Reflow Soldering Parameters

For lead-free (Pb-free) assembly, the following reflow profile is recommended:

• Pre-heat: 150–200°C
• Pre-heat Time: Maximum 120 seconds.
• Peak Temperature: Maximum 260°C at the component leads.
• Time Above Liquidus: The component should be exposed to the peak temperature for a maximum of 10 seconds. Reflow should be performed a maximum of two times.

This profile aligns with JEDEC standards and ensures the package integrity is maintained while forming reliable solder joints.

6.2 Manual Soldering (If Required)

If manual rework is necessary, use a soldering iron with a temperature not exceeding 300°C. The contact time with the solder pad should be limited to a maximum of 3 seconds for a single operation only. Excessive heat or time can damage the plastic package or the internal wire bonds.

6.3 Cleaning

If post-solder cleaning is required, only use specified solvents. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. Unspecified or aggressive chemicals can damage the lens material or the package epoxy.

6.4 Storage and Moisture Sensitivity

The LEDs are packaged in a moisture-proof bag with desiccant. In this sealed state, they should be stored at ≤30°C and ≤90% RH and used within one year. Once the original bag is opened, the devices are rated at Moisture Sensitivity Level 3 (MSL3). This means they must be subjected to IR reflow soldering within one week of exposure to factory ambient conditions (≤30°C/60% RH). For longer storage after opening, they must be stored in a sealed container with desiccant or in a nitrogen environment. Devices exposed for more than one week require a bake at 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking due to vapor pressure during reflow).

6.5 Electrostatic Discharge (ESD) Precautions

AlInGaP LEDs are sensitive to electrostatic discharge. Proper ESD controls must be in place during handling and assembly. This includes the use of grounded wrist straps, anti-static mats, and ensuring all equipment is properly grounded. ESD can cause immediate failure or latent damage that shortens the device's lifespan.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied for automated assembly in embossed carrier tape wound on 7-inch (178 mm) diameter reels.

• Tape Width: 8 mm.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Pocket Coverage: Empty pockets are sealed with cover tape.
• Missing Components: A maximum of two consecutive missing LEDs is allowed per the packing standard.

The packaging conforms to ANSI/EIA-481 specifications, ensuring compatibility with standard tape feeders on placement machines.

8. Application Design Considerations

8.1 Drive Circuit Design

Since the two colors have independent cathodes, they can be driven separately. A simple constant-current source or a current-limiting resistor is sufficient for each channel. Given the similar V_F, the same resistor value can often be used for both colors if driven from the same voltage rail, though separate calculations are recommended for precision. For multiplexing or PWM dimming, ensure the drive current and switching speeds are within the device's ratings.

8.2 Thermal Management

While the power dissipation is low (75 mW max per chip), effective thermal management on the PCB is still important for maintaining stable optical output and long-term reliability, especially in high ambient temperatures or when driven at the maximum continuous current. Ensure the PCB pads have adequate thermal relief or connection to a copper plane to dissipate heat.

8.3 Optical Integration

The side-viewing nature of this LED requires careful mechanical design. Light guides, reflectors, or diffusers may be necessary to direct the light to the desired viewing area or to create uniform backlighting. The wide 130-degree viewing angle helps in illuminating larger areas without hotspots.

9. Technical Comparison and Differentiation

The LTST-S326KGJRKT differentiates itself in the market through its specific combination of features:

• vs. Single-Color Side-View LEDs: It offers dual functionality in the same footprint, saving PCB space and assembly time compared to mounting two separate single-color LEDs.
• vs. Top-View Dual-Color LEDs: The side-emitting characteristic is its primary differentiator, enabling unique mechanical designs where light must be emitted parallel to the PCB surface.
• vs. Other Dual-Color Technologies: The use of AlInGaP technology for both colors provides high efficiency and good color saturation for red and green, compared to older technologies like GaP.
• vs. RGB LEDs: This is a two-primary (red/green) device. It cannot produce blue or white light. It is chosen for applications specifically requiring only red and green indicators (e.g., power/status, go/warning signals).

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive both the red and green LEDs simultaneously to create yellow/orange?
A: Yes, by turning on both chips at the same time, the combined light output will be perceived as a yellow or yellow-orange color, depending on the relative intensity of each chip. The exact hue can be tuned by adjusting the current ratio between the two channels.

Q2: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P) is the wavelength at which the spectral power distribution is highest. Dominant Wavelength (λ_d) is derived from the CIE color coordinates and represents the single wavelength of a monochromatic light that would appear to have the same color. λ_d is more relevant for color specification in applications.

Q3: Why is there a binning system, and how do I specify which bin I need?
A> The binning system accounts for natural variations in semiconductor manufacturing. It allows customers to select LEDs that meet specific brightness and color consistency requirements for their product. You must specify the desired Intensity Bin Code (e.g., \"N\") and, for green, the Hue Bin Code (e.g., \"D\") when ordering to ensure you receive parts within those performance windows.

Q4: Is a heat sink required for this LED?
A: Under normal operating conditions (I_F ≤ 30mA, Ta ≤ 85°C), a dedicated heat sink is not typically required. However, good PCB thermal design—such as using adequate copper pads and traces—is recommended to keep the junction temperature as low as possible, which maximizes light output and lifespan.

11. Practical Application Examples

Example 1: Portable Device Status Indicator: In a handheld medical device, the LED can be mounted on the edge of the main PCB. Green can indicate \"Ready/On,\" red can indicate \"Error/Low Battery,\" and both on simultaneously can indicate \"Standby/Charging.\" The side emission allows the light to be visible through a thin slit in the device housing.

Example 2: Industrial Control Panel Backlighting: An array of these LEDs can be placed along the side of a translucent membrane switch panel. The side light couples into the panel material, providing even, low-glare backlighting for labels or symbols. The dual colors can differentiate between operational modes (e.g., green for auto, red for manual).

12. Technology Principle Introduction

The LTST-S326KGJRKT utilizes Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material for its light-emitting chips. AlInGaP is a direct bandgap III-V compound semiconductor. By precisely controlling the ratios of aluminum, indium, and gallium, the bandgap energy of the material can be tuned. When forward-biased, electrons and holes recombine in the active region of the chip, releasing energy in the form of photons. The wavelength (color) of these photons is determined by the bandgap energy: a larger bandgap produces shorter wavelengths (green), and a slightly smaller bandgap produces longer wavelengths (red). The device contains two such chips, fabricated with different material compositions, housed in a reflective plastic package with a diffused lens that shapes the light output into a wide side-emitting pattern.

13. Industry Trends and Context

The development of side-viewing SMD LEDs like this one is driven by the ongoing miniaturization of electronic devices and the demand for more sophisticated user interfaces in smaller form factors. Trends influencing this product segment include:

• Increased Integration: Moving from multiple discrete indicators to multi-chip, multi-color packages to save space and simplify assembly.
• Higher Efficiency: Continuous improvement in AlInGaP and InGaN (for blue/green) epitaxial growth techniques leads to higher luminous efficacy (more light output per electrical watt).
• Demand for Color Consistency: Tighter binning specifications and advanced wafer-level testing are becoming more common to meet the needs of applications where color matching is critical, such as in multi-LED arrays or signage.
• Robustness for Harsh Environments: Enhancements in package materials and sealing techniques improve reliability against moisture, thermal cycling, and chemical exposure, expanding use into automotive and outdoor applications.

The LTST-S326KGJRKT represents a mature, well-characterized solution within this evolving landscape, offering a reliable combination of dual-color functionality, side emission, and manufacturability.