LTST-S327KGJRKT Dual Color SMD LED Datasheet - Package Dimensions - Green/Red - 30mA - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a dual-color, surface-mount device (SMD) LED lamp. The component is designed in a miniature package suitable for automated printed circuit board (PCB) assembly processes, making it ideal for applications where space is at a premium. Its primary function is to serve as a visual indicator or backlight source.

1.1 Core Advantages and Target Market

The LED offers several key advantages for modern electronics manufacturing. It is compliant with RoHS (Restriction of Hazardous Substances) directives. The package features a side-looking design with tin plating on the terminals, enhancing solderability and reliability. It utilizes ultra-bright AlInGaP semiconductor technology for efficient light output. The component is supplied in industry-standard 8mm tape on 7-inch diameter reels, facilitating high-speed automated pick-and-place assembly. It is fully compatible with infrared (IR) reflow soldering processes, aligning with modern lead-free (Pb-free) assembly lines. The device is also designed to be directly compatible with integrated circuit (IC) logic levels.

The target applications are broad, covering telecommunications equipment, office automation devices, home appliances, and industrial control systems. Specific uses include backlighting for keypads and keyboards, status indication, integration into micro-displays, and general signal or symbol illumination.

2. Technical Parameters: In-Depth Objective Interpretation

This section details the absolute limits and operational characteristics of the device. All parameters are defined at an ambient temperature (Ta) of 25°C unless otherwise stated.

2.1 Absolute Maximum Ratings

These values represent stress limits that must not be exceeded under any conditions, as doing so may cause permanent damage to the device. Operation outside these limits is not implied.

• Power Dissipation (Pd): 75 mW maximum for both the green and red chips. This is the total power (forward voltage * forward current) that can be safely dissipated as heat.
• Peak Forward Current (I_FP): 80 mA maximum, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This allows for brief, high-intensity flashes.
• DC Forward Current (I_F): 30 mA maximum continuous current. This is the standard operating current for which most optical characteristics are specified.
• Reverse Voltage (V_R): 5 V maximum. Applying a reverse voltage higher than this can break down the LED's semiconductor junction.
• Operating Temperature Range: -30°C to +85°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +85°C. The device can be stored without degradation within these limits.
• Infrared Soldering Condition: Withstands a peak temperature of 260°C for a maximum of 10 seconds during reflow soldering.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under standard test conditions (I_F = 20mA, Ta=25°C).

• Luminous Intensity (I_V): Ranges from a minimum of 18.0 mcd to a maximum of 112.0 mcd for both colors. The typical value falls within this range and is subject to binning (see Section 3).
• Viewing Angle (2θ_1/2): 130 degrees (typical). This wide viewing angle indicates a diffuse, non-focused emission pattern suitable for wide-area illumination.
• Peak Emission Wavelength (λ_P): 574 nm (typical) for green, 639 nm (typical) for red. This is the wavelength at which the spectral output is strongest.
• Dominant Wavelength (λ_d): 571 nm (typical) for green, 631 nm (typical) for red. This is the single wavelength perceived by the human eye that defines the color.
• Spectral Line Half-Width (Δλ): 15 nm (typical) for green, 20 nm (typical) for red. This parameter defines the color purity; a smaller value indicates a more monochromatic light.
• Forward Voltage (V_F): 2.0 V (typical), with a maximum of 2.4 V at 20mA. This is the voltage drop across the LED when operating.
• Reverse Current (I_R): 10 μA maximum at a reverse voltage of 5V.

3. Binning System Explanation

To ensure consistent performance in production, LEDs are sorted into bins based on key optical parameters. This allows designers to select components with tightly controlled characteristics.

3.1 Luminous Intensity (I_V) Binning

Both the green and red chips are binned identically for luminous intensity at 20mA. The bins are defined as follows, with a tolerance of ±15% within each bin:

• Bin Code M: 18.0 mcd (Min) to 28.0 mcd (Max)
• Bin Code N: 28.0 mcd to 45.0 mcd
• Bin Code P: 45.0 mcd to 71.0 mcd
• Bin Code Q: 71.0 mcd to 112.0 mcd

3.2 Hue (Dominant Wavelength) Binning for Green

The green chip is further binned by its dominant wavelength to control color consistency. The tolerance for each bin is ±1 nm.

• Bin Code C: 567.5 nm to 570.5 nm
• Bin Code D: 570.5 nm to 573.5 nm
• Bin Code E: 573.5 nm to 576.5 nm

Note: The datasheet does not specify hue binning for the red chip in the provided content.

4. Performance Curve Analysis

While the specific graphical curves are not detailed in the text extract, typical LED datasheets include several key plots for design analysis. Based on standard practice, the following curves would be essential:

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

This curve shows the nonlinear relationship between the current flowing through the LED and the voltage across it. It is crucial for designing the current-limiting circuitry (e.g., series resistor or constant-current driver). The curve will show a threshold voltage (around 1.8-2.0V for these AlInGaP LEDs) after which current increases rapidly with a small increase in voltage.

4.2 Luminous Intensity vs. Forward Current

This plot illustrates how light output increases with drive current. It is generally linear over a range but will saturate at higher currents due to thermal effects and efficiency droop. Operating at or below the recommended 20mA ensures optimal efficiency and longevity.

4.3 Luminous Intensity vs. Ambient Temperature

LED light output decreases as junction temperature increases. This curve is vital for applications operating over a wide temperature range, as it allows designers to derate the expected brightness or implement thermal management if necessary.

4.4 Spectral Distribution

These graphs would show the relative radiant power emitted across the visible spectrum for both the green and red chips, centered around their peak wavelengths of 574nm and 639nm, respectively, with the specified half-widths.

5. Mechanical and Package Information

5.1 Package Dimensions and Polarity Identification

The LED is housed in a standard SMD package. The lens is water clear. The pin assignment is critical for correct operation: Pin A1 is the anode for the green chip, and Pin A2 is the anode for the red chip. The cathodes are likely common, but the schematic should be verified from the package diagram. All dimensions are provided in millimeters with a standard tolerance of ±0.1mm unless otherwise noted.

5.2 Recommended PCB Pad Design and Soldering Orientation

The datasheet includes a recommended land pattern (footprint) for the PCB pads to ensure reliable solder joint formation during reflow. It also indicates the proper orientation of the component on the tape relative to the PCB for automated assembly.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters for Pb-Free Process

A suggested infrared reflow profile is provided. While specific ramp rates are not detailed in the text, the key parameters are the peak temperature (260°C max) and the time above liquidus (likely tailored to lead-free solder paste). The profile should include a pre-heat stage (e.g., 150-200°C) to activate flux and minimize thermal shock, followed by a controlled ramp to peak temperature and a controlled cooling phase.

6.2 Hand Soldering

If hand soldering is necessary, it should be performed with a temperature-controlled iron set to a maximum of 300°C. The soldering time per lead must not exceed 3 seconds, and this should be done only once to prevent thermal damage to the plastic package and the semiconductor die.

6.3 Cleaning

If cleaning after soldering is required, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. Unspecified chemicals may damage the package material or the lens.

6.4 Storage and Handling

Electrostatic Discharge (ESD): The device is sensitive to ESD. Proper handling procedures must be followed, including the use of grounded wrist straps, anti-static mats, and ESD-safe packaging and equipment.

Moisture Sensitivity: The package is rated at MSL3 (Moisture Sensitivity Level 3). This means that once the original moisture-barrier bag is opened, the components must be subjected to reflow soldering within 168 hours (one week) when stored at conditions ≤ 30°C / 60% RH. For longer storage after opening, components should be baked at approximately 60°C for at least 20 hours before assembly to remove absorbed moisture and prevent \"popcorning\" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied on 8mm wide embossed carrier tape. The tape is wound onto standard 7-inch (178mm) diameter reels. Each reel contains 3000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies for remainder parts. The packaging conforms to ANSI/EIA-481 standards.

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

The most common drive method is a simple series resistor. The resistor value (R_s) is calculated using Ohm's Law: R_s = (V_supply - V_F) / I_F. Using the maximum V_F (2.4V) ensures sufficient current even with component variation. For example, with a 5V supply and a target I_F of 20mA: R_s = (5V - 2.4V) / 0.020A = 130 Ohms. A standard 130Ω or 150Ω resistor would be suitable. For precise current control or multiplexing many LEDs, a constant-current driver IC is recommended.

8.2 Design Considerations

• Current Limiting: Always use a current-limiting device (resistor or driver). Connecting the LED directly to a voltage source will cause excessive current flow and immediate failure.
• Thermal Management: While the power dissipation is low, PCB layout should still consider heat dissipation, especially if multiple LEDs are clustered or operated in high ambient temperatures. Adequate copper area around the thermal pads (if any) or vias to inner layers can help.
• Binning Selection: For applications requiring uniform brightness or color, specify the appropriate bin codes (e.g., Bin Q for highest brightness, Bin D for a specific green hue).
• Reverse Voltage Protection: If there is any possibility of a reverse voltage being applied (e.g., in back-to-back configurations or with inductive loads), consider adding a protection diode in parallel with the LED.

9. Technical Comparison and Differentiation

This dual-color LED's primary differentiation lies in its combination of two distinct light sources (AlInGaP green and red) in a single, compact SMD package. Compared to using two separate single-color LEDs, this saves PCB space, reduces component count, and simplifies assembly. The use of AlInGaP technology for both colors offers higher efficiency and better temperature stability compared to older technologies like standard GaP. The wide 130-degree viewing angle is a key feature for applications requiring broad visibility, as opposed to narrow-angle LEDs used for focused beams.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED at 30mA continuously?

A: Yes, 30mA is the maximum rated continuous DC forward current. However, for optimal longevity and to account for real-world thermal conditions, designing for the typical operating current of 20mA is recommended.

Q: What is the difference between peak wavelength and dominant wavelength?

A: Peak wavelength (λ_P) is the physical point of highest intensity in the emitted spectrum. Dominant wavelength (λ_d) is a calculated value based on human color perception (CIE chromaticity) that represents the \"color\" we see. They are often close but not identical.

Q: Why is there a binning system?

A: Manufacturing variations cause slight differences in performance. Binning sorts LEDs into groups with similar characteristics (brightness, color), allowing manufacturers to offer consistent products and designers to select parts that meet their specific needs for uniformity.

Q: How critical is the 260°C for 10 seconds reflow specification?

A: Very critical. Exceeding this time-temperature combination can overstress the internal wire bonds, degrade the epoxy lens, or damage the semiconductor chip, leading to immediate failure or reduced lifetime.

11. Practical Use Case Example

Scenario: Dual-State Status Indicator on a Network Router

A designer needs a single indicator to show two states: \"System On/Active\" (Green) and \"Network Error\" (Red). Using the LTST-S327KGJRKT simplifies the design. One microcontroller GPIO pin can be connected to the green anode (A1), another to the red anode (A2), with both cathodes connected to ground. The microcontroller can independently turn on the green or red chip. A single current-limiting resistor can be placed on the common cathode if both LEDs are never on simultaneously, or separate resistors can be used on each anode for independent control. The wide viewing angle ensures the indicator is visible from various angles around the device.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type material recombine with holes from the p-type material in the active region. This recombination releases energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material used. This device uses Aluminum Indium Gallium Phosphide (AlInGaP) for both the red and green chips, which is a material system known for high efficiency in the yellow-to-red spectrum, with specific doping and structure adjustments to achieve the green emission.

13. Technology Trends

The general trend in SMD indicator LEDs is toward higher efficiency (more light output per unit of electrical power), smaller package sizes, and improved reliability. There is also a move toward tighter binning tolerances to meet the demands of applications requiring high color and brightness consistency, such as full-color displays and automotive lighting. The integration of multiple colors or even RGB chips into a single package continues to be a significant trend for space-constrained multi-indicator applications. Furthermore, compatibility with increasingly stringent automotive and industrial temperature and reliability standards is a key driver for product development.