Dual Color SMD LED LTST-C395KGKSKT Datasheet - Package 3.2x2.8x1.9mm - Voltage 1.8-2.4V - Power 75mW - Green/Yellow - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a dual-color, surface-mount device (SMD) LED. The component integrates two independent light-emitting chips within a single, compact package, offering both green and yellow illumination from a single footprint. Designed for automated printed circuit board (PCB) assembly processes, it is ideal for space-constrained applications across consumer electronics, telecommunications, and industrial equipment.

1.1 Core Features and Target Market

The primary advantages of this LED include its compliance with RoHS (Restriction of Hazardous Substances) directives, making it suitable for global markets with strict environmental regulations. It utilizes Ultra Bright AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for both colors, which typically offers higher efficiency and better performance stability compared to older technologies. The device is supplied in industry-standard 8mm tape on 7-inch diameter reels, conforming to EIA standards, facilitating high-speed pick-and-place automation. It is fully compatible with infrared (IR) reflow soldering processes, which is the standard for modern surface-mount technology (SMT) assembly lines.

Target applications are diverse, focusing on areas requiring compact, reliable indicators and backlighting. Key markets include telecommunication devices (e.g., cellular phones, network equipment), office automation products (e.g., notebooks, peripherals), home appliances, and various industrial control systems. Specific uses encompass keyboard/keypad backlighting, status and power indicators, micro-displays, and symbolic illumination in control panels.

2. Technical Parameters: In-Depth Objective Interpretation

The performance of the LED is defined by a set of absolute maximum ratings and standard operating characteristics, all specified at an ambient temperature (Ta) of 25°C. Exceeding the absolute maximum ratings may cause permanent damage.

2.1 Absolute Maximum Ratings and Thermal Characteristics

The device has a maximum power dissipation of 75 milliwatts (mW) for each color channel. The continuous DC forward current should not exceed 30 mA per chip. For pulsed operation, a peak forward current of 80 mA is permissible under specific conditions: a 1/10 duty cycle and a pulse width of 0.1 milliseconds. The maximum reverse voltage that can be applied is 5 Volts. The operational environment is specified from -30°C to +85°C, while the storage temperature range is slightly wider, from -40°C to +85°C. A critical parameter for assembly is the infrared soldering condition, rated for a peak temperature of 260°C for a duration of 10 seconds, which is typical for lead-free (Pb-free) solder processes.

2.2 Electrical and Optical Characteristics

Under a standard test condition of 20mA forward current (IF=20mA), the luminous intensity (Iv) for the green chip ranges from a minimum of 28.0 millicandelas (mcd) to a maximum of 112.0 mcd. The yellow chip exhibits a higher output, ranging from 45.0 mcd to 180.0 mcd. The typical viewing angle, defined as 2θ1/2 (the full angle at which intensity drops to half its axial value), is 130 degrees, indicating a wide viewing pattern.

The peak emission wavelength (λP) is typically 574.0 nm for green and 591.0 nm for yellow. The dominant wavelength (λd), a key parameter for color specification, is defined within bins. For green, it ranges from 567.5 nm to 576.5 nm, and for yellow, from 587.0 nm to 594.5 nm. The spectral line half-width (Δλ) is typically 15 nm for both colors, describing the spectral purity.

The forward voltage (VF) at 20mA ranges from 1.8V (min) to 2.4V (max) for both chips. The reverse current (IR) is guaranteed to be less than or equal to 10 microamperes (μA) when a 5V reverse bias is applied.

3. Binning System Explanation

To ensure color and brightness consistency in production, the LEDs are sorted into bins based on luminous intensity and dominant wavelength.

3.1 Luminous Intensity (Iv) Binning

For the green LED, intensity bins are labeled N, P, and Q, with ranges of 28.0-45.0 mcd, 45.0-71.0 mcd, and 71.0-112.0 mcd, respectively. For the yellow LED, bins are P, Q, and R, with ranges of 45.0-71.0 mcd, 71.0-112.0 mcd, and 112.0-180.0 mcd, respectively. A tolerance of +/-15% is applied to each bin.

3.2 Hue (Dominant Wavelength) Binning

Green LEDs are binned for dominant wavelength into codes C (567.5-570.5 nm), D (570.5-573.5 nm), and E (573.5-576.5 nm). Yellow LEDs are binned into codes J (587.0-589.5 nm), K (589.5-592.0 nm), and L (592.0-594.5 nm). The tolerance for each wavelength bin is +/- 1 nm. This precise binning allows designers to select LEDs that match specific color coordinate requirements for their application.

4. Mechanical and Package Information

4.1 Package Dimensions and Pin Assignment

The LED features a water-clear lens. The package dimensions are provided in a detailed drawing. All critical dimensions are specified in millimeters, with a standard tolerance of ±0.1 mm unless otherwise noted. The pin assignment is crucial for correct circuit design: Pins 1 and 3 are assigned to the green AlInGaP chip, while pins 2 and 4 are assigned to the yellow AlInGaP chip. This configuration allows for independent control of the two colors.

4.2 Recommended PCB Attachment Pad Layout

A recommended land pattern (footprint) for the printed circuit board is provided to ensure proper soldering, mechanical stability, and thermal performance. Adhering to this design is essential for achieving reliable solder joints during the reflow process and for the long-term reliability of the assembly.

5. Soldering and Assembly Guidelines

5.1 Reflow Soldering Parameters

The component is qualified for lead-free (Pb-free) infrared reflow soldering processes. A suggested reflow profile is provided, which typically includes a pre-heat stage, a temperature ramp, a peak temperature zone, and a cooling phase. The critical parameter is a maximum peak body temperature of 260°C, which should not be exceeded for more than 10 seconds. It is emphasized that the optimal profile depends on the specific PCB design, solder paste, and oven characteristics, and board-level characterization is recommended.

5.2 Manual Soldering and Rework

If manual soldering with an iron is necessary, the maximum recommended tip temperature is 300°C, and the soldering time per lead should not exceed 3 seconds. This should be performed only once to avoid thermal damage to the plastic package and the semiconductor die.

5.3 Storage and Handling Precautions

The LEDs are sensitive to electrostatic discharge (ESD). Handling with a grounded wrist strap or anti-static gloves is recommended, and all equipment must be properly grounded. For storage, unopened moisture-proof bags (with desiccant) should be kept at 30°C or less and 90% relative humidity (RH) or less, with a shelf life of one year. Once the original packaging is opened, the components should be stored in an environment not exceeding 30°C and 60% RH. It is advised to complete the IR reflow process within one week of opening (Moisture Sensitivity Level 3, MSL 3). For longer storage outside the original bag, baking at approximately 60°C for at least 20 hours before soldering is required to remove absorbed moisture and prevent \"popcorning\" during reflow.

5.4 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. The use of unspecified or aggressive chemicals can damage the epoxy lens and package.

6. Packaging and Ordering Information

6.1 Tape and Reel Specifications

The standard packaging is 8mm carrier tape wound on 7-inch (178mm) diameter reels. Each reel contains 4000 pieces. The tape pockets are sealed with a top cover tape. Industry standards (ANSI/EIA 481) are followed for packaging. For quantities less than a full reel, a minimum packing quantity of 500 pieces is specified for remainders. The packaging specification also notes that a maximum of two consecutive component pockets may be empty.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

This dual-color LED is optimally used in devices requiring multi-status indication from a single point. Examples include: a single button that lights green for \"on/active\" and yellow for \"standby/charging\"; a panel indicator that shows green for normal operation and yellow for a warning condition; or backlighting that can switch between two colors for different modes in consumer electronics. Its small size makes it perfect for modern, miniaturized portable devices.

7.2 Design and Circuit Considerations

Designers must incorporate appropriate current-limiting resistors in series with each LED chip (Green: Pins 1/3, Yellow: Pins 2/4) to ensure the forward current does not exceed the maximum DC rating of 30mA. The resistor value is calculated using Ohm's Law: R = (Vsupply - Vf_LED) / If, where Vf_LED is the forward voltage of the LED (use max value for a conservative design). For applications involving multiplexing or PWM (Pulse Width Modulation) for dimming, ensure the instantaneous current during the \"on\" pulse does not exceed the peak forward current rating. The wide viewing angle (130°) should be considered for the mechanical design of light guides or diffusers if a specific beam pattern is required.

8. Technical Comparison and Differentiation

The key differentiator of this component is the integration of two high-performance AlInGaP chips in one package. Compared to using two separate single-color LEDs, this saves significant PCB space, reduces component count, and simplifies assembly. AlInGaP technology itself generally offers advantages in luminous efficiency and temperature stability over traditional GaP or GaAsP technologies, especially in the amber/yellow/green spectrum. The combination of a clear lens and wide viewing angle provides good off-axis visibility, which is beneficial for status indicators.

9. Frequently Asked Questions Based on Technical Parameters

Q: Can I drive both the green and yellow chips simultaneously at 20mA each?
A: Yes, but you must consider the total power dissipation. At 20mA and a typical Vf, the power per chip is around 40-48mW. Running both simultaneously would be 80-96mW, which exceeds the absolute maximum power dissipation rating of 75mW per chip. For continuous simultaneous operation, you must derate the current to keep the total device power within safe limits, considering the thermal environment.

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the single wavelength at which the emission spectrum has its highest intensity. Dominant wavelength (λd) is a calculated value derived from the CIE chromaticity diagram; it represents the single wavelength of a pure monochromatic light that would appear to have the same color as the LED to the human eye. λd is often more relevant for color specification in applications.

Q: The datasheet mentions \"I.C. Compatible.\" What does this mean?
A: This indicates that the LED can be driven directly by the output pins of most standard integrated circuits (ICs), such as microcontrollers or logic gates, without requiring additional buffering or driver transistors, as its forward voltage and current requirements are within the typical output capabilities of such ICs.

10. Practical Application Case Study

Consider a portable medical device with a single multi-function button. The design requirement is to provide clear, unambiguous status feedback: solid green when the device is on and functioning normally, flashing yellow when the battery is low, and off when the device is powered down. Using the LTST-C395KGKSKT, the designer can place a single component under the button. The microcontroller can independently control the green and yellow anodes via two GPIO pins, with appropriate series resistors. This solution uses minimal board space, provides two distinct colors from one location, and simplifies the optical design compared to trying to align two separate LEDs under a small button.

11. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. This phenomenon is called electroluminescence. In an AlInGaP LED, the semiconductor material is composed of Aluminum, Indium, Gallium, and Phosphorus. When a forward voltage is applied across the p-n junction, electrons from the n-type region recombine with holes from the p-type region in the active layer, releasing energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material, which is controlled by the precise composition of the AlInGaP alloy. A clear epoxy lens encapsulates the chip, providing environmental protection, mechanical stability, and helping to shape the light output.

12. Industry Trends and Developments

The trend in SMD LED technology continues towards higher efficiency (more lumens per watt), smaller package sizes for increased density, and improved color consistency and rendering. There is also a growing focus on reliability under higher temperature conditions, driven by applications like automotive lighting and high-power electronics. The integration of multiple chips (multi-color or RGB) into a single package, as seen in this component, is a common strategy to save space and cost in complex indicator and backlighting systems. Furthermore, compatibility with automated assembly and stringent soldering profiles remains a fundamental requirement for mass production across all electronics sectors.