LTST-C170KRKT Red SMD LED Datasheet - Ultra Bright AlInGaP - 20mA - 2.4V - English Technical Document

1. Product Overview

This document details the specifications for a high-performance, surface-mount LED utilizing an advanced AlInGaP (Aluminum Indium Gallium Phosphide) chip technology. The primary application is in electronic equipment requiring a reliable, bright red indicator light source. Its core advantages include compliance with environmental regulations, high luminous intensity, and compatibility with modern automated assembly and soldering processes.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device is designed to operate within strict environmental and electrical limits to ensure long-term reliability. The maximum continuous forward current is rated at 30 mA at an ambient temperature (Ta) of 25°C. Beyond 50°C, the allowable DC current must be derated linearly at a rate of 0.4 mA per degree Celsius increase in temperature. The maximum power dissipation is 75 mW. The device can withstand a reverse voltage of up to 5 V. The operational and storage temperature range is specified from -55°C to +85°C, making it suitable for a wide variety of environments.

2.2 Electro-Optical Characteristics

Key performance metrics are measured at a standard test condition of Ta=25°C and a forward current (IF) of 20 mA. The luminous intensity (Iv) has a typical value of 54.0 millicandelas (mcd), with a minimum specified value of 18.0 mcd. The viewing angle (2θ1/2), defined as the full angle at which intensity drops to half its on-axis value, is 130 degrees, providing a wide field of illumination. The dominant wavelength (λd), which defines the perceived color, is 631 nm, placing it in the red spectrum. The forward voltage (Vf) typically measures 2.4 V with a maximum of 2.4 V at 20 mA. Reverse current (Ir) is limited to a maximum of 10 μA at the full 5 V reverse bias.

3. Binning System Explanation

To ensure consistency in applications, the luminous output of these LEDs is sorted into specific intensity bins. The binning is based on the measured luminous intensity at 20 mA. The available bin codes are: M (18.0-28.0 mcd), N (28.0-45.0 mcd), P (45.0-71.0 mcd), Q (71.0-112.0 mcd), and R (112.0-180.0 mcd). A tolerance of +/-15% is applied to each intensity bin. This system allows designers to select components that meet precise brightness requirements for their application, ensuring visual uniformity in products using multiple LEDs.

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet (e.g., Fig.1 for spectral emission, Fig.6 for viewing angle), the provided tabular data allows for critical analysis. The relationship between forward current and luminous intensity is typically super-linear for AlInGaP LEDs, meaning brightness increases more than proportionally with current up to a point. The forward voltage shows a logarithmic relationship with current. The spectral half-width of 20 nm indicates a relatively pure, saturated red color. Performance will vary with ambient temperature; luminous intensity generally decreases as temperature increases, while forward voltage decreases slightly.

5. Mechanical and Package Information

The LED is housed in a standard EIA-compatible surface-mount package. Detailed dimensional drawings specify the exact length, width, height, and lead positions. The lens is water-clear, which maximizes light output by minimizing internal absorption. The component is supplied on 8mm wide tape, wound onto 7-inch diameter reels, which is the standard for automated pick-and-place assembly equipment. The tape and reel specifications comply with ANSI/EIA 481-1-A-1994, ensuring compatibility with industry-standard feeders.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering

The device is compatible with both infrared (IR) and vapor phase reflow soldering processes, which are essential for high-volume PCB assembly. A suggested reflow profile for lead-free (Pb-free) solder is provided. Key parameters include a pre-heat zone up to 150-200°C, a peak body temperature not exceeding 260°C, and a time above 260°C limited to a maximum of 10 seconds. The LED can withstand this reflow cycle a maximum of two times.

6.2 Manual Soldering & Storage

If manual soldering with an iron is necessary, the tip temperature must not exceed 300°C, and contact time should be limited to 3 seconds per pad, for one time only. For storage, LEDs should be kept in an environment not exceeding 30°C and 70% relative humidity. Components removed from their original moisture-barrier packaging should be reflowed within 672 hours (28 days). If storage exceeds this period, a baking process at approximately 60°C for 24 hours is recommended before assembly to remove absorbed moisture and prevent "popcorning" during reflow.

6.3 Cleaning

If post-solder cleaning is required, only specified alcohol-based solvents like ethyl alcohol or isopropyl alcohol should be used. The LED should be immersed at normal temperature for less than one minute. The use of unspecified chemical cleaners can damage the plastic package material.

7. Packaging and Ordering Information

The standard packaging is a 7-inch reel containing 3000 pieces. For quantities less than a full reel, a minimum pack of 500 pieces is available for remainder quantities. The tape system ensures components are correctly oriented and spaced. The packaging specifications note that empty pockets in the carrier tape are sealed with cover tape, and a maximum of two consecutive missing components is allowed, which are standard quality assurances for automated handling.

8. Application Recommendations

8.1 Drive Circuit Design

LEDs are current-driven devices. To ensure uniform brightness when driving multiple LEDs in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED (Circuit Model A). Driving LEDs directly in parallel without individual resistors (Circuit Model B) is not recommended, as slight variations in the forward voltage (Vf) characteristic from one LED to another can cause significant differences in current sharing and, consequently, brightness.

8.2 Electrostatic Discharge (ESD) Protection

This component is sensitive to electrostatic discharge. Proper ESD control measures must be implemented during handling and assembly. These include the use of grounded wrist straps and work surfaces, anti-static gloves, and ionizers to neutralize static charge that may accumulate on the plastic lens. ESD damage can manifest as high reverse leakage current, abnormally low forward voltage, or failure to illuminate at low currents. A simple test for ESD damage is to check for illumination and a forward voltage greater than 1.4V at a very low test current of 0.1mA.

8.3 Application Scope and Cautions

This LED is intended for use in ordinary electronic equipment such as office equipment, communication devices, and household appliances. It is not designed or qualified for safety-critical applications where failure could jeopardize life or health (e.g., aviation, medical life-support, transportation safety systems). For such applications, components with appropriate reliability qualifications must be sourced.

9. Technical Comparison and Differentiation

The use of AlInGaP semiconductor material is a key differentiator. Compared to older technologies like standard GaP, AlInGaP LEDs offer significantly higher luminous efficiency, resulting in much brighter output for the same drive current. The 130-degree wide viewing angle is advantageous for applications requiring broad visibility. The compatibility with high-temperature, lead-free reflow profiles makes it a modern component suitable for RoHS-compliant manufacturing lines. The defined binning structure provides a level of brightness consistency that is critical for multi-LED displays and indicator panels.

10. Frequently Asked Questions (Based on Technical Parameters)

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

A: Peak wavelength (λP) is the single wavelength at which the spectral power output is highest (639 nm typical). Dominant wavelength (λd) is derived from the CIE color chart and represents the single wavelength that best matches the perceived color of the light (631 nm). Dominant wavelength is more relevant for color specification.

Q: Can I drive this LED at its maximum DC current of 30mA continuously?

A: Yes, but only if the ambient temperature is at or below 25°C. At higher ambient temperatures, the current must be reduced according to the derating factor of 0.4 mA/°C above 50°C to avoid exceeding the maximum junction temperature and compromising reliability.

Q: Why is an individual series resistor recommended for each LED in parallel?

A: The forward voltage (Vf) of LEDs has a production tolerance. Without individual resistors, LEDs with a slightly lower Vf will draw disproportionately more current, becoming brighter and potentially overheating, while those with a higher Vf will be dimmer. The resistor acts as a simple current regulator for each LED.

11. Practical Design and Usage Examples

Example 1: Status Indicator Panel: A control panel requires ten uniformly bright red status indicators. The designer selects LEDs from the same intensity bin (e.g., Bin P) to ensure visual consistency. Each LED is driven by a 5V supply through a series resistor. The resistor value is calculated as R = (Vsupply - Vf_LED) / I_LED. Using a typical Vf of 2.4V and a target current of 20mA, R = (5 - 2.4) / 0.02 = 130 Ohms. A standard 130Ω or 150Ω resistor would be used for each LED independently.

Example 2: High-Temperature Environment: An LED is needed inside an enclosure where the local ambient temperature near the PCB is measured to be 70°C. The maximum allowable DC current must be derated. The derating starts at 50°C. Temperature rise above 50°C is 70°C - 50°C = 20°C. Current reduction = 20°C * 0.4 mA/°C = 8 mA. Therefore, the maximum safe continuous current at 70°C ambient is 30 mA - 8 mA = 22 mA. The drive circuit should be designed to not exceed this current.

12. Operating Principle Introduction

Light emission in this LED is based on the principle of electroluminescence in a semiconductor p-n junction made of AlInGaP materials. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the active region where they recombine. The energy released during this recombination is emitted in the form of photons (light). The specific composition of the Aluminum, Indium, Gallium, and Phosphide in the crystal lattice determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, red. The water-clear epoxy lens encapsulates the chip, provides mechanical protection, and shapes the light output pattern.

13. Technology Trends and Context

AlInGaP technology represents a mature and highly efficient solution for red, orange, and yellow LEDs. Its development was a significant step forward from earlier technologies, offering vastly improved brightness and efficiency. Current trends in indicator LEDs focus on increasing efficiency (lumens per watt) further, enabling lower power consumption and reduced heat generation. There is also a drive towards miniaturization of packages while maintaining or increasing light output. Furthermore, the industry continues to emphasize compatibility with harsh assembly processes (like high-temperature lead-free reflow) and stringent reliability requirements for automotive and industrial applications, areas where components like this are commonly deployed.