SMD LED LTST-020KRKT Datasheet - 2.0x1.25x1.1mm - 2.4V - 72mW - Red AlInGaP - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a miniature surface-mount device (SMD) light-emitting diode (LED). This component is designed for automated printed circuit board (PCB) assembly processes, making it ideal for high-volume manufacturing. Its compact form factor addresses the needs of space-constrained applications across a broad spectrum of modern electronics.

1.1 Core Advantages

The LED offers several key advantages for design engineers and manufacturers. It is compliant with RoHS (Restriction of Hazardous Substances) directives, ensuring environmental safety. The component is supplied in industry-standard 12mm tape on 7-inch reels, which is fully compatible with automated pick-and-place machinery, streamlining the assembly line. Furthermore, it is designed to withstand infrared (IR) reflow soldering processes, which are standard for lead-free (Pb-free) PCB assembly. Its electrical characteristics are compatible with integrated circuit (IC) logic levels, simplifying drive circuit design.

1.2 Target Market and Applications

The versatility of this SMD LED makes it suitable for a wide range of electronic equipment. Primary application areas include telecommunications devices such as cordless and cellular phones, portable computing like notebooks and tablets, and networking systems. It is also commonly used in home appliances for status indication and in various industrial equipment. Specific functions within these devices encompass status indicators, backlighting for front panels and keypads, and low-level illumination for symbols and signals.

2. In-Depth Technical Parameter Analysis

A thorough understanding of the electrical and optical parameters is crucial for reliable circuit design and achieving consistent performance.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are specified at an ambient temperature (Ta) of 25°C. The maximum continuous DC forward current (IF) is 30 mA. Under pulsed conditions with a 1/10 duty cycle and 0.1ms pulse width, a peak forward current of 80 mA is permissible. The total power dissipation (Pd) must not exceed 72 mW. The device is rated for operation within a temperature range of -40°C to +85°C and can be stored in environments from -40°C to +100°C.

2.2 Electro-Optical Characteristics

These characteristics are measured under standard test conditions (Ta=25°C, IF=20mA) and define the typical performance. The luminous intensity (Iv) has a typical value within a defined range, with specific minimum and maximum values detailed in the binning section. The viewing angle (2θ1/2), where intensity is half the on-axis value, is 110 degrees, providing a wide beam pattern. The light emitted is in the red spectrum, with a peak emission wavelength (λp) of 639 nm and a dominant wavelength (λd) of 631 nm. The spectral bandwidth (Δλ) is approximately 20 nm. The forward voltage (VF) typically measures 2.0 volts, with a maximum of 2.4 volts at 20mA. The reverse current (IR) is limited to a maximum of 10 μA at a reverse voltage (VR) of 5V; note that the device is not designed for operation under reverse bias.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. This allows designers to select components that meet specific minimum performance criteria for their application.

3.1 Luminous Intensity Binning

The luminous intensity is categorized into distinct bins, each defined by a code (R1, R2, S1, S2) and a min/max intensity range measured in millicandelas (mcd) at 20mA. For example, bin R1 covers intensities from 112 to 140 mcd, while bin S2 covers 220 to 280 mcd. A tolerance of +/-11% applies within each bin. This system enables procurement of LEDs with guaranteed minimum brightness levels.

4. Performance Curve Analysis

Graphical data provides deeper insight into device behavior under varying conditions, which is essential for robust design.

4.1 Forward Current vs. Luminous Intensity

The relationship between forward current (IF) and luminous intensity (Iv) is generally linear within the operating range. Increasing the current increases light output, but designers must stay within the absolute maximum current and power dissipation limits to ensure longevity.

4.2 Forward Voltage vs. Forward Current

This curve shows the diode's IV characteristic. The forward voltage increases logarithmically with current. Understanding this curve is important for designing the current-limiting resistor in series with the LED to set the desired operating point and compensate for supply voltage variations.

4.3 Temperature Dependence

LED performance is temperature-sensitive. Typically, the forward voltage (VF) decreases slightly with increasing junction temperature, while the luminous intensity (Iv) also decreases. Designs for high ambient temperature environments or high-power operation must account for this derating.

5. Mechanical and Package Information

5.1 Package Dimensions

The device conforms to an industry-standard SMD package outline. Key dimensions include a body length of 2.0 mm, a width of 1.25 mm, and a height of 1.1 mm. All dimensional tolerances are typically ±0.1 mm unless otherwise specified. Detailed mechanical drawings should be consulted for precise land pattern design.

5.2 Polarity Identification and Pad Design

The cathode is typically marked on the device, often by a notch, a green dot, or a different lead length. The recommended PCB land pattern (footprint) is provided to ensure proper solder joint formation during reflow. This pattern is crucial for achieving reliable mechanical and electrical connection while preventing solder bridging or tombstoning.

6. Soldering and Assembly Guidelines

Proper handling and assembly are critical to maintaining device reliability and performance.

6.1 Recommended IR Reflow Profile

For lead-free (Pb-free) soldering processes, a specific reflow temperature profile is recommended, compliant with standards such as J-STD-020. This profile includes a preheat stage, a temperature ramp, a time above liquidus (TAL), a peak temperature not exceeding 260°C, and a controlled cooling rate. Adherence to this profile prevents thermal shock and damage to the LED package.

6.2 Storage Conditions

SMD LEDs are moisture-sensitive devices (MSD). When stored in their original sealed moisture-barrier bag with desiccant, they should be kept at ≤30°C and ≤70% relative humidity (RH) and used within one year. Once the bag is opened, the \"floor life\" begins. Components should be stored at ≤30°C and ≤60% RH and are recommended to be processed (reflow soldered) within 168 hours (7 days). If exposed for longer, a baking procedure (e.g., 60°C for 48 hours) is required to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.3 Cleaning

If cleaning after soldering is necessary, 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. Harsh or unspecified chemicals can damage the epoxy lens or the package material.

7. Packaging and Handling

The components are supplied on embossed carrier tape with a protective cover tape, wound onto 7-inch (178 mm) diameter reels. Standard reel quantities are 4000 pieces per reel. The packaging complies with ANSI/EIA-481 specifications. Proper ESD (electrostatic discharge) precautions should be observed during handling.

8. Application Notes and Design Considerations

8.1 Drive Circuit Design

LEDs are current-driven devices. To ensure consistent brightness and prevent current hogging, each LED in a parallel configuration must have its own current-limiting resistor. The resistor value is calculated using Ohm's Law: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the LED forward voltage, and IF is the desired forward current. Driving the LED with a constant current source is the most stable method.

8.2 Thermal Management

Although power dissipation is low, effective thermal management on the PCB can enhance longevity and maintain stable light output. Ensuring adequate copper area around the LED pads helps dissipate heat. For applications involving high ambient temperatures or high drive currents, thermal considerations become more critical.

8.3 Optical Design

The 110-degree viewing angle provides a wide emission pattern suitable for status indicators. For applications requiring a more focused beam, secondary optics such as lenses or light pipes may be employed. The choice of lens color (water clear in this case) affects the perceived color and diffusion of the emitted light.

9. Reliability and Cautions

This product is designed for use in standard commercial and industrial electronic equipment. For applications requiring exceptional reliability where failure could risk safety (e.g., aviation, medical life-support), additional qualification and consultation with the component manufacturer are mandatory. Always operate the device within its published Absolute Maximum Ratings and recommended operating conditions.

10. Technical Comparison and Trends

This AlInGaP-based red LED offers advantages in efficiency and color stability compared to older technologies like GaAsP. The trend in SMD LEDs continues toward higher luminous efficacy (more light output per watt), smaller package sizes, and improved reliability under harsh environmental conditions. The adoption of lead-free and RoHS-compliant materials and processes is now standard across the industry.