SMD LED LTST-C990NRKT-PO Datasheet - AlInGaP Red - 20mA - 900-2240mcd - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) LED lamp. This component is designed for automated printed circuit board (PCB) assembly, featuring a miniature form factor ideal for space-constrained applications. Its primary function is to serve as a visual indicator or backlight source across a diverse range of electronic equipment.

1.1 Core Advantages and Target Market

The LED offers several key advantages for modern electronics manufacturing. It utilizes an Ultra Bright AlInGaP (Aluminum Indium Gallium Phosphide) chip, which provides high luminous efficiency for red emission. The device is packaged on 8mm tape wound onto 7-inch diameter reels, conforming to EIA standards, making it fully compatible with high-speed automatic pick-and-place equipment. Furthermore, it is designed to withstand standard infrared (IR) reflow soldering processes commonly used in Pb-free (lead-free) assembly lines, ensuring reliable attachment to the PCB. The product is compliant with the Restriction of Hazardous Substances (RoHS) directive.

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

2. In-Depth Technical Parameter Analysis

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

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed.

• Power Dissipation (Pd): 62.5 mW. This is the maximum amount of power the LED package can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 60 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to manage thermal stress.
• Continuous DC Forward Current (I_F): 25 mA. This is the maximum recommended current for continuous operation.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage exceeding this value can cause breakdown and failure.
• Operating Temperature Range: -30°C to +85°C. The ambient temperature range over which the LED is designed to function.
• Storage Temperature Range: -40°C to +85°C. The temperature range for non-operational storage.
• Infrared Soldering Condition: 260°C for 10 seconds. The maximum thermal profile the package can endure during reflow soldering.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under standard test conditions.

• Luminous Intensity (I_V): 900.0 - 2240.0 mcd (millicandela). Measured at a forward current (I_F) of 20mA. The intensity is measured using a sensor and filter combination that approximates the photopic (CIE eye-response) curve. The wide range indicates a binning system is used (see Section 4).
• Viewing Angle (2θ_1/2): 75 degrees. This is the full angle at which the luminous intensity is half the value measured on the central axis (0°). A 75-degree angle provides a relatively wide viewing cone.
• Peak Emission Wavelength (λ_P): 639 nm (nanometers). This is the wavelength at which the spectral power distribution of the emitted light is at its maximum.
• Dominant Wavelength (λ_d): 624.0 - 632.0 nm. This is derived from the CIE chromaticity diagram and represents the perceptual color of the LED, which is in the red region of the spectrum.
• Spectral Line Half-Width (Δλ): 20 nm. This indicates the spectral bandwidth, measured as the full width at half maximum (FWHM) of the emission peak. A value of 20nm is typical for a monochromatic AlInGaP red LED.
• Forward Voltage (V_F): 1.7 - 2.5 V. The voltage drop across the LED when driven at 20mA. This range accounts for normal manufacturing variance in the semiconductor chip.
• Reverse Current (I_R): 10 μA (max). The small leakage current that flows when the maximum reverse voltage (5V) is applied.

3. Binning System Explanation

To ensure consistency in applications, LEDs are sorted (binned) based on key optical parameters after manufacture.

3.1 Luminous Intensity Binning

The primary binning parameter for this LED is its luminous intensity. The product is categorized into several bins, each with a defined minimum and maximum intensity value when driven at 20mA. The bin code, printed on the reel or packaging, allows designers to select LEDs with consistent brightness for their application. The tolerance within each bin is +/- 15%. The bin list is as follows:

• Bin Code V2: 900.0 - 1120.0 mcd
• Bin Code W1: 1120.0 - 1400.0 mcd
• Bin Code W2: 1400.0 - 1800.0 mcd
• Bin Code X1: 1800.0 - 2240.0 mcd

Selecting a higher bin code (e.g., X1) guarantees a higher minimum brightness, which is crucial for applications requiring uniform high visibility or where driving current may be limited.

4. Performance Curve Analysis

Graphical data provides deeper insight into the LED's behavior under varying conditions. Typical curves included in the datasheet illustrate the relationship between key parameters.

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

This curve shows the non-linear relationship between the current flowing through the LED and the voltage across it. The 'knee' of the curve, typically around 1.7V to 2.0V for this device, is where the LED begins to emit light significantly. Above this knee, a small increase in voltage causes a large increase in current. Therefore, LEDs are always driven with a current-limiting mechanism, not a fixed voltage source.

4.2 Luminous Intensity vs. Forward Current

This graph demonstrates how light output increases with drive current. For most LEDs, the relationship is approximately linear within the recommended operating range (up to 25mA for this device). Driving the LED beyond its maximum continuous current rating will not produce proportionally more light and will generate excessive heat, reducing lifespan and reliability.

4.3 Spectral Distribution

The spectral plot shows the relative radiant power emitted across different wavelengths. It will feature a single, dominant peak centered around 639 nm (the peak wavelength) with a characteristic shape defined by the 20 nm half-width. This confirms the monochromatic red color output.

5. Mechanical and Packaging Information

5.1 Device Dimensions and Polarity

The LED package has specific physical dimensions critical for PCB footprint design. The datasheet provides a detailed dimensional drawing. Key features include the overall length, width, and height. The package also has a polarity indicator, typically a notch, a green dot, or a cathode mark on one end, which must be aligned correctly with the PCB footprint to ensure proper electrical connection (anode vs. cathode).

5.2 Recommended PCB Attachment Pad Layout

A suggested land pattern (copper pad layout) for the PCB is provided. This pattern is designed to ensure a reliable solder joint during reflow, provide adequate thermal relief, and prevent solder bridging. Following this recommendation is essential for successful assembly and long-term mechanical stability.

5.3 Tape and Reel Packaging Specifications

For automated assembly, components are supplied in carrier tape on reels. The datasheet specifies the dimensions of the tape pockets that hold each LED, the tape width, and the reel dimensions (7-inch diameter). Standard reel quantities are 3000 pieces. The packaging conforms to ANSI/EIA-481 specifications. Notes include details on cover tape, maximum consecutive missing components (2), and minimum order quantities for remnants (500 pieces).

6. Soldering, Assembly, and Handling Guidelines

6.1 Recommended IR Reflow Profile

For Pb-free soldering processes, a specific thermal profile is recommended to prevent damage. Key parameters include:

• Pre-heat Temperature: 150-200°C
• Pre-heat Time: Maximum 120 seconds
• Peak Body Temperature: Maximum 260°C
• Time Above 260°C: Maximum 10 seconds (maximum of two reflow cycles allowed)

The profile should be developed in accordance with JEDEC standards and validated with the specific PCB design, solder paste, and oven used in production.

6.2 Storage Conditions

Proper storage is vital due to the moisture sensitivity of the plastic package (MSL 3).

• Sealed Package: Store at ≤30°C and ≤90% RH. Use within one year of the pack date.
• Opened Package: For components removed from their moisture-proof bag, the ambient should not exceed 30°C and 60% RH. It is recommended to complete IR reflow within one week. For storage beyond one week, bake the LEDs at 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent 'popcorning' during reflow.

6.3 Cleaning

If cleaning after soldering is necessary, use only approved solvents. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is specified. Harsh or unspecified chemicals can damage the plastic lens and package.

6.4 Electrostatic Discharge (ESD) Caution

The semiconductor chip inside the LED is sensitive to electrostatic discharge and voltage surges. Handling precautions are required: use a grounded wrist strap or anti-static gloves, and ensure all equipment and work surfaces are properly grounded.

7. Application Design Considerations

7.1 Drive Circuit Design

LEDs are current-driven devices. The most critical aspect of the drive circuit is current regulation. To ensure uniform brightness, especially when multiple LEDs are connected in parallel, a current-limiting resistor should be placed in series with each individual LED. A simple drive circuit consists of a voltage source (V_CC), the LED, and a series resistor (R_S). The resistor value is calculated using Ohm's Law: R_S = (V_CC - V_F) / I_F, where V_F is the forward voltage of the LED at the desired current I_F (e.g., 20mA). Using a resistor for each LED compensates for minor variations in V_F from device to device.

7.2 Thermal Management

While the power dissipation is low (62.5 mW max), effective thermal management extends LED life and maintains stable light output. The PCB itself acts as a heat sink. Ensuring a good thermal connection from the LED's solder pads to copper planes on the PCB helps dissipate heat. Avoid operating the LED at its absolute maximum current and temperature limits for extended periods.

7.3 Application Scope and Limitations

This LED is intended for general-purpose electronic equipment. For applications requiring exceptional reliability where failure could jeopardize safety (e.g., aviation, medical life-support, transportation safety systems), additional qualification and consultation with the component manufacturer are necessary prior to design-in.

8. Technical Comparison and Differentiation

Compared to older technologies like GaAsP (Gallium Arsenide Phosphide) red LEDs, the AlInGaP chip used here offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. The dome lens design helps achieve the specified 75-degree viewing angle, providing a good balance between axial brightness and off-axis visibility. The compatibility with automated placement and IR reflow makes it a cost-effective choice for high-volume manufacturing, differentiating it from LEDs requiring manual soldering.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Why is my LED dim or has inconsistent brightness compared to others on the board?
A: The most common cause is not using individual current-limiting resistors for each LED when they are connected in parallel. Small variations in forward voltage (V_F) cause current sharing to be unequal. Always use a series resistor for each LED. Also, check that you are using LEDs from the same luminous intensity bin.

Q: Can I drive this LED with 3.3V without a resistor?
A: No. Connecting an LED directly to a voltage source like 3.3V would cause excessive current to flow, likely exceeding the maximum DC forward current (25mA) and destroying the device. A series resistor is mandatory to limit the current to a safe value (e.g., 20mA).

Q: The datasheet shows a forward voltage range of 1.7V to 2.5V. Which value should I use for my resistor calculation?
A: For a conservative design that ensures the current does not exceed your target (e.g., 20mA) even with a low-V_F LED, use the minimum V_F value (1.7V) in your calculation. This results in a slightly higher resistor value and a slightly lower current for LEDs with higher V_F, but guarantees safety for all devices.

Q: What does 'MSL 3' mean for storage?
A> Moisture Sensitivity Level 3 indicates the package can be exposed to factory floor conditions (≤30°C/60% RH) for up to 168 hours (one week) before it requires baking prior to reflow soldering. Exceeding this time risks internal package damage during the high-temperature reflow process.

10. Design and Usage Case Study

Scenario: Designing a status indicator panel with 10 uniformly bright red LEDs.
1. Circuit Design: Use a 5V supply rail. Target I_F = 20mA. Assuming a typical V_F of 2.1V, calculate R_S = (5V - 2.1V) / 0.020A = 145 Ohms. The nearest standard value is 150 Ohms. Place one 150-ohm resistor in series with the anode of each of the 10 LEDs. Connect all cathode sides to ground.
2. PCB Layout: Use the recommended land pattern from the datasheet. Ensure polarity markings on the PCB silkscreen match the LED's polarity indicator. Provide a solid ground plane for thermal dissipation and electrical return.
3. Procurement: Specify the required luminous intensity bin code (e.g., W2 for 1400-1800 mcd) to the distributor to ensure all 10 LEDs have similar brightness.
4. Assembly: Follow the recommended IR reflow profile. After assembly, if cleaning is needed, use isopropyl alcohol.
This approach ensures reliable operation, consistent visual appearance, and long-term stability for the indicator panel.

11. Operating Principle Introduction

An LED is a semiconductor diode. Its core is a p-n junction made from direct bandgap materials like AlInGaP. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the junction region. When an electron recombines with a hole, energy is released. In an LED, this energy is released in the form of a photon (light particle). The wavelength (color) of the emitted photon is determined by the bandgap energy of the semiconductor material. AlInGaP has a bandgap corresponding to red light. The dome-shaped epoxy lens serves to protect the semiconductor chip and to shape the light output beam, extracting more light from the chip and defining the viewing angle.

12. Technology Trends

The general trend in SMD indicator LEDs continues toward higher efficiency, smaller package sizes, and increased reliability. While AlInGaP remains the dominant technology for high-efficiency red and amber LEDs, other materials like InGaN (Indium Gallium Nitride) cover the blue, green, and white spectrum. There is ongoing development in chip-scale packaging (CSP) where the LED chip is mounted directly without a traditional plastic package, enabling even smaller form factors. Furthermore, integration of control electronics, such as constant-current drivers, within the LED package itself is a growing trend to simplify circuit design and improve performance consistency.