SMD LED LTST-010KRKT Datasheet - AlInGaP Red - 20mA - 2.0V Typ - English Technical Document

1. Product Overview

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

The LED utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material to produce red light. This material technology is known for its high efficiency and good performance in the red to amber spectral regions. The device is encapsulated in a water-clear lens package, which typically offers a wider viewing angle compared to diffused or colored lenses, as the light is not scattered by pigment within the epoxy.

1.1 Core Advantages and Target Market

The primary advantages of this SMD LED stem from its package design and manufacturing compatibility. It conforms to standard EIA package outlines, ensuring mechanical compatibility with industry-standard pick-and-place machines and feeder systems. The device is fully compatible with infrared (IR) reflow soldering processes, which is the dominant method for assembling surface-mount components. This compatibility is crucial for achieving reliable, high-strength solder joints in automated production lines.

Its application space is broad, targeting consumer, communication, and industrial electronics. Key target markets include status indication and backlighting for front panels in devices such as cellular phones, notebook computers, networking equipment, and various home appliances. It is also suitable for indoor signboard applications where reliable, low-power illumination is required.

2. In-Depth Technical Parameter Analysis

A thorough understanding of the electrical and optical parameters is essential for proper circuit design and performance prediction.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation (Pd): 72 mW. This is the maximum amount of power the device can dissipate as heat without exceeding its maximum junction temperature. Exceeding this limit risks thermal runaway and failure.
• DC Forward Current (IF): 30 mA. The maximum continuous forward current that can be applied.
• Peak Forward Current: 80 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This allows for brief periods of higher brightness, such as in blinking indicators, without overheating.
• Reverse Voltage (VR): 5 V. LEDs are not designed for reverse bias operation. Exceeding this voltage can cause immediate and catastrophic failure due to avalanche breakdown.
• Operating & Storage Temperature: -40°C to +85°C (operating), -40°C to +100°C (storage). These ranges ensure reliable performance in harsh environments.

2.2 Electrical & Optical Characteristics (Typical at 25°C)

These parameters are measured under standard test conditions and represent typical performance.

• Luminous Intensity (Iv): Measured at a forward current (IF) of 20 mA. The value is specified in millicandelas (mcd). The luminous intensity is measured using a sensor and filter combination that approximates the photopic (human eye) response curve (CIE standard).
• Forward Voltage (VF): Typically 2.0 V, with a maximum of 2.4 V at 20 mA. This parameter has a tolerance of ±0.1 V. It is crucial for calculating the series current-limiting resistor value. A lower VF generally indicates higher electrical efficiency.
• Viewing Angle (2θ½): 110 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on-axis (0 degrees). A 110-degree angle indicates a relatively wide beam pattern, suitable for indicators that need to be seen from various angles.
• Peak Wavelength (λP): 639 nm. This is the wavelength at which the spectral power output is greatest.
• Dominant Wavelength (λD): 631 nm. This is the single wavelength perceived by the human eye that matches the color of the LED's light. It is the more relevant parameter for color specification.
• Spectral Line Half-Width (Δλ): 20 nm. This indicates the spectral purity or bandwidth of the emitted light. A smaller value means a more monochromatic (pure color) output.
• Reverse Current (IR): Maximum 10 μA at VR=5V. This is a leakage current specification for the reverse bias test condition only.

3. Bin Ranking System

To manage production variations, LEDs are sorted into performance bins. This ensures consistency within a specific order. The datasheet defines bins based on Luminous Intensity at 20 mA.

The intensity bins for the red LED are as follows:

• R1: 112.0 mcd (Min) to 140.0 mcd (Max)
• R2: 140.0 mcd to 180.0 mcd
• S1: 180.0 mcd to 224.0 mcd
• S2: 224.0 mcd to 280.0 mcd

A tolerance of ±11% is applied to each bin. This means an LED labeled as bin S1 could have an actual intensity between approximately 160 mcd and 248 mcd. Designers must account for this variation, especially when multiple LEDs are used together and uniform brightness is desired. Using a constant-current driver or individual series resistors for each LED (as recommended in the drive method section) is critical to minimize brightness differences caused by forward voltage (VF) variation, which is independent of the intensity bin.

4. Mechanical and Package Information

The physical dimensions of the component are critical for PCB layout (footprint design). The datasheet provides a detailed package drawing with all critical dimensions. Key takeaways include:

• The package is a standard SMD outline.
• All dimensions are provided in millimeters.
• A standard tolerance of ±0.1 mm applies unless otherwise noted.
• The drawing clearly shows the cathode identifier (typically a notch, green mark, or other visual cue on the package). Correct polarity orientation during assembly is mandatory.

4.1 Recommended PCB Attachment Pad

The datasheet includes a diagram for the recommended solder pad layout on the PCB. Following this layout is essential for achieving a reliable solder joint during reflow. The pad design accounts for factors like solder fillet formation, component self-alignment during reflow, and prevention of solder bridging or tombstoning.

5. Soldering, Assembly, and Handling Guidelines

Proper handling and assembly are vital for reliability.

5.1 IR Reflow Soldering Profile

The datasheet provides a suggested reflow profile compliant with J-STD-020B for lead-free (Pb-free) solder processes. Key parameters include:

• Pre-heat: Temperature range and time to gradually heat the board and activate the flux.
• Peak Temperature: Maximum of 260°C. The component body must not exceed this temperature.
• Time Above Liquidus (TAL): The time the solder is in a molten state, critical for joint formation.
• Ramp Rates: Controlled heating and cooling rates to prevent thermal shock.

The profile is a guideline; the final profile must be characterized for the specific PCB assembly, considering board thickness, component density, and solder paste used.

5.2 Storage and Moisture Sensitivity

The LEDs are moisture-sensitive. If the sealed moisture-proof bag is opened, the components are exposed to ambient humidity.

• Floor Life: It is recommended to complete IR reflow within 168 hours (7 days) after opening the original bag.
• Extended Storage: If not used within 168 hours, components should be stored in a sealed container with desiccant or baked (e.g., 60°C for 48 hours) before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

5.3 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used. The datasheet recommends alcohol-based cleaners like isopropyl alcohol (IPA) or ethyl alcohol. Immersion should be at normal temperature and for less than one minute to avoid damaging the package epoxy.

5.4 Drive Method

LEDs are current-driven devices. Their light output is proportional to forward current, not voltage. The datasheet strongly recommends using a series current-limiting resistor for each LED when connecting multiple LEDs in parallel (Circuit Model A). This is because the forward voltage (VF) of LEDs can vary from unit to unit, even within the same bin. Connecting them directly in parallel without individual resistors can cause significant current imbalance, leading to uneven brightness and potential over-current in the LED with the lowest VF. Using a resistor with each LED helps equalize the current and protects the devices.

6. Packaging and Ordering

The components are supplied in a tape-and-reel format suitable for automated assembly equipment.

• Reel Size: 7-inch diameter reel.
• Tape Width: 12 mm.
• Quantity per Reel: 4000 pieces.
• Minimum Order Quantity: 500 pieces for remainder quantities.
• The packaging conforms to ANSI/EIA-481 specifications.

Detailed dimensions for the carrier tape, cover tape, and reel are provided to ensure compatibility with assembly machine feeders.

7. Application Notes and Design Considerations

7.1 Thermal Management

While the power dissipation is relatively low (72 mW max), proper thermal design is still important for longevity, especially at high ambient temperatures or when driven near maximum current. The PCB layout should provide adequate copper area around the LED pads to act as a heat sink and conduct heat away from the junction.

7.2 Current Setting and Resistor Calculation

To operate the LED at a desired current (e.g., 20 mA for rated intensity), a series resistor (R) is calculated using Ohm's Law: R = (V_supply - VF_LED) / I_desired. Using the maximum VF (2.4V) in the calculation ensures the current does not exceed the desired value even with worst-case component variation. For example, with a 5V supply and a desired 20mA current: R = (5V - 2.4V) / 0.02A = 130 Ohms. The nearest standard value (e.g., 120 or 150 Ohms) would be selected, considering the resulting current and power rating of the resistor (P = I²R).

7.3 Application Reliability

The datasheet includes a cautionary note regarding applications requiring exceptional reliability, such as in aviation, medical, or safety-critical systems. For these applications, additional qualification, derating, and consultation with the component manufacturer are strongly advised. The standard product is intended for general-purpose consumer and industrial electronics.

8. Technical Comparison and Trends

This AlInGaP red LED represents a mature and reliable technology. Compared to older technologies like Gallium Arsenide Phosphide (GaAsP), AlInGaP offers significantly higher luminous efficiency and better performance at elevated temperatures. Its dominant wavelength of 631 nm places it in a standard red color region.

In the broader LED market, trends continue towards higher efficiency (more lumens per watt), smaller package sizes, and higher maximum drive currents for increased brightness. There is also a move towards tighter binning tolerances for color and intensity to meet the demands of applications like full-color displays and architectural lighting, where color consistency is paramount. While this specific component is a single-color, discrete indicator LED, the underlying packaging and assembly principles are shared with more advanced LED products, including power LEDs and integrated LED modules.