SMD LED LTST-C150KDKT-10A Datasheet - 1.6x0.8x0.6mm - 2.4V - 50mW - Red AllnGaP - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a surface-mount device (SMD) LED lamp. Designed for automated printed circuit board (PCB) assembly, this component is ideal for space-constrained applications across a broad spectrum of electronic equipment.

1.1 Features

• Compliant with RoHS environmental directives.
• Utilizes an ultra-bright Aluminum Indium Gallium Phosphide (AllnGaP) semiconductor chip emitting red light.
• Packaged on 8mm tape wound onto 7-inch diameter reels for automated handling.
• Standard EIA package footprint.
• Input compatible with standard integrated circuit (IC) logic levels.
• Designed for compatibility with automated pick-and-place assembly equipment.
• Withstands standard infrared (IR) reflow soldering processes.

1.2 Target Applications

This LED is suitable for a wide range of applications requiring a compact, reliable indicator or backlight source, including but not limited to:

• Telecommunication devices, office automation equipment, home appliances, and industrial control systems.
• Backlighting for keypads and keyboards.
• Status and power indicators.
• Micro-displays and panel indicators.
• Signal and symbolic illumination.

2. Technical Parameters: In-Depth Objective Interpretation

The following sections provide a detailed analysis of the device's electrical, optical, and environmental specifications.

2.1 Absolute Maximum Ratings

These values represent the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 50 mW. This is the maximum amount of power the device can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 40 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• Continuous Forward Current (I_F): 20 mA. This is the maximum recommended DC current for continuous operation.
• Reverse Voltage (V_R): 5 V. Applying a reverse bias voltage exceeding this value can cause junction breakdown.
• Operating Temperature Range: -30°C to +85°C. The ambient temperature range over which the device is designed to function.
• Storage Temperature Range: -40°C to +85°C. The temperature range for non-operational storage.
• Infrared Reflow Soldering Condition: 260°C peak temperature for a maximum of 10 seconds. This defines the thermal profile the package can withstand during assembly.

2.2 Electro-Optical Characteristics

These parameters define the typical performance of the device under normal operating conditions (Ta=25°C, I_F=10mA unless noted).

• Luminous Intensity (I_V): 2.8 to 28.0 mcd (millicandela). The perceived brightness of the light output. The wide range is managed through a binning system.
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on-axis. A wide viewing angle like this provides a broad, diffuse light pattern suitable for indicators.
• Peak Emission Wavelength (λ_P): 650.0 nm (nanometers). The wavelength at which the spectral power output is maximum.
• Dominant Wavelength (λ_d): 630.0 to 645.0 nm. This is the single wavelength perceived by the human eye that defines the color (red, in this case). It is derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 20 nm (typical). This indicates the spectral purity or bandwidth of the emitted light, measured as the width of the spectrum at half its maximum power.
• Forward Voltage (V_F): 1.6 to 2.4 V. The voltage drop across the LED when driven at the specified test current (10mA).
• Reverse Current (I_R): 10 μA (microamperes) maximum. The small leakage current that flows when the maximum reverse voltage (5V) is applied.

3. Binning System Explanation

To ensure consistency in brightness for production applications, LEDs are sorted into performance groups, or \"bins.\"

3.1 Luminous Intensity Bin Code

The primary binning for this product is based on luminous intensity measured at 10mA. The tolerance within each bin is +/-15%.

• Bin H: 2.8 - 4.5 mcd
• Bin J: 4.5 - 7.1 mcd
• Bin K: 7.1 - 11.2 mcd
• Bin L: 11.2 - 18.0 mcd
• Bin M: 18.0 - 28.0 mcd

This system allows designers to select an appropriate brightness grade for their specific application, balancing cost and performance.

4. Performance Curve Analysis

While specific graphical data is referenced in the source document, the key relationships are described here based on standard LED physics and the provided parameters.

4.1 Current vs. Voltage (I-V) Characteristic

An LED is a diode. Its forward voltage (V_F) has a logarithmic relationship with forward current (I_F). The specified V_F range of 1.6V to 2.4V at 10mA is typical for a red AllnGaP LED. Operating above the recommended continuous current (20mA) will cause V_F to increase slightly but will primarily generate excessive heat, reducing efficiency and lifespan.

4.2 Luminous Intensity vs. Forward Current

The light output (I_V) is approximately proportional to the forward current over a significant range. However, efficiency tends to drop at very high currents due to increased thermal effects and other non-ideal semiconductor behaviors. Driving the LED at the typical 10mA or 20mA ensures optimal efficiency and reliability.

4.3 Temperature Dependence

LED performance is temperature-sensitive. As the junction temperature increases:

• Forward Voltage (V_F): Decreases. This has a negative temperature coefficient.
• Luminous Intensity (I_V): Decreases. Higher temperatures reduce the internal quantum efficiency of the semiconductor, leading to lower light output for the same current.
• Dominant Wavelength (λ_d): May shift slightly, potentially altering the perceived color hue.

Proper thermal management in the PCB design is crucial for maintaining consistent performance.

4.4 Spectral Distribution

The emission spectrum centers around a peak wavelength (λ_P) of 650 nm with a typical half-width (Δλ) of 20 nm. This results in a saturated red color. The dominant wavelength (λ_d), which defines the perceived color, falls between 630 nm and 645 nm.

5. Mechanical and Package Information

5.1 Package Dimensions

The device conforms to a standard surface-mount package outline. Key dimensions include a body size of approximately 1.6mm in length, 0.8mm in width, and 0.6mm in height (specific drawing referenced in source). All dimensional tolerances are ±0.1mm unless otherwise specified. The lens is water-clear, allowing the native red color of the AllnGaP chip to be visible.

5.2 Recommended PCB Land Pattern

A suggested solder pad layout for the printed circuit board is provided to ensure reliable soldering and proper alignment. This pattern is designed to facilitate good solder fillet formation during reflow while minimizing the risk of solder bridging.

5.3 Polarity Identification

The cathode (negative terminal) is typically indicated by a visual marker on the LED package, such as a notch, a green dot, or a cut corner on the lens. Correct polarity must be observed during assembly, as applying reverse voltage can damage the device.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

The device is compatible with lead-free (Pb-free) soldering processes. A recommended reflow profile is provided, adhering to JEDEC standards.

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum 120 seconds.
• Peak Body Temperature: Maximum 260°C.
• Time Above 260°C: Maximum 10 seconds.
• Number of Reflow Passes: Maximum two times.

The specific profile must be characterized for the actual PCB design, solder paste, and oven used.

6.2 Hand Soldering (If Necessary)

If manual soldering is required, extreme care must be taken:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per lead.
• Number of Soldering Attempts: One time only per connection.

Prolonged heat application can damage the internal wire bonds and the epoxy package.

6.3 Storage Conditions

Moisture sensitivity level (MSL) is a critical factor for SMD components.

• Sealed Package (with desiccant): Store at ≤30°C and ≤90% RH. Use within one year of the dry-pack date.
• Opened Package: Store at ≤30°C and ≤60% RH. Components should be subjected to IR reflow within one week (MSL 3).
• Extended Storage (Out of Bag): Store in a sealed container with desiccant or in a nitrogen desiccator. If stored for more than one week, a bake at 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.4 Cleaning

If post-solder cleaning is necessary, use only approved alcohol-based solvents such as isopropyl alcohol (IPA) or ethyl alcohol. Immersion should be at normal temperature for less than one minute. Unspecified chemical cleaners may damage the LED lens or package material.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The components are supplied on embossed carrier tape for automated assembly.

• Carrier Tape Width: 8mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 3000 pieces (standard full reel).
• Minimum Order Quantity (MOQ) for Remainders: 500 pieces.
• Pocket Sealing: Empty pockets are sealed with cover tape.
• Missing Components: A maximum of two consecutive missing lamps is allowed, per industry standards (ANSI/EIA 481).

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

An LED is a current-driven device. To ensure uniform brightness and prevent current hogging, especially when driving multiple LEDs in parallel, a current-limiting resistor must be used in series with each LED. The resistor value (R) is calculated using Ohm's Law: R = (V_SUPPLY - V_F) / I_F, where V_F is the forward voltage of the LED at the desired current I_F. Using the maximum V_F from the datasheet (2.4V) in the calculation ensures the current does not exceed the target even with device-to-device variation.

8.2 Design Considerations

• Thermal Management: Although power dissipation is low (50mW max), ensuring a good thermal path via the PCB pads helps maintain stable light output and longevity, especially in high ambient temperatures or at higher drive currents.
• ESD (Electrostatic Discharge) Protection: LEDs are sensitive to static electricity. Proper ESD controls (wrist straps, grounded workstations, conductive flooring) must be implemented during handling and assembly.
• Optical Design: The 130-degree viewing angle provides wide illumination. For more focused light, external lenses or light guides may be required.

9. Technical Comparison and Differentiation

This AllnGaP red LED offers specific advantages:

• vs. Traditional GaAsP Red LEDs: AllnGaP technology provides significantly higher luminous efficiency, resulting in brighter output at the same current, or equivalent brightness at lower power.
• vs. Standard Through-Hole LEDs: The SMD package enables much higher assembly density, is compatible with fully automated production lines, and eliminates the need for lead bending and hole drilling on the PCB.
• Key Advantage: The combination of high brightness from AllnGaP, a wide viewing angle, and a compact, reflow-solderable package makes this device highly versatile for modern electronics.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive this LED directly from a 3.3V or 5V logic pin?

No, not without a current-limiting resistor. Connecting it directly would attempt to pull a very high current, limited only by the pin's current capability and the LED's dynamic resistance, which would likely destroy the LED or damage the driving IC. Always use a series resistor.

10.2 Why is there such a wide range in Luminous Intensity (2.8 to 28.0 mcd)?

This is due to natural variations in semiconductor manufacturing. The binning system (H through M) sorts parts by measured brightness. For consistent appearance in an application, specify and use LEDs from the same intensity bin.

10.3 What happens if I exceed the 20mA continuous current rating?

Exceeding the rating increases the junction temperature. This accelerates the degradation of the semiconductor material, leading to a permanent and rapid decrease in light output (lumen depreciation) and potentially causing catastrophic failure. Always design circuits to operate within the Absolute Maximum Ratings.

11. Practical Use Case Example

11.1 Design Case: Status Indicator Panel

Scenario: Designing a control panel with 10 identical red status indicators, powered from a 5V rail. Uniform brightness is critical.
Design Steps:

1. Choose Drive Current: Select I_F = 10mA for good brightness and long life.
2. Calculate Resistor Value: Use the maximum V_F (2.4V) for worst-case design. R = (5V - 2.4V) / 0.01A = 260 Ohms. The nearest standard E24 value is 270 Ohms.
3. Calculate Resistor Power: P = I² * R = (0.01)² * 270 = 0.027W. A standard 1/8W (0.125W) or 1/10W resistor is sufficient.
4. Specify LED Bin: To ensure all 10 indicators match, specify LEDs from a single luminous intensity bin (e.g., Bin L: 11.2-18.0 mcd) in the purchase order.
5. PCB Layout: Use the recommended land pattern. Ensure the panel design allows for the 130-degree viewing angle so the indicator is visible from the intended user positions.

12. Principle of Operation Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that convert electrical energy directly into light through a process called electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy. In an AllnGaP (Aluminum Indium Gallium Phosphide) LED, this energy is released primarily as photons (light) in the red portion of the visible spectrum. The specific wavelength (color) is determined by the bandgap energy of the semiconductor material, which is engineered during the crystal growth process by adjusting the ratios of aluminum, indium, and gallium.

13. Technology Trends and Developments

The field of optoelectronics continues to evolve. General trends observable in the industry include:

• Increased Efficiency: Ongoing materials science and chip design research leads to LEDs that produce more lumens per watt (lm/W), reducing power consumption for the same light output.
• Miniaturization: Package sizes continue to shrink (e.g., 0402, 0201 metric sizes) to enable even higher density on PCBs for ultra-compact devices.
• Improved Color Consistency: Advances in epitaxial growth and binning techniques allow for tighter tolerances on dominant wavelength and luminous intensity, giving designers more precise control over color and brightness.
• Integration: Trends include integrating multiple LED chips (RGB) into a single package for color mixing, or combining control ICs with LEDs for \"smart\" lighting solutions.

These developments aim to provide designers with more capable, efficient, and reliable components for an expanding range of applications.