Infrared LED Component Datasheet - Peak Wavelength 940nm - English Technical Document

1. Product Overview

This document provides technical specifications for an infrared (IR) light-emitting diode (LED) component. The primary application for such components is in systems requiring non-visible light sources, such as remote controls, proximity sensors, night vision illumination, and optical data transmission. The core advantage of this specific component is its emission at a peak wavelength of 940nm, which is ideal for applications where minimal visible light emission is desired, as it is largely invisible to the human eye. The target market includes consumer electronics, industrial automation, security systems, and automotive applications.

2. In-Depth Technical Parameter Analysis

The provided content specifies a key photometric parameter: the peak wavelength (λp). This is a critical specification for IR LEDs.

2.1 Photometric Characteristics

Peak Wavelength (λp): 940 nanometers (nm). This parameter defines the wavelength at which the LED emits its maximum optical power. A 940nm wavelength falls within the near-infrared spectrum. This wavelength is commonly used because silicon photodiodes, which are typical receivers in IR systems, have high sensitivity around this range. Furthermore, 940nm light is less perceptible as a faint red glow compared to shorter IR wavelengths like 850nm, making it preferable for covert illumination.

Analysis: The selection of 940nm indicates this component is optimized for efficiency in detection systems using standard silicon sensors and for applications requiring low visible light pollution. The radiant intensity and viewing angle, common complementary specs, are not provided but are crucial for calculating the effective range and coverage area in a design.

2.2 Electrical Parameters

While specific forward voltage (Vf), forward current (If), and reverse voltage (Vr) values are not listed in the excerpt, these are fundamental for any LED. Designers must consult the full datasheet for absolute maximum ratings and typical operating conditions to ensure reliable operation and longevity. Exceeding the maximum forward current is a primary cause of LED failure due to excessive heat generation.

2.3 Thermal Characteristics

Thermal management is paramount for LED performance and lifespan. Key parameters include the thermal resistance from the junction to the ambient air (RθJA) and the maximum junction temperature (Tj max). Efficient heat sinking through the LED's package and the printed circuit board (PCB) is necessary to maintain Tj within safe limits, especially when operating at high currents or in elevated ambient temperatures.

3. Binning System Explanation

LED manufacturing involves natural variations. A binning system categorizes components based on key parameters to ensure consistency within a production batch.

3.1 Wavelength Binning

For an IR LED, the peak wavelength is the primary binning parameter. Components might be sorted into bins with a tight tolerance around the nominal 940nm (e.g., 935nm to 945nm). This ensures that all LEDs in a system have nearly identical emission characteristics, which is critical for the performance of optical filters and sensor tuning in the receiver.

3.2 Forward Voltage Binning

LEDs are also binned by forward voltage (Vf) at a specified test current. Grouping LEDs with similar Vf values helps in designing driver circuits, particularly when multiple LEDs are connected in series, to ensure uniform current distribution and brightness.

4. Performance Curve Analysis

Graphical data is essential for understanding component behavior under various conditions.

4.1 Current vs. Voltage (I-V) Curve

The I-V curve shows the relationship between the forward voltage and the current through the LED. It is non-linear. The "knee" voltage is the approximate point where the LED begins to conduct significantly and emit light. The curve's slope in the operating region helps determine the dynamic resistance of the LED.

4.2 Temperature Characteristics

LED performance is temperature-dependent. Typically, the forward voltage (Vf) decreases as the junction temperature increases. Conversely, the luminous intensity or radiant power also decreases with rising temperature. Graphs showing relative intensity vs. junction temperature and forward voltage vs. temperature are critical for designing circuits that compensate for thermal effects.

3.3 Spectral Distribution

A spectral distribution graph plots radiant power against wavelength. For a 940nm LED, this graph would show a dominant peak at or near 940nm with a certain spectral bandwidth (e.g., Full Width at Half Maximum - FWHM). A narrower FWHM indicates a more monochromatic light source, which can be important for applications using optical filters.

5. Mechanical and Package Information

The excerpt mentions packaging types but not the specific LED package (e.g., 5mm, 3mm, surface-mount device like 0805 or 1206). A complete datasheet would include a detailed mechanical drawing.

5.1 Dimension Drawing

A dimensioned diagram is required, showing the length, width, height, lead spacing (for through-hole), or pad dimensions (for SMD). Tolerances for all dimensions must be specified.

5.2 Pad Layout Design (for SMD)

For surface-mount packages, a recommended PCB land pattern (footprint) is provided. This includes the size, shape, and spacing of the copper pads to ensure proper soldering and mechanical stability.

5.3 Polarity Identification

The method for identifying the anode and cathode must be clearly indicated. For through-hole LEDs, the cathode is typically the shorter lead or the lead next to a flat spot on the lens. For SMD LEDs, a marking such as a dot, notch, or shaded corner on the package denotes the cathode.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

For SMD components, a detailed reflow profile is necessary. This includes preheat temperature and time, soak time, peak temperature, time above liquidus (TAL), and cooling rate. Adherence to this profile prevents thermal shock and ensures reliable solder joints.

6.2 Precautions

General precautions include: avoiding mechanical stress on the LED lens, using ESD protection during handling (as LEDs are sensitive to electrostatic discharge), and ensuring no contamination on the optical surface. For through-hole parts, lead bending should be done at a sufficient distance from the package body.

6.3 Storage Conditions

LEDs should be stored in a cool, dry environment, typically within a specified temperature and humidity range. They are often supplied in moisture-sensitive packaging with a desiccant, and may require baking before use if the packaging has been opened for an extended period.

7. Packaging and Ordering Information

The PDF excerpt explicitly lists packaging elements, which is a key part of the provided content.

7.1 Packaging Specification

The packaging hierarchy is defined as:

• Electrostatic Bag: The primary container, designed to protect the components from electrostatic discharge (ESD) and moisture.
• Inner Carton: A box or tray that holds multiple ESD bags or reels of components.
• Outside Carton: The master shipping carton containing multiple inner cartons.

7.2 Packing Quantity

The specific quantity of LED components per ESD bag, per inner carton, and per outside carton must be specified. Common quantities are in multiples of 1000, 2000, or 5000 pieces for SMD parts on reels, or specific counts for bulk packaging.

7.3 Labeling Information

Each packaging level should have a label indicating the part number, quantity, date code, lot number, and ESD/moisture sensitivity level (MSL).

7.4 Model Number Naming Rules

The full part number typically encodes key attributes. For example, a model number might indicate the package size, peak wavelength, viewing angle, and flux bin. A code like "IR940-45D" could imply an IR LED, 940nm, 45-degree viewing angle, and a specific radiant intensity bin 'D'.

8. Application Recommendations

8.1 Typical Application Scenarios

This 940nm IR LED is suitable for:

• Infrared Remote Controls: For TVs, audio systems, and set-top boxes.
• Proximity and Presence Sensors: In smartphones, appliances, and automatic faucets.
• Night Vision Illumination: Paired with IR-sensitive cameras in security and surveillance systems.
• Optical Switches and Encoders: For detecting position or rotation.
• Data Transmission: In IrDA-compliant devices for short-range wireless communication.

8.2 Design Considerations

Driver Circuit: A constant current source is recommended over a voltage source with a series resistor for stable output, especially over temperature variations. The driver must be rated for the LED's forward current.
Optical Design: The lens or cover material between the LED and the target must be transparent to 940nm light. Many plastics are suitable, but some types of glass or tinted materials may attenuate the signal.
Heat Sinking: Ensure adequate PCB copper area or an external heatsink if operating at high continuous currents.
Receiver Matching: The photodetector (e.g., phototransistor, photodiode) should have peak sensitivity around 940nm. An optical filter matched to the LED's spectrum can improve signal-to-noise ratio by blocking ambient light.

9. Technical Comparison

Compared to other IR LEDs, a 940nm component offers specific advantages and trade-offs.

vs. 850nm IR LEDs: 850nm LEDs often provide slightly higher radiant output for the same electrical input due to better material efficiency at that wavelength. However, 850nm emits a faint red glow that can be visible in dark conditions, which may be undesirable for covert applications. 940nm is virtually invisible, making it superior for discreet illumination.

vs. Visible LEDs: The primary differentiator is the wavelength. IR LEDs enable functionality invisible to users, allowing for features like automatic operation (sensors) or control (remotes) without emitting distracting light.

10. Frequently Asked Questions (FAQs)

Q: Why is the peak wavelength 940nm important?
A: It matches the high sensitivity range of common silicon photodetectors while minimizing visible light emission, making it ideal for sensor and covert illumination applications.

Q: How do I drive this LED?
A: Use a constant current driver circuit. A simple implementation is a voltage source with a current-limiting resistor, calculated using the LED's typical forward voltage (Vf) and desired forward current (If) from the full datasheet: R = (Vsource - Vf) / If.

Q: Can I see the light from this LED?
A: The 940nm wavelength is outside the visible spectrum for most humans. Some individuals might perceive a very deep red glow under extremely dark conditions, but it is largely invisible. A smartphone camera, however, can usually see it clearly, as camera sensors are sensitive to near-IR.

Q: What is the purpose of the electrostatic bag?
A: It protects the LED from electrostatic discharge (ESD), which can damage the semiconductor junction even if the discharge is not felt by a person.

11. Practical Use Cases

Case Study 1: Automatic Soap Dispenser. A 940nm IR LED is paired with a phototransistor to create a proximity sensor. The LED constantly emits an invisible beam. When a hand interrupts the beam, the change in detected light triggers the pump motor. The 940nm wavelength ensures the operation is seamless and without any visible light indication.

Case Study 2: Long-Range TV Remote. An array of 940nm LEDs is used in a universal remote control. The high radiant intensity (ensured by proper binning and drive current) allows the signal to reach the TV sensor from wide angles and longer distances. The lack of visible light prevents distraction in a dark home theater.

12. Principle Introduction

An Infrared Light Emitting Diode (IR LED) is a semiconductor p-n junction diode. When forward biased, electrons from the n-region recombine with holes from the p-region in the active region. This recombination process releases energy in the form of photons (light). The specific wavelength of the emitted photons is determined by the bandgap energy of the semiconductor materials used in the construction of the LED (typically aluminum gallium arsenide - AlGaAs for 940nm). A larger bandgap results in a shorter wavelength (bluer light), and a smaller bandgap results in a longer wavelength (redder or infrared light). The 940nm output is a direct result of engineering the semiconductor composition to achieve this specific bandgap energy.

13. Development Trends

The field of IR LEDs is driven by demands for higher efficiency, smaller packages, and greater integration.

Increased Efficiency: Research focuses on improving the internal quantum efficiency (the percentage of electron-hole recombinations that produce photons) and the light extraction efficiency (getting the generated photons out of the semiconductor material). This leads to higher radiant output for the same electrical input, enabling longer battery life in portable devices.

Miniaturization: The trend towards smaller consumer electronics drives the development of IR LEDs in ever-smaller surface-mount packages (e.g., 0402, 0201 metric sizes) while maintaining or improving performance.

Integrated Solutions: There is a move towards combining the IR LED, photodetector, and control logic into a single module or chip. This simplifies design for end-users, reduces PCB footprint, and improves system reliability by ensuring matched optical characteristics.

New Wavelengths: While 850nm and 940nm dominate, other wavelengths are being developed for specialized applications, such as spectroscopy, gas sensing, and optical communications using plastic optical fibers.