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

1. Product Overview

This document provides technical specifications for an infrared (IR) light-emitting diode (LED) component. The primary application for this device is in systems requiring non-visible light sources, such as remote controls, proximity sensors, and night-vision illumination. The core advantage of this component lies in its specific peak wavelength, which is optimized for compatibility with silicon-based photodetectors and offers low visibility to the human eye. The target market includes consumer electronics, industrial automation, security systems, and automotive applications where reliable infrared signaling or sensing is required.

2. In-Depth Technical Parameter Analysis

The provided data specifies a key photometric parameter for this IR LED.

2.1 Photometric Characteristics

The most critical parameter defined is the peak wavelength (λp).

• Peak Wavelength (λp): 940 nanometers (nm). This value indicates the specific point in the electromagnetic spectrum where the LED emits its maximum optical power. A wavelength of 940nm is firmly within the near-infrared (NIR) range. This wavelength is particularly advantageous because it aligns well with the peak sensitivity of common silicon photodiodes and phototransistors, ensuring efficient signal transmission and reception. Furthermore, 940nm light is less visible as a faint red glow compared to shorter IR wavelengths like 850nm, making it more suitable for covert applications.

Other typical photometric parameters for an IR LED, such as radiant intensity (in milliwatts per steradian, mW/sr), viewing angle (in degrees), and forward voltage at a specific current, are not explicitly provided in the excerpt but are essential for complete circuit design.

2.2 Electrical Parameters

While specific values are not listed in the provided text, the electrical behavior of an IR LED is defined by several key parameters that a designer must consider.

• Forward Voltage (Vf): The voltage drop across the LED when it is conducting current. For typical GaAs-based IR LEDs, this usually ranges from 1.2V to 1.6V at their nominal forward current.
• Forward Current (If): The recommended continuous operating current. Exceeding the maximum rated forward current can lead to rapid degradation or catastrophic failure.
• Reverse Voltage (Vr): The maximum voltage the LED can withstand when biased in the non-conducting direction. IR LEDs typically have a very low reverse voltage rating (often around 5V) and are susceptible to damage from reverse voltage spikes.
• Power Dissipation: The total electrical power converted into heat and light (Vf * If). Proper thermal management is necessary to prevent overheating.

2.3 Thermal Characteristics

Thermal management is crucial for LED longevity and stable performance.

• Junction Temperature (Tj): The temperature at the semiconductor chip's active region. The maximum allowable Tj is a critical limit.
• Thermal Resistance (Rθj-a): This parameter, measured in degrees Celsius per watt (°C/W), indicates how effectively heat travels from the LED junction to the ambient air. A lower value signifies better heat dissipation capability. The packaging design heavily influences this value.
• Derating Curve: A graph showing how the maximum allowable forward current decreases as the ambient temperature or junction temperature increases. Operating within these limits is essential for reliability.

3. Binning System Explanation

High-volume LED manufacturing produces variations in key parameters. Binning is the process of sorting components into groups (bins) based on measured performance to ensure consistency for the end-user.

3.1 Wavelength Binning

For this 940nm IR LED, components would be tested and sorted into bins based on their actual peak wavelength. For example, bins might be defined as 935-940nm, 940-945nm, etc. This allows designers to select LEDs with tighter wavelength tolerances if their application requires precise spectral matching.

3.2 Radiant Intensity / Optical Power Binning

LEDs are also binned according to their radiant output. This is crucial for applications requiring uniform brightness or a specific signal strength. Bins are defined by minimum and maximum radiant intensity values (e.g., 20-25 mW/sr, 25-30 mW/sr) at a standardized test current.

3.3 Forward Voltage Binning

To simplify current-limiting circuit design and ensure consistent behavior in parallel arrays, LEDs are binned by forward voltage (Vf). Common bins might group LEDs with Vf between 1.2V-1.3V, 1.3V-1.4V, and so on.

4. Performance Curve Analysis

Graphical data is essential for understanding device behavior under different operating conditions.

4.1 Current-Voltage (I-V) Characteristic Curve

This curve plots the forward current (If) against the forward voltage (Vf). It shows the exponential relationship typical of a diode. The curve is used to determine the operating point and to design an appropriate current-limiting resistor or driver circuit. The "knee" voltage, where current begins to increase rapidly, is a key feature.

4.2 Temperature Dependence

Several curves illustrate temperature effects.

• Forward Voltage vs. Temperature: Typically shows that Vf decreases linearly as junction temperature increases (approximately -2mV/°C for IR LEDs). This is important for constant-current drivers.
• Radiant Intensity vs. Temperature: Shows how optical output decreases as temperature rises. This derating is critical for applications operating in high ambient temperatures.
• Relative Spectral Distribution vs. Temperature: Demonstrates how the peak wavelength may shift slightly (usually to longer wavelengths) as temperature increases.

4.3 Spectral Distribution

This graph plots relative radiant power against wavelength. It shows the peak at 940nm and the spectral bandwidth (typically Full Width at Half Maximum, or FWHM, often around 40-50nm for IR LEDs). A narrower bandwidth indicates more monochromatic light.

5. Mechanical and Packaging Information

The provided excerpt contains specific packaging details.

5.1 Packaging Hierarchy

The component is protected by a multi-layer packaging system:

• Electrostatic Discharge (ESD) Protective Bag: The primary container for the individual LED components or reels. This bag is made from a static-dissipative material to prevent damage from electrostatic discharge during handling and storage.
• Inner Carton: A smaller box or tray that holds multiple ESD bags or reels, providing physical structure and additional protection.
• Outside Carton: The master shipping container that holds multiple inner cartons. It is designed for robustness during transportation and storage.

5.2 Packing Quantity

The document explicitly lists "Packing Quantity" as a key parameter. This refers to the number of individual LED components contained within one standard shipping unit (e.g., per reel, per tube, or per bag within the inner carton). Common quantities are 1000, 2000, or 5000 pieces per reel for surface-mount devices.

5.3 Physical Dimensions and Polarity

While exact dimensions are not provided, a typical IR LED package (like a 3mm or 5mm through-hole LED, or a surface-mount package like 0805 or 1206) would have a detailed mechanical drawing. This drawing specifies the body length, width, height, lead spacing (pitch), and lead dimensions. Crucially, it includes polarity identification, usually indicating the cathode (negative side) via a flat edge on the lens, a shorter lead, a dot on the package, or a specific pad marking on the footprint.

6. Soldering and Assembly Guidelines

Proper assembly is vital for reliability.

6.1 Reflow Soldering Profile

For surface-mount IR LEDs, a recommended reflow profile must be followed. This includes:

• Preheat/Ramp-up Rate: Typically 1-3°C per second to avoid thermal shock.
• Soak Zone: A period at a temperature below the solder liquidus to activate flux and equalize board temperature.
• Reflow (Liquidus) Zone: The peak temperature, which must be high enough to melt the solder (e.g., 240-250°C for SAC305) but low enough and brief enough to not damage the LED (maximum package body temperature is often 260°C for 10 seconds).
• Cooling Rate: A controlled cool-down to solidify the solder joints properly.

6.2 Key Precautions

• ESD Protection: Always handle components in an ESD-safe environment using grounded wrist straps and conductive mats.
• Moisture Sensitivity Level (MSL): If applicable, the package will have an MSL rating (e.g., MSL 3). Components exceeding their floor life must be baked before reflow to prevent "popcorning" damage.
• Cleaning: Use only compatible cleaning solvents that will not damage the LED lens or epoxy.
• Mechanical Stress: Avoid applying direct pressure to the LED lens during placement or testing.

6.3 Storage Conditions

Components should be stored in their original, unopened ESD bags in a controlled environment. Recommended conditions are typically a temperature between 5°C and 30°C and a relative humidity below 60%. Avoid exposure to direct sunlight, corrosive gases, or excessive dust.

7. Packaging and Ordering Information

The document's lifecycle data indicates a "Revision: 5" and "Expired Period: Forever," suggesting this is a stable, non-obsolescence-controlled document released on 2013-05-27. The packaging specification is clearly defined in section 5.1. The ordering code or model number would typically follow a naming convention that encodes key attributes like package type, wavelength bin, intensity bin, and packing quantity (e.g., "IR940-SMD1206-B2-2K" might indicate a 940nm IR LED in a 1206 package, intensity bin B2, supplied on a 2000-piece reel).

8. Application Recommendations

8.1 Typical Application Scenarios

• Infrared Remote Controls: For TVs, audio systems, and set-top boxes. The 940nm wavelength is the industry standard.
• Proximity and Presence Sensors: Used in smartphones to disable touchscreens during calls, in automatic faucets, and in security light switches.
• Object Counting and Detection: In vending machines, industrial assembly lines, and printing equipment.
• Night Vision Illumination: Paired with an IR-sensitive camera for surveillance in low-light conditions.
• Optical Data Transmission: For short-range, low-speed serial communication (IrDA) or industrial data links.

8.2 Design Considerations

• Driver Circuit: Always use a series current-limiting resistor or a constant-current driver. Never connect an LED directly to a voltage source.
• Heat Sinking: For high-current operation or high ambient temperatures, ensure adequate PCB copper area or an external heatsink to manage the LED's thermal resistance.
• Optical Design: Consider the LED's viewing angle. Use lenses or reflectors to collimate or diffuse the beam as needed for the application.
• Photodetector Matching: Ensure the selected photodetector (photodiode, phototransistor) has high sensitivity at 940nm. Use an IR filter to block visible light if the environment is noisy.
• Electrical Noise Immunity: In sensor applications, modulate the IR signal (e.g., with a 38kHz carrier) and use a tuned receiver to reject ambient light interference from sunlight or fluorescent lamps.

9. Technical Comparison

Compared to other IR sources, this 940nm LED offers specific advantages.

• vs. 850nm IR LEDs: 940nm light is much less visible as a faint red glow, making it superior for covert surveillance. However, silicon photodetectors are slightly less sensitive at 940nm than at 850nm, and atmospheric absorption is marginally higher.
• vs. Incandescent IR Lamps: LEDs are far more efficient, have a faster response time (enabling high-speed modulation), are more mechanically robust, and have a much longer operational lifetime (tens of thousands of hours).
• vs. Laser Diodes: LEDs have a broader spectral output and a much larger emission area, producing a diffuse beam that is easier to work with for general illumination and sensing. They are also significantly less expensive and do not require the complex drive and safety circuitry of laser diodes.

10. Frequently Asked Questions (FAQ)

Q1: What is the purpose of the 940nm peak wavelength?
A1: The 940nm wavelength is optimal because it is well-matched to the sensitivity of silicon photodetectors while being nearly invisible to the human eye, making it ideal for discreet sensing and remote control applications.

Q2: How do I determine the correct current-limiting resistor value?
A2: Use Ohm's Law: R = (Vsupply - Vf) / If. You must know your supply voltage (Vsupply), the LED's forward voltage (Vf) from its datasheet or bin, and the desired forward current (If). Always ensure the resistor's power rating (P = (Vsupply - Vf) * If) is sufficient.

Q3: Can I use this LED outdoors?
A3: Yes, but with precautions. The epoxy lens may degrade under prolonged UV exposure. More critically, bright sunlight contains strong IR components that can saturate receivers. Using optical filters and modulated signals is essential for reliable outdoor operation.

Q4: Why is ESD protection so important for LEDs?
A4: The semiconductor junction in an LED is extremely sensitive to high-voltage electrostatic discharges. An ESD event can instantly degrade the optical output, increase leakage current, or cause complete failure without any visible damage.

Q5: What does "Packing Quantity" refer to?
A5: It specifies the number of individual LED components supplied in one standard sales unit, such as on a reel, in a tube, or within an anti-static bag. This is crucial for production planning and inventory management.

11. Practical Use Case Examples

11.1 Simple Proximity Sensor

A basic reflective sensor can be built by placing the 940nm IR LED and a phototransistor side-by-side. The LED is driven with a pulsed current. When an object comes near, it reflects the IR light back to the phototransistor, causing its collector current to increase. A comparator circuit can then trigger a digital output signal. This design is used in paper detection in printers and hand-dryer activation.

11.2 Long-Range IR Illuminator for CCTV

For night-vision security cameras, an array of multiple high-power 940nm LEDs is constructed. The LEDs are driven by a constant-current driver capable of several hundred milliamps. A Fresnel lens is placed in front of the array to collimate the light into a beam, extending the effective illumination range to tens of meters. Thermal management via a large aluminum heatsink is critical for this high-power design.

12. Principle of Operation

An Infrared Light Emitting Diode (IR LED) is a semiconductor p-n junction device. When forward-biased (positive voltage applied to the p-side relative to the n-side), electrons from the n-region are injected across the junction into the p-region, and holes from the p-region are injected into the n-region. These minority carriers recombine with majority carriers in the opposing regions. In a direct bandgap semiconductor like Gallium Arsenide (GaAs), commonly used for IR LEDs, this recombination event releases energy in the form of a photon (light particle). The wavelength (color) of the emitted photon is determined by the bandgap energy (Eg) of the semiconductor material, according to the equation λ = hc/Eg, where h is Planck's constant and c is the speed of light. By adjusting the semiconductor alloy composition (e.g., using AlGaAs or InGaAs), the bandgap and thus the emitted wavelength can be precisely controlled, resulting in the 940nm output specified here.

13. Technology Trends

The field of IR LED technology continues to evolve. Key trends include:

• Increased Power and Efficiency: Ongoing materials science and packaging improvements are yielding IR LEDs with higher radiant flux and wall-plug efficiency (electrical-to-optical power conversion), enabling smaller devices or longer range for the same input power.
• Miniaturization: The drive for smaller consumer electronics is pushing IR LEDs into ever-smaller surface-mount packages (e.g., 0402, 0201) and chip-scale packages (CSP).
• Integrated Solutions: There is a trend towards combining the IR LED, photodetector, driver circuitry, and signal processing (like ambient light rejection) into a single module or system-in-package (SiP), simplifying design for end-users.
• Expansion into New Wavelengths: While 850nm and 940nm dominate, there is growing interest in other IR wavelengths for specialized applications, such as 1050nm for eye-safe LiDAR or specific bands for gas sensing.
• Improved Thermal Management: New package designs with lower thermal resistance and materials with better thermal conductivity are extending LED lifetimes and enabling higher drive currents.