SMD LED 19-218/T1D-CQ2R2TY/3T White LED Datasheet - Pure White - 5mA - 90-180mcd - English Technical Document

1. Product Overview

The 19-218/T1D-CQ2R2TY/3T is a surface-mount device (SMD) light-emitting diode (LED) designed for modern electronic applications requiring compact, efficient, and reliable illumination. This component represents a significant advancement over traditional lead-frame LEDs, enabling substantial miniaturization and performance improvements in end-user equipment.

1.1 Core Advantages and Product Positioning

The primary advantage of this SMD LED is its significantly reduced physical footprint. By eliminating bulky lead frames, it allows for smaller printed circuit board (PCB) designs, higher component packing density, and reduced overall equipment size. Its lightweight construction further makes it ideal for portable and miniature applications where weight and space are critical constraints. The device is packaged on 8mm tape wound onto a 7-inch diameter reel, ensuring compatibility with high-speed automated pick-and-place assembly equipment, which is standard in modern electronics manufacturing.

1.2 Target Market and Applications

This LED is targeted at a broad range of industrial and consumer electronics applications. Its key application areas include backlighting for instrument panels, switches, and keypads. In telecommunications, it serves as status indicators and backlighting for devices such as telephones and fax machines. It is also suitable for providing flat, uniform backlighting for liquid crystal displays (LCDs) and for general-purpose indicator use where a reliable, compact light source is required.

2. In-Depth Technical Parameter Analysis

A thorough understanding of the electrical and optical parameters is essential for reliable circuit design and ensuring long-term performance.

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 and should be avoided for reliable performance.

• Reverse Voltage (V_R): 5V. Exceeding this voltage in reverse bias can cause junction breakdown.
• Continuous Forward Current (I_F): 25mA. This is the maximum DC current recommended for continuous operation.
• Peak Forward Current (I_FP): 100mA. This pulsed current rating (at 1/10 duty cycle, 1kHz) allows for brief over-current conditions, such as during power-on surges.
• Power Dissipation (P_d): 95mW. This is the maximum power the package can dissipate without exceeding its thermal limits, calculated as Forward Voltage (V_F) multiplied by Forward Current (I_F).
• Electrostatic Discharge (ESD) Human Body Model (HBM): 150V. This indicates a moderate sensitivity to static electricity, necessitating proper ESD handling procedures during assembly.
• Operating & Storage Temperature: -40°C to +85°C (operating), -40°C to +90°C (storage). The wide range ensures functionality in harsh environments.
• Soldering Temperature: The device is compatible with both reflow (260°C for 10 sec max) and hand soldering (350°C for 3 sec max) processes, adhering to Pb-free assembly requirements.

2.2 Electro-Optical Characteristics

These parameters, measured at a standard junction temperature of 25°C, define the device's performance under normal operating conditions.

• Luminous Intensity (I_v): 90.0 mcd (Min) to 180 mcd (Max) at a test current of 5mA. The typical value falls within this bin range. A tolerance of ±11% applies to the luminous intensity.
• Viewing Angle (2θ_1/2): 130 degrees (Typical). This wide viewing angle ensures good visibility over a broad area, making it suitable for indicator applications.
• Forward Voltage (V_F): 2.6V (Min) to 3.0V (Max) at 5mA. The typical forward voltage is around 2.8V. A tight tolerance of ±0.05V is specified.
• Reverse Current (I_R): Maximum 50 µA at a reverse bias of 5V. This low leakage current indicates good junction quality.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on key parameters. This allows designers to select components that meet specific application requirements.

3.1 Luminous Intensity Binning

The luminous output is categorized into distinct bins, each with a defined minimum and maximum value measured at I_F = 5mA.

• Bin Q2: 90.0 mcd to 112 mcd
• Bin R1: 112 mcd to 140 mcd
• Bin R2: 140 mcd to 180 mcd

This binning allows selection based on required brightness levels for a given application.

3.2 Forward Voltage Binning

Forward voltage is also binned to aid in circuit design, particularly for current-limiting resistor calculation and power supply design.

• Bin 28: 2.6V to 2.7V
• Bin 29: 2.7V to 2.8V
• Bin 30: 2.8V to 2.9V
• Bin 31: 2.9V to 3.0V

3.3 Chromaticity Coordinate Binning

The color of the emitted white light is precisely controlled through chromaticity coordinate binning on the CIE 1931 diagram, with a tolerance of ±0.01. The datasheet defines four bins (1, 2, 3, 4), each specifying a quadrilateral region on the x,y color coordinate chart. This ensures the white color point is consistent within a tight specification, which is critical for applications like display backlighting where color uniformity is paramount.

4. Performance Curve Analysis

Graphical data provides deeper insight into the device's behavior under varying conditions.

4.1 Spectral Distribution

The spectrum distribution curve shows the relative intensity of light emitted across different wavelengths. For a white LED using an InGaN chip with a yellow phosphor, the spectrum typically features a dominant blue peak from the chip and a broader yellow emission from the phosphor, combining to produce white light. The curve helps assess color rendering properties.

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

This fundamental curve illustrates the exponential relationship between current and voltage across the LED's p-n junction. It is crucial for designing the driving circuit. The curve shows the turn-on voltage and how the forward voltage increases with current. Designers use this to calculate the appropriate current-limiting resistor value for a given supply voltage.

4.3 Luminous Intensity vs. Forward Current

This curve demonstrates how light output increases with forward current. It is generally linear over a range but will saturate at higher currents due to thermal and efficiency effects. Operating within the linear region is recommended for predictable brightness control via current modulation.

4.4 Luminous Intensity vs. Ambient Temperature

LED light output is temperature-dependent. This curve shows the relative luminous intensity decreasing as the ambient temperature rises. Understanding this derating is vital for applications operating in elevated temperature environments to ensure sufficient brightness is maintained.

4.5 Forward Current Derating Curve

To prevent overheating, the maximum allowable continuous forward current must be reduced as the ambient temperature increases. This derating curve provides the safe operating area, specifying the maximum I_F for any given ambient temperature up to the maximum rated temperature.

4.6 Radiation Diagram

The radiation pattern, or spatial distribution of light, is depicted. The 130-degree viewing angle indicates a lambertian or near-lambertian emission pattern, where intensity is highest at 0 degrees (perpendicular to the emitting surface) and decreases towards the edges.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The datasheet provides a detailed mechanical drawing of the LED package. Key dimensions include the overall length, width, and height, as well as the size and position of the solderable terminals. All tolerances are typically ±0.1mm unless otherwise specified. This drawing is essential for creating the PCB footprint (land pattern).

5.2 Recommended Solder Pad Design

A suggested solder pad layout is provided as a reference for PCB design. This recommendation aims to ensure a reliable solder joint and proper alignment during reflow. The datasheet explicitly states that this is a reference only and designers should modify the pad dimensions based on their specific manufacturing process, PCB material, and reliability requirements.

5.3 Polarity Identification

The cathode (negative terminal) is typically identified on the package, often by a marking such as a notch, a dot, a green tint, or a different shape on the cathode side. Correct polarity must be observed during assembly to ensure proper function.

6. Soldering and Assembly Guidelines

Proper handling and soldering are critical to maintaining device reliability and performance.

6.1 Reflow Soldering Profile

A detailed Pb-free reflow temperature profile is specified:

• Pre-heating: 150–200°C for 60–120 seconds to gradually heat the board and components, minimizing thermal shock.
• Time Above Liquidus (TAL): Time above 217°C should be 60–150 seconds.
• Peak Temperature: Maximum 260°C, held for a maximum of 10 seconds.
• Heating/Cooling Rates: Maximum heating rate of 3°C/sec up to 255°C, and maximum cooling rate of 6°C/sec.

The datasheet strongly advises that reflow soldering should not be performed more than two times to avoid excessive thermal stress on the package and wire bonds.

6.2 Hand Soldering Instructions

If hand soldering is necessary, specific precautions must be taken:

• Use a soldering iron with a tip temperature less than 350°C.
• Apply heat to each terminal for no more than 3 seconds.
• Use an iron with a power rating less than 25W.
• Allow an interval of at least 2 seconds between soldering each terminal.
• The document cautions that damage often occurs during hand soldering, so care is essential.

6.3 Storage and Moisture Sensitivity

The LEDs are packaged in a moisture-resistant barrier bag with desiccant to prevent absorption of atmospheric moisture, which can cause \"popcorning\" (package cracking) during reflow.

• Before Opening: Store at ≤30°C and ≤90% Relative Humidity (RH).
• After Opening: The \"floor life\" is 1 year under ≤30°C and ≤60% RH. Unused devices should be resealed in a moisture-proof package.
• Baking: If the desiccant indicator changes color or the storage time is exceeded, a bake at 60 ±5°C for 24 hours is required before reflow to drive out moisture.

7. Packaging and Ordering Information

7.1 Reel and Tape Specifications

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

• Carrier Tape Width: 8mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 3000 pieces.

Detailed dimensional drawings for the carrier tape pockets and the reel are provided to ensure compatibility with automated equipment feeders.

7.2 Label Explanation

The reel label contains critical information for traceability and correct application:

• P/N: Product Number (the full part number, e.g., 19-218/T1D-CQ2R2TY/3T).
• CAT: Luminous Intensity Rank (e.g., R1, R2).
• HUE: Chromaticity Coordinates & Dominant Wavelength Rank.
• REF: Forward Voltage Rank (e.g., 29, 30).
• LOT No: Lot Number for manufacturing traceability.
• QTY: Packing Quantity on the reel.

8. Application Design Considerations

8.1 Current Limiting and Protection

Critical Design Rule: An external current-limiting resistor must be used in series with the LED. The forward voltage of an LED has a negative temperature coefficient and a tight manufacturing tolerance. A slight increase in supply voltage or a decrease in V_F due to temperature can cause a large, potentially destructive increase in current if not limited by a resistor. The resistor value (R) is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Always use the maximum V_F from the datasheet for a conservative design that ensures I_F does not exceed the maximum rating under worst-case conditions.

8.2 Thermal Management

While SMD LEDs are efficient, a portion of the input electrical power is converted to heat. For optimal longevity and stable light output:

• Adhere to the power dissipation (95mW) and current derating specifications.
• Provide adequate copper area on the PCB connected to the LED's thermal pads (if any) or terminals to act as a heat sink.
• Ensure good ventilation in the end-product enclosure, especially in high ambient temperature environments.

8.3 ESD Protection

With an ESD HBM rating of 150V, this device has moderate sensitivity. Implement standard ESD precautions during handling, assembly, and testing:

• Use grounded workstations and wrist straps.
• Store and transport components in conductive or anti-static packaging.
• Consider adding transient voltage suppression (TVS) diodes or other protection circuits on the PCB if the LED is connected to external interfaces prone to ESD events.

9. Technical Comparison and Differentiation

Compared to older through-hole LED packages, this SMD LED offers distinct advantages:

• Size & Density: Drastically smaller, enabling high-density PCB layouts impossible with leaded parts.
• Assembly Cost & Speed: Fully compatible with automated surface-mount technology (SMT) lines, reducing assembly time and cost compared to manual insertion and soldering.
• Performance: Often provides better thermal path to the PCB (through the solder joints) than epoxy-bodied through-hole LEDs, potentially offering slightly better longevity at similar drive currents.
• Pb-free & RoHS: Manufactured with RoHS-compliant materials, meeting global environmental regulations.

The primary trade-off is the requirement for more precise PCB fabrication and assembly processes.

10. Frequently Asked Questions (FAQ) Based on Technical Parameters

10.1 What resistor value should I use with a 5V supply?

Using the maximum V_F of 3.0V from the datasheet and a target I_F of 20mA (below the 25mA max for margin), the calculation is: R = (5V - 3.0V) / 0.020A = 100 Ohms. The power dissipated in the resistor is P = I²R = (0.02)² * 100 = 0.04W, so a standard 1/8W (0.125W) or 1/4W resistor is suitable. Always verify brightness with the actual bin of LEDs received.

10.2 Can I drive this LED without a current-limiting resistor using a constant current source?

Yes, a constant current driver is an excellent and often preferred method, especially for maintaining consistent brightness over temperature and voltage variations. Set the constant current source to the desired I_F (e.g., 20mA). The driver will automatically adjust the voltage across the LED to maintain that current. This method is more efficient and precise than using a series resistor.

10.3 Why is the luminous intensity specified at 5mA instead of the maximum 25mA?

The 5mA test condition is a standard industry reference point that allows for easy comparison between different LED models from various manufacturers. It represents a common, moderate operating point. Designers can use the performance curves (Luminous Intensity vs. Forward Current) to extrapolate the expected brightness at their intended operating current, such as 20mA.

10.4 How do I interpret the chromaticity coordinate bins?

Each bin number (1, 2, 3, 4) corresponds to a specific quadrilateral area on the CIE 1931 (x,y) color chart provided in the datasheet. The coordinates define the color point of the white light. For applications requiring color matching (e.g., multi-LED backlights), specifying and using LEDs from the same chromaticity bin is crucial to avoid visible color differences between adjacent LEDs.

11. Practical Design and Usage Examples

11.1 Dashboard Switch Backlighting

In an automotive dashboard, multiple switches require uniform, reliable backlighting. Several 19-218 LEDs can be placed behind translucent switch caps. By driving all LEDs from the same constant current circuit and ensuring they are from the same luminous intensity (CAT) and chromaticity (HUE) bins, consistent brightness and color across all switches can be achieved. The wide 130-degree viewing angle ensures the light is visible from the driver's perspective.

11.2 Status Indicator on a Network Device

For a power or link status indicator on a router, a single LED driven at 10-15mA provides ample brightness. The SMD package allows it to be placed very close to a small light pipe or diffused lens on the device casing. The current-limiting resistor can be calculated based on the device's internal logic voltage (e.g., 3.3V). The Pb-free compliance ensures the device meets environmental standards for global sale.

12. Operating Principle Introduction

This LED is based on a semiconductor p-n junction fabricated using Indium Gallium Nitride (InGaN) materials. When a forward voltage exceeding the junction's turn-on voltage (approximately 2.6-3.0V) is applied, electrons and holes are injected across the junction. Their recombination releases energy in the form of photons (light). The InGaN chip itself emits light in the blue spectrum. To create white light, the component incorporates a yellow phosphor coating (resin color is yellow diffused). Part of the blue light from the chip excites this phosphor, causing it to emit yellow light. The combination of the remaining blue light and the generated yellow light is perceived by the human eye as white. This method is known as phosphor-converted white LED technology.

13. Technology Trends and Context

The 19-218 LED represents a mature and widely adopted SMD package technology. The general trend in LED development continues towards several key areas:

• Increased Efficiency (Lumens per Watt): Ongoing improvements in epitaxial growth, chip design, and phosphor technology yield more light output for the same electrical input, reducing energy consumption and thermal load.
• Higher Color Rendering Index (CRI): For applications where accurate color perception is important (e.g., retail lighting, photography), LEDs with multi-phosphor blends or novel structures are developed to emit a fuller spectrum, improving CRI values.
• Miniaturization: Even smaller package footprints (e.g., 0402, 0201 metric sizes) are available for extremely space-constrained applications, though often with a trade-off in total light output and thermal handling capability.
• Integrated Solutions: The market sees growth in LEDs with built-in current-limiting resistors, protection diodes, or even full driver ICs, simplifying circuit design for end-users.
• Smart and Controllable LEDs: Integration with pulse-width modulation (PWM) dimming circuits and digital addressable interfaces (like WS2812) is common, allowing for dynamic color and brightness control.

While this specific component is a standard, single-color, non-addressable device, its reliable performance and compatibility with automated processes ensure its continued relevance in a vast array of indicator and backlighting applications where simplicity, cost-effectiveness, and robustness are primary design goals.