SMD LED 18-225/R6G6C-A01/3T Specification - Size 1.6x0.8x0.5mm - Voltage 2.0V - Power 60mW - Brilliant Red/Yellow Green - English Technical Document

1. Product Overview

The 18-225 series represents a compact, surface-mount LED component designed for modern electronic applications requiring miniaturization and high reliability. This datasheet covers two primary variants identified by their chip codes: R6 (Brilliant Red) and G6 (Brilliant Yellow Green). The core advantage of this product lies in its significantly reduced footprint compared to traditional lead-frame LEDs, enabling designers to achieve smaller printed circuit board (PCB) sizes, higher component packing density, and ultimately more compact end-user equipment. Its lightweight construction further makes it an ideal choice for portable and miniature applications.

1.1 Core Features and Advantages

The device is supplied on 8mm tape wound onto 7-inch diameter reels, ensuring compatibility with standard automated pick-and-place assembly equipment, which streamlines high-volume manufacturing processes. It is qualified for use with both infrared (IR) and vapor phase reflow soldering techniques, adhering to common Pb-free assembly requirements. The product is confirmed to be compliant with the Restriction of Hazardous Substances (RoHS) directive. Being a mono-color type, each component emits a single, specific wavelength of light, defined by its chip material.

1.2 Target Applications and Markets

The 18-225 LED finds use across a broad spectrum of applications where small, reliable indicator lighting is required. Primary application areas include backlighting for instrument panel dashboards and membrane switches. In telecommunications equipment, it serves as status indicators and keypad backlights. It is also suitable for providing flat backlighting for liquid crystal displays (LCDs), switch legends, and symbols. Its general-purpose nature makes it a versatile component for consumer electronics, industrial controls, and various embedded systems.

2. Technical Parameter Deep-Dive

This section provides a detailed, objective analysis of the electrical, optical, and thermal parameters specified for the 18-225 LED, crucial for reliable circuit design and performance prediction.

2.1 Absolute Maximum Ratings

The Absolute Maximum Ratings define the stress limits beyond which permanent damage to the device may occur. These are not conditions for normal operation. For both the R6 and G6 variants, the maximum continuous forward current (I_F) is rated at 25 mA. A higher peak forward current (I_FP) of 60 mA is permissible under pulsed conditions with a duty cycle of 1/10 at 1 kHz. The maximum reverse voltage (V_R) is 5 V. The power dissipation (P_d) for each LED is limited to 60 mW. The device can withstand an Electrostatic Discharge (ESD) of 2000 V per the Human Body Model (HBM). The operating temperature range (T_opr) is specified from -40°C to +85°C, with a slightly wider storage temperature (T_stg) range of -40°C to +90°C. Soldering temperature profiles are critical: reflow soldering must not exceed 260°C for 10 seconds, while hand soldering should be limited to 350°C for 3 seconds.

2.2 Electro-Optical Characteristics

The Electro-Optical Characteristics are measured at a standard junction temperature (T_a) of 25°C and a forward current (I_F) of 20 mA, unless otherwise noted. These represent typical operating conditions.

2.2.1 Luminous Intensity and Viewing Angle

Luminous intensity (I_v) is the perceived brightness of the LED. For the R6 (Red) chip, the minimum intensity is 45.0 mcd, with a maximum of 112 mcd. The G6 (Yellow Green) chip has a minimum of 28.5 mcd and a maximum of 72.0 mcd. The datasheet notes a tolerance of ±11% on luminous intensity. Both LEDs feature a wide viewing angle (2θ1/2) of 120 degrees, providing a broad, diffuse light emission pattern suitable for indicator applications.

2.2.2 Spectral Characteristics

The peak wavelength (λ_p) for the R6 chip is typically 632 nm, and for the G6 chip, it is 575 nm. The dominant wavelength (λ_d), which correlates more closely with perceived color, is specified with a range: 617.0 nm to 625.0 nm for R6, and 567.5 nm to 575.5 nm for G6, with a tolerance of ±1 nm. The spectral bandwidth (Δλ) for both is approximately 20 nm, indicating the spectral purity of the emitted light.

2.2.3 Electrical Parameters

The forward voltage (V_F) for both LED types at 20 mA has a typical value of 2.0 V, with a minimum of 1.7 V and a maximum of 2.4 V. The tolerance is noted as ±0.10 V. The reverse current (I_R) is specified at a maximum of 10 μA when a reverse bias of 5 V is applied, indicating good diode characteristics.

3. Binning System Explanation

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

3.1 Luminous Intensity Binning

The R6 (Red) LED is binned into four luminous intensity groups: P1 (45.0-57.0 mcd), P2 (57.0-72.0 mcd), Q1 (72.0-90.0 mcd), and Q2 (90.0-112 mcd). The G6 (Yellow Green) LED is binned into four groups: N1 (28.5-36.0 mcd), N2 (36.0-45.0 mcd), P1 (45.0-57.0 mcd), and P2 (57.0-72.0 mcd).

3.2 Dominant Wavelength Binning (G6 only)

For the G6 variant, an additional binning is performed based on dominant wavelength. The bins are C15 (567.5-569.5 nm), C16 (569.5-571.5 nm), C17 (571.5-573.5 nm), and C18 (573.5-575.5 nm). This allows for precise color matching in applications where specific green-yellow hues are critical.

4. Performance Curve Analysis

Graphical data provides insight into how LED performance varies with operating conditions, which is essential for robust design.

4.1 Forward Current vs. Forward Voltage (IV Curve)

The typical curve shows the exponential relationship between forward current and forward voltage. For both R6 and G6 types, at the recommended 20 mA operating point, the voltage is typically 2.0V. Designers must use a current-limiting resistor or constant-current driver to ensure the LED operates within its specified current range, as a small increase in voltage can lead to a large, potentially damaging increase in current.

4.2 Luminous Intensity vs. Forward Current

This curve demonstrates that luminous intensity increases approximately linearly with forward current up to a point. Operating at the specified 20 mA provides the rated luminous output. Exceeding the maximum continuous current may increase brightness temporarily but will reduce lifespan and reliability due to increased junction temperature.

4.3 Luminous Intensity vs. Ambient Temperature

The output of an LED decreases as the ambient (and consequently, junction) temperature rises. The derating curve is crucial for applications operating in elevated temperature environments. The LED's output can drop significantly as temperature approaches the maximum operating limit of 85°C. Designers must account for this thermal derating to ensure sufficient brightness under all operating conditions.

4.4 Spectrum Distribution

The spectral plots for R6 and G6 show the relative intensity of light emitted across wavelengths. The R6 plot centers around 632 nm (red), while the G6 plot centers around 575 nm (yellow-green). The 20 nm bandwidth indicates a relatively narrow, saturated color emission.

4.5 Radiation Diagram

The polar radiation pattern visually confirms the 120-degree viewing angle. The intensity is highest along the central axis (0°) and decreases symmetrically to 50% of its peak value at ±60° from the axis.

5. Mechanical and Package Information

5.1 Package Dimensions and Drawings

The 18-225 LED has a compact surface-mount package. Key dimensions include a body length of 1.6 mm, a width of 0.8 mm, and a height of 0.5 mm (with a tolerance of ±0.1 mm unless otherwise specified). The package features two electrodes on the bottom side.

5.2 Polarity Identification and Pad Design

Polarity is clearly marked. The cathode is identified by a green marking on the top of the package for the G6 LED and a red marking for the R6 LED. On the bottom side, the cathode is the larger pad or the one with a chamfered corner. A recommended solder pad layout is provided, suggesting dimensions to ensure a reliable solder joint and proper alignment during reflow. The datasheet emphasizes that these pad dimensions are for reference only and should be modified based on specific PCB design rules and process requirements.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

For Pb-free assembly, a specific temperature profile must be followed. The pre-heating zone should be between 150°C and 200°C for 60-120 seconds. The time above the solder liquidus temperature (217°C) should be 60-150 seconds. The peak package body temperature must not exceed 260°C, and the time above 255°C should be limited to a maximum of 30 seconds. The maximum heating rate should be 6°C/sec, and the maximum cooling rate should be 3°C/sec. Adherence to this profile prevents thermal shock and ensures reliable solder connections without damaging the LED epoxy or semiconductor die.

6.2 Storage and Moisture Sensitivity

The LEDs are packaged in a moisture-resistant bag with desiccant. The bag should not be opened until the components are ready for use. Before opening, storage conditions should be 30°C or less and 90% relative humidity (RH) or less. After opening, the components have a "floor life" of one year if stored at 30°C/60% RH or less. Unused LEDs should be resealed in a moisture-proof package. If the desiccant indicator shows moisture absorption or the storage time is exceeded, a baking treatment at 60°C ±5°C for 24 hours is required to remove absorbed moisture and prevent "popcorning" (package cracking) during reflow soldering.

7. Packaging and Ordering Information

7.1 Reel and Tape Specifications

The components are supplied on embossed carrier tape with a width of 8 mm, wound onto a standard 7-inch (178 mm) diameter reel. Each reel contains 3000 pieces. Detailed reel and tape dimensions are provided to ensure compatibility with automated feeders.

7.2 Label Explanation

The reel label contains several key codes: CPN (Customer's Product Number), P/N (Manufacturer's Product Number, e.g., 18-225/R6G6C-A01/3T), QTY (Packing Quantity), CAT (Luminous Intensity Rank/Bin Code), HUE (Chromaticity Coordinates & Dominant Wavelength Rank), REF (Forward Voltage Rank), and LOT No (Traceable Lot Number). Understanding these codes is essential for inventory control and ensuring the correct component bin is used in production.

8. Application Design Considerations

8.1 Current Limiting is Mandatory

A critical design note is the necessity of using a series current-limiting resistor (or an active constant-current driver) with this LED. The forward voltage has a tolerance and a negative temperature coefficient (decreases as temperature rises). Without current limiting, even a small increase in supply voltage or a decrease in V_F due to heating can cause a runaway increase in current, leading to rapid failure. The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F, where V_F is the typical or maximum value from the datasheet, and I_F is the desired operating current (e.g., 20 mA).

8.2 Thermal Management

While the package is small, managing heat is important for longevity and stable light output. The maximum power dissipation is 60 mW. At 20 mA and a typical V_F of 2.0V, the power dissipated is 40 mW, which is within limits. However, in high ambient temperature environments or if driven at higher currents, attention must be paid to the PCB layout. Providing adequate copper area around the LED pads helps to conduct heat away from the junction. The derating curve should be consulted to estimate brightness loss in hot environments.

8.3 Optical Design

The 120-degree viewing angle provides a wide, diffuse glow. For applications requiring a more directed beam, secondary optics such as lenses or light pipes may be employed. The small size of the LED makes it suitable for integration into tight spaces behind panels or displays.

9. Technical Comparison and Differentiation

The 18-225 LED's primary differentiation lies in its miniature 1.6x0.8mm footprint, which is smaller than many traditional SMD LEDs like the 0603 (1.6x0.8mm) or 0402 (1.0x0.5mm) packages, though its height profile is similar. Its key advantage is the availability of a specific brilliant yellow-green (G6) color with precise wavelength binning, which is less common than standard green. The combination of a wide 120-degree viewing angle and relatively high luminous intensity for its size (especially the R6 variant) offers a good balance between brightness and viewing area coverage. Its compatibility with standard Pb-free reflow processes and RoHS compliance aligns it with modern environmental regulations.

10. Frequently Asked Questions (FAQ)

10.1 What is the difference between peak wavelength and dominant wavelength?

Peak wavelength (λ_p) is the wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength (λ_d) is the single wavelength of monochromatic light that would match the perceived color of the LED. For LEDs with a narrow spectrum, they are often close, but λ_d is more relevant for color specification in applications like indicators and displays.

10.2 Can I drive this LED at 30 mA for more brightness?

Driving the LED at 30 mA exceeds the Absolute Maximum Rating for continuous forward current (25 mA). While it might produce more light initially, it will significantly increase junction temperature, accelerate lumen depreciation (light output decay over time), and drastically shorten the operational lifespan. It is not recommended for reliable design.

10.3 How do I interpret the bin codes (CAT, HUE) on the label?

The CAT code corresponds to the luminous intensity bin (e.g., P1, N2). The HUE code corresponds to the color/wavelength bin (e.g., C16 for G6). Using components from the same bin across a product ensures uniform brightness and color appearance. For non-critical applications, any bin within specification may be used, but for consistency, specifying and controlling the bin code in procurement is essential.

11. Practical Design and Usage Examples

11.1 Example: Dashboard Indicator Circuit

Consider designing a 12V automotive dashboard indicator using the R6 LED. Assuming a typical V_F of 2.0V and a desired I_F of 20 mA. The required series resistor is R = (12V - 2.0V) / 0.020A = 500 Ohms. The nearest standard value is 510 Ohms. Recalculating the current: I_F = (12V - 2.0V) / 510Ω ≈ 19.6 mA, which is safe and within specification. The power dissipated in the resistor is (10V)^2 / 510Ω ≈ 0.196W, so a 1/4-watt resistor is sufficient. The wide viewing angle ensures the indicator is visible from various driver positions.

11.2 Example: Multi-LED Backlight with Consistent Color

For a keypad backlight requiring several G6 LEDs to have matching color, it is imperative to specify the HUE bin code (e.g., C17) during procurement. Furthermore, driving all LEDs from the same constant-current source or using individual resistors with tight tolerance (1%) helps minimize brightness variations caused by differences in forward voltage. The compact size allows for tight spacing between keys.

12. Operational Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type material recombine with holes from the p-type material. This recombination process releases energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material used. The R6 LED uses an AlGaInP (Aluminum Gallium Indium Phosphide) chip, which is engineered to produce red light. The G6 LED also uses an AlGaInP chip but with a different composition to produce yellow-green light. The epoxy resin encapsulant serves to protect the chip, shape the light output beam, and can include phosphors or dyes, though in this "Water Clear" version, it is transparent.

13. Technology Trends and Context

The 18-225 LED represents a mature product in the landscape of SMD indicator LEDs. The general trend in this sector continues toward even smaller package sizes (e.g., 01005, 0.4x0.2mm), higher efficiency (more lumens per watt), and improved reliability. There is also a growing integration of driver electronics within the LED package itself ("smart LEDs"). However, components like the 18-225 remain highly relevant due to their proven reliability, low cost, ease of use, and wide availability. They serve as fundamental building blocks in countless electronic devices where simple, reliable indicator lighting is required. The emphasis on Pb-free and RoHS-compliant manufacturing, as seen in this datasheet, reflects the industry-wide shift toward environmentally conscious electronics production.