LTW-C281DS5 White SMD LED Datasheet - Dimensions 2.8x1.0x0.35mm - Voltage 2.55-3.15V - Power 70mW - English Technical Document

1. Product Overview

This document provides comprehensive technical information for a specific model of surface-mount device (SMD) light-emitting diode (LED). The product is an ultra-thin, high-brightness white LED designed for modern electronic assembly processes. Its primary applications include backlighting, status indicators, and general illumination in compact electronic devices where space and efficiency are critical.

The core advantages of this component are its minimal profile, compatibility with automated pick-and-place machinery, and adherence to RoHS (Restriction of Hazardous Substances) and green product standards. The target market encompasses consumer electronics, communication devices, and various embedded systems requiring reliable, low-profile indicator lighting.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the limits beyond which permanent damage to the device may occur. These are not conditions for normal operation.

• Power Dissipation (Pd): 70 mW. This is the maximum amount of power the LED package can dissipate as heat without degrading performance or causing failure.
• Peak Forward Current (I_FP): 100 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 of the semiconductor junction.
• DC Forward Current (I_F): 20 mA. This is the recommended maximum continuous forward current for reliable long-term operation.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage exceeding this value can cause immediate and catastrophic failure of the LED junction.
• Operating & Storage Temperature: The device is rated for an ambient operating temperature range of -30°C to +80°C and can be stored in temperatures from -55°C to +105°C.
• Infrared Reflow Soldering: The component can withstand a peak temperature of 260°C for a maximum of 10 seconds during the reflow soldering process.

2.2 Electro-Optical Characteristics

These parameters are measured at a standard test condition of an ambient temperature (T_a) of 25°C and a forward current (I_F) of 5 mA, unless otherwise noted.

• Luminous Intensity (I_V): Ranges from a minimum of 45.0 mcd to a typical maximum of 180.0 mcd. This measures the perceived brightness of the LED to the human eye, using a filter that approximates the CIE photopic response curve.
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity is half of the intensity measured at 0 degrees (on-axis). A wide viewing angle like this indicates a Lambertian or near-Lambertian emission pattern, suitable for area illumination.
• Chromaticity Coordinates (x, y): Typical values are x=0.294, y=0.286. These coordinates define the color point of the white light on the CIE 1931 chromaticity diagram, indicating a cool white or neutral white color temperature.
• Forward Voltage (V_F): Ranges from 2.55 V (min) to 3.15 V (max) at 5 mA. This is the voltage drop across the LED when it is conducting current. The actual value for a specific unit depends on its bin code.
• Reverse Current (I_R): Maximum of 10 μA when a reverse voltage of 5V is applied. A low reverse current is desirable.

3. Binning System Explanation

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

3.1 Forward Voltage (V_F) Binning

The V_F is categorized into six bins (V1 to V6), each with a 0.1V range from 2.55V to 3.15V at I_F = 5mA. A tolerance of ±0.05V is applied to each bin. Selecting LEDs from the same V_F bin helps maintain uniform current distribution when multiple LEDs are connected in parallel.

3.2 Luminous Intensity (I_V) Binning

The luminous intensity is sorted into three bins (P, Q, R) with minimum values of 45.0, 71.0, and 112.0 mcd respectively, all at I_F = 5mA. The maximum for the R bin is 180.0 mcd. A tolerance of ±15% is applied to each bin. This binning is crucial for applications requiring consistent brightness levels across multiple LEDs.

3.3 Hue (Chromaticity) Binning

The color point is defined within six regions (S1 to S6) on the CIE 1931 chromaticity diagram. Each bin is a quadrilateral defined by specific (x, y) coordinate boundaries. A tolerance of ±0.01 is applied to the coordinates. This system ensures color uniformity, which is critical for backlighting and aesthetic lighting applications. The provided diagram visually maps these S1-S6 regions.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 6 for viewing angle, Figure 1 for chromaticity), their typical behavior can be described based on standard LED physics.

• I-V (Current-Voltage) Characteristic: The forward voltage (V_F) exhibits a logarithmic relationship with forward current (I_F). A small increase in V_F leads to a large increase in I_F once the turn-on voltage is exceeded. The V_F also has a negative temperature coefficient, meaning it decreases slightly as the junction temperature increases.
• Luminous Intensity vs. Current: The light output (I_V) is generally proportional to the forward current in the normal operating range. However, efficiency may drop at very high currents due to increased heat and droop effects in the semiconductor material.
• Temperature Dependence: The luminous intensity of InGaN-based white LEDs typically decreases as the junction temperature rises. This is a critical factor for thermal management in high-power or high-density applications.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED features an EIA (Electronic Industries Alliance) standard package footprint. A key specification is its ultra-thin profile of 0.35 mm. Detailed dimensional drawings are provided, specifying the length, width, height, pad sizes, and their positional tolerances (typically ±0.10 mm).

5.2 Pad Design and Polarity

The datasheet includes suggested soldering pad dimensions for PCB (Printed Circuit Board) layout. Proper pad design is essential for reliable solder joint formation and mechanical strength. The component has anode and cathode terminals; correct polarity must be observed during assembly to ensure proper function.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters

The component is fully compatible with infrared (IR) reflow soldering processes. A recommended profile is provided, with key parameters including a pre-heat zone (150-200°C), a maximum peak temperature of 260°C, and a time above liquidus not exceeding 10 seconds. The profile should comply with JEDEC standards to prevent thermal shock.

6.2 Storage and Handling

• Moisture Sensitivity: The LEDs are packaged in moisture-barrier bags with desiccant. Once the original bag is opened, the components should be used within 672 hours (28 days) or baked at 60°C for at least 20 hours before soldering if stored longer.
• ESD (Electrostatic Discharge) Precautions: LEDs are sensitive to static electricity. Proper ESD controls, such as grounded workstations, wrist straps, and conductive containers, are mandatory during handling.
• Cleaning: If cleaning is necessary after soldering, only specified solvents like ethyl alcohol or isopropyl alcohol should be used at room temperature for less than one minute. Unspecified chemicals may damage the epoxy lens.

7. Packaging and Ordering Information

The LEDs are supplied on 8mm wide embossed carrier tape wound onto 7-inch (178mm) diameter reels. Each reel contains 5000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces is available. The tape and reel specifications conform to ANSI/EIA 481-1 standards, ensuring compatibility with automated feeders.

8. Application Notes and Design Considerations

8.1 Typical Application Scenarios

This LED is ideal for space-constrained applications such as mobile device keypad backlights, status indicators on ultra-thin laptops or tablets, panel indicators in automotive dashboards, and decorative lighting in consumer gadgets. Its wide viewing angle makes it suitable for even illumination of small areas or light guides.

8.2 Circuit Design Considerations

• Current Limiting: An LED is a current-driven device. A series current-limiting resistor or a constant-current driver circuit is essential to prevent exceeding the maximum DC forward current, which would lead to rapid degradation.
• Thermal Management: Although the power dissipation is low, ensuring adequate PCB copper area or thermal vias under the LED's thermal pad (if present) helps dissipate heat, maintaining luminous output and longevity.
• Parallel Connections: Connecting LEDs directly in parallel is generally not recommended due to variations in V_F. If necessary, using LEDs from the same V_F bin and including individual small-value series resistors for each LED can help balance currents.

9. Technical Comparison and Differentiation

The primary differentiating factor of this LED is its 0.35mm thickness, which is exceptionally low for a standard SMD LED. Compared to thicker packages (e.g., 0.6mm or 1.0mm), this enables design of even slimmer end products. The combination of high brightness (up to 180 mcd at 5mA) within this thin profile offers a favorable brightness-to-size ratio. The defined binning structure for color and intensity provides a level of consistency that may not be guaranteed with unbinned or broadly binned commodity LEDs.

10. Frequently Asked Questions (FAQ)

10.1 What is the difference between Peak Forward Current and DC Forward Current?

The DC Forward Current (20 mA) is the safe limit for continuous operation. The Peak Forward Current (100 mA) is a much higher value allowed only for very short pulses (0.1ms) at a low duty cycle (10%). Exceeding the DC current rating, even briefly, can cause permanent damage.

10.2 How do I interpret the Chromaticity Bin codes (S1-S6)?

The S-codes define regions on the CIE color chart. S1 and S2 represent cooler white tones (higher blue content), while S5 and S6 represent warmer white tones (higher yellow/red content). S3 and S4 are typically in the neutral white region. Designers should specify the required bin(s) based on the color temperature needs of their application.

10.3 Can I use a soldering iron instead of reflow?

Hand soldering with an iron is possible but not recommended for volume production. If necessary, the iron tip temperature must not exceed 300°C, and the soldering time per lead must be limited to 3 seconds maximum. Care must be taken to avoid mechanical stress and excessive localized heat on the component.

11. Practical Design and Usage Examples

Example 1: Mobile Device Status Indicator: A designer needs a single, bright white LED to indicate charging status. They select an LED from the R brightness bin for high visibility. They drive it at 10 mA using a GPIO pin from a microcontroller with a series resistor calculated as (Supply Voltage - V_F) / 0.01A. They choose an LED from the V3 voltage bin (2.75-2.85V) for predictable behavior. The 0.35mm height fits within the device's ultra-thin bezel.

Example 2: Backlighting a Small LCD: An engineer needs to evenly illuminate a 2-inch monochrome LCD from the side using a light guide. They use four LEDs placed along one edge. To ensure uniform color and brightness, they specify all LEDs must come from the same Hue bin (e.g., S4) and the same Luminous Intensity bin (e.g., Q). They are connected in series and driven by a constant-current driver set to 15 mA to ensure consistent output and simplify the circuit.

12. Technical Principle Introduction

This LED is based on InGaN (Indium Gallium Nitride) semiconductor technology. The core of a white LED is typically a blue-emitting InGaN chip. A phosphor layer, often composed of yttrium aluminum garnet (YAG) doped with cerium, is deposited on top of this chip. When the blue light from the chip excites the phosphor, it down-converts a portion of the blue photons into yellow light. The combination of the remaining blue light and the emitted yellow light is perceived by the human eye as white. The specific mix of phosphors determines the correlated color temperature (CCT), resulting in cool, neutral, or warm white light. The ultra-thin package is achieved through advanced wafer-level packaging and molding techniques.

13. Industry Trends and Developments

The trend in SMD LEDs for consumer electronics continues toward higher efficiency (more lumens per watt), smaller footprints, and thinner profiles, enabling ever-slimmer end products. There is also a strong focus on improved color rendering index (CRI) for better light quality and tighter binning tolerances to reduce color and brightness variation in production batches. Furthermore, the integration of driver ICs directly with LED packages ("LED modules" or "smart LEDs") is becoming more common for simplified design. The underlying InGaN technology is also being refined for higher power density and reliability. Environmental regulations continue to drive the elimination of hazardous substances, solidifying RoHS compliance as a standard requirement.