White LED SMD 1608 Specification - 1.6x0.8x0.55mm - 2.6-3.4V - 68mW - English Technical Document

1. Product Overview

This document details the specifications for a compact, surface-mount white LED designed for modern electronic applications. The device utilizes a blue LED chip combined with a phosphor coating to produce white light, offering a balance of performance and miniaturization suitable for space-constrained designs.

1.1 Core Advantages and Target Market

The primary advantage of this LED is its extremely wide viewing angle of 120 degrees, ensuring uniform light distribution. It is fully compatible with standard SMT assembly and soldering processes, classified under Moisture Sensitivity Level (MSL) 3, and complies with RoHS environmental standards. Its target applications include optical indicators, switch and symbol backlighting, displays, household appliances, and general-purpose lighting where a small, reliable white light source is required.

2. In-Depth Technical Parameter Analysis

A thorough understanding of the device's parameters is crucial for successful integration into a circuit design.

2.1 Electrical and Optical Characteristics

The key performance metrics are defined at a standard test condition of an ambient temperature (Ts) of 25°C and a forward current (IF) of 5mA.

• Forward Voltage (VF): The device is offered in multiple voltage bins, ranging from a minimum of 2.6V (F1 bin) to a maximum of 3.4V (I2 bin). Designers must account for this variation when designing the driving circuitry to ensure consistent current and brightness.
• Luminous Intensity (Iv): The light output is also binned, with categories ranging from I00 (230-350 mcd) to L10 (800-1000 mcd). This allows for selection based on the required brightness level for the application.
• Reverse Current (IR): The maximum leakage current when a reverse voltage of 5V is applied is 10 µA, indicating good diode characteristics.
• Viewing Angle (2θ1/2): The typical full viewing angle at half intensity is 120 degrees, which is notably wide for an SMD LED.

2.2 Absolute Maximum Ratings and Thermal Management

Exceeding these limits may cause permanent damage to the device.

• Power Dissipation (Pd): The maximum allowable power dissipation is 68 mW.
• Forward Current (IF): The maximum continuous forward current is 20 mA.
• Peak Pulse Current (IFP): A higher pulse current of 60 mA is permissible under specific conditions (0.1ms pulse width, 1/10 duty cycle).
• Thermal Resistance (RθJ-S): The junction-to-solder point thermal resistance is 450 °C/W. This is a critical parameter for thermal management. The power dissipated (Pd = VF * IF) and this thermal resistance determine the temperature rise of the LED junction above the solder point. The maximum junction temperature (Tj) must not exceed 95°C.
• Operating & Storage Temperature: The device can function and be stored within a range of -40°C to +85°C.
• Electrostatic Discharge (ESD): The Human Body Model (HBM) ESD rating is 1000V, which is standard for many LEDs but necessitates standard ESD handling precautions during assembly.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins.

3.1 Forward Voltage Binning

The forward voltage is categorized into eight distinct bins (F1, F2, G1, G2, H1, H2, I1, I2), each covering a 0.1V range from 2.6V to 3.4V. This allows designers to select LEDs with tighter voltage tolerances for applications requiring uniform power consumption.

3.2 Luminous Intensity Binning

The light output is grouped into four intensity bins (I00, J00, K00, L10). This enables the selection of LEDs for applications where a specific minimum brightness is required or where brightness matching across multiple LEDs is important.

3.3 Chromaticity Binning

The document references CIE chromaticity coordinates for specific white color bins (TW22, TW23, TW24). These coordinates define a quadrilateral area on the CIE 1931 color space diagram. LEDs whose color output falls within these defined areas are grouped together, ensuring a consistent white color tone (e.g., cool white, neutral white) within a batch.

4. Performance Curve Analysis

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

4.1 Forward Voltage vs. Forward Current (IV Curve)

The typical IV curve shows the non-linear relationship between the voltage across the LED and the current flowing through it. The curve will show a turn-on voltage (around the lower end of the VF bin range) after which the current increases rapidly with a small increase in voltage. This characteristic is fundamental for designing constant-current drivers, which are preferred over constant-voltage drivers for LEDs.

5. Mechanical and Package Information

5.1 Package Dimensions and Tolerances

The device is housed in a compact 1608 package, measuring 1.6mm in length, 0.8mm in width, and 0.55mm in height. All dimension tolerances are ±0.2mm unless otherwise specified. Detailed top, side, and bottom views are provided in the specification, along with critical dimensions like the pad spacing (1.2mm ± 0.05mm).

5.2 Polarity Identification and Recommended Footprint

The bottom view clearly indicates the anode and cathode pads. The cathode is typically marked. A recommended solder pad land pattern is provided to ensure proper soldering and mechanical stability. The pad design is crucial for achieving a reliable solder joint and for effective heat transfer away from the LED die.

6. Soldering and Assembly Guidelines

6.1 SMT Reflow Soldering Instructions

The LED is suitable for all standard SMT reflow soldering processes. Due to its MSL 3 rating, the components must be baked before soldering if the moisture barrier bag has been opened for more than 168 hours (7 days) under factory floor conditions (30°C/60% RH). The specific reflow profile (preheat, soak, reflow peak temperature, cooling rate) should follow the recommendations for similar small SMD components, typically with a peak temperature not exceeding 260°C.

6.2 Handling and Storage Precautions

• Always handle with ESD protection.
• Store in the original moisture barrier bag with desiccant when not in use.Follow the MSL 3 baking procedures if exposure limits are exceeded.
• Avoid mechanical stress on the LED lens.
• Do not exceed the absolute maximum ratings during testing or operation.

7. Packaging and Ordering Information

7.1 Packaging Specification

The LEDs are supplied in industry-standard embossed carrier tape on reels, suitable for automated pick-and-place machines. Detailed dimensions for the carrier tape pockets and the reel are provided to ensure compatibility with assembly equipment. A label specification for the reel is also included.

7.2 Moisture-Resistant Packing and Carton

The reels are packaged in moisture barrier bags with desiccant to maintain the MSL 3 rating during storage and transport. These bags are then packed in cardboard boxes for shipment.

8. Application Suggestions and Design Considerations

8.1 Typical Application Scenarios

• Status Indicators: Ideal for power, connectivity, or function status lights in consumer electronics, appliances, and industrial equipment due to their small size and wide viewing angle.
• Backlighting: Can be used to backlight buttons, keypads, or small symbols on control panels.
• Decorative Lighting: Suitable for accent lighting in compact devices.
• General Illumination: Can be used in arrays for low-level task lighting or as a component in larger lighting modules.

8.2 Critical Design Considerations

• Current Limiting: Always use a series resistor or a constant-current driver to limit the forward current. Do not connect directly to a voltage source.
• Thermal Design: Given the relatively high thermal resistance, ensure adequate PCB copper area (thermal pads) and possibly ventilation if operating near maximum current, to keep the junction temperature below 95°C. High junction temperatures accelerate lumen depreciation and reduce lifespan.
• Optical Design: The 120-degree viewing angle may require light guides or diffusers if a more focused beam is needed. Conversely, it is advantageous for area illumination.
• Binning Selection: For applications requiring color or brightness uniformity, specify the required VF, intensity, and chromaticity bins.

9. Reliability and Quality Assurance

9.1 Reliability Test Items and Conditions

The specification references a set of reliability tests performed to ensure product longevity. While the specific conditions are detailed in a separate document, typical tests for LEDs include: High Temperature Operating Life (HTOL), Low Temperature Storage, Temperature Cycling, Humidity testing, and Solder Heat Resistance. These tests simulate the stresses the component will encounter during its lifetime.

9.2 Failure Judgment Criteria

Criteria for judging a device as failed during these reliability tests are established. Common failure criteria include a significant drop in luminous intensity (e.g., >30%), a large shift in forward voltage, a change in chromaticity coordinates beyond specified limits, or catastrophic failure (no light output).

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 What is the purpose of the different voltage bins?

Voltage bins allow designers to select LEDs with similar electrical characteristics. In applications using multiple LEDs in series or parallel, matching VF bins helps ensure uniform current distribution and consistent brightness across all LEDs, preventing some from being overdriven or underdriven.

10.2 How do I calculate the required series resistor?

Use Ohm's Law: R = (Vsupply - VF) / IF. Use the maximum VF from the selected bin for a conservative design to ensure the current does not exceed the desired IF. For example, with a 5V supply, an IF of 5mA, and an LED from the I2 bin (VF max = 3.4V): R = (5 - 3.4) / 0.005 = 320 Ohms. Use the nearest standard value (e.g., 330 Ohms).

10.3 Why is thermal management important for such a small LED?

Despite its small size, the LED chip generates heat. The thermal resistance of 450°C/W means that for every watt dissipated, the junction temperature rises 450°C above the solder point temperature. Even at 20mA and 3.4V (68mW), the temperature rise is significant (approx. 30.6°C). Poor heat sinking can quickly push the junction temperature over the 95°C limit, leading to rapid brightness degradation and shortened lifespan.

11. Working Principle and Technology Trends

11.1 Basic Operating Principle

This is a phosphor-converted white LED. A semiconductor chip emitting blue light (typically based on InGaN) is encapsulated with a yellow (or a mix of red and green) phosphor. Part of the blue light is absorbed by the phosphor and re-emitted as longer wavelength yellow light. The combination of the remaining blue light and the converted yellow light appears white to the human eye. This method is efficient and allows for tuning the white color temperature by adjusting the phosphor composition.

11.2 Industry Trends

The trend in SMD LEDs for indicator and general lighting continues towards higher efficiency (more lumens per watt), smaller package sizes for higher density designs, improved color rendering index (CRI) for better light quality, and tighter binning for greater consistency. There is also a focus on enhancing reliability and thermal performance to support higher drive currents in compact formats. The 1608 package represents a mature, widely adopted form factor balancing size, performance, and manufacturability.