SMD3528 Blue LED Datasheet - Size 3.5x2.8mm - Voltage 3.2V - Power 0.144W - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a single-chip blue LED in the SMD3528 package. This surface-mount device is designed for general lighting, backlighting, and indicator applications requiring a reliable and efficient blue light source. The core advantage of this component lies in its standardized package, consistent performance parameters, and well-defined binning system, ensuring predictable behavior in circuit design.

2. Technical Parameters Deep Objective Interpretation

The following section details the absolute maximum ratings and typical electrical/optical characteristics of the LED. All parameters are measured at a standard test condition of T_s = 25°C.

2.1 Absolute Maximum Ratings

• Forward Current (I_F): 30 mA (Continuous)
• Forward Pulse Current (I_FP): 40 mA (Pulse width ≤ 10ms, Duty cycle ≤ 1/10)
• Power Dissipation (P_D): 144 mW
• Operating Temperature (T_opr): -40°C to +80°C
• Storage Temperature (T_stg): -40°C to +80°C
• Junction Temperature (T_j): 125°C
• Soldering Temperature (T_sld): Reflow soldering at 200°C or 230°C for 10 seconds.

2.2 Typical Technical Parameters

Measured at a forward current (I_F) of 20 mA.

• Forward Voltage (V_F): Typical 3.2 V, Maximum 3.6 V
• Reverse Voltage (V_R): 5 V
• Dominant Wavelength (λ_d): 460 nm
• Reverse Current (I_R): Maximum 10 µA
• Viewing Angle (2θ_1/2): 120°

3. Binning System Explanation

The product is classified into bins based on key performance parameters to ensure consistency. The binning codes are part of the product model number.

3.1 Luminous Flux Binning

Luminous flux is measured at I_F = 20 mA. The tolerance for flux measurement is ±7%.

3.2 Wavelength Binning

The dominant wavelength is binned to control the specific shade of blue light.

3.3 Forward Voltage Binning

Forward voltage is binned to aid in current regulation circuit design. The tolerance for voltage measurement is ±0.08V.

3.4 Product Nomenclature Rule

The model number follows a specific structure: T [Package Code] [Chip Count] [Lens Code] [Internal Code] - [Flux Code] [Wavelength Code].

• Package Code (e.g., 32): Denotes the SMD3528 package.
• Chip Count (e.g., S): 'S' for a single small-power chip.
• Lens Code: '00' for no lens, '01' for with lens.
• Color: Defined by letter (B for Blue).

4. Performance Curve Analysis

The characteristic curves illustrate the relationship between key parameters, which is crucial for thermal and drive circuit management.

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

The I-V curve shows the exponential relationship typical of a diode. The forward voltage increases with current. Designers must ensure the driver circuit provides adequate voltage headroom, especially considering the voltage bin spread, to achieve the desired current without exceeding the maximum ratings.

4.2 Relative Luminous Flux vs. Forward Current

This curve demonstrates that light output increases with current but may not be perfectly linear, especially at higher currents. Operating above the recommended 20mA may yield diminishing returns in efficiency and increase junction temperature, potentially affecting longevity.

4.3 Relative Spectral Energy vs. Junction Temperature

The graph indicates that as the junction temperature rises from 25°C to 125°C, the relative spectral energy output decreases. This highlights the importance of thermal management in the application design to maintain consistent light output and color stability over the product's lifetime.

4.4 Spectral Power Distribution

The spectral curve confirms a peak emission around the 460nm dominant wavelength, characteristic of a blue InGaN LED chip. The narrow bandwidth is typical for a monochromatic LED.

5. Mechanical and Packaging Information

5.1 Outline Dimensions

The SMD3528 package has nominal dimensions of 3.5mm (length) x 2.8mm (width). The exact dimensional drawing with tolerances (e.g., .X: ±0.10mm, .XX: ±0.05mm) is provided for PCB footprint design.

5.2 Recommended Pad Pattern and Stencil Design

A detailed land pattern (footprint) and solder paste stencil design are supplied to ensure proper soldering and alignment during the Surface Mount Technology (SMT) assembly process. Adhering to these recommendations is critical for achieving reliable solder joints and optimal thermal transfer from the LED to the PCB.

5.3 Polarity Identification

The cathode is typically marked on the LED package, often with a green tint on the lens or a notch/chamfer on one corner of the plastic body. The pad layout diagram clearly indicates the anode and cathode pads.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters

The LED is rated for standard reflow soldering processes. The maximum body temperature during soldering should not exceed 200°C for 10 seconds or 230°C for 10 seconds. It is essential to follow the recommended temperature profile to prevent damage to the internal die and the epoxy lens material.

6.2 Handling and Storage Precautions

• Store in a dry, anti-static environment within the specified temperature range (-40°C to +80°C).
• Avoid mechanical stress on the lens.
• Use within 12 months of the manufacturing date under recommended storage conditions to ensure solderability.

7. Packaging and Ordering Information

7.1 Tape and Reel Specification

The LEDs are supplied on embossed carrier tape wound on reels, suitable for automated pick-and-place machines. Key tape dimensions (pocket size, pitch) and the required cover tape peel strength (0.1 - 0.7N at a 10-degree angle) are specified to ensure compatibility with SMT equipment.

8. Application Suggestions

8.1 Typical Application Scenarios

• Backlighting: For LCD displays, keypads, or signage.
• Status Indicators: On consumer electronics, appliances, and industrial equipment.
• Decorative Lighting: In accent lighting, mood lighting, or architectural features.
• General Illumination: As a component in LED modules, strips, or bulbs, often combined with phosphors to create white light.

8.2 Design Considerations

• Current Limiting: Always drive the LED with a constant current source or a current-limiting resistor. Do not connect directly to a voltage source.
• Thermal Management: Design the PCB with adequate copper area or thermal vias to dissipate heat, especially when operating near maximum current. High junction temperatures accelerate lumen depreciation.
• ESD Protection: Although not explicitly stated as highly sensitive, implementing basic ESD protection on the driving circuit is a good practice for reliability.
• Optical Design: Consider the 120-degree viewing angle when designing lenses or light guides for the intended application.

9. Technical Comparison

Compared to through-hole LEDs, the SMD3528 offers significant advantages in automated assembly, board space savings, and better thermal performance due to direct PCB attachment. Within the SMD family, the 3528 package is a mature and widely used standard, offering a good balance of size, light output, and cost. Compared to smaller packages like 3020 or 3014, the 3528 typically can handle slightly higher current and may have a larger luminous area. Compared to larger packages like 5050, it is more compact.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 What is the recommended operating current?

The technical parameters are specified at 20mA, which is the standard test current and a common operating point for good efficiency and longevity. It can be operated up to the absolute maximum of 30mA continuous, but this will generate more heat and may reduce lifespan.

10.2 How do I select the correct current-limiting resistor?

Use Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the bin (e.g., 3.6V for bin 4) for a conservative design to ensure the current does not exceed the desired value. For a 5V supply and 20mA target: R = (5V - 3.6V) / 0.02A = 70Ω. Choose the nearest standard value (e.g., 68Ω or 75Ω) and calculate the actual current and resistor power dissipation.

10.3 Why is luminous flux binned, and which bin should I choose?

Manufacturing variations cause slight differences in light output. Binning groups LEDs with similar performance. Choose a bin based on the minimum required brightness for your application. Using a higher bin (e.g., B3) ensures brighter, more consistent units but may come at a higher cost.

10.4 Can I use this LED for outdoor applications?

The operating temperature range is -40°C to +80°C, which covers most outdoor environments. However, the LED itself is not waterproof or UV-stabilized. For outdoor use, it must be properly encapsulated or housed within a sealed, weatherproof fixture that also manages heat dissipation.

11. Practical Design Case

Scenario: Designing a low-power status indicator for a USB-powered device (5V).
Goal: Provide a clear blue indicator light.
Design Steps:
1. LED Selection: Choose this SMD3528 blue LED (e.g., wavelength bin B4 for a pure blue).
2. Current Setting: Target 15mA for adequate brightness and lower power consumption.
3. Resistor Calculation: Assume worst-case V_F = 3.6V (Bin 4). R = (5V - 3.6V) / 0.015A ≈ 93.3Ω. Use a standard 100Ω resistor.
4. Actual Current Check: Using typical V_F of 3.2V, I = (5V - 3.2V) / 100Ω = 18mA (within safe limits).
5. PCB Layout: Place the 100Ω resistor in series with the LED's anode. Use the recommended pad layout. Ensure no other traces or components are too close to obstruct the 120-degree viewing angle if needed.
6. Thermal Check: Power dissipation in LED: P = V_F * I_F ≈ 3.2V * 0.018A = 57.6mW, well below the 144mW maximum. No special heatsinking is required.

12. Principle Introduction

This LED is based on a semiconductor diode structure. When a forward voltage exceeding the diode's threshold is applied, electrons and holes recombine in the active region (the InGaN quantum well in this blue LED), releasing energy in the form of photons. The specific material composition (Indium Gallium Nitride - InGaN) determines the bandgap energy, which directly corresponds to the wavelength of the emitted light, in this case, blue (~460nm). The epoxy lens encapsulates the chip, provides mechanical protection, and shapes the light output beam.

13. Reliability Test Standards

The product undergoes rigorous reliability testing based on industry standards (JESD22, MIL-STD-202G) to ensure long-term performance. Key tests include:

• Operating Life Test: At room temperature, high temperature (85°C), and low temperature (-40°C) for 1008 hours under maximum current.
• High Humidity Operating Life: 60°C / 90% RH for 1008 hours.
• Temperature Cycling: Between -20°C and 60°C with humidity.
• Thermal Shock: -40°C to 125°C for 100 cycles.

Failure Criteria: Tests are deemed failed if samples show a forward voltage shift >200mV, luminous flux degradation >15% (for InGaN LEDs), reverse leakage current >10µA, or catastrophic failure (open/short circuit).

14. Development Trends

The general trend in SMD LEDs like the 3528 is towards higher luminous efficacy (more lumens per watt), improved color consistency (tighter binning), and increased reliability at higher operating temperatures. While this package remains popular, there is ongoing development in even smaller packages (e.g., 2016, 1010) for miniaturization and in chip-scale packages (CSP) that eliminate the traditional plastic body for better thermal performance and optical design flexibility. The drive for higher efficiency and lower cost per lumen continues across all LED form factors.