SMD3528 Single Chip Green LED Datasheet - Size 3.5x2.8mm - Voltage 3.2V - Power 0.108W - English Technical Document

1. Product Overview

The SMD3528 is a surface-mount device (SMD) light-emitting diode (LED) featuring a single-chip green light source encapsulated within the industry-standard 3528 package footprint. This LED is designed for general-purpose indicator lighting, backlighting applications, and decorative lighting where consistent green color output and reliable performance are required. Its compact size and surface-mount design make it suitable for automated assembly processes on printed circuit boards (PCBs).

2. Technical Parameters Deep Objective Interpretation

2.1 Photoelectric and Electrical Characteristics

The core performance of the LED is defined under standard test conditions (T_s=25°C). The typical forward voltage (V_F) is 3.2V at a drive current of 20mA, with a maximum allowable value of 3.6V. This parameter is crucial for designing the current-limiting circuitry. The dominant wavelength (λ_d) is specified at 525nm, defining its green color point. The device exhibits a wide viewing angle of 120 degrees (2θ_1/2), providing a broad emission pattern suitable for area illumination.

2.2 Absolute Maximum Ratings and Thermal Characteristics

To ensure long-term reliability, the device must not be operated beyond its absolute maximum ratings. The maximum continuous forward current (I_F) is 30mA. A higher pulsed forward current (I_FP) of 60mA is permissible under specific conditions (pulse width ≤10ms, duty cycle ≤1/10). The maximum power dissipation (P_D) is 108mW. The junction temperature (T_j) must not exceed 125°C. The operational ambient temperature range is from -40°C to +80°C, with an identical storage temperature range. For soldering, a reflow profile with a peak temperature of either 200°C or 230°C for a maximum of 10 seconds is specified.

3. Binning System Explanation

The product is classified into bins to ensure color and brightness consistency within an application. The binning system covers three key parameters: luminous flux, wavelength, and forward voltage.

3.1 Luminous Flux Binning

Luminous flux, measured in lumens (lm) at 20mA, is categorized into several bins (e.g., A2, A3, B1, B2, B3, C1, C2). Each bin specifies a minimum and typical value. For example, bin B1 has a minimum of 1.5 lm and a typical value of 2.0 lm. The measurement tolerance is ±7%.

3.2 Wavelength Binning

The dominant wavelength is binned to control the precise shade of green. Bins are defined as G5 (519-522.5nm), G6 (522.5-526nm), and G7 (526-530nm). This allows designers to select LEDs with very specific color coordinates.

3.3 Forward Voltage Binning

Forward voltage (V_F) is binned to aid in circuit design for voltage-driven applications or to match LEDs in series strings. Bins are: Code 1 (2.8-3.0V), Code 2 (3.0-3.2V), Code 3 (3.2-3.4V), and Code 4 (3.4-3.6V), with a measurement tolerance of ±0.08V.

4. Performance Curve Analysis

4.1 IV Characteristic Curve

The relationship between forward voltage (V_F) and forward current (I_F) is non-linear, typical of a diode. The curve shows that a small increase in voltage beyond the turn-on point results in a rapid increase in current. This underscores the importance of using a constant-current driver rather than a constant-voltage source to prevent thermal runaway and ensure stable light output.

4.2 Relative Luminous Flux vs. Current

The light output increases with drive current but not linearly. At higher currents, efficiency typically drops due to increased thermal effects and other non-ideal semiconductor behaviors. Operating the LED significantly above the recommended 20mA may yield diminishing returns in brightness while drastically reducing lifespan.

3.3 Spectral and Thermal Characteristics

The relative spectral energy distribution curve shows how the light output is distributed across wavelengths. The curve for this green LED peaks around 525nm. The graph illustrating relative spectral energy versus junction temperature indicates that the emission spectrum and intensity can shift with temperature. As the junction temperature rises from 25°C to 125°C, the relative spectral energy generally decreases, which is a critical consideration for thermal management in high-power or densely packed applications.

5. Mechanical and Packaging Information

5.1 Physical Dimensions and Outline Drawing

The LED conforms to the SMD 3528 package standard, with nominal dimensions of 3.5mm in length and 2.8mm in width. The exact dimensional drawing provides critical tolerances: dimensions specified to one decimal place (e.g., .X) have a tolerance of ±0.10mm, while those specified to two decimal places (.XX) have a tighter tolerance of ±0.05mm. The package height is also defined in the drawing.

5.2 Recommended Pad Pattern and Stencil Design

A recommended land pattern (footprint) for PCB design is provided to ensure proper soldering and mechanical stability. A corresponding stencil design for solder paste application is also suggested. Adhering to these recommendations helps achieve reliable solder joints, good alignment, and effective heat dissipation from the LED's thermal pad (if present).

5.3 Polarity Identification

The cathode is typically marked on the device, often by a green dot, a notch in the package, or a chamfered corner. The pad layout diagram clearly indicates the anode and cathode pads. Correct polarity is essential for device operation.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters

The LED is compatible with standard infrared or convection reflow soldering processes. The maximum allowable soldering temperature is specified as 200°C or 230°C at the package body, with a maximum exposure time of 10 seconds above the liquidus temperature. It is critical to follow a profile that preheats adequately to minimize thermal shock, allows for proper flux activation and solder wetting, and cools at a controlled rate.

6.2 Handling and Storage Precautions

LEDs are sensitive to electrostatic discharge (ESD). They should be handled in an ESD-protected environment using grounded wrist straps and conductive mats. The devices should be stored in their original moisture-barrier bags with desiccant, in conditions not exceeding the specified storage temperature and humidity ranges. Exposure to high humidity may require baking before reflow to prevent "popcorning" (package cracking due to rapid vapor expansion).

7. Packaging and Ordering Information

7.1 Tape and Reel Packaging Specification

The LEDs are supplied on embossed carrier tape wound onto reels, suitable for automated pick-and-place machines. Detailed dimensions for the carrier tape pockets, cover tape, and reel are provided. The peel strength of the cover tape is specified to be between 0.1N and 0.7N when peeled at a 10-degree angle, ensuring it holds the component securely during shipping but releases easily during assembly.

7.2 Product Model Numbering Rule

A detailed alphanumeric coding system defines the product model. The code structure includes fields for: package outline (e.g., '32' for 3528), number of chips ('S' for single small-power chip), lens/optic code ('00' for no lens, '01' with lens), color code ('G' for green), internal code, and luminous flux bin code. This allows for precise ordering of a specific combination of characteristics.

8. Application Suggestions

8.1 Typical Application Scenarios

This LED is well-suited for a variety of applications including status indicators on consumer electronics and industrial equipment, backlighting for LCD displays and keypads, decorative lighting in signage and architectural accents, and channel letter lighting. Its wide viewing angle makes it good for area illumination where a diffuse light source is needed.

8.2 Design Considerations

Current Limiting: Always use a series current-limiting resistor or, preferably, a constant-current driver circuit. Calculate the resistor value based on the supply voltage (V_supply), the LED's forward voltage (V_F from its bin), and the desired current (I_F, typically 20mA). Formula: R = (V_supply - V_F) / I_F.
Thermal Management: While this is a low-power device, effective PCB layout is important. Ensure adequate copper area connected to the thermal pad (if applicable) to dissipate heat, especially when operating at or near maximum ratings or in high ambient temperatures.
Optical Design: Consider the 120-degree viewing angle. For focused beams, secondary optics (lenses) may be required. The binning for wavelength and flux should be matched within a single product for uniform appearance.

9. Reliability and Quality Standards

9.1 Reliability Test Standards

The product undergoes rigorous reliability testing based on industry standards (JESD22, MIL-STD-202G). Key tests include:
Operating Life Tests: Conducted at room temperature, high temperature (85°C), and low temperature (-40°C) for 1008 hours each under maximum current.
Environmental Tests: High Humidity High Temperature Operating Life (HHHTOHL) at 60°C/90% RH, and temperature cycling with humidity.
Thermal Shock: Cycling between -40°C and 125°C.

9.2 Failure Criteria

A test is considered a failure if any sample exhibits: a forward voltage shift >200mV; luminous flux degradation >15% for InGaN-based LEDs (which includes this green LED); reverse leakage current >10μA; or catastrophic failure (open or short circuit). These stringent criteria ensure a high level of product robustness.

10. Technical Comparison and Differentiation

Compared to older through-hole green LEDs, the SMD3528 offers significant advantages in size, suitability for automated assembly, and typically better thermal performance due to the PCB acting as a heat sink. Within the SMD3528 category, this specific product is differentiated by its detailed binning system for flux, wavelength, and voltage, allowing for tighter performance matching in critical applications. Its wide 120-degree viewing angle may be an advantage over narrower-angle LEDs for some applications but a disadvantage for others requiring a focused beam.

11. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 5V supply?
A: No. You must use a current-limiting resistor. For example, with a 5V supply and a typical V_F of 3.2V at 20mA, the required resistor is (5V - 3.2V) / 0.02A = 90 Ohms. Use the next standard value (e.g., 91 Ohms).
Q: What is the difference between bins G5, G6, and G7?
A: They represent different ranges of dominant wavelength. G5 is the shortest wavelength (bluish-green, ~520nm), G7 is the longest (yellowish-green, ~528nm), and G6 is in between. Choose based on the desired color point.
Q: How long will this LED last?
A> LED lifetime is typically defined as the point where light output degrades to a certain percentage (e.g., 70% or 50%) of its initial value. While not explicitly stated here, the rigorous reliability testing (1008+ hours under stress) suggests a long operational life when used within specifications, especially with proper thermal management.
Q: Is a lens needed?
A: The standard product has no integral lens (code '00'), providing a Lambertian emission pattern. A lens (code '01') would be used to collimate or otherwise shape the light beam for specific applications.

12. Design and Usage Case Study

Scenario: Designing a Status Indicator Panel: A product requires ten uniform green status indicators. Design Steps: 1. Select all LEDs from the same luminous flux bin (e.g., B2) and wavelength bin (e.g., G6) to ensure identical brightness and color. 2. Design the PCB with the recommended pad layout. 3. For a 12V supply rail, calculate the current-limiting resistor. Using the maximum V_F from bin 4 (3.6V) for safety: R = (12V - 3.6V) / 0.02A = 420 Ohms. A 430 Ohm resistor would be suitable. 4. Ensure the PCB has sufficient copper pour for heat dissipation, as all ten LEDs will be clustered. 5. Specify the exact part number including all bin codes to the supplier to guarantee consistency.

13. Operating Principle Introduction

Light is produced through a process called electroluminescence. The LED chip is a semiconductor diode with a p-n junction made from indium gallium nitride (InGaN) materials specifically engineered to emit green light. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the active region (the junction). When an electron recombines with a hole, it releases energy in the form of a photon (light particle). The specific energy bandgap of the InGaN material determines the wavelength (color) of the emitted photon, which in this case is green (~525nm). The epoxy or silicone encapsulant protects the chip and often acts as a primary lens.

14. Technology Trends and Developments

The general trend in SMD LEDs like the 3528 is towards higher efficiency (more lumens per watt), which allows for either brighter output at the same power or the same brightness with lower power consumption and less heat. There is also continuous improvement in color consistency and stability over time and temperature. While this is a mature package size, the underlying semiconductor materials and manufacturing processes are constantly refined. For green LEDs specifically, achieving high efficiency and pure color saturation has been a historical challenge, but ongoing material science advancements continue to push performance boundaries.