SMD3528 White 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) white light-emitting diode (LED) utilizing a single-chip design. This LED is characterized by its compact footprint of 3.5mm x 2.8mm, making it suitable for applications requiring high-density placement and efficient space utilization. It is engineered to deliver consistent white light output across various correlated color temperatures (CCT), ranging from warm white to cool white. The device is designed for automated assembly processes and is a common choice for backlighting, indicator lights, and general illumination in consumer electronics, signage, and decorative lighting.

1.1 Core Features

• Single-Chip White LED: Provides uniform white light emission from a single semiconductor die.
• Standard SMD3528 Package: Industry-standard dimensions for compatibility with existing PCB layouts and pick-and-place equipment.
• Wide Viewing Angle: A typical half-intensity angle (2θ1/2) of 120 degrees ensures broad light distribution.
• Moisture Sensitivity: Classified per IPC/JEDEC J-STD-020C, requiring proper handling to prevent damage during reflow soldering.

2. Technical Parameter Analysis

This section provides a detailed, objective interpretation of the LED's key electrical, optical, and thermal characteristics as defined in the Absolute Maximum Ratings and Typical Technical Parameters.

2.1 Absolute Maximum Ratings (Ta=25°C)

These values represent the limits beyond which permanent damage to the device may occur. Operation under or at these conditions is not guaranteed.

• Forward Current (IF): 30 mA (DC)
• Forward Pulse Current (IFP): 60 mA (Pulse width ≤10ms, Duty cycle ≤1/10)
• Power Dissipation (PD): 108 mW
• Operating Temperature (Topr): -40°C to +80°C
• Storage Temperature (Tstg): -40°C to +80°C
• Junction Temperature (Tj): 125°C
• Soldering Temperature (Tsld): Reflow soldering at 200°C or 230°C for a maximum of 10 seconds.

2.2 Typical Electrical & Optical Parameters (Ta=25°C)

These are the expected performance values under standard test conditions.

• Forward Voltage (VF): Typical 3.2V, Maximum 3.6V (at IF=20mA). This parameter is crucial for driver design and power supply selection.
• Reverse Voltage (VR): 5V. Exceeding this voltage in reverse bias can damage the LED.
• Reverse Current (IR): Maximum 10 µA.
• Viewing Angle (2θ1/2): 120 degrees (typical). This defines the angular spread where light intensity is at least half of the peak intensity.

3. Binning System Explanation

The LED's performance is categorized into bins to ensure consistency. The product naming rule defines these bins.

3.1 Model Number Structure

The model follows the pattern: T [Luminous Flux Code] [CCT Code] [Internal Code] - [Voltage Code] [Package/Other Code]. For example, T3200SL(C,W)A.

• Luminous Flux Code: Indicates the minimum light output bin (e.g., codes like B6, B7, B8).
• CCT Code: Defines the correlated color temperature and sometimes the color rendering index (CRI).
  • Warm White: L (<3700K)
  • Neutral White: C (3700-5000K)
  • Cool White: W (>5000K)
  • Other codes exist for high CRI versions (e.g., CRI 80, CRI 90).
• Chip Count: 'S' denotes a single small-power chip.
• Optics Code: '00' for no lens, '01' for with lens.
• Package Code: '32' specifically identifies the 3528 package.
• Voltage Code: Letters from B to J define forward voltage ranges (e.g., F: 3.2-3.3V).

3.2 Correlated Color Temperature (CCT) Binning

White LEDs are binned into specific CCT ranges with associated chromaticity regions on the CIE diagram. Standard ordering CCTs include 2700K, 3000K, 3500K, 4000K, 4500K, 5000K, 5700K, 6500K, and 8000K. Each CCT corresponds to a set of chromaticity boxes (e.g., 8A, 8B, 8C, 8D for 2700K). Products are guaranteed to be within the ordered CCT's chromaticity region.

3.3 Luminous Flux Binning

Flux is binned by minimum value at 20mA. Different bins are defined for combinations of CCT and CRI. For example, a 70 CRI Neutral White (3700-5300K) LED may have bins B6 (7.0-7.5 lm min), B7 (7.5-8.0 lm min), B8 (8.0-8.5 lm min), and B9 (8.5-9.0 lm min). Note that shipped parts may exceed the minimum flux value but will remain within the specified chromaticity region.

3.4 Forward Voltage Binning

Voltage is binned into ranges from 2.8-2.9V (Code B) up to 3.5-3.6V (Code J). This allows for better current matching when multiple LEDs are connected in parallel.

3.5 Standard Chromaticity Regions

The datasheet includes a graphical representation of the standard chromaticity regions (boxes) on the CIE 1931 color space diagram for the various CCT bins. This visual reference is essential for color-critical applications to understand the allowable variation in color point.

4. Performance Curve Analysis

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

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

This curve shows the exponential relationship between current and voltage. It is fundamental for determining the operating point and designing constant-current drivers. The typical knee voltage is around 3.0V.

4.2 Relative Luminous Flux vs. Forward Current

This graph illustrates how light output increases with current. It typically shows a sub-linear relationship, where efficiency (lumens per watt) may decrease at higher currents due to increased heat and droop effects. Operating at or below the recommended 20mA ensures optimal efficiency and longevity.

4.3 Relative Spectral Power Distribution

The spectral curve plots relative intensity against wavelength (typically 400-750nm). It shows the characteristic blue pump peak and the broader phosphor-converted yellow emission band that combine to create white light. The shape of this curve varies with CCT: cooler whites have more blue content, while warmer whites have more yellow/red content. This data is critical for calculating color rendering index (CRI) and understanding the light's spectral quality.

4.4 Junction Temperature vs. Relative Spectral Energy

This curve demonstrates how the LED's spectrum shifts with increasing junction temperature. Typically, as temperature rises, the phosphor conversion efficiency can change, potentially leading to a shift in CCT and a decrease in overall luminous flux. This underscores the importance of thermal management in maintaining consistent color and light output.

5. Mechanical & Packaging Information

5.1 Outline Dimensions

The SMD3528 package has a body size of 3.5mm (length) x 2.8mm (width). The dimensional drawing specifies all critical measurements, including lens height and lead dimensions. Tolerances are typically ±0.10mm for .X dimensions and ±0.05mm for .XX dimensions.

5.2 Pad Layout & Stencil Design

The datasheet provides recommended PCB land pattern (pad) geometry and solder paste stencil aperture design. Adhering to these recommendations is vital for achieving reliable solder joints, proper alignment, and effective heat dissipation during reflow. The pad design typically includes thermal relief connections to manage heat sinking into the PCB.

5.3 Polarity Identification

The LED has an anode (+) and cathode (-). Polarity is usually indicated by a marking on the top of the LED (such as a green dot, a cut corner, or a notch) and/or by different lead shapes or sizes on the underside. Correct polarity is essential for circuit operation.

6. Soldering & Assembly Guidelines

6.1 Moisture Sensitivity and Baking

The SMD3528 LED is moisture-sensitive (MSL classified per J-STD-020C). If the original sealed moisture barrier bag is opened and the components are exposed to ambient humidity beyond specified limits, absorbed moisture can vaporize during reflow soldering, causing internal delamination or cracking (\"popcorning\").

• Storage: Unopened bags should be stored below 30°C/85% RH. After opening, store at 5-30°C/<60% RH, preferably in a dry cabinet or sealed container with desiccant.
• Floor Life: Use within 12 hours after bag opening if ambient conditions are <30°C/60% RH.
• Baking Requirements: Bake if the humidity indicator card shows exposure or if floor life is exceeded.
• Baking Method: Bake at 60°C for 24 hours on the original reel. Do not exceed 60°C. Use or re-bag within 1 hour after baking.

6.2 Reflow Soldering Profile

The maximum soldering temperature is specified as 200°C or 230°C for 10 seconds. A standard lead-free reflow profile with a peak temperature not exceeding 260°C and time above 240°C limited to 30-60 seconds is generally applicable. The specific profile must be validated for the PCB assembly.

7. Application Notes & Design Considerations

7.1 Driver Circuit Design

LEDs are current-driven devices. A constant current driver is strongly recommended over a constant voltage source with a series resistor for stable operation, especially over temperature variations. The driver should be designed to supply the desired current (e.g., 20mA) while accommodating the forward voltage bin range of the LEDs used.

7.2 Thermal Management

Although a small device, effective heat sinking is crucial for maintaining performance and lifetime. The PCB acts as the primary heat sink. Use sufficient copper area (thermal pads) connected to the LED's thermal pad, and consider using thermal vias to transfer heat to inner or bottom layers. High ambient temperatures or poor thermal design will lead to elevated junction temperature, reducing light output, shifting color, and accelerating lumen depreciation.

7.3 Optical Design

The 120-degree viewing angle is suitable for wide-area illumination. For focused beams, secondary optics (lenses, reflectors) are required. The presence or absence of a primary lens (code 00 vs. 01) affects the initial angular distribution and compatibility with secondary optics.

7.4 Series/Parallel Connections

Connecting LEDs in series ensures identical current through each device, simplifying driver design but requiring a higher supply voltage. Parallel connections require closely matched forward voltages (using tight voltage bins) to prevent current imbalance, which can lead to uneven brightness and potential overstress of lower-voltage LEDs.

8. Technical Comparison & Trends

8.1 Comparison with Other Packages

The SMD3528 was a very popular package but has been largely succeeded by the SMD2835 and SMD3030 in many general lighting applications due to their better thermal performance and higher efficacy (lumens per watt). The 3528 remains relevant in cost-sensitive applications, backlighting, and where its specific form factor is required.

8.2 Technology Trends

The general trend in white LED technology is toward higher efficacy, improved color rendering (higher R9 values, full-spectrum designs), and better reliability at higher operating temperatures. Phosphor technology continues to advance, enabling narrower CCT bins and more stable color over lifetime and temperature. The principles of operation for this SMD3528—blue chip excitation of phosphor—remain the industry standard for white LEDs.

9. Frequently Asked Questions (FAQ)

9.1 What is the difference between the luminous flux 'minimum' and 'typical' values?

The 'minimum' value is the guaranteed lower limit for that bin. The 'typical' value is the expected average performance. Parts shipped will be at or above the minimum but are not guaranteed to reach the typical value, though many will.

9.2 Why is baking necessary, and can I skip it?

Baking removes absorbed moisture that can cause catastrophic failure during reflow. Skipping baking when required (based on humidity exposure) significantly increases the risk of yield loss due to cracked dies or packages. Always check the humidity indicator card and follow the handling guidelines.

9.3 Can I drive this LED at 30mA continuously?

While the absolute maximum rating is 30mA, continuous operation at this current will generate significant heat, likely pushing the junction temperature beyond recommended limits unless exceptional cooling is provided. For reliable long-term operation, it is advisable to drive the LED at or below the test current of 20mA.

9.4 How do I interpret the chromaticity region codes (e.g., 5A, 5B)?

These codes correspond to specific quadrangles (boxes) on the CIE chromaticity diagram defined by ANSI standards. They ensure color consistency. When ordering a CCT (e.g., 4000K), you are guaranteed LEDs whose color points fall within the set of boxes (5A, 5B, 5C, 5D) associated with that CCT.