LED Datasheet 2835 Cool White - Package 2.8x3.5mm - Voltage 2.8V - Luminous Flux 28lm - English Technical Document

1. Product Overview

This document details the technical specifications for a high-performance, surface-mount Cool White LED in the industry-standard 2835 package format. The device is engineered for reliability and consistent performance in demanding environments, featuring a wide 120-degree viewing angle and robust construction suitable for a variety of illumination and indication applications.

The core advantages of this component include its high luminous efficacy, stable color characteristics over varying operating conditions, and compliance with stringent automotive-grade qualification standards (AEC-Q101). Its primary target markets encompass automotive interior lighting systems, backlighting for displays and switches, and general-purpose indicator applications where consistent white light output is required.

2. In-Depth Technical Parameter Analysis

2.1 Photometric and Electrical Characteristics

The device operates with a typical forward current (I_F) of 60mA, within a permissible range of 10mA to 80mA. At this typical current, it delivers a luminous flux (Φ_v) of 28 lumens (lm), with a minimum of 24 lm and a maximum of 40 lm as per the binning structure. The associated typical forward voltage (V_F) is 2.8 volts, ranging from 2.5V to 3.5V. The dominant wavelength is characterized by Cool White light with CIE 1931 chromaticity coordinates typically at x=0.3292, y=0.3424, with a tolerance of ±0.005. The Color Rendering Index (Ra) is specified as a minimum of 80, ensuring good color fidelity for illuminated objects.

2.2 Thermal and Reliability Parameters

Thermal management is critical for LED longevity. The junction-to-solder point thermal resistance is specified with two values: an electrical measurement (R_{th JS el}) of 50 K/W and a real measurement (R_{th JS real}) of 100 K/W. The absolute maximum junction temperature (T_J) is 125°C. The device is rated for an operating temperature range of -40°C to +110°C. It features robust ESD protection, capable of withstanding up to 8 kV (Human Body Model). The component is qualified to Moisture Sensitivity Level (MSL) 2 and includes preconditioning per JEDEC J-STD-020D.

2.3 Absolute Maximum Ratings

Adherence to these limits is essential to prevent permanent damage. The maximum continuous power dissipation (P_d) is 280 mW. The forward current must not exceed 80 mA continuously. A surge current (I_FM) of 1500 mA is specified for pulse conditions. The device is not designed for reverse bias operation. The maximum soldering temperature during reflow is 260°C for 30 seconds.

3. Binning System Explanation

The LED output is categorized into bins to ensure consistency in production lots. The primary binning is based on Luminous Flux and correlated Luminous Intensity.

3.1 Luminous Flux Bins

The available flux bins for this product are highlighted in the datasheet table. They range from lower output groups like B1 (21-24 lm) to higher output groups. The typical part, as listed in the characteristics, falls within the B7 bin (27-30 lm) or similar, based on the 28 lm typical value. Designers must select the appropriate bin code during ordering to guarantee the required light output for their application.

4. Performance Curve Analysis

4.1 Forward Current vs. Forward Voltage (IV Curve)

The graph shows a non-linear relationship, typical for LEDs. The voltage increases with current but the rate of increase diminishes slightly at higher currents. This curve is essential for designing the current-limiting driver circuit.

4.2 Relative Luminous Flux vs. Forward Current

Light output increases super-linearly with current at lower levels and becomes more linear approaching the typical 60mA point. Operating significantly above 60mA yields diminishing returns in efficiency and increases thermal stress.

4.3 Relative Luminous Flux vs. Junction Temperature

This is a critical graph for thermal design. Luminous flux decreases as junction temperature rises. The output at 100°C is significantly lower than at 25°C. Effective heat sinking is required to maintain stable light output over the product's lifetime.

4.4 Chromaticity Shift vs. Junction Temperature and Current

The graphs for ΔCIE x and ΔCIE y show minor shifts in color coordinates with changes in both junction temperature and forward current. The shifts are within a small range (±0.02), indicating good color stability, which is vital for applications requiring consistent white point.

4.5 Forward Current Derating Curve

This curve defines the maximum allowable continuous forward current as a function of the solder pad temperature. For example, at a pad temperature of 90°C, the maximum current is 80 mA. At 110°C, it derates to approximately 53 mA. Operation below 10mA is not recommended.

4.6 Permissible Pulse Handling Capability

This graph allows designers to determine safe peak pulse currents (I_F(A)) for various pulse widths (t_p) and duty cycles (D). It enables the use of higher instantaneous currents for pulsed operation, such as in multiplexed lighting or blinking indicators, without exceeding the average power limits.

4.7 Spectral Distribution

The relative spectral power distribution graph shows a peak in the blue wavelength region (around 450-460nm) from the LED chip, combined with the broader yellow emission from the phosphor, resulting in the Cool White spectrum. The absence of significant output in the deep red or infrared regions is typical for white LEDs.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED uses the 2835 package footprint, which typically has dimensions of approximately 2.8mm in length and 3.5mm in width. The exact dimensional drawing, including height, lens shape, and pad locations, is provided in the mechanical dimension section of the datasheet. Tolerances are critical for automated pick-and-place assembly.

5.2 Polarity Identification and Pad Design

The anode and cathode are marked on the device, typically with a visual indicator like a notch or a green marking on the cathode side. The recommended soldering pad layout is provided to ensure a reliable solder joint, proper thermal conduction to the PCB, and to prevent tombstoning during reflow. The pad design often includes thermal vias under the device's thermal pad to transfer heat to other PCB layers or a heatsink.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A detailed reflow profile is specified to prevent thermal shock and damage. Key parameters include a preheat ramp, a soak zone, a peak temperature not exceeding 260°C, and a controlled cooling rate. The time above liquidus (TAL) and the time within 5°C of the peak temperature are critical constraints that must be followed to maintain solder joint integrity and LED reliability.

6.2 Precautions for Use

General handling precautions include avoiding mechanical stress on the lens, preventing contamination of the optical surface, and using appropriate ESD safeguards during handling. The device should be stored in its original moisture-barrier bag with desiccant if the MSL level has been exceeded or the bag has been opened for more than the specified floor life.

7. Packaging and Ordering Information

The LEDs are supplied on tape and reel for compatibility with high-speed automated assembly equipment. The packaging information details the reel dimensions, tape width, pocket spacing, and orientation of the components on the tape. The part number structure encodes key attributes such as the base product code (e.g., 67-11S-C80600H-AM), which may correlate to specific flux/color bins. The ordering information section clarifies how to specify the desired bin codes and packaging quantities.

8. Application Recommendations

8.1 Typical Application Scenarios

• Automotive Interior Lighting: Dashboard illumination, switch backlighting, reading lamps, and infotainment system buttons. The AEC-Q101 qualification makes it suitable for these harsh-environment applications.
• Backlighting: Ideal for edge-lit or direct-lit LCD panels, membrane switches, symbolic indicators, and small advertising displays due to its high brightness and wide viewing angle.
• General Indication: Status indicators, panel lights, and decorative lighting where a cool white point is desired.

8.2 Design Considerations

• Driver Circuit: A constant-current driver is mandatory to ensure stable light output and color. The driver must be designed based on the V_F range and the required I_F.
• Thermal Management: The PCB layout must facilitate heat dissipation. Use of a thermal relief pad connected through multiple vias to a ground plane or dedicated copper pour is highly recommended. The derating curve must be consulted for the expected operating ambient temperature.
• Optical Design: The 120-degree viewing angle is a Lambertian-like distribution. For focused or directed light, secondary optics (lenses, reflectors) will be necessary. The lens material of the LED itself should be considered when designing overlays or diffusers.

9. Technical Comparison and Differentiation

Compared to standard commercial-grade 2835 LEDs, this device's key differentiators are its automotive qualification (AEC-Q101) and higher reliability specifications. It offers a robust solution for applications where temperature cycling, humidity, and long-term reliability are critical. The specified 8kV ESD protection is also superior to many basic LEDs, offering better handling robustness. The detailed binning structure provides tighter control over light output for applications requiring consistency across multiple units.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 3.3V or 5V supply?

A: No. An LED is a current-driven device. You must use a series current-limiting resistor or, preferably, a constant-current driver circuit. The required resistor value depends on the supply voltage and the LED's forward voltage at the desired current.

Q: Why are there two different thermal resistance values (50 K/W and 100 K/W)?

A: The electrical method (50 K/W) is a faster measurement but can underestimate the true thermal resistance. The real measurement (100 K/W) is more accurate and should be used for serious thermal modeling. Always use the more conservative (higher) value for reliable design.

Q: What happens if I operate the LED at the maximum junction temperature of 125°C?

A: Operating at the absolute maximum rating will drastically reduce the LED's lifetime due to accelerated lumen depreciation and potential phosphor degradation. Design should aim to keep the junction temperature as low as possible, ideally below 85°C for long life.

Q: How do I interpret the bin code when ordering?

A>The bin code (e.g., B7) defines the guaranteed minimum and maximum luminous flux for that batch of LEDs. You must specify the required bin in your order to ensure you receive LEDs with the performance needed for your application's brightness consistency.

11. Practical Design and Usage Examples

11.1 Automotive Dashboard Cluster Backlighting

In this application, multiple LEDs are arranged to provide even backlighting for gauges and an LCD screen. Design considerations include: selecting a uniform flux bin (e.g., B7) to avoid bright/dark spots; using a PWM-dimmable constant-current driver array to control brightness; implementing a robust thermal design on the PCB to handle the high ambient temperature inside a car dashboard; and ensuring the optical design (light guides, diffusers) is compatible with the LED's 120-degree emission pattern to achieve uniform illumination.

11.2 Industrial Control Panel Indicator

For a status indicator on a factory machine, a single LED might be used. A simple circuit with a series resistor from a 24V DC supply can be designed, calculating the resistor value as R = (24V - V_F) / I_F. Using the maximum V_F of 3.5V ensures the current does not exceed 60mA even for the highest V_F devices. The wide viewing angle ensures the indicator is visible from various operator positions.

12. Operational Principle

This is a phosphor-converted white LED. The core is a semiconductor chip (typically based on InGaN) that emits light in the blue spectrum when forward biased (electroluminescence). This blue light strikes a layer of yellow (and often red) phosphor coating deposited on or around the chip. The phosphor absorbs a portion of the blue light and re-emits it as a broader spectrum of yellow and red light. The mixture of the remaining blue light and the converted yellow/red light is perceived by the human eye as white light. The exact ratio of blue to phosphor-converted light determines the correlated color temperature (CCT), resulting in the \"Cool White\" specification of this device.

13. Technology Trends

The general trend in SMD LEDs like the 2835 package is toward higher luminous efficacy (more lumens per watt), improved color rendering (higher CRI and R9 values for red rendition), and greater reliability at higher operating temperatures. There is also a drive for tighter color consistency (smaller MacAdam ellipses) and lower cost per lumen. In automotive applications, the demand is for LEDs that can withstand even higher temperature ranges and more aggressive thermal cycling. The integration of driver electronics and multiple LED chips into single packages (COB - Chip-on-Board, or integrated LED modules) is another significant trend, though discrete components like this 2835 LED remain essential for flexible, distributed lighting designs.