LTPL-C035BH470 LED Datasheet - 3.5x3.5mm Package - 3.1V Typ - 2.8W Max - 460-480nm Blue/White - English Technical Document

1. Product Overview

The LTPL-C035BH470 is a high-power white LED designed as an energy-efficient and ultra-compact light source. It combines the long lifetime and reliability inherent to Light Emitting Diodes with high brightness levels, positioning it as a viable alternative to conventional lighting technologies. This device offers design flexibility and is targeted at solid-state lighting applications seeking to displace traditional light sources.

1.1 Key Features

• Integrated Circuit (I.C.) compatible drive.
• Compliant with RoHS (Restriction of Hazardous Substances) directives and is lead (Pb) free.
• Designed for lower operational costs compared to conventional lighting.
• Contributes to reduced maintenance costs due to its long operational life.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• DC Forward Current (If): 700 mA maximum.
• Power Consumption (Po): 2.8 Watts maximum.
• Operating Temperature Range (Topr): -40°C to +85°C.
• Storage Temperature Range (Tstg): -55°C to +100°C.
• Junction Temperature (Tj): 125°C maximum.

Critical Note: Prolonged operation under reverse bias conditions may lead to component damage or failure.

2.2 Electro-Optical Characteristics

Measured at an ambient temperature (Ta) of 25°C with a forward current (If) of 350mA, unless otherwise specified. These are the typical performance parameters for design calculations.

• Forward Voltage (Vf):
  
  Minimum: 2.6 V
  
  Typical: 3.1 V
  
  Maximum: 3.6 V
• Radiant Flux (Φe):
  
  Minimum: 420 mW
  
  Typical: 510 mW
  
  Maximum: 600 mW
  
  Note: Radiant flux is the total optical power output measured with an integrating sphere.
• Dominant Wavelength (Wd):
  
  Minimum: 460 nm
  
  Maximum: 480 nm
  
  This indicates the LED emits in the blue spectrum, which is typically converted to white light using a phosphor coating.
• Viewing Angle (2θ1/2):
  
  Typical: 130 degrees. This defines the angular spread where the luminous intensity is at least half of the peak intensity.
• Thermal Resistance, Junction to Case (Rth jc):
  
  Typical: 9.5 °C/W (measurement tolerance ±10%).
  
  This parameter is crucial for thermal management, indicating how effectively heat flows from the semiconductor junction to the package case. A lower value signifies better heat dissipation.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted into performance bins. The bin code is marked on each packing bag.

3.1 Forward Voltage (Vf) Binning

LEDs are categorized based on their forward voltage drop at 350mA.

• V0: 2.6V - 2.8V
• V1: 2.8V - 3.0V
• V2: 3.0V - 3.2V
• V3: 3.2V - 3.4V
• V4: 3.4V - 3.6V

Tolerance: ±0.1V.

3.2 Radiant Flux (Φe) Binning

LEDs are sorted by their optical power output at 350mA.

• U1: 420 mW - 450 mW
• U2: 450 mW - 480 mW
• U3: 480 mW - 510 mW
• W1: 510 mW - 540 mW
• W2: 540 mW - 570 mW
• W3: 570 mW - 600 mW

Tolerance: ±10%.

3.3 Dominant Wavelength (Wd) Binning

LEDs are grouped by the peak wavelength of their blue emission at 350mA.

• D4M: 460 nm - 465 nm
• D4N: 465 nm - 470 nm
• D4P: 470 nm - 475 nm
• D4Q: 475 nm - 480 nm

Tolerance: ±3nm.

4. Performance Curve Analysis

The following typical curves (referenced in the datasheet as Fig. 1-5) provide insight into the device's behavior under varying conditions. All curves are typically measured at 25°C unless noted.

4.1 Relative Radiant Flux vs. Forward Current

This curve shows how the light output (radiant flux) changes with increasing drive current. It is typically non-linear, with efficiency often decreasing at very high currents due to increased heat generation (droop effect). Designers use this to select an optimal operating point that balances brightness and efficacy.

4.2 Relative Spectral Distribution

This graph plots the intensity of light emitted across different wavelengths. For a white LED based on a blue chip and phosphor, it typically shows a sharp peak in the blue region (from the chip) and a broader peak or plateau in the yellow/green/red region (from the phosphor). The combination creates the perceived white light.

4.3 Radiation Characteristics

This is a polar diagram illustrating the spatial distribution of light (radiation pattern). The 130-degree viewing angle specified is derived from this curve. It helps in optical design for applications requiring specific beam angles.

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

This fundamental curve depicts the relationship between the voltage across the LED and the current flowing through it. LEDs are diodes and exhibit an exponential I-V characteristic. The curve is essential for designing the current-limiting circuitry, as a small change in voltage can cause a large change in current.

4.5 Relative Radiant Flux vs. Junction Temperature

This critical curve demonstrates the thermal dependence of light output. As the junction temperature (Tj) increases, the radiant flux typically decreases. The slope of this curve quantifies the thermal derating factor. Effective heat sinking is paramount to maintain stable light output and ensure long-term reliability.

5. Mechanical and Package Information

5.1 Outline Dimensions

The device has a compact surface-mount package. Key dimensional notes include:

• All dimensions are in millimeters (mm).
• General dimension tolerance is ±0.2mm.
• Lens height and ceramic substrate length/width have a tighter tolerance of ±0.1mm.
• The thermal pad on the bottom of the package is electrically isolated (neutral) from the anode and cathode electrical pads. This allows it to be connected directly to a PCB thermal land for heat dissipation without creating an electrical short.

5.2 Recommended PCB Attachment Pad

A land pattern design is provided to ensure proper soldering and thermal performance. Adhering to this recommended footprint is crucial for mechanical stability, electrical connection, and optimal heat transfer from the LED's thermal pad to the printed circuit board.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested reflow soldering temperature profile is provided. Important considerations:

• All temperature references are for the top side of the package body.
• The profile may need adjustment based on the specific solder paste used.
• A rapid cooling rate from peak temperature is not recommended.
• Operating at the lowest possible soldering temperature is desirable.
• The LED should not be subjected to dip soldering methods.

6.2 Hand Soldering

If hand soldering is necessary, it should be limited to a maximum temperature of 300°C for a maximum duration of 2 seconds, and performed only once per pad.

6.3 Cleaning

If cleaning is required after soldering, only alcohol-based solvents like isopropyl alcohol should be used. Unspecified chemical cleaners may damage the LED package.

7. Packaging and Handling Information

7.1 Tape and Reel Specifications

The LEDs are supplied on embossed carrier tape and reels for automated assembly.

• Component pockets are sealed with a top cover tape.
• Standard 7-inch reels are used, with a maximum capacity of 500 pieces per reel.The specification allows for a maximum of two consecutive missing components in the tape.
• Packaging conforms to EIA-481-1-B standards.

7.2 Manual Handling

The LED should be handled carefully, preferably by the edges of the package, to avoid contamination or mechanical damage to the lens and wire bonds.

8. Application Suggestions and Design Considerations

8.1 Drive Method

LEDs are current-operated devices. For reliable operation:

• Constant Current Drive is Recommended: To ensure uniform brightness, especially when connecting multiple LEDs in parallel, a current-limiting resistor should be placed in series with each LED. A simple resistor-based circuit (Model A in the datasheet) is shown as the recommended method. Driving multiple LEDs in parallel without individual current regulation (Model B) can lead to brightness mismatch due to natural variations in the forward voltage (Vf) of each device.
• Avoid Reverse Bias: The LED must be operated under forward bias. Continuous application of reverse voltage can cause damage.

8.2 Thermal Management

Given the typical thermal resistance of 9.5 °C/W and a maximum power of 2.8W, effective heat sinking is non-negotiable. The PCB should have a sufficiently large copper area connected to the LED's thermal pad, potentially using thermal vias to transfer heat to inner or bottom layers. Failure to manage junction temperature will lead to reduced light output, accelerated aging, and potential premature failure.

8.3 Environmental Considerations

The device should not be used in the following conditions without thorough validation of performance and reliability:

• Environments with sulfur-containing materials (e.g., certain seals, adhesives).
• Areas with high humidity (over 85% RH), condensation, salty air, or corrosive gases (Chlorine, Hydrogen Sulfide, Ammonia, Sulfur Dioxide, Nitrogen Oxides, etc.).

8.4 Typical Application Scenarios

Based on its specifications (high power, wide viewing angle, blue/white emission), this LED is suitable for:

• General solid-state lighting modules.
• Architectural and decorative lighting.
• High-brightness indicator or status lights.
• Backlighting units for medium-sized panels.
• Specialty lighting applications requiring a compact, robust source.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the difference between Radiant Flux (mW) and Luminous Flux (lm)?

Radiant flux (Φe) measures the total optical power emitted in watts. Luminous flux measures the perceived brightness by the human eye in lumens, weighted by the eye's sensitivity curve (photopic vision). This datasheet specifies radiant flux. To estimate luminous flux for a white LED, the radiant flux would be multiplied by a luminous efficacy factor (lm/W), which depends on the phosphor conversion efficiency and spectral output.

9.2 Why is a 350mA test current specified when the maximum current is 700mA?

The 350mA point is a standard test condition that represents a typical operating point for characterizing performance (Vf, Φe, Wd). It allows for consistent comparison between different LED models. The maximum current (700mA) is an absolute limit for short-term or peak operation, but operating continuously at this level would generate excessive heat and likely reduce lifetime. The optimal drive current for a given application is determined by balancing desired brightness with thermal constraints and efficacy.

9.3 How do I select the right bin for my application?

Selection depends on the application's requirements for consistency:

• Voltage Bin (Vf): Important for power supply design. Using LEDs from the same Vf bin ensures more uniform current distribution in parallel strings and stable driver performance.
• Flux Bin (Φe): Critical for achieving consistent brightness levels. For applications where multiple LEDs are used together (e.g., an array), specifying a tight flux bin (e.g., W1 only) minimizes visible brightness variations.
• Wavelength Bin (Wd): For white LEDs, the dominant wavelength of the blue chip can affect the correlated color temperature (CCT) and color rendering index (CRI) of the final white light. Tighter wavelength bins lead to more consistent color appearance.

10. Design and Usage Case Study

10.1 Designing a Simple LED Module

Consider designing a module with four LTPL-C035BH470 LEDs in parallel, driven from a 12V DC supply, targeting an operating current of 300mA per LED.

1. Thermal Design: First, design the PCB with a large, exposed copper pad for each LED's thermal pad. Use multiple thermal vias under each pad to connect to a bottom-layer copper plane acting as a heat spreader.
2. Electrical Design: Since the LEDs are in parallel, each needs its own current-limiting resistor to compensate for Vf variations. For a typical Vf of 3.1V at 300mA (extrapolated from 350mA data), the resistor value is R = (Vsupply - Vf) / If = (12V - 3.1V) / 0.3A ≈ 29.7 Ω. A standard 30 Ω resistor would be selected. The resistor power rating must be at least P = I²R = (0.3)² * 30 = 2.7W, so a 3W or 5W resistor is necessary.
3. Bin Selection: To ensure uniform brightness, specify LEDs from the same Radiant Flux bin (e.g., W1: 510-540mW). Specifying the same Voltage bin (e.g., V2: 3.0-3.2V) would further improve current balance.
4. Assembly: Follow the recommended reflow profile. After soldering, inspect for proper alignment and any solder bridging.

This case highlights the interplay between electrical design (resistor calculation, binning), thermal management (PCB layout), and assembly process.

11. Principle Introduction

The LTPL-C035BH470 is based on a semiconductor light-emitting diode principle. Electroluminescence occurs when electrical current is passed through the semiconductor material (typically based on Gallium Nitride - GaN for blue light), causing electrons and holes to recombine and release energy in the form of photons (light). The specific material composition determines the photon's energy and thus the wavelength (color) of the emitted light. In this white LED, the primary emission from the blue semiconductor chip is partially converted to longer wavelengths (yellow, green, red) by a layer of phosphor material coating the chip. The mixture of unconverted blue light and the phosphor-generated light is perceived by the human eye as white light. The package serves to protect the semiconductor die, provide electrical connections, house the phosphor, and shape the lens for the desired optical output.

12. Development Trends

The solid-state lighting industry, of which this LED is a part, continues to evolve along several key trajectories:

• Increased Efficacy: The primary trend is achieving higher lumens per watt (lm/W), meaning more light output for the same electrical input, improving energy savings.
• Improved Color Quality: Advancements in phosphor technology aim to provide higher Color Rendering Index (CRI) values and more consistent Correlated Color Temperature (CCT), allowing LEDs to match or exceed the light quality of traditional sources.
• Higher Power Density: Developing packages that can handle higher drive currents and dissipate heat more effectively, enabling brighter and more compact light engines.
• Enhanced Reliability and Lifetime: Ongoing improvements in materials, packaging, and thermal management are pushing the operational lifetimes of LEDs further, reducing total cost of ownership.
• Smart and Connected Lighting: Integration of control electronics and communication interfaces directly with LED modules is becoming more common, enabling tunable white light (CCT adjustment) and integration into IoT (Internet of Things) systems.

Devices like the LTPL-C035BH470 represent a mature point in this evolution, offering a balance of performance, reliability, and cost for a wide range of general lighting applications.