LTPL-C034UVD395 UV LED Datasheet - 3.6x3.0x1.6mm - 3.6V - 2W - 395nm Peak Wavelength - English Technical Document

1. Product Overview

The LTPL-C034UVD395 is a high-power ultraviolet (UV) light-emitting diode (LED) designed for professional applications requiring a reliable and efficient solid-state UV light source. This product represents a significant advancement in UV technology, combining the long operational lifetime and robustness inherent to LEDs with a high radiant output suitable for displacing conventional UV lamp technologies.

The core application for this device is in UV curing processes, where precise and consistent UV radiation is critical for initiating photochemical reactions in adhesives, inks, coatings, and resins. Its energy efficiency leads to substantially lower operating costs compared to traditional mercury-vapor or arc lamps. Furthermore, the elimination of hazardous materials like mercury and the extended service life contribute to reduced maintenance requirements and total cost of ownership.

Key advantages of this UV LED series include full compatibility with integrated circuit (IC) drive systems, compliance with RoHS (Restriction of Hazardous Substances) directives ensuring it is lead-free, and its compact surface-mount design which offers significant design freedom for integration into modern, miniaturized equipment.

2. Technical Specifications and Objective Interpretation

2.1 Absolute Maximum Ratings

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

• DC Forward Current (If): 500 mA. This is the absolute maximum continuous current the LED can withstand. For reliable long-term operation, the typical drive current is set lower, at 350mA.
• Power Consumption (Po): 2 W. This rating considers both the forward current and voltage. Exceeding this power level risks overheating the semiconductor junction.
• Operating Temperature Range (Topr): -40°C to +85°C. The LED is designed to function within this ambient temperature range. Performance, particularly radiant output, will vary with temperature.
• Storage Temperature Range (Tstg): -55°C to +100°C. The device can be stored without applied power within these limits.
• Junction Temperature (Tj): 110°C. This is the maximum allowable temperature at the semiconductor chip itself. Proper thermal management is essential to keep the junction below this limit during operation.

Critical Note: The datasheet explicitly warns against operating the LED under reverse bias conditions for extended periods, as this can lead to immediate or latent failure.

2.2 Electro-Optical Characteristics

These parameters are measured at a standard test condition of Ta=25°C and a forward current (If) of 350mA, which is considered the typical operating point.

• Forward Voltage (Vf): 3.6V (Typical), with a range from 2.8V (Min) to 4.4V (Max). This variation is addressed by the binning system. The voltage increases with current and decreases slightly with rising junction temperature.
• Radiant Flux (Φe): 580mW (Typical), ranging from 460mW to 700mW. This is the total optical power output in the UV spectrum, measured with an integrating sphere. It is the key metric for application efficacy.
• Peak Wavelength (λp): Centered at 395nm, with bins from 390-395nm and 395-400nm. This places the emission in the near-UV (UVA) spectrum, which is commonly used in curing and inspection applications.
• Viewing Angle (2θ1/2): 130° (Typical). This wide beam angle provides broad, even illumination suitable for area curing.
• Thermal Resistance (Rθjc): 6.4 °C/W (Typical). This parameter defines how effectively heat travels from the semiconductor junction to the case (package body). A lower value indicates better thermal performance. Combined with the power dissipation, it is used to calculate the necessary heatsinking to maintain a safe junction temperature.

3. Binning System Explanation

To ensure consistency in production runs, LEDs are sorted into performance bins. The LTPL-C034UVD395 uses a three-dimensional binning system.

3.1 Forward Voltage (Vf) Binning

LEDs are grouped into four voltage bins (V0 to V3), each spanning 0.4V. This allows designers to select LEDs with similar electrical characteristics for parallel connections or to predict power supply requirements more accurately. The bin code is marked on the product packaging.

3.2 Radiant Flux (Φe) Binning

Optical output is binned into six categories (R1 to R6), each representing a 40mW step in radiant flux. This is crucial for applications requiring uniform UV intensity across multiple LEDs or consistent process results over time.

3.3 Peak Wavelength (Wp) Binning

The wavelength is sorted into two tight bins: P3T (390-395nm) and P3U (395-400nm). This precision is vital as many photo-initiators in curing chemistry are tuned to activate at specific wavelengths.

4. Performance Curve Analysis

4.1 Relative Radiant Flux vs. Forward Current

This curve shows that radiant output increases super-linearly with forward current. While driving at higher currents yields more UV power, it also generates significantly more heat, accelerating lumen depreciation and potentially shortening lifespan. The 350mA operating point represents a balance between output and reliability.

4.2 Relative Spectral Distribution

The spectral plot confirms a narrow emission band centered around 395nm, typical of a gallium nitride-based LED. There is minimal emission in the visible spectrum, making it a pure UV source. The full width at half maximum (FWHM) of the peak is typically narrow, ensuring spectral purity.

4.3 Radiation Pattern

The polar diagram illustrates the 130° viewing angle. The intensity distribution is typically Lambertian or near-Lambertian, meaning the perceived intensity is highest when viewed head-on and decreases according to the cosine of the viewing angle.

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

This graph demonstrates the exponential relationship characteristic of a diode. The forward voltage has a negative temperature coefficient; for a given current, Vf decreases as the junction temperature rises. This must be considered in constant-voltage drive scenarios.

4.5 Relative Radiant Flux vs. Junction Temperature

This is one of the most critical curves for thermal design. It shows that UV output decreases as the junction temperature increases. Effective heatsinking is not just about reliability; it is directly tied to maintaining consistent optical performance. The curve quantifies the output loss per degree Celsius rise in junction temperature.

5. Mechanical and Package Information

5.1 Outline Dimensions

The device is a surface-mount component with a compact footprint. Key dimensions include a body size of approximately 3.6mm x 3.0mm. The lens height and ceramic substrate dimensions have tighter tolerances (±0.1mm) compared to other body dimensions (±0.2mm). The package features a central thermal pad which is electrically isolated from the anode and cathode, allowing it to be connected directly to a grounded copper pour on the PCB for optimal heat dissipation.

5.2 Recommended PCB Pad Layout

The datasheet provides a land pattern design for the surface mount pads and the large thermal pad. Following this recommendation is essential for achieving reliable solder joints, proper alignment, and maximizing thermal transfer from the thermal pad to the PCB. The thermal pad should be connected to a substantial copper area, often with multiple thermal vias to inner or bottom layers for heat spreading.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A detailed temperature-time profile is provided, conforming to standard lead-free (Pb-free) reflow processes. Key parameters include a preheat stage, a controlled ramp to a peak temperature (recommended not to exceed 260°C measured on the package body), and a specific cooling rate. The datasheet cautions against rapid cooling. The LED can withstand a maximum of three reflow cycles. Hand soldering is permissible but must be limited to 300°C for a maximum of 2 seconds per pad.

6.2 Cleaning and Handling

If cleaning is required post-soldering, only alcohol-based solvents like isopropyl alcohol (IPA) should be used. Harsh or unspecified chemicals can damage the silicone lens or package material. For manual handling, the LED should only be contacted by its sides to avoid putting mechanical stress on the lens or wire bonds. Vacuum pick-up is the preferred method for automated assembly.

7. Packaging and Ordering Information

The LEDs are supplied on embossed carrier tape for automated pick-and-place machines. The tape dimensions and reel specifications (7-inch reel holding up to 500 pieces) are provided, adhering to the EIA-481-1-B standard. The bin classification code for Vf, Φe, and Wp is marked on each packing bag, allowing for traceability and selection.

8. Application Notes and Design Considerations

8.1 Drive Circuit Design

LEDs are current-operated devices. For stable and uniform operation, a constant current driver is strongly recommended. If multiple LEDs are connected in parallel, each should have its own current-limiting resistor to compensate for variances in forward voltage (Vf binning), preventing current hogging and uneven brightness or output. The datasheet explicitly warns against using the LEDs under continuous reverse bias.

8.2 Thermal Management

Given the 2W power dissipation and the sensitivity of output to junction temperature, thermal design is paramount. The low thermal resistance (6.4°C/W) from junction to case is only effective if the case is properly coupled to a heatsink. This involves using the recommended PCB pad layout with ample copper area and thermal vias. For high-power arrays, active cooling or metal-core PCBs may be necessary.

8.3 Environmental Considerations

The device should not be used in environments with high sulfur content (e.g., certain seals, adhesives), high humidity (over 85% RH), condensing moisture, salty air, or corrosive gases (Cl2, H2S, NH3, SO2, NOx). These conditions can lead to corrosion of the gold-plated electrodes and other package materials.

9. Technical Comparison and Differentiation

Compared to traditional UV sources like mercury lamps, this LED offers instant on/off capability, no warm-up time, and no hazardous materials. Its solid-state nature makes it more resistant to shock and vibration. The narrow emission spectrum targets specific photo-initiators more efficiently, potentially reducing energy waste and enabling faster cure times in optimized systems. The primary trade-off is the need for more sophisticated thermal management and current control compared to simply powering a lamp.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED at 500mA for maximum output?

A: While the absolute maximum rating is 500mA, the electro-optical characteristics are specified at 350mA. Driving at 500mA will significantly increase junction temperature, accelerate degradation, and may not provide a linear increase in UV output due to efficiency droop. It is not recommended for continuous operation.

Q: How do I interpret the bin codes for my design?

A: For applications requiring color or wavelength consistency (e.g., curing), specify the Wp bin (P3T or P3U). For uniform intensity across an array, specify a tight Radiant Flux bin (e.g., R3-R4). For parallel connections or precise voltage supply design, specify a tight Vf bin.

Q: What heatsink is required?

A: This depends on your operating current, ambient temperature, and required luminous maintenance. Using the thermal resistance (Rθjc), the power dissipation (P=I_f*V_f), and the target junction temperature (well below 110°C), you can calculate the required thermal resistance from case to ambient (Rθca) and select an appropriate heatsink.

11. Practical Application Example

Scenario: Designing a compact UV spot-curing system. An engineer selects the LTPL-C034UVD395 for its high radiant flux in a small package. They design a PCB with a 1.5mm thick aluminum core for thermal management. The recommended pad layout is used, with the thermal pad soldered to a large exposed copper area on the aluminum PCB. A constant-current driver set to 350mA is implemented. An array of 4 LEDs is used, each from the same Radiant Flux bin (R4) and Wavelength bin (P3U) to ensure uniform curing intensity and spectral match. A simple convex lens is placed over the array to focus the wide 130° beam into a more concentrated spot for higher irradiance at the target. The system achieves fast, reliable curing of a specific adhesive tuned for 395nm light.

12. Operating Principle

The LTPL-C034UVD395 is based on semiconductor physics. When a forward voltage exceeding the diode's bandgap energy is applied, electrons and holes recombine in the active region of the chip, releasing energy in the form of photons. The specific material composition (typically aluminum gallium nitride, AlGaN) determines the bandgap energy, which in turn dictates the wavelength of the emitted light. In this case, the bandgap is engineered to produce photons in the near-ultraviolet spectrum around 395 nanometers.

13. Technology Trends

The field of UV LEDs is advancing rapidly. Key trends include continuous improvements in wall-plug efficiency (optical power out / electrical power in), which reduces thermal load and energy consumption. There is also ongoing development to increase output power per chip and to expand available wavelengths further into the UVC spectrum (200-280nm) for sterilization applications. Packaging technology is evolving to handle higher power densities and improve thermal performance. Furthermore, cost reduction through manufacturing scale and process refinement is making UV LED solutions economically viable for an ever-wider range of applications previously dominated by traditional lamps.