LTPL-C034UVD385 UV LED Datasheet - 3.8V 600mW 385nm - English Technical Document

1. Product Overview

The LTPL-C034UVD385 is a high-power ultraviolet (UV) light-emitting diode (LED) designed for professional UV curing applications and other common UV processes. It represents a solid-state lighting solution that combines the energy efficiency, long operational lifetime, and reliability inherent to LED technology with a high radiant output suitable for displacing conventional UV light sources like mercury vapor lamps.

1.1 Core Advantages and Target Market

This UV LED series is engineered to offer significant advantages over traditional UV technologies. Key features include full RoHS compliance and being lead-free, ensuring environmental and regulatory compatibility. It offers lower operating and maintenance costs due to its solid-state nature, eliminating the need for frequent bulb replacements and reducing energy consumption. The device is also I.C. compatible, facilitating integration into modern electronic control systems. The primary target market includes industrial UV curing systems for inks, coatings, and adhesives, as well as scientific, medical, and disinfection equipment requiring a stable 385nm UV-A light source.

2. Technical Parameter Deep Dive

This section provides a detailed, objective analysis of the key electrical, optical, and thermal parameters specified for the LTPL-C034UVD385 UV LED.

2.1 Absolute Maximum Ratings

The device is rated for a maximum continuous forward current (If) of 500 mA and a maximum power consumption (Po) of 2 Watts. The operating temperature range (Topr) is specified from -40°C to +85°C, with a wider storage temperature range (Tstg) of -55°C to +100°C. The maximum allowable junction temperature (Tj) is 110°C. It is critical to operate within these limits to ensure reliability and prevent permanent damage. The datasheet explicitly warns against prolonged operation under reverse bias conditions.

2.2 Electro-Optical Characteristics

Measured at a standard test condition of 25°C ambient temperature and a forward current of 350mA, the key parameters are defined. The forward voltage (Vf) has a typical value of 3.8V, with a range from 2.8V (Min) to 4.4V (Max). The radiant flux (Φe), which is the total optical power output in the UV spectrum, has a typical value of 600 milliwatts (mW), ranging from 460mW (Min) to 700mW (Max). The peak wavelength (Wp) is centered in the 385nm region, with a bin range from 380nm to 390nm. The viewing angle (2θ1/2) is typically 130 degrees, defining the radiation pattern. The thermal resistance from junction to case (Rthjc) is typically 13.2 °C/W, a crucial parameter for thermal management design.

2.3 Thermal Characteristics Analysis

The thermal resistance value of 13.2 °C/W indicates the temperature rise per watt of power dissipated between the semiconductor junction and the package case. For example, at the typical operating point of 350mA and 3.8V (1.33W input power, assuming ~600mW optical output means ~730mW of heat), the temperature difference between the junction and case would be approximately 9.6°C. Effective heat sinking is essential to keep the junction temperature below its 110°C maximum, especially in high ambient temperature environments or during continuous operation.

3. Binning System Explanation

The LTPL-C034UVD385 employs a binning system to categorize units based on key performance variations, allowing designers to select LEDs matching specific application requirements.

3.1 Forward Voltage (Vf) Binning

LEDs are sorted into four voltage bins (V0 to V3). V0 bins have the lowest forward voltage (2.8V - 3.2V), while V3 bins have the highest (4.0V - 4.4V). The tolerance within a bin is +/- 0.1V. This allows for better current matching when multiple LEDs are driven in series, as LEDs from the same Vf bin will have more uniform voltage drops.

3.2 Radiant Flux (Φe) Binning

Optical output power is categorized into six bins, labeled R1 through R6. R1 represents the lowest output range (460mW - 500mW), and R6 represents the highest (660mW - 700mW). The tolerance is +/- 10%. This binning is critical for applications requiring consistent UV intensity, such as in curing processes where exposure dose is a key parameter.

3.3 Peak Wavelength (Wp) Binning

The UV wavelength is binned into two categories: P3R (380nm - 385nm) and P3S (385nm - 390nm), with a tolerance of +/- 3nm. The specific peak wavelength can be important for applications where certain photo-initiators in resins or coatings have optimal activation spectra.

4. Performance Curve Analysis

The datasheet includes several characteristic curves that provide deeper insight into the device's behavior under varying conditions.

4.1 Relative Radiant Flux vs. Forward Current

This curve shows that the optical output (radiant flux) increases with forward current but is not perfectly linear, especially at higher currents where efficiency may drop due to increased thermal effects. It helps designers choose an operating current that balances output power with efficiency and lifetime.

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

The I-V curve illustrates the exponential relationship typical of diodes. It is essential for designing the correct driver circuitry. The curve will shift with temperature; forward voltage decreases as junction temperature increases for a given current.

4.3 Relative Radiant Flux vs. Junction Temperature

This is one of the most critical curves for thermal management. It demonstrates how the optical output power degrades as the junction temperature rises. Maintaining a low junction temperature is paramount to achieving consistent, high output and maximizing the LED's operational lifespan.

4.4 Relative Spectral Distribution

This graph depicts the intensity of light emitted across the UV spectrum. It confirms the narrowband nature of the LED's output, centered around 385nm, with a typical full width at half maximum (FWHM) characteristic of LED technology. This is in contrast to the broad spectrum of traditional mercury lamps.

4.5 Radiation Characteristics

This polar diagram visualizes the spatial distribution of light (viewing angle). The typical 130-degree viewing angle indicates a wide, lambertian-like emission pattern, which is useful for evenly illuminating an area.

5. Mechanical and Package Information

5.1 Outline Dimensions

The LED package has specific mechanical dimensions provided in the datasheet drawings. Critical tolerances are noted: most dimensions have a tolerance of ±0.2mm, while the lens height and ceramic substrate length/width have a tighter tolerance of ±0.1mm. The thermal pad on the bottom of the package is noted as being electrically isolated (neutral) from the anode and cathode electrical pads, which simplifies PCB layout for thermal vias.

5.2 Recommended PCB Attachment Pad

A land pattern (footprint) is provided for PCB design. This includes the size and spacing for the anode, cathode, and thermal pad connections. Following this recommended layout is crucial for ensuring proper solder joint formation, electrical connection, and most importantly, efficient heat transfer from the thermal pad to the PCB copper pour and any underlying heatsink.

5.3 Polarity Identification

The datasheet diagram clearly indicates the anode and cathode pads. Correct polarity must be observed during assembly to prevent reverse bias application, which can damage the device.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A detailed reflow soldering profile is provided, specifying critical parameters like preheat, soak, reflow peak temperature (not exceeding 260°C for 10 seconds as per the reflow test condition), and cooling rates. The notes emphasize that all temperatures refer to the package body surface. A rapid cooling process is not recommended. The lowest possible soldering temperature that achieves a reliable joint is always desirable to minimize thermal stress on the LED.

6.2 Hand Soldering Instructions

If hand soldering is necessary, the maximum recommended condition is 300°C for a maximum of 2 seconds, and this should be performed only once per LED. The total number of soldering operations (reflow or hand) should not exceed three times.

6.3 Cleaning and Handling Cautions

For cleaning, only alcohol-based solvents like isopropyl alcohol should be used. Unspecified chemical cleaners can damage the LED package. The device must be handled with care to avoid electrostatic discharge (ESD) and mechanical damage to the lens.

7. Packaging and Ordering Information

7.1 Tape and Reel Packaging

The LEDs are supplied on embossed carrier tape and reel for automated pick-and-place assembly. The datasheet provides detailed dimensions for both the tape pockets and the standard 7-inch reel. Key specifications include: empty pockets are sealed with cover tape, a maximum of 500 pieces per reel, and a maximum of two consecutive missing components allowed on the tape, in accordance with EIA-481-1-B standards.

7.2 Bin Code Marking

The bin classification code (for Vf, Φe, and Wp) is marked on each packing bag, allowing traceability and selection of specific performance grades.

8. Application Suggestions

8.1 Typical Application Scenarios

The primary application is UV curing for industrial processes, including curing of inks on printing equipment, coatings on various substrates, and adhesives in electronics assembly. Other potential uses include fluorescence analysis, counterfeit detection, and medical therapy devices requiring specific UV-A wavelengths. Its solid-state nature makes it suitable for portable or instant-on equipment.

8.2 Design Considerations and Driver Requirements

An LED is a current-operated device. To ensure uniform intensity and stable operation, especially when driving multiple LEDs, a constant current driver is mandatory, not a constant voltage source. The driver must be designed to supply the required current (e.g., 350mA) while accommodating the forward voltage range of the LED(s). For series connections, the driver voltage must be higher than the sum of the maximum Vf of all LEDs in the string. Parallel connection of LEDs is generally not recommended without individual current balancing. Thermal management is the most critical aspect of the mechanical design. A high-quality thermal interface and an adequate heatsink are required to maintain the junction temperature within safe limits, ensuring output stability and long life.

9. Reliability and Testing

The datasheet outlines a comprehensive reliability test plan, demonstrating the product's robustness. Tests include Low, Room, and High Temperature Operating Life (LTOL, RTOL, HTOL), Wet High Temperature Operating Life (WHTOL), Thermal Shock (TMSK), Resistance to Soldering Heat (Reflow), and Solderability. All tests showed 0 failures out of 10 samples under the specified conditions. The criteria for judging a device as failed after testing are a shift in forward voltage (Vf) beyond ±10% or a shift in radiant flux (Φe) beyond ±30% of the initial typical value.

10. Technical Comparison and Differentiation

Compared to traditional UV light sources like mercury arc lamps, this UV LED offers distinct advantages: instant on/off capability, no warm-up time, longer lifetime (typically tens of thousands of hours), higher energy efficiency, no hazardous mercury content, and compact size enabling new form factors. Compared to other UV LEDs, the specific combination of 385nm wavelength, high typical radiant flux (600mW), wide 130-degree viewing angle, and a robust package with a isolated thermal pad for efficient cooling forms its key differentiation. The detailed binning system also allows for higher precision in system design compared to unbinned or loosely binned alternatives.

11. Frequently Asked Questions (Based on Technical Parameters)

Q: What driver current should I use?
A: The device is characterized at 350mA, which is a typical operating point offering a good balance of output and efficiency. It can be driven up to the Absolute Maximum Rating of 500mA, but this will increase junction temperature and may reduce lifetime; robust thermal management is essential.

Q: How do I interpret the Radiant Flux value?
A: Radiant Flux (Φe) is the total optical power emitted in watts (or milliwatts), measured across all wavelengths. For this UV LED, it represents the useful UV power, not visible light. It is a key metric for calculating exposure dose (Energy = Power × Time) in curing applications.

Q: Why is thermal management so important?
A: As shown in the \"Relative Radiant Flux vs. Junction Temperature\" curve, output power decreases as temperature increases. Excessive temperature also accelerates the degradation mechanisms inside the LED, drastically shortening its lifespan. The 13.2 °C/W thermal resistance defines how effectively heat can be removed.

Q: Can I use a constant voltage power supply?
A: No. The forward voltage of an LED varies with temperature and between individual units. A constant voltage source can lead to thermal runaway, where increased current causes more heat, which lowers Vf, causing even more current, potentially destroying the LED. Always use a constant current driver.

12. Design and Usage Case Study

Scenario: Designing a benchtop UV curing station for PCB solder mask.
A designer needs uniform UV exposure over a 10cm x 10cm area. Using the LTPL-C034UVD385 with its 130° viewing angle, they can calculate the necessary height and array spacing of LEDs to achieve even irradiance. They select LEDs from the R5 or R6 flux bin for higher intensity, and from the same Vf bin (e.g., V1) for consistent current draw when wired in series. A constant current driver capable of delivering the total required current for the series string is selected. The aluminum PCB is designed with the recommended pad layout, incorporating a large copper pour and thermal vias connected to an external heatsink with a fan. The reflow profile from the datasheet is programmed into the pick-and-place machine. After assembly, the station provides instant, consistent curing without the heat and ozone associated with mercury lamps.

13. Operating Principle Introduction

An LED is a semiconductor p-n junction diode. 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. When these charge carriers recombine, energy is released in the form of photons (light). The wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor materials used in the active region. For the LTPL-C034UVD385, specific semiconductor compounds (typically based on aluminum gallium nitride - AlGaN) are engineered to have a bandgap corresponding to photons in the 385nm ultraviolet (UV-A) range. The package includes a primary optic (lens) to shape the light output and protect the semiconductor die.

14. Technology Trends and Outlook

The UV LED market is driven by the global phase-out of mercury-based lamps (Minamata Convention) and the demand for more efficient, compact, and controllable light sources. Key trends include continuous improvement in Wall-Plug Efficiency (WPE), which is the ratio of optical output power to electrical input power. Higher efficiency means less waste heat for the same UV output. There is also ongoing development to increase the maximum optical power output per single LED package and to improve reliability and lifetime at higher operating temperatures and currents. Furthermore, research is focused on expanding the available wavelength ranges, particularly into the deeper UV-C spectrum for germicidal applications, though different materials like aluminum nitride (AlN) are required. The trend towards system-level integration, combining LEDs, drivers, and sensors into smart modules, is also evident.