UVA LED 2835 SMD Datasheet - 2.8x3.5mm Package - 3.2-3.8V - 60mA - 365-370nm - English Technical Documentation

1. Product Overview

This document provides the complete technical specifications for a series of high-performance Ultraviolet-A (UVA) Light Emitting Diodes (LEDs) housed in a compact surface-mount device (SMD) package. The primary application domain for these components is in systems requiring controlled ultraviolet emission within the 365-370 nanometer range.

The core advantages of this product series include its high radiant efficacy, which translates to more optical output per unit of electrical input, and its low power consumption profile. The device features a wide viewing angle of 120 degrees, ensuring broad and uniform irradiation in its target applications. Its form factor, measuring 2.8mm in length and 3.5mm in width, makes it suitable for integration into space-constrained modern electronic assemblies.

The product is designed to comply with major international environmental and safety standards. It is confirmed to be RoHS (Restriction of Hazardous Substances) compliant, is manufactured using lead-free (Pb-free) processes, and adheres to the EU REACH regulation. Furthermore, it meets halogen-free requirements, with bromine (Br) and chlorine (Cl) content kept below specified limits (Br <900ppm, Cl <900ppm, Br+Cl <1500ppm).

1.1 Target Applications

The specific wavelength and output characteristics make this LED series ideal for several niche applications:

• UV Nail Curing: Used in devices for curing gel-based nail polishes.
• UV Counterfeit Detection: Employed in scanners and detectors to reveal security features on banknotes, documents, or products that fluoresce under UVA light.
• UV Mosquito Traps: Integrated into insect-catching devices where UVA light attracts flying insects.

2. Technical Parameter Deep-Dive

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.

• Maximum DC Forward Current (I_F): 120 mA
• Maximum ESD Resistance (Human Body Model): 2000 V
• Thermal Resistance (R_th): 25 °C/W. This parameter indicates how effectively heat travels from the LED junction to the solder pad. A lower value is better for thermal management.
• Maximum Junction Temperature (T_J): 110 °C. The temperature at the semiconductor chip itself must not exceed this limit.
• Operating Temperature Range (T_Opr): -40 °C to +85 °C.
• Storage Temperature Range (T_Stg): -40 °C to +100 °C.

2.2 Electro-Optical Characteristics

The typical operating point and performance for the listed order code are defined below. All measurements are typically taken at a solder pad temperature of 25°C unless otherwise specified.

• Forward Current (I_F): 60 mA (Typical Operating Point)
• Forward Voltage (V_F): 3.2 V to 3.8 V (at I_F = 60mA)
• Peak Wavelength (λ_P): 365 nm to 370 nm
• Radiant Flux (Φ_e):
  • Minimum: 70 mW
  • Typical: 90 mW
  • Maximum: 130 mW

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. This allows designers to select components that meet specific minimum criteria for their application.

3.1 Radiant Flux Binning

LEDs are categorized based on their minimum radiant flux output at the operating current. The bin codes (R5, R6, R7, R8, R9, S1) represent increasing output levels, from a minimum of 70mW (R5) up to 130mW (S1). Measurement tolerance is ±10%.

3.2 Peak Wavelength Binning

The wavelength is tightly controlled. All devices in this series fall within a single bin labeled "U36", which guarantees a peak wavelength between 365nm and 370nm, with a measurement tolerance of ±1nm.

3.3 Forward Voltage Binning

Devices are also sorted by their forward voltage drop at 60mA. Three bins are defined:

• 3234: V_F = 3.2V - 3.4V
• 3436: V_F = 3.4V - 3.6V
• 3638: V_F = 3.6V - 3.8V

4. Performance Curve Analysis

4.1 Forward Voltage vs. Forward Current (IV Curve)

The provided curve illustrates the non-linear relationship between the voltage applied across the LED and the resulting current. For a constant-current driver set to 60mA, the expected voltage drop will fall within the 3.2V-3.8V range as defined in the electrical characteristics. The curve shows how voltage increases with current, emphasizing the need for proper current regulation, not voltage regulation, to control light output and prevent thermal runaway.

4.2 Relative Radiant Flux vs. Forward Current

This graph demonstrates that the optical output (radiant flux) is approximately proportional to the forward current. Increasing the drive current will increase the light output. However, operating above the recommended 60mA will generate more heat, potentially reducing efficacy and lifespan, as shown in the derating curve.

4.3 Relative Radiant Flux vs. Junction Temperature

This is a critical characteristic for thermal management. The curve shows that as the junction temperature (T_J) increases, the radiant flux output decreases. This negative temperature coefficient highlights the importance of an effective thermal design (e.g., using a PCB with thermal vias, adequate copper area, and possibly a heatsink) to maintain the LED's junction temperature as low as possible during operation, ensuring stable and maximum light output.

4.4 Peak Wavelength vs. Junction Temperature

The peak emission wavelength of an LED has a slight dependency on temperature. This graph quantifies that shift for this UVA device. Understanding this shift is important for applications where the exact wavelength is critical, such as in certain curing or fluorescence processes.

4.5 Spectral Distribution

The relative spectral distribution plot shows the intensity of light emitted across different wavelengths. For this UVA LED, the emission is centered around the 365-370nm peak with a characteristic spectral width. This information is vital for applications sensitive to specific UV spectral bands.

4.6 Derating Curve

The derating curve provides the maximum allowable continuous forward current based on the temperature measured at the solder pad (anode side). As the solder pad temperature rises, the maximum safe operating current must be reduced to prevent exceeding the maximum junction temperature of 110°C. This curve is essential for designing reliable systems, especially in high ambient temperature environments.

5. Mechanical and Packaging Information

5.1 Mechanical Dimensions

The LED package has a rectangular footprint of 2.8mm x 3.5mm. Detailed dimensional drawings specify the exact placement of the solder pads, the lens geometry, and the location of the thermal pad. The thermal pad is noted to be electrically connected to the cathode. Standard dimensional tolerances are ±0.2mm unless otherwise noted. A critical handling note warns against applying force to the lens, as this can cause device failure.

5.2 Soldering Pad Design and Polarity

The soldering pattern diagram clearly identifies the anode and cathode pads. Correct polarity must be observed during assembly. The design includes a central thermal pad to facilitate heat transfer from the LED die to the printed circuit board (PCB).

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Process

This UVA LED series is suitable for standard Surface-Mount Technology (SMT) assembly processes. Key guidelines include:

• Reflow soldering should not be performed more than two times on the same device to avoid thermal stress.
• Mechanical stress on the LED body during the heating phase of soldering must be minimized.
• The circuit board should not be bent or flexed after the LEDs are soldered in place.
• If adhesive is used, its curing process must follow standard oven profiles compatible with the component.

A typical reflow soldering profile is suggested, showing the recommended time-temperature relationship for preheat, soak, reflow, and cooling phases to ensure a reliable solder joint without damaging the LED.

7. Packaging and Ordering Information

7.1 Emitter Tape and Reel Packaging

For automated pick-and-place assembly, the LEDs are supplied on embossed carrier tape wound onto reels. The standard packaging quantity is 2000 pieces per reel. Detailed dimensional drawings for the carrier tape pockets and the reel itself are provided, with typical tolerances of ±0.1mm.

7.2 Moisture Sensitivity and Storage

The components are packaged in moisture-resistant barrier bags to prevent absorption of atmospheric moisture, which could cause "popcorning" (package cracking) during the high-temperature reflow process. Once the sealed bag is opened, the components should be used within a specified timeframe or baked according to standard IPC/JEDEC guidelines before soldering.

7.3 Product Nomenclature (Order Code)

The full order code is a structured string that encodes all key specifications. For example: UVA2835TZ0112-PUA6570120X38060-2T breaks down as follows:

• UVA2835TZ0112: Base part number (UVA, 2835 package, PCT material, with Zener, 1 chip, 120° angle).
• P: Chip orientation (P-side up).
• UA: Color Rendering Index code (UVA).
• 6570: Wavelength range code.
• 120: Maximum radiant flux spec code.
• X38: Forward voltage range (3.2V-3.8V).
• 060: Forward current rating (60mA).
• 2: Packaging type (2,000 pieces per reel).
• T: Tape packaging code.

7.4 Label Explanation

The reel label contains several fields for traceability and identification:

• P/N: The manufacturer's production number.
• QTY: The quantity of components on the reel.
• CAT / HUE / REF: Codes for the Radiant Flux bin, Color (Wavelength) bin, and Forward Voltage bin, respectively.
• LOT No: Manufacturing lot number for traceability.

8. Application Suggestions and Design Considerations

8.1 Thermal Management

Given the thermal resistance of 25°C/W and the negative impact of temperature on output and wavelength, effective heat sinking is paramount. Designers should:

• Use a PCB with a dedicated thermal pad land pattern connected to internal ground planes or large copper areas.
• Incorporate multiple thermal vias under the LED's thermal pad to conduct heat to other PCB layers or an external heatsink.
• Refer to the derating curve to ensure the operating current is appropriate for the expected maximum solder pad temperature in the application.

8.2 Electrical Drive

LEDs are current-driven devices. A constant-current driver circuit is strongly recommended over a simple series resistor or voltage source, especially for consistent output and longevity. The driver should be designed to supply a stable 60mA (or a lower current as per the derating requirements) and must be capable of withstanding the forward voltage range of 3.2V to 3.8V.

8.3 Optical Design

The 120-degree viewing angle provides a wide beam. For applications requiring focused or collimated UV light, secondary optics (lenses or reflectors) will be necessary. The material of these optics must be transparent to UVA wavelengths (e.g., specialized glass or UV-stable plastics like PMMA).

9. Technical Comparison and Differentiation

Compared to older through-hole UV lamps or larger SMD packages, this 2835 UVA LED offers significant advantages:

• Size and Integration: The compact 2835 footprint allows for higher density placement and integration into smaller, modern devices.
• Efficiency: High radiant efficacy leads to lower power consumption and reduced heat generation for a given light output.
• Lifetime: Solid-state LEDs typically have a much longer operational lifetime than traditional UV bulbs.
• Instant On/Off: LEDs reach full output instantly, unlike some bulbs that require warm-up time.
• Environmental: RoHS, Halogen-Free, and REACH compliance meets stringent global environmental regulations.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 What is the difference between radiant flux (mW) and luminous flux (lm)?

Luminous flux (measured in lumens) is weighted by the sensitivity of the human eye (photopic vision). Radiant flux (measured in watts) is the total optical power emitted, regardless of visibility. Since UVA light is largely invisible to humans, its performance is correctly specified in radiant flux (mW).

10.2 Why is a constant current driver necessary?

The forward voltage of an LED varies with temperature and from unit to unit (as seen in the binning). A constant voltage source would cause large variations in current, leading to inconsistent light output and potential overcurrent damage. A constant current source ensures stable, predictable performance.

10.3 Can I drive this LED at its maximum current of 120mA?

The Absolute Maximum Rating of 120mA is a stress limit, not a recommended operating condition. Continuous operation at this current would generate excessive heat, likely exceeding the maximum junction temperature unless an exceptional cooling solution is used. The recommended operating current is 60mA, as defined in the electrical characteristics table. The derating curve must be consulted for any operation above room temperature.

10.4 How do I interpret the binning codes when ordering?

Select bins based on your application's minimum requirements. For example, if your system needs at least 90mW of UV output, you should specify bins R7, R8, R9, or S1. If your driver circuit has tight voltage constraints, you may need to specify a particular forward voltage bin (e.g., 3234). The full order code incorporates these bin selections.

11. Design and Usage Case Study

11.1 Case: Portable UV Counterfeit Detector

Design Goal: Create a handheld, battery-powered device to check currency.

Implementation: An array of 4-6 of these UVA LEDs can be driven in series by a small, efficient boost converter/constant-current driver powered by a 3.7V Li-ion battery. The wide 120° beam angle eliminates the need for complex optics, allowing simple placement behind a UV-transmissive window. The compact 2835 size keeps the PCB small. Thermal management is less critical here due to the intermittent, short-duration use typical of such a device. The designer would select a radiant flux bin (e.g., R7 or higher) to ensure adequate illumination intensity.

12. Technical Principle Introduction

UVA LEDs operate on the principle of electroluminescence in semiconductor materials. When a forward voltage is applied across the p-n junction of the LED chip, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific wavelength of these photons (in this case, 365-370nm) is determined by the bandgap energy of the semiconductor materials used in the chip's construction, typically involving aluminum gallium nitride (AlGaN) or similar III-nitride compounds. The emitted UVA radiation is not visible to the human eye but can cause fluorescence in certain materials and initiate photochemical reactions, which is the basis for its applications in curing and detection.

13. Technology Trends

The field of UV LEDs is advancing rapidly. Key trends include:

• Increased Efficacy: Ongoing research aims to improve the wall-plug efficiency (optical power out / electrical power in) of UVA LEDs, reducing energy consumption and thermal load.
• Shorter Wavelengths: Development continues towards reliable and efficient UVB and UVC LEDs for applications in sterilization, medical therapy, and sensing.
• Higher Power Density: Improvements in chip design and packaging thermal management are enabling single devices with higher radiant flux output.
• Improved Lifetime and Reliability: Advancements in materials and packaging are extending the operational lifetime of UV LEDs, making them viable for more demanding industrial applications.
• Cost Reduction: As manufacturing volumes increase and processes mature, the cost per milliwatt of UV output continues to decrease, opening up new market applications.