UV LED 3.7x3.7x3.45mm SMD Specification - Forward Voltage 4.6-7.6V - Radiant Flux up to 20mW - 260-270nm Wavelength - English Technical Document

1. Product Overview

This document details the specifications for a high-reliability, surface-mount Ultraviolet (UV) Light Emitting Diode (LED). The device is engineered for applications requiring effective ultraviolet emission, such as disinfection, sterilization, and air purification systems. Its compact SMD (Surface-Mount Device) package is designed for compatibility with automated assembly processes, offering good thermal performance for stable operation.

1.1 Core Advantages and Target Market

The primary advantages of this UV LED include its standardized SMT footprint, which allows for easy integration into modern printed circuit board (PCB) designs, and its stated high reliability. The product is targeted at the growing market for solid-state ultraviolet light sources, which are increasingly replacing traditional mercury-vapor lamps in applications like:

• Germicidal Irradiation: For disinfecting surfaces, water, and air by inactivating microorganisms.
• Air Purification Systems: Integrated into HVAC systems or standalone air purifiers to neutralize airborne pathogens and volatile organic compounds (VOCs).
• Medical and Laboratory Equipment: For sterilization of tools and surfaces.
• General UV Curing: Although specific curing performance data is not provided, the wavelength range suggests potential use in initiating photochemical reactions.

2. In-Depth Technical Parameter Analysis

The performance of the LED is defined by a comprehensive set of electrical, optical, and thermal parameters measured under controlled conditions (Ts=25°C).

2.1 Electrical & Optical Characteristics

The key performance metrics are summarized in the specification tables. A critical parameter is the Peak Wavelength (λp), which falls within the 260-270 nanometer (nm) range. This places the emission firmly in the UVC band (100-280 nm), known for its high germicidal effectiveness. The specific wavelength bin (e.g., UA33 for 260-265nm, UA34 for 265-270nm) must be selected based on the application's requirements, as the effectiveness against different pathogens can vary with wavelength.

The Total Radiant Flux (Φe), or optical power output, is specified up to 20 milliwatts (mW) at a drive current of 150 mA. Designers must note that this is radiant flux, not luminous flux, as UVC light is invisible to the human eye. The Forward Voltage (V_F) exhibits a binning structure from 4.6V to 7.6V at 150mA. This wide range is typical for deep-UV LEDs and has significant implications for driver circuit design, affecting efficiency and thermal management.

The Viewing Angle (2θ_1/2) is 60 degrees, indicating a moderately directional light output. The Spectrum Half Width (Δλ) is typically 10 nm, which describes the spectral purity of the emitted light.

2.2 Absolute Maximum Ratings and Thermal Management

Adherence to Absolute Maximum Ratings is crucial for device longevity and preventing catastrophic failure. Key limits include:

• Maximum Junction Temperature (T_J): 60°C. This is a critical constraint. The junction temperature must be kept below this limit during operation, which directly ties into the PCB's thermal design and heat sinking capabilities.
• Maximum Power Dissipation (P_D): 1.2 Watts.
• Peak Forward Current (I_FP): 200 mA (under pulsed conditions, 0.1ms pulse width, 1/10 duty cycle).

The Thermal Resistance (R_θJ-S) from junction to solder point is specified as 45°C/W. Using this value, engineers can calculate the expected junction temperature rise above the solder point temperature for a given operating power (P_D = V_F * I_F). For example, at a typical V_F of 6.0V and I_F of 150mA, the power is 0.9W. The temperature rise would be approximately 0.9W * 45°C/W = 40.5°C. Therefore, if the PCB solder point is at 35°C, the junction would reach ~75.5°C, exceeding the 60°C maximum. This highlights the necessity for effective thermal management, possibly requiring a lower drive current, an improved thermal pad design, or active cooling.

2.3 Binning System Explanation

The product employs a binning system to categorize units based on key parameters, ensuring consistency within a production batch. Designers must specify the required bins when ordering.

• Forward Voltage (V_F) Binning: Coded B19 through B33, covering 4.6V to 7.6V in ~0.2V steps at 150mA.
• Peak Wavelength (λp) Binning: Coded UA33 (260-265nm) and UA34 (265-270nm).
• Radiant Flux (Φe) Binning: Coded 1J03 (6-10mW), 1J04 (10-15mW, with 14mW typical), and another 1J04 bin (15-20mW). Note the code reuse for different flux ranges, which requires careful attention to the associated value table.

3. Performance Curve Analysis

The provided characteristic curves offer valuable insights into device behavior under non-standard conditions.

3.1 Forward Voltage vs. Forward Current (IV Curve)

This curve shows the non-linear relationship between voltage and current. It is essential for determining the operating point and for designing constant-current drivers, which are mandatory for LEDs. The curve will shift with temperature; typically, forward voltage decreases as junction temperature increases.

3.2 Forward Current vs. Relative Radiant Power

This curve illustrates the light output's dependence on drive current. It is generally sub-linear; doubling the current does not double the optical output due to efficiency droop, a common phenomenon in LEDs, especially at higher currents and temperatures. Operating the LED at or below the recommended test current (150mA) is advised for optimal efficiency and lifetime.

4. Mechanical & Package Information

4.1 Dimensions and Tolerances

The package is a 3.7mm x 3.7mm footprint with a height of 3.45mm. All dimensional tolerances are ±0.2mm unless otherwise specified. The drawings provide top, side, and bottom views, which are necessary for PCB footprint design and clearance checks.

4.2 Pad Design and Polarity Identification

A recommended solder pad layout is provided (Fig. 1-5). The pad dimensions are 3.20mm x 2.20mm for the thermal/electrical pad and 1.20mm x 1.20mm for the secondary electrical pad. The polarity is clearly marked on the bottom view of the component. Correct orientation is vital, as applying reverse voltage exceeding the maximum rating (10V) can damage the device.

5. Soldering & Assembly Guidelines

5.1 SMT Reflow Soldering

The component is suitable for all standard SMT assembly processes. A standard lead-free reflow profile with a peak temperature typically not exceeding 260°C is implied. The Moisture Sensitivity Level (MSL) is Level 3. This means the device can be exposed to factory floor conditions (≤30°C/60% RH) for up to 168 hours (7 days) before it must be soldered. If this time is exceeded, the parts must be baked according to IPC/JEDEC standards to remove absorbed moisture and prevent "popcorning" (package cracking) during reflow.

5.2 Handling and Storage Precautions

• ESD Protection: The device is rated for a Human Body Model (HBM) Electrostatic Discharge of 1000V, with a yield over 90%. This is a relatively modest ESD rating. Handling must occur in an ESD-protected area using grounded wrist straps and conductive mats.
• Storage Conditions: The storage temperature range is -20°C to +65°C. Long-term storage outside this range should be avoided.
• Moisture Barrier Bag: As per MSL-3, the components are shipped in a moisture barrier bag with a humidity indicator card. The bag should only be opened in a controlled environment, and time-out of the bag should be tracked.

6. Packaging and Ordering Information

The product is supplied on tape and reel for automated pick-and-place machines. The specification includes dimensions for the carrier tape and the reel. Labeling specifications for the reel are also provided to ensure traceability. The model number provided (e.g., RF-C37P6-UPH-AR) likely encodes information about the package size, chip technology, and possibly the performance bins, though the exact naming rule is not detailed in the excerpt.

7. Application Design Considerations

7.1 Driver Circuit Design

A constant-current driver is mandatory. The driver must be capable of supplying the required current (e.g., 150mA) across the entire forward voltage bin range (4.6V-7.6V). This wide range significantly impacts the driver's efficiency and voltage headroom requirements. For battery-operated devices, a boost converter may be necessary to ensure sufficient voltage is available for LEDs in the higher V_F bins.

7.2 Thermal Design

As calculated from the thermal resistance, managing junction temperature is paramount. The PCB should use a thermal relief pattern under the LED's central pad, connected to large copper planes or an external heatsink. Thermal vias under the pad can help transfer heat to inner or bottom layers. The maximum drive current may need to be derated in high ambient temperature environments or in applications with poor airflow.

7.3 Optical and Safety Design

UVC radiation is harmful to human skin and eyes. The end-product design must incorporate safety features such as interlock switches, shielding, and warning labels to prevent user exposure. The 60-degree viewing angle should be considered when designing reflectors or lenses to direct the UV light effectively onto the target area. Materials used in the optical path (lenses, windows) must be transparent to UVC wavelengths; many common plastics like polycarbonate are not suitable.

8. Technical Comparison & Differentiation

Compared to older UV light sources like mercury lamps, this LED offers instant on/off capability, longer lifetime (when properly heatsunk), no hazardous materials like mercury, compact size, and design flexibility. Within the UV LED market, the key differentiators for this specific part would be its package size (3.7x3.7mm is a common footprint), its radiant flux output in the 10-20mW range, and its specific wavelength bins in the 260-270nm germicidal range. Designers would compare these parameters against alternatives to find the optimal balance of optical power, efficiency, cost, and size for their application.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 Why is the forward voltage range so wide (4.6V-7.6V)?

This is characteristic of aluminum gallium nitride (AlGaN) based deep-UV LEDs. Variations in epitaxial growth and chip processing lead to differences in semiconductor resistance and the precise composition of the active layers, resulting in a distribution of forward voltages. Binning ensures you get LEDs with consistent electrical behavior within your order.

9.2 Can I drive this LED with a constant voltage source?

No. LED brightness is controlled by current. A constant voltage source would lead to uncontrolled current flow, potentially exceeding the maximum rating and destroying the LED due to the diode's exponential IV characteristic and negative temperature coefficient. A constant-current driver is essential.

9.3 The junction temperature rating is only 60°C. Is this normal for UV LEDs?

Yes, it is common for UVC LEDs to have lower maximum junction temperatures compared to visible-light LEDs. High-energy photons and the materials used in deep-UV emitters make them more sensitive to thermal degradation. Meticulous thermal management is non-negotiable for performance and reliability.

10. Practical Design Case Study

Scenario: Designing a compact, battery-powered surface disinfection wand.

Design Steps:

1. Parameter Selection: Choose a high radiant flux bin (e.g., 15-20mW) for effectiveness. Select a mid-range V_F bin (e.g., B25, 5.8-6.0V) to simplify driver design.
2. Driver Design: Use a boost converter constant-current driver IC that can take a 3.7V Li-ion battery input and provide a stable 150mA output up to at least 6.5V to cover the selected V_F bin.
3. Thermal Design: Design a small metal core PCB (MCPCB) or use a standard FR4 board with an extensive thermal pad and multiple vias to act as a heatsink. Limit continuous on-time based on thermal modeling or empirical testing to keep T_J < 60°C.
4. Optical/Safety Design: Enclose the LED in a housing with a UVC-transparent quartz window. Include a proximity sensor or physical guard that must be in contact with a surface for the LED to turn on, preventing accidental exposure.

11. Operating Principle

This is a semiconductor light source. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region. Their recombination releases energy in the form of photons. The specific wavelength of these photons (in the UVC range) is determined by the bandgap energy of the semiconductor material used, typically aluminum gallium nitride (AlGaN) with a high aluminum content for shorter wavelengths.

12. Technology Trends

The UV LED market, particularly for UVC applications, is focused on increasing wall-plug efficiency (optical power out / electrical power in), which historically has been lower than for visible LEDs. Improvements in epitaxial growth, light extraction techniques, and packaging are steadily driving higher output power and longer lifetimes while reducing cost per milliwatt. This enables the expansion of UV LED technology from niche applications into broader consumer and industrial markets for disinfection and sensing.