FAQs

Frequently Asked Questions

UV lamps utilize bulbs containing mercury vapor to emit broadband UV radiation. There are low-pressure UV lamps and medium-pressure UV lamps, which both use mercury but differ in the ionization and pressure of the mercury. UV LEDs are diodes that are grown from InGaN or AlGaN templates on sapphire. UV LEDs emit narrowband UV radiation and contain no mercury.

The advantages of UV LEDs are instant turn on/off with no cooldown period, narrowband radiation, reduced heat generation, longer lifetime, smaller form factor, lower power consumption, and no presence of mercury. Disadvantages of UV LEDs are the low efficiency in certain wavelengths (UVC range) and high pricing.

The lifetime of a UV LED is expressed as a LT70 or L70 value. LT70 represents the number of hours until the UV LED reaches 70% of its initial output. The exact UV LED lifetime depends on the wavelength and operating conditions of the LED. UVA LEDs boast LT70 values of over 10,000 hours, while UVB and UVC LEDs have LT70 values of at least 5,000 hours. Please contact the Violumas team to learn more about lifetime information regarding each LED product. It is important to note that effective heat dissipation and maintenance of low junction temperatures are critical to extending an LED’s lifetime.

Our team can help to identify the best UV LED components for your application with consideration of the optical output, beam angle, and mechanical/electrical requirements. In order to determine the optimal UV LED solution, we recommend the use of optical simulations to better understand the expected irradiance and uniformity for various settings. First, a list of target specifications is generated including information such as the exposure area, wavelength, throw distance, irradiance, uniformity, and mechanical and electrical restrictions. Using the target requirements, optical specialists at Violumas can help you determine the best optics and required number of LEDs for the application. Learn more about custom UV LED solutions here: https://www.violumas.com/custom/

Output and intensity from UV LEDs can be measured through integrating spheres, spectrometers, or radiometers. 

Integrating spheres are the industry standard for manufacturers as they measure wavelength, output power, and full width half maximum (FWHM) and collect all of the flux emitted by an LED. An alternative way to measure the optical output of a UV LED is by using a goniometer, which measures the radiant flux from many different angles to produce a combined flux distribution. At Violumas, all UV LEDs are measured with integrating spheres to produce accurate and consistent results in a single, pulsed measurement.

Spectrometers or radiometers are commonly used devices that can measure the intensity or irradiance (e.g. W/cm2). For measurement of UV LEDs, spectrometers are most commonly used due to the presence of sensors that can measure the light output separated at individual wavelengths. For the use of radiometers, which cannot distinguish wavelengths, filters are recommended in order to obtain accurate measurements at a specific wavelength.

With all measurement methods, frequent instrument calibration is required in order to ensure that measurements are accurate and reliable. It is highly recommended to measure and validate the optical output of UV LEDs on the customer’s side due to the current lack of industry standards for reliable and accurate measurements that are consistent among UV LED suppliers. Please contact the Violumas team to learn more about recommended measurement equipment.

We recommend operating UV LEDs with constant-current power supplies, which support limited voltage ranges and maintain the set current without over-driving the LEDs. If a constant voltage driver is used instead and the current is not regulated, as the LED temperature increases when powered ON, the LED forward voltage would decrease accordingly which would eventually lead to thermal runaway. Learn more about selecting an appropriate power supply for your UV LEDs here: https://www.violumas.com/2022/11/22/violumas-led-driver-selection/.

A proper cooling solution such as a heatsink is critical for operating UV LEDs. UV LEDs dissipate heat through the backside, so it is important to have a suitable cooling solution with good thermal dissipation made from materials such as copper or aluminum and to apply thermal interface material between the LED and heatsink. UV LEDs with lower power consumption can be passively cooled through convection with heatsinks. High power UV LEDs with high electrical consumption may require fan-cooled heatsinks.

Finally, liquid cooling is recommended for high power UV LEDs that cannot be cooled with forced convection from fans. Please contact the Violumas team to learn more about designing an appropriate heatsink for your specific application.

UV irradiation can be harmful to human eyes and skin. Avoid exposure to UV light during LED operation. Do not look directly into the UV light during LED operation. Protect the body, skin, and eyes with UV protective equipment. Also, attach warning labels on all products and systems that use UV LEDs. Please see the full list of safety and precaution recommendations on any Violumas datasheet.

UV irradiation can cause degradation such as yellowing, cracking, and becoming brittle on certain materials. Materials that will be exposed to UV irradiation should be UV-resistant or tested for repeated exposure to UV irradiation.

Surface Mount Device (SMD) LEDs are commonly available, square packages of LED chips available in compact form factors ranging from 3x3mm to 6x6mm. SMD UV LEDs need to be mounted to PCBs or MCPCBs to be powered on. A more recent development in LED packaging is the Chip-On-Board (COB) LED, which consist of LED chips directly mounted onto the PCB or MCPCB for improved heat dissipation. COBs do not require additional MCPCBs and can offer high density, flexible arrangements of LED die.

Violumas-Specific Questions

Samples can be purchased directly from our sales office in Fremont, California. The typical lead time is 1-2 weeks.

The price for a custom UV LED solution depends on the complexity of the design and number of LED chips. The typical lead time is 5-6 weeks for a custom UV LED solution. Both low and high volume projects can be supported by Violumas. Please contact the Violumas team to learn more about custom solutions: https://www.violumas.com/custom/.

Violumas provides a multitude of lens options for UV LEDs depending on the wavelength. We can provide UV LEDs with 15°, 30°, 60°, 90°, 120°, or 135° flat panel optics. We can also remove the lens completely to maintain the naturally wide angle of the LED chip if that is preferred.

3-PAD LEDs are exclusively manufactured by Violumas and designed with an additional thermal pad, which is an electrically-isolated structure for efficient heat extraction. The thermal pad rapidly conducts heat from the chip’s junction to the heat sink via a copper pillar mesa structure on our specialized Pillar MCPCBs. The combination of 3-PAD LEDs on Pillar MCPCBs allows for extremely low thermal resistance and rapid heat dissipation. Learn more about the advantages of 3-PAD technology here: https://www.violumas.com/our-technology/.

Violumas manufactures UV LEDs in Taiwan. The UV LED chip epitaxy is performed by our OEMs in Japan and South Korea.

Yes, please contact us for CAD files and/or ray files. We also have some CAD files available in the downloads section of our website.

Yes, we are able to accommodate specific wavelength constraints for the UV LEDs. We can select specific wavelength bins to ensure that all products are between a set wavelength tolerance. The pricing for UV LEDs with specific wavelength constraints may be higher than our standard offerings as the yield for some wavelengths may be low.

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We provide application support and documentation to help you get the most out of your UV LEDs.