What Is The 3535 UV-C LED 275nm And What Are Its Core Values?

In simple terms, the 3535 UV-C LED with a wavelength of 275nm is a semiconductor light source that utilizes deep ultraviolet radiation to destroy the DNA or RNA structure of microorganisms. It adopts a standard ceramic package measuring 3.5mm × 3.5mm and can operate within the wavelength range of 270nm to 280nm, which represents the optimal balance between germicidal efficacy and mass-production cost-effectiveness at present. In comparison with traditional light sources, it is more eco-friendly, features a longer service life and boasts an extremely fast start-up speed.

Golden Wavelength Band: The 275nm wavelength is close to the absorption peak of microorganisms, delivering exceptionally high germicidal efficacy.

High Reliability: Employing a ceramic substrate package, its thermal dissipation performance far surpasses that of conventional plastic bracket packages.

Standard Size: The 3535 form factor is an industry-standard dimension, facilitating engineers in PCB layout and design.

Instant Operation: No preheating is required, with nanosecond-level response time, making it ideal for inductive disinfection equipment.

Eco-friendly & Safe: Completely mercury-free, it complies with the Minamata Convention and RoHS environmental requirements.

Wide Application: Serving as a core disinfection component, it is widely applied in scenarios ranging from air purifiers to water treatment modules.

QQ20251204-184534

To understand the value of this LED chip, you must first grasp its working mechanism. UV-C (deep ultraviolet light) is known as the "scalpel" in the field of physical sterilization. When ultraviolet radiation with a wavelength ranging from 200 nm to 280 nm irradiates bacteria, viruses or spores, high-energy photons can penetrate the cell walls of microorganisms.

After the energy of UV-C photons is absorbed by the base pairs in the nuclei of microorganisms, the double helix structure of DNA (Deoxyribonucleic Acid) or RNA (Ribonucleic Acid) is broken, resulting in the formation of dimers. This not only prevents the replication of pathogens but also immediately inactivates them.

This is completely different from chemical disinfection. It does not induce any drug resistance nor leave any chemical residues. For scenarios requiring high-frequency and rapid disinfection and sterilization, this physical inactivation method is the safest option.

Many customers often ask: "Isn't it true that 254nm delivers the optimal germicidal effect? Why are LEDs manufactured at 275nm?" This is an excellent technical question.

Although the emission peak of conventional low-pressure mercury lamps is at 253.7nm, which is very close to the maximum absorption peak of DNA (approximately 265nm), fabricating 254nm LEDs presents extreme manufacturing challenges and results in extremely low luminous efficacy. With current AlGaN (Aluminum Gallium Nitride) material technology, the 275nm wavelength achieves the optimal balance between Wall-Plug Efficiency (WPE) and manufacturing costs.

In practice, the germicidal efficacy of 275nm is only marginally lower than that of 265nm. However, driven by the same current, 275nm LEDs can output a higher optical power, which compensates for the minor wavelength deviation in terms of total radiant energy.

When selecting UV-C LEDs, Radiant Flux is a more critical metric than electrical power. Never judge a LED bead solely by its electrical power rating, such as 1W or 3W. Instead, focus on the actual ultraviolet radiant power it outputs, measured in milliwatts (mW).

Take the 3535 275nm UV-C germicidal LED bead as an example. A high-quality 3535 LED bead typically delivers a radiant flux of approximately 40 mW. What does this signify? According to the dose formula: Dose = Intensity × Time, a higher radiant flux translates to a shorter time required to achieve the target germicidal reduction rate-for instance, Log 4, equivalent to a 99.99% sterilization rate.

For applications involving flowing water disinfection or air duct disinfection, where the fluid residence time is extremely short, a high radiant flux represents an indispensable, non-negotiable performance requirement.

Unlike general-purpose lighting LEDs, which typically operate at 3V, UV-C LEDs feature a relatively wide band gap of their semiconductor materials, resulting in a higher forward voltage (Vf).

Voltage Range: The forward voltage generally falls within the range of 5 V to 7 V.

Current Range: The typical driving current ranges from 100 mA to 150 mA.

When designing the driving circuit, constant current driving must be used instead of constant voltage driving. UV-C LEDs are highly thermally sensitive. A temperature increase will lead to a decrease in forward voltage. If a constant voltage source is employed, the current will surge sharply, instantly burning out these costly LED beads.

A high-quality 3535 UV-C LED should feature a very narrow full width at half maximum (FWHM), typically around 10 nm. This indicates that it emits highly pure light, with the vast majority of its energy concentrated within the effective germicidal wavelength range of 270–280 nm.

If low-quality chips are used, the wavelength may drift to 285 nm or even above 300 nm, resulting in a sharp decline in germicidal efficacy. Furthermore, such chips will produce a large amount of visible light or UVA stray light, which not only wastes electrical energy but also generates unnecessary heat.

Deep-UV LEDs have a prominent drawback: their photoelectric conversion efficiency is still relatively low at present (typically <5%). This means that more than 95% of the input electrical energy is converted into heat. If the heat cannot be dissipated effectively, the junction temperature (Tj) will rise, leading to a drastic reduction in the chip's service life.

This is precisely why ceramic substrates are essential. Ceramic materials such as aluminum nitride (AlN) boast extremely high thermal conductivity, which can rapidly transfer the heat generated by the chip to the solder pads at the bottom. In contrast, conventional FR4 boards and even some metal substrates fail to meet the stringent heat dissipation requirements of UV-C LEDs.

Conventional LED packaging typically employs silicone or epoxy resin for lenses. However, under prolonged exposure to high-energy UV-C radiation, these organic materials undergo rapid photodegradation, turning yellow and becoming brittle, which results in a significant decrease in light transmittance.

3535 ceramic packages are usually paired with quartz glass lenses. As an inorganic material, quartz is nearly perfectly transparent to deep ultraviolet light and exhibits exceptional aging resistance. The quartz lens is bonded to the ceramic submount via eutectic soldering or specialized adhesive bonding processes, forming a fully inorganic, hermetically sealed package that ensures high-efficiency output of the LED throughout its service life.

L70 refers to the length of time it takes for the luminous flux of an LED to decay to 70% of its initial value. For general lighting LEDs, this period typically amounts to tens of thousands of hours. However, for UV-C LEDs, the packaging process directly determines their service life, owing to the destructive nature of high-energy photons.

QQ20260129-161820

Many application scenarios do not require 24-hour continuous sterilization. Examples include intelligent toilet seats, portable water cups, or inductive door handles.

Traditional mercury lamps require preheating once turned on, and frequent switching will severely shorten their service life. In contrast, LEDs are semiconductor devices that support high-frequency PWM dimming and unlimited switching. This means you can design an intelligent logic of "turning on when people leave and turning off when people arrive", which is both safe and energy-efficient.

How to judge whether the LED beads provided by the supplier are of good quality? Check the luminous decay curve.

For high-quality UV-C LEDs, the luminous decay in the first 1000 hours should be within 3-5% under the high-temperature (60℃) and high-humidity (85% RH) aging test. If the optical power drops by 20% in the first few hundred hours, it means the package hermeticity is faulty or the chip's electrode process is not up to standard.

Is there a significant difference in actual germicidal efficacy between 275nm and 254nm?

There is a difference, but not a massive one. Although the single-photon absorption rate at 254nm is slightly higher, the system-level germicidal efficacy of 275nm LEDs in practical applications is often superior, thanks to their high radiant intensity output. Furthermore, 275nm LEDs pose no risk of mercury contamination.

Do UV-C LEDs generate ozone?

No. Ozone generation requires wavelengths below 185nm to ionize oxygen in the air. The 275nm wavelength is far longer than this threshold, making it a truly ozone-free disinfection solution. It is highly suitable for use in environments where humans and machines coexist (provided that direct exposure to the human body is avoided).

How to calculate the number of UV-C LEDs required for a specific space?

This depends on the dimensions of the space, the target germicidal reduction rate, and the treatment duration. It is generally recommended to consult a professional packaging manufacturer or solution provider. For simple static surface disinfection (e.g., a 10×10cm area), one 40mW 3535 LED bead, irradiating at a distance of 5–10cm for one minute, is usually sufficient.