Today, with the high development of science and technology, the replacement of electronic products is getting faster and faster, and the technology of LED lights is also constantly developing, decorating our cities colorfully.
UVC technology originated in the early 20th century, when mercury lamps were first mass-produced. Ultraviolet emitting lamps were used in drinking water disinfection in 1910. However, that prototype factory was shut down as it proved unreliable. In the 1950s, new UVC water treatment systems were trialled, and by the mid-1980s there were about 1500 plants in Europe. Currently, UVC LEDs are primarily used to sterilize medical instruments, water, and other everyday consumer products.
Thermal management refers to the use of reasonable cooling and heat dissipation technology and structural optimization design for heat-consuming components and systems in packaging to control their internal temperature to ensure the normal reliability of electronic equipment and systems. The purpose is to dissipate this heat using various methods to keep the temperature of the package within the allowable range.
UVC LED technology is still in its infancy, and the biggest challenge is the thermal management of UVC LEDs. Like any electronic component, LEDs are very sensitive to heat. UVC LEDs have particularly low external quantum efficiency (EQE) – they convert only about 5% of the input power into light. The remaining 95% of the power is converted into heat, which must be removed quickly to keep the LED chip below its maximum operating temperature. If the LED chip is not cooled in time, it will eventually shorten its lifespan or even become unusable.
254nm is the best wavelength for sterilization, which is a misunderstanding because the peak wavelength of low pressure mercury lamps (determined only by the physical characteristics of the lamp) is 253.7nm. In fact, as mentioned above, a range of wavelengths has a germicidal effect. However, the wavelength of 265 nm is generally considered to be optimal because this wavelength is the peak of the DNA absorption curve. Therefore, UVC is the most suitable strip for sterilization.
Like any electronic component, UVC LEDs are sensitive to heat. UVC LEDs have lower external quantum efficiency. Of the input power, typically less than 5% of the power is converted into light (currently, industrial products from related manufacturers are said to be more than 5% efficient), while the remaining more than 95% of the power is converted into light and heat. This causes the UVC LED chips to generate unusually severe heat. At this time, if the heat cannot be quickly removed and the LED chip is kept below the maximum operating temperature, the lifespan and reliability of the UVC LED will be directly affected, and it may even become unusable.
UVC LED light power files available on the market range from 2mW, 10mW to 100mW. Different applications have different power requirements. Generally speaking, light power can be matched by combining illumination distance, dynamic demand or static demand. The greater the illumination distance, the greater the dynamic demand and the greater the required optical power.
As the UVC LED market expands, manufacturers need to consider new ways to meet this challenge. Now, the question that remains is how to deal with the high thermal demands of UV LEDs, while ensuring that the components remain cost-effective, durable, and resistant to wear and tear from the UV light source itself. Due to the small size of UVC LEDs, most of the heat cannot be dissipated from the front, so the back of the LED becomes the only way to efficiently dissipate heat. The task of improving thermal dissipation has shifted to downstream packages and modules. At this time, how to do a good job of thermal management in the packaging process is particularly important.
The light output angle of lamp beads with flat lenses is usually between 120-140°, while the light output angle of packages with spherical lenses is adjustable between 60-140°. In fact, no matter how large the UVC LEDs are chosen, enough LEDs can be designed to fully cover the required sterilization space. In scenes that are not sensitive to the sterilization range, a smaller light exit angle can make the light more concentrated, thereby shortening the sterilization time.
Therefore, the PCB on which the LEDs are mounted must have high thermal conductivity. For visible light LEDs, it is usually a metal-based printed circuit board (MCPCB). However, these are not suitable for UVC applications. Metal substrates based on epoxy dielectrics can be used in visible light applications, but UV light (especially UVC) can degrade organic substances such as epoxy resins, which can greatly shorten the life of metal substrates in UV applications. The only viable alternative is to use electronic grade ceramics.
As the UVC LED market expands further, manufacturers need to consider new ways to meet this challenge. Now, the question remains how to handle the high thermal demands of UV LEDs while ensuring that the components remain cost-effective, durable and resistant to wear and tear from the UV light source itself. UVC disinfection technology enabled by LEDs can bring real transformative effects, and the industry needs to ensure that the thermal challenges faced by UV LEDs can be overcome.
Although LEDs can be seen everywhere in life, there are still some deficiencies in LEDs that require our designers to have more professional knowledge reserves, so as to design products that are more in line with the needs of life.