Today, with the rapid development of science and technology, the upgrading of electronic products is faster and faster, and the technology of LED lamp is also developing constantly, which decorates our city with various colors.
UVC technology originated in the early 20th century, when mercury lamps were first mass-produced. Ultraviolet emission lamps were used to disinfect drinking water in 1910. However, the prototype plant was shut down because it proved to be unreliable. In the 1950s, new UVC water treatment systems were put on trial. By the mid-1980s, there were about 1500 plants in Europe. At present, uvleds are mainly used to disinfect medical instruments, water and other daily consumer goods.
Thermal management refers to the use of reasonable cooling and heat dissipation technology and structural optimization design for the heat consuming components and systems in packaging to control their internal temperature and ensure the normal reliability of electronic equipment and systems. The purpose is to dissipate the heat in various ways to keep the temperature of the package within the allowable range.
UVLED technology is still in its infancy, and the biggest challenge is the thermal management of UVLED. Like any electronic component, LEDs are very sensitive to heat. Uvleds have extremely 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, its service life will be shortened or even can not be used.
254nm is the best wavelength for sterilization, which is a misunderstanding, because the peak wavelength of low-pressure mercury lamp (only determined by the physical characteristics of the lamp) is 253.7nm. In fact, as mentioned above, a certain range of wavelengths has bactericidal effect. However, the wavelength of 265 nm is generally considered to be the best because it is the peak of the DNA absorption curve. Therefore, UVC is the most suitable strip for sterilization.
Like any electronic component, uvleds are thermally sensitive. Uvleds have low external quantum efficiency. Generally, less than 5% of the input power is converted to light (at present, it is said that the efficiency of industrial products of relevant manufacturers has exceeded 5%), while the remaining more than 95% is converted to photothermal. This can cause the UVC LED chip to generate extremely severe heat. At this time, if the heat can not be removed quickly and the LED chip can not be kept below the maximum operating temperature, the life and reliability of UVC LED will be directly affected, or even can not be used.
The optical 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 larger the irradiation distance is, the larger the dynamic demand is and the larger the optical power is.
With the expansion of UVC LED market, manufacturers need to consider new ways to deal with this challenge. Now, the problem is how to deal with the high heat demand of UVLED, while ensuring that the components remain cost-effective, durable and resistant to the wear of UV light source itself. Due to the small size of UVC led, most of the heat can not be dissipated from the front, so the back of LED becomes the only way to effectively dissipate heat. The task of improving heat dissipation has shifted to downstream packaging and modules. At this point, how to do a good job in the packaging process of thermal management is particularly important.
The light output angle of the lamp bead with a plane lens is usually 120-140 ° The optical output angle of the package with spherical lens is 60-140 ° Adjustable between. In fact, no matter how large UVC LED is selected, enough LEDs can be designed to completely cover the required sterilization space. In the scene which is not sensitive to the sterilization range, a smaller light output angle can make the light more concentrated, thus shortening the sterilization time.
Therefore, PCB with LED must have high thermal conductivity. For visible LED, it is usually 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 ultraviolet (especially UVC) can degrade organic substances, such as epoxy resin, which can greatly shorten the service life of metal substrates in ultraviolet applications. The only viable alternative is to use electronic grade ceramics.
With the further expansion of UVLED market, manufacturers need to consider new ways to deal with this challenge. Now, the problem is still how to deal with the high heat demand of UVLED, while ensuring that the components remain cost-effective, durable and resistant to the wear and tear of the UV light source itself. UVC disinfection technology realized by LED can bring real change effect. In the development of industry, we need to ensure that we can overcome the thermal challenges faced by UVLED.
Although LED can be seen everywhere in our life, there are still some deficiencies in LED, which need our designers to have more professional knowledge, so as to design products more in line with the needs of life.