The continuous warming of UVC LED makes the market hot. Everyone knows that UVC LED has a significant sterilization and disinfection effect. Under a certain dose and distance, it only takes a few seconds to tens of seconds to kill common bacteria.
Due to the small size of UVC LEDs, most of the heat cannot be dissipated from the surface, so the back of the LED becomes the only way to effectively dissipate heat. At this time, how to do a good job of thermal management in the package joint is particularly important.
In terms of materials, after years of development, UVC LEDs currently on the market are basically based on flip-chip solutions with high thermal conductivity aluminum nitride substrates. Aluminum nitride has excellent thermal conductivity, can withstand the aging of the ultraviolet light source itself, and meets the requirements of high thermal management of UVC LEDs.
In terms of process, there are currently several die bonding methods on the market. The first is to use silver paste. Although this method has good binding force, it is easy to cause silver migration and cause device failure. The second method is to use solder paste soldering. In this method, since the melting point of the solder paste is only about 220 degrees, after the device is mounted, the melting phenomenon will occur again after the device is mounted again, and the chip is easy to fall off and fail, which affects the reliability of the UVC LED. Therefore, the third type of die bonding method is mostly adopted on the market: using Au-Sn eutectic soldering. Compared with the first two die bonding methods, eutectic welding is mainly performed by flux, which can effectively improve the bonding strength of the chip and the substrate, and the thermal conductivity is more reliable, which is conducive to the quality control of UVC LEDs.
UVC ultraviolet is a kind of invisible light, and it is also a kind of high-energy non-radiative rays. Depending on the wavelength, it has different energy and penetration capabilities. At present, there are mainly three types of ultraviolet rays that are widely used by human industry, namely short-wave ultraviolet (uvc, wavelength 100-280 nanometers); medium-wave ultraviolet (uvc, wavelength 280-315 nanometers) and long-wave ultraviolet (uva, wavelength 315-450) Nano).
Among them, the longer the wavelength of ultraviolet light, the stronger the penetrating power, the greater the lethality to living beings. So in theory, the sterilization effect of long-wave ultraviolet or ultra-long-wave ultraviolet is the strongest, and the sterilization effect of short-wave ultraviolet is the weakest among these three. But everyone, please pay attention to the term "destructive power to living things" that I just mentioned.
The strong sunlight that can cause skin cancer is high-power ultraviolet lamps used in hospital disinfection. These are long-wave or ultra-long-wave ultraviolet rays. These extremely high-energy rays can cause irreversible and genetic damage to all organisms. This is why the ultraviolet disinfection rooms of all hospitals are forbidden to enter for a period of time after the disinfection is completed.
