UVC LED application encounters the thermal management challenges British company developed countermeasures of breaking industry problems

The British Cambridge company Nanotherm John Cafferkey said, before there is a saying that "the heat generated more than light, now it also summarizes the UVC LED facing the growing market of the" heat challenge". At present, UVC LED is mainly used for medical equipment, water and other daily consumer goods disinfection.

UVC originated in the early twentieth Century, when the first batch production of mercury lamp.

The ultraviolet emission lamp used for the disinfection of drinking water in 1910. However, the prototype plant because proved to be unreliable, so shut down.

In 1950s, UVC water treatment system is a new trial, by the middle of 1980s, there were about 1500 factories in europe.

In addition to water treatment, UVC used a series of applications, including cleaning of medical equipment and hospital room air conditioning system for disinfection to prevent pathogen proliferation.

Although mercury vapor lamp is very effective in these large-scale applications, but the lamp is very fragile, and the use of dangerous mercury means that they are not suitable for applications more portable and environmentally friendly.

In recent years, LED manufacturers to develop a more effective UVC LED. Although not as good as UVA LED (for curing ink and paint) is less effective, but they can be used for low power applications.

Therefore, industry analysts believe that UVC LED will be the next few years rapid development. This boom is UVC application LED is a portable UVC, consumer friendly in creating a market. For example, consumers will buy a portable disinfection "magic wand", they can be used for disinfection of daily necessities, such as intelligent mobile phone, tablet or computer keyboard.

Manufacturers of consumer goods can be LED UVC technology embedded in the products of self disinfection. For example, after the toothbrush on the shelf, can carry out automatic disinfection; can press the button, it can automatically sterilized baby bottles; when in use, the tap can to sterilize the water. These possibilities are endless.

The potential to save lives

However, some of the more in-depth application of UVC is of concern. Portable sterilizing bottle can provide clean drinking water to the citizens of developing countries need to improve, when drinking, can disinfect water. This is especially valuable in some areas, such as no centralized disinfection of water infrastructure in the area, or you can quickly provide safe water areas.

In addition to new applications, and even hospitals (UVC in the hospital has been used for many years) can benefit. Worldwide, more than 700 thousand patients per year when infected, 75000 people died. UVC technology can be embedded in medical devices, such as a scalpel and stethoscope, can be sterilized in a few seconds.

UVC LED has the potential to disinfection ability of UVC into the mass market, may have a significant impact on public health.

Heat challenge

The technology is still in its infancy, one of the challenges is the thermal management of LED UVC. Like any electronic components, LED is sensitive to heat.

UVC LED has a particularly low external quantum efficiency (EQE) - they are only about 5% of the input power will be converted into light. The remaining 95% of the power is converted into heat, heat must be removed rapidly, in order to maintain the maximum working temperature is lower than the LED chip. If there is no time to LED chip cooling, will shorten the service life, can not even use.

With UVC LED more powerful, manufacturers need to consider new ways to deal with this challenge. Now, the problem is still high demand how to deal with UV LED, at the same time ensure cost-effective, durable, resistant component wear UV light source itself.

Because UV LED is too small, a large amount of heat can not spread from the surface, so the only way to make effective heat discharge through the LED back. The heat must be derived from the LED chip through the PCB module, arrive at the heat sink, and then released into the atmosphere.

Heat the problem is PCB

The installation of the LED PCB must have high thermal conductivity, the visible light LED is usually a metal base printed circuit board (MCPCB). However, these are not suitable for UVC applications. MCPCB consists of a piece of metal (usually made of copper, aluminum or copper) circuit layer with a layer of dielectric layer, a conductive epoxy resin but electrically insulating composition.

Epoxy dielectric MCPCB can be used for visible light based applications, but UV (especially UVC) will degrade the organic material such as epoxy resin, MCPCB and UV in the application of life significantly decreased. The only viable alternative is the use of electronic grade ceramics.

Among them, aluminum nitride (AIN) has excellent thermal conductivity (140W/mK-170W/ mK), but it is very expensive. Alumina (Al2O3) is a more cost-effective alternative, but did not provide the required rate of thermal conductivity UV LED (20W/mK-30W/mK). At the same time, both of which are very fragile and easily damaged, which means they are not easy to use screws, and are not suitable for the application of more powerful.

The alternative is nano ceramic with sputtering layer circuit. The thermal conductivity of more than 150 W/mK rate, and the heat in the desired range.

The electrochemical oxidation of British Cambridge (ECO) Nanotherm using patented technology, using this method will change the surface of aluminum into alumina micron thin ceramic (Al2O3).

Alumina (Al2O3) ceramic layer as a dielectric between the circuit and the top of aluminum. The ECO production process of alumina ceramic layer is very thin, so the heat can pass easily, so it has better thermal conductivity.

The thin film processing or sputtering step follows ECO process, directly to the copper circuit layer attached to the nano ceramic dielectric, to further improve the thermal efficiency. Because there is no use of organic epoxy resin at any stage, so