UV LEDs had their ‘day in the sun’ this year, due to being used by many companies to perform UV surface sterilization, but they’re really useful for many scientific purposes and its great to see these LEDs make it into a binned, surface mount, high current package.
UV LEDs, are as you can expect, are LEDs that emit light in the UV band, which ranges from 10 to 400nm. Note that visible light is 400~700nm so the range of the UV band is quite wide. UV light is ‘higher power’ than visible light – it’s what is emitted from the sun that gives us sun burns, it is also mutagenic – so wear that sunscreen!
Because there isn’t a lot of it on Earth, but it can affect chemical bonds, it’s very useful for when we want to control a chemical reaction such as UV curing or disinfection or bleaching, with pinpoint control. For example, 3D resin printers use UV lenses or lasers to selectively cure layers of a print with high precision – called stereolithography. It’s also very popular in dentistry where hard composite resins are UV-cured quickly and safely.
We first started using UV lamps when doing in-house PCB etching at school – at the time we used a 15W UV fluorescent bulb.
If you like getting your nails done with a strong and durable polish, you’re probably familiar with using a UV lamp to cure a gel manicure in a minute or two.
Now, historically, folks have used UV fluorescent bulbs for getting UV light, but these are becoming less common in many use cases because UV CCFLs are cheap, but are delicate (made of glass), are physically large and hard to focus on a small area, dim over time, are hard to dispose of (they often contain mercury or other metals), require a complex ballast/driver, and can take a while to warm up. In contrast, UV LEDs are a great alternative with better precision, long life, and easy driving.
These UV LEDs from Broadcom are ‘true’ UV LEDs, and come binned for three different center frequencies: 365nm, 385nm and 395nm. When buying low cost LEDs, they often have some variation which can reduce efficiency in the desired band. And of course, the band has to be aligned with whatever you’re curing or disinfecting. These would do the job admirably whenever you want a durable, long-lasting UV source with exactly the right emission spectrum, particularly when small space and high efficiency such as a battery-operated device is concerned.
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