Which UV tubes to use for UV Exposure Box

Hi,

I am building a UV exposure box here. Need some help here.

I found out that there are three types of UV tube available in the market.

1)Black light which is used to check notes(dollar) and used for clubbing. It is in black color when off.

2)This one is used to attract flies, look like fluorescent light. When light on, it will emit light purple color ray.

3)The third one is used to kill germs in the water, which is known to be emit UVC and is harmful for eyes.


Which one should I use?

You want a wavelength in the region 360-400nm, that is in the near end of UVA. The Microtrac brand that I use works with UV from 360-450nm.

'Black light' tubes are variable depending on design so check their wavelength. There used to be a consensus that the cheap 'black light' tubes were not very good for PCB use though.

I don't know what wavelength the fly attracting ones are exactly, again 'it depends', but they are not 'black' simply because they do not have a filter to block the visible light that all these tubes give off. Without that, they will probably give more UV output than the above, so might be better. More like the tubes actually sold for PCB's like I bought. Maybe the same!

You definitely do not want the germicidal UVC tubes, although they are useful for erasing old UV-erasable EPROMS. I use them for keeping my pond clear of algae.

A lot of people are now using UV LED's (which can be had around the 380-400nm range). If you source these cheaply, it can work out less expensive than fluorescent tubes especially by the time you've had to replace the tubes once or twice. It also has the benefit that you can buy narrow-beam (like 10-20 degree) LED's which help getting fine traces on the board. The wide 360 degree beam from tubes undercuts the transparency.

I've made two UV-tube UV boxes in the past (a double sided one in an MDF case and a single sided one in an old scanner case) but would definitely use UV LED's if I ever made another.

xylon89del said:

Hi,

I am building a UV exposure box here. Need some help here.

I found out that there are three types of UV tube available in the market.

1)Black light which is used to check notes(dollar) and used for clubbing. It is in black color when off.

2)This one is used to attract flies, look like fluorescent light. When light on, it will emit light purple color ray.

3)The third one is used to kill germs in the water, which is known to be emit UVC and is harmful for eyes.


Which one should I use?

Click to expand...

1) Lower UV radiation than 2

3) DO NOT USE. Those are Short Wave UV producing tubes (~270 nm). Short Wave UV is fully absorbed in atmosphere and does not reach Earth's surface, that's why these tubes are used for killing germs (by destructing of their genetic material). They MAY and CAN damage your retina if you are staring at them, an the damage is irreversible, i.e. PERMANENT.

I use Philips TL20W/09N (you ban see my 'contraption' at https://zastos.com/wp), these are declared as lamps for photo reprography.

Another useful resource is this link:
https://www.electricstuff.co.uk/pcbs.html
(Page-down a little bit, to the 'Exposure' section). According to that:
The tubes you want "look white when off (just like normal white lamps), and light up with a light purple, which makes flourescent paper etc. glow brightly. DO NOT use short-wave UV lamps like EPROM eraser tubes or germicidal lamps, which have clear glass - these emit short-wave UV which can cause eye and skin damage, and are not suitable for PCB exposure"