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#1
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Has anyone home brewed a UV exposure box for making PC boards ?
I've got a couple of 8w UV tubes & a 0-30min timer and looking at pictures of commercial designs I think all I have to do is: 1. Mount the tubes & timer in a light proof box. 2. Fix a sheet of glass 1-2" above them to act as a flat mount for the photo sensitised PC board & photo master. 3. Fix a mask to the glass, blanking off all but a working area directly above the UV tubes. 4. Make a lid for the box & fit a foam pad inside it that'll press the PC board and master firmly down onto the sheet of glass thus stopping those sneaky photons from getting round the corners of the PC master. Is it as simple as this or am I missing something blindingly obvious ?? Is 1-2" a suitable spacing between the tubes & glass plate & will normal, thin, glass sheet be suitable ?? -- Dick GM0MNL Fra' Auld Reekie |
#2
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On Fri, 28 Nov 2003 16:30:48 +0000, Dick
wrote: Has anyone home brewed a UV exposure box for making PC boards ? I've got a couple of 8w UV tubes & a 0-30min timer and looking at pictures of commercial designs I think all I have to do is: 1. Mount the tubes & timer in a light proof box. 2. Fix a sheet of glass 1-2" above them to act as a flat mount for the photo sensitised PC board & photo master. 3. Fix a mask to the glass, blanking off all but a working area directly above the UV tubes. 4. Make a lid for the box & fit a foam pad inside it that'll press the PC board and master firmly down onto the sheet of glass thus stopping those sneaky photons from getting round the corners of the PC master. Is it as simple as this or am I missing something blindingly obvious ?? Is 1-2" a suitable spacing between the tubes & glass plate & will normal, thin, glass sheet be suitable ?? Basically, you are right, it is relatively simple. Some standard glass will not pass certain bands of UV. Test first (put a sliver of the glass partially over some sensitized material for a standard exposure time and note any difference.) You may not need the glass if the mask adheres well to the substrate. You want enough spacing to get reasonably even coverage, but too much will increase exposure time. Consistency is more important, so you can develop a standard timing for the unit. Consider mounting the lights to face down, as a safety precaution. Also, you might add a microswitch and relay to prevent your box from lighting up with the cover open. This would be a lot worse for your eyes than a photocopier. Happy trails, Gary (net.yogi.bear) ------------------------------------------------ at the 51st percentile of ursine intelligence Gary D. Schwartz, Needham, MA, USA Please reply to: garyDOTschwartzATpoboxDOTcom |
#3
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On Fri, 28 Nov 2003 16:30:48 +0000, Dick
wrote: Has anyone home brewed a UV exposure box for making PC boards ? I've got a couple of 8w UV tubes & a 0-30min timer and looking at pictures of commercial designs I think all I have to do is: 1. Mount the tubes & timer in a light proof box. 2. Fix a sheet of glass 1-2" above them to act as a flat mount for the photo sensitised PC board & photo master. 3. Fix a mask to the glass, blanking off all but a working area directly above the UV tubes. 4. Make a lid for the box & fit a foam pad inside it that'll press the PC board and master firmly down onto the sheet of glass thus stopping those sneaky photons from getting round the corners of the PC master. Is it as simple as this or am I missing something blindingly obvious ?? Is 1-2" a suitable spacing between the tubes & glass plate & will normal, thin, glass sheet be suitable ?? Basically, you are right, it is relatively simple. Some standard glass will not pass certain bands of UV. Test first (put a sliver of the glass partially over some sensitized material for a standard exposure time and note any difference.) You may not need the glass if the mask adheres well to the substrate. You want enough spacing to get reasonably even coverage, but too much will increase exposure time. Consistency is more important, so you can develop a standard timing for the unit. Consider mounting the lights to face down, as a safety precaution. Also, you might add a microswitch and relay to prevent your box from lighting up with the cover open. This would be a lot worse for your eyes than a photocopier. Happy trails, Gary (net.yogi.bear) ------------------------------------------------ at the 51st percentile of ursine intelligence Gary D. Schwartz, Needham, MA, USA Please reply to: garyDOTschwartzATpoboxDOTcom |
#4
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Glass could stop UV? Depends on the ingredients. Some are OK, others are
not. Some plexiglass does not transmit UV either. Some types are formulated for outdoor use and have a built in UV filter. Check with a piece of white cotton if it fluorescenses (cheapo UV indicator) Wim |
#5
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Glass could stop UV? Depends on the ingredients. Some are OK, others are
not. Some plexiglass does not transmit UV either. Some types are formulated for outdoor use and have a built in UV filter. Check with a piece of white cotton if it fluorescenses (cheapo UV indicator) Wim |
#6
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![]() Dick wrote: Has anyone home brewed a UV exposure box for making PC boards ? I've got a couple of 8w UV tubes & a 0-30min timer and looking at pictures of commercial designs I think all I have to do is: 1. Mount the tubes & timer in a light proof box. 2. Fix a sheet of glass 1-2" above them to act as a flat mount for the photo sensitised PC board & photo master. 3. Fix a mask to the glass, blanking off all but a working area directly above the UV tubes. 4. Make a lid for the box & fit a foam pad inside it that'll press the PC board and master firmly down onto the sheet of glass thus stopping those sneaky photons from getting round the corners of the PC master. Is it as simple as this or am I missing something blindingly obvious ?? Is 1-2" a suitable spacing between the tubes & glass plate & will normal, thin, glass sheet be suitable ?? I made my own from three pieces of MDF, some wood strips and a sheet of glass. It's got the tubes etc. in the MDF base and two upright pieces of MDF with two strips of wood acting as a shelf for the glass, about 9" above the tubes, to give a bit of collimation. Glass is quite transparent to the long-wave UV used for PCBs. I just put a book on top of the board to press it down when exposing. I keep meaning to make a proper lid with a foam pressure pad, but can't really see the point as I don't use it much. It's some distance away, so I'm not bothered about getting sunburnt. 8-) Leon |
#7
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![]() Dick wrote: Has anyone home brewed a UV exposure box for making PC boards ? I've got a couple of 8w UV tubes & a 0-30min timer and looking at pictures of commercial designs I think all I have to do is: 1. Mount the tubes & timer in a light proof box. 2. Fix a sheet of glass 1-2" above them to act as a flat mount for the photo sensitised PC board & photo master. 3. Fix a mask to the glass, blanking off all but a working area directly above the UV tubes. 4. Make a lid for the box & fit a foam pad inside it that'll press the PC board and master firmly down onto the sheet of glass thus stopping those sneaky photons from getting round the corners of the PC master. Is it as simple as this or am I missing something blindingly obvious ?? Is 1-2" a suitable spacing between the tubes & glass plate & will normal, thin, glass sheet be suitable ?? I made my own from three pieces of MDF, some wood strips and a sheet of glass. It's got the tubes etc. in the MDF base and two upright pieces of MDF with two strips of wood acting as a shelf for the glass, about 9" above the tubes, to give a bit of collimation. Glass is quite transparent to the long-wave UV used for PCBs. I just put a book on top of the board to press it down when exposing. I keep meaning to make a proper lid with a foam pressure pad, but can't really see the point as I don't use it much. It's some distance away, so I'm not bothered about getting sunburnt. 8-) Leon |
#8
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Thanks for all suggestions, think I've enough info to get the project
finished. -- Dick GM0MNL Fra' Auld Reekie |
#9
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Thanks for all suggestions, think I've enough info to get the project
finished. -- Dick GM0MNL Fra' Auld Reekie |
#10
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