I'd like to make a custom PCB, and the UV exposure method sounds more reliable toner transfer. I'm doing it on the (super) cheap though, and already have an old UV tube from a house party. Is this enough to expose the board? Even if I have to leave it under it for 10x as long as a proper light box, would it get there in the end?
Also, is there any downside to overexposing. i.e. presumably the light can't get through the tonor at all, so I could just expose it for several hours?
I just use a BLB CFL (compact florescent black light bulb from wal mart) in a box for 10 minutes at about four inches away. I can't remember the wattage, but its fairly low. Works perfect. I have used Injectorall and MG Chemicals positive coated PCBs with success this way.
Just to throw this out there. I tried mounting a light on the bottom and on the top with a sheet of clear acrylic (about 1/16" thick) to set my frame on to expose double sided boards at the same time. Found out the hard way the the acrylic I have blocked the needed wavelengths at certain angles and didn't expose the bottom layer properly. Now I just do one side at a time until I get a plate of clear glass.
Also good to test small pieces until you get it worked out as not to ruin an entire pcb.
Dave