DavidBanner Posted March 25, 2007 Report Posted March 25, 2007 I bought a small UV lightbox off ebay a while ago and last night was the 1st time I got a chance to fire it up and test it. Keeping in mind I've never used the UV PCB method, can someone please give me some advice.It's one of these http://rswww.com/cgi-bin/bv/rswww/searchBrowseAction.do?D=uv%20pcb&Nr=AND%28avl%3auk%2csearchDiscon_uk%3aN%29&Ntk=I18NAll&Nty=1&Ntt=uv%20pcb&Dx=mode%20matchpartial&Ntx=mode%20matchpartial&N=0&name=SiteStandard&forwardingPage=line&R=0555279&callingPage=/jsp/search/search.jsp&BV_SessionID=@@@@0984123078.1174819839@@@@&BV_EngineID=ccccaddkhijjihkcefeceeldgondhgf.0&cacheID=uknetscapefrom RS / Maplin / Mega with 2 x 8 watt tubes.The artwork transfers fine in some places on the PCB, but towards the edges the tracks thin and disapear. I checked the location of the tubes and it seems like the artwork directly over the tube is the best and the stuff at the middle edge between the 2 tubes suffers (PCB is 1/3 of the width of the exposure area).So I put this down to an underexposure issue, but:Mega recommend a 3:30 exposure time. I've tried everything from 2:30 - 5 mins at 30 sec intervals. I got the best result at 3:30, but the 1st time I tried it at 3:30 it was rubbish.My guess at the moment is that the tubes are past their useful life - what say you, the good people of uCapps?I'm using the Seno applicators to develop & strip - any tips using those would be great too! Is it me or is it possible to rub off the exposed photoresist with the developer applicator? Or is this an idication of under/overexposure?I've noticed that the manual says diffusion occurs at the edges of the artwork, so I've fattened up all my tracks, esp at the edges and I'll do another batch today to see what gives... Quote
DavidBanner Posted March 27, 2007 Author Report Posted March 27, 2007 I tried the fatter tracks but still big problems, I'm on a 10:1 ratio of failed boards to "good" pcbs (which even then I have to fix some broken tracks).any suggestions would be very much appreciated.... Quote
stryd_one Posted March 29, 2007 Report Posted March 29, 2007 *bump*Sorry I can't help cause I don't DIY my PCB's... Maybe someone else has some tips? Quote
DavidBanner Posted March 30, 2007 Author Report Posted March 30, 2007 ah-ha!!found the problem...it was down to a dodgy batch of photoboard - tried some new cheaper stuff from Mega and it's all cool and groovey now...As a side note to anyone thinking of starting out with UV - I'm having great success, but the best tip is to use the "Value" photoboard, it's cheaper, works better (in this case anyway or at least the same) and you can cut it with a stanley knife - I was having major dramas cutting the other stuff.... Quote
audiocommander Posted March 30, 2007 Report Posted March 30, 2007 Hi David,I never did PCB exposures, but I'm working as Designer and therefore I know something about printings and films. Your issue (thinning at the edges) sounds like the light is "straying"; if your paths are getting thinner that means there must be some tiny light-particles entering the space between your sheet and the PCB. Sometimes the thickness of the transfer-medium is enough to be the reason for this, so normally the medium-print is mirrored to enable a tight connection without any gaps.Cheers,Michael Quote
DavidBanner Posted March 30, 2007 Author Report Posted March 30, 2007 cheers for the tip Michael, I'm already on that - ink is in direct contact with the board...some tiny light-particlesextra small photons eh? mmm, the tricky bastards, I was only making provisions for the large kind... ;)but as said b4, the problem is sorted - it was a moody batch of PhotoBoard, or possibly down to me not storing correctly - has been hanging around for a few months Quote
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