From - Thu Nov 06 23:21:12 1997 From: "Ken Farmer" Subject: Re: PCBoard fabrication question Newsgroups: sci.electronics.basics,sci.electronics.cad,sci.electronics.components,sci.electronics.misc,sci.electronics.repair References: <345E3065.4680@concentric.net> Message-ID: <01bceb34$e18e08e0$64c8c8c8@p166> X-Newsreader: Microsoft Internet News 4.70.1161 NNTP-Posting-Host: 166.72.198.72 Date: 7 Nov 97 04:23:59 GMT Lines: 61 Path: news.bc!News1.Vancouver.iSTAR.net!news.istar.net!newsfeed.direct.ca!newsfeed.internetmci.com!165.87.194.248!newsm.ibm.net!ibm.net!news1.ibm.net!166.72.198.72 Xref: news.bc sci.electronics.basics:4038 sci.electronics.cad:1402 sci.electronics.components:3359 sci.electronics.misc:3547 sci.electronics.repair:8764 Amy Torelli wrote in article <345E3065.4680@concentric.net>... > Hello all, > > I am trying to find a technique to transfer a circuit board layout > printed by my laser printer onto copper clad. I sometimes get > satisfactory results feeding aluminum foil into my laser printer then > using a hot iron to transfer the image onto the copper clad. I have tried every press on, peel off, iron on, spray on, toner transfer trick that everyone has come up with and they are all lousy. I finally decided that if I was going to make good PCBs then I would find out how they are really made. A little research and a trip to a big city and I was in the PCB hobby. Find a PCB supplier and get a roll of DuPont RISTON film. This is the stuff that motherboard companies use so it is the real McCoy. This is usually ironed on to the blank board with a machine, but you can get very good results with a hand held hot air blower like the model airplane builders use. The film can be handled under a bright yellow light. Cut a piece of film large enough for the board, strip the backing off of the film making sure that it doesn't fold over and stick to itself. Place it on the board and smooth out all of the wrinkles. Using about a 212 degree setting, blow hot air on the board and iron the film with your fingers or with a print brayer roller (from your local print shop). You now have a board ready to expose. Place your negative on the board, then place over it a thin sheet of glass, like from a picture frame, and expose it to a bright white light. I use a mercury vapor lamp like the one that you use outside on a pole. You will have to determine the exposure based on the intensity of your lamp. If you get a soft resist when developing, you have not exposed long enough. After exposure, you can develop it in a solution of baking soda or some other alkaline solution. I bought five gallons of developer while I was there. Don't remember what it cost but it wasn't much. At a recommended dilution of 44 to 1 I should have enough to last to about the year 2035. Properly developed, the resist is very hard and almost damage proof. It will also hold very fine lines, something that I never could get with toner transfer methods. (How does two traces between each DIP pin in addition to the traces going to the pins grab you?) Etch with your favorite chemical. Scrub off the resist with steel wool. Or, using the easy method, place a very small amount of sodium hydroxide from your local grocery store into a pan, drop the board in, and heat to almost boiling. The resist peels off in a minute or so leaving bright copper behind. Note, that everything else above is non-toxic, but I would be real careful about handling boiling lye. Outside would be a good idea if you don't have an area that you can control access to. I use PADS PCB for my artwork and a Lexmark laser for the transparencies. ken+farmer@technologist.com Ken Farmer remove the antispam + for a valid address