It's the best and most accurate way to make a good board. Especially when dealing with very fine 10mil tracks. Nothing comes close to photoetching, even for prototyping 3#-) Adios, LarZ ------------------- TAMA - The Strongest Name in Drums -------------------- -----Original Message----- From: richard skinner [SMTP:rwskinner@WORLDNET.ATT.NET] Sent: Thursday, January 29, 1998 1:32 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: New PCB etching technique... I use the GC Electronics Positive Boards, a Laser Printed Transparency, and a standard Heat Lamp for like in Bathrooms. I set my heat lamp 11" from the Transparency, I expose for 90 seconds, drop the board in developer for 2 to 3 minutes, then Etch. I would say my success rate is 99.5% and I do get two traces between each Ic Pin with .100 spacing. I'm not using the "suggested" Light, but this one is quick! When first learning, which I just did a couple of months ago, I bought 1 4"x6" board and cut it into 4 sections. I experimented with exposer time and distance on each section until I found the results I wanted. The Only thing I can suggest about this, is when you use a larger board, raise the light so you have an even intensity over the entire board. I found in "my" testing that 5 seconds addition exposer for every inch above the 11" work fine. My first board was a single sided 4x6 with 6 16 pin dips, 2 40 pin dips, and 2 18 pin dips. I had 10 traces running vertical under each 16 pin dip (.300 wide) and had Zero problems. If I remember right, they are .010 traces with .010" between, with some to spare around the ic pads, not bad? The GC Boards are Postive Coated and are a little more than bare copper, but much less than alot of other brands. They are readily available (here anyways) and have a foil bag and a protective liner stuck to them. It makes them easy to cut in regular light with exposing the entire board. Just my experiences..... Richard Skinner rwskinner@worldnet.att.net http://home.att.net/~rwskinner ---------- > From: Wynn Rostek > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: New PCB etching technique... > Date: Wednesday, January 28, 1998 1:59 PM > > At 11:35 AM 1/28/98 -0500, you wrote: > > >I have a question regarding this whole thread: I have tried using the > >special paper that you print onto using a laser printer and then "iron" on > >to the board, and I have had very little luck > > I have tried (over the years) the following: > > > Plotting directly on the PCB with various resist pens. > > This worked fine for wide traces on small boards. I had problems with > larger boards, which I suspect could be cured by going to a flat bed > plotter. (I have purchased one, but have no documentation on it so far. Sigh) > > > Press-N-Peel (A forerunner of TEC-200) > > This was just a mylar sheet with teflon on it. Toner would not stick to it > very well. Never really had any luck with this at all. > > > TEC-200 (The blue stuff) > > I had problems at first with the toner sticking to the PCB. I bought a > laminator that is sold with the Eagle Design stuff, and used the laminator > to apply the blue stuff to the PCB. Not too bad. You can get some fairly > narrow traces. The big problem is that the toner tends to smear towards the > end, which limits the size board you can do. I suspect you can run up to 8" > by 5" with this set up. > > > PrintGoCo > > This is a small silk screen set up for doing screen printing at home. I > used up two batches of supplies (10 screens total) figuring out how to get a > good clean master screen. They supply a filter sheet that you are supposed > to use when exposing a laser printer/copier. This is a thermal unit, they > use two very large flash bulbs to heat the carbon in a special ink, or the > toner. A thin plastic film on the screen melts. The problem I kept running > into was some of the toner kept sticking to the master, and that portion > would not print. I found that by running the laser printer copy through the > laminator, with a plain sheet of paper over it, would fuse the toner enough > to allow production of a good master. The screen appears to be way under > 100 threads per inch, so I suspect you would not be able to run more than > one trace between .1" pads. The ink supplied with the unit is good for > printing on paper, but does not work for PCBs. I suspect this system may > turn out to work fairly well for small runs (10-100) 3" x 5" PCBs once I > find a suitable ink. > > (The unit costs about $125 US and comes with enough supplies for 5 masters.) > > > Gel Paper (Sugar Paper) > > A lot like the blue stuff, except that the paper coating dissolves in water. > I don't I would try this without the laminator. I found getting good toner > adhesion fairly tricky. > > > Still to try: > > Photo exposed silk screening. Speedball makes a small screen printing set. > I have actually finished getting the screen preped. (You have tape the > edges and shellac them, and then bolt the screen to a hunk of plywood. The > speedball screen appears to have about 200 threads per inch. You coat the > screen with a compound, and then expose the screen. I have not yet come up > with an exposure box, but I may be able to do this in the net couple of months. > > The nice thing about this approach is the board size you can work with. I > purchased a 300 thread per inch 30" by 24" screen in Orlando for less than $50. > > If you allow the developed screen to sit around for a few days, the pattern > becomes fairly permanent. Not really bad if don't mind spending $20-$25 for > a pattern you want to keep around and print once in a while. > > As always, I'll try and keep everyone posted. > > > If anyone could get me the information on where to buy the copper sheet, I'd > like to try laser printing on it, and plotting on it directly. > > Anyone have additional information on Home PCB fabrication they don't mind > sharing? Might save me a little time and money. :-) > > Wynn Rostek