I read up on techniques for making PCB's, there is a process that uses a laser printer or copy machine and photo paper. It sounded like there were a good number of people having some success with the process, so I thought I'd give it a try. I should go back a little I guess, and describe the path I took to get to where I am now.
The first thing I did was to buy some copper clad fiberglass board and some ferric chloride. The blank board has a thin copper film on one side, and bare fiberglass on the other side. The idea is to get the circuit pathways drawn on the copper with a material that resists the chemical etching later. The ferric chloride will quickly eat away (etch) the thin film of copper and leave the resisted areas, or circuit pathways. I bought a pack of transfer film, you could rub off the transfer to the copper board, and the transfer would resist the etching. This really did work great, but boy was it slow. It took about 30 minutes just to get all those transfers rubbed off. Not a big deal if your only doing one once in a while. But not good if you're doing a number of them. Then, there is always the chance you forget a trace somewhere, and the circuit doesn't work.
I had read about an etch resistant pen, sounded like a good deal. Just draw your traces on the board with the pen, etch away the rest of the copper any you're done. So I ordered a couple of the pens and gave it a try. Problem is, the pen is really hard to work with on the tiny traces around an IC chip. And the resist ability of the pen wasn't very good, leaving some of the traces open. And again, it was fairly time consuming, left chances of error and didn't look very good either.
So I decided to give the photo paper/laser printer a try. I didn't have a laser printer, but a friend of mine has a copier. Copiers and laser printers use toner as opposed to ink, the toner has plastic particles in it and the plastic particles are melted to the paper as it goes through the fuser in the machine. Ink jet printers won't work, because they use ink rather than toner.
So I designed my timer circuit in a photo editing program and printed the circuit on regular paper using my ink jet printer. Then went to my friends house and made a copy on glossy photo paper in his photo copier. Back home, I cut out the circuit, using a clothes iron on it's high setting I applied heat to the image as it laid on a piece of the copper board. The idea is to remelt the toner, this time leaving it on the copper rather than the paper. Once the image was on the copper clad board, I soaked it in warm water to remove the paper. It took forever to get the paper off the board, and when it finally was all peeled and scrubbed off, the circuit traces were all pretty much gone too.
I did manage to make a couple of PC boards that way. But they needed to be repaired with jumper wires where the traces were missing. One of the web sites I visited had said of all the papers he tried, Staples brand photo glossy paper worked the best. So I decided to pick some up and try that, hoping for the best. While I was at Staples, they had nice little Lexmark E238 laser printer at a good price. It was kind of a crap shoot, not knowing if this laser printer would do the job or not. But, I really could use a faster printer anyway, and for volume printing a laser printer is the way to go. So I headed out the door with a new laser printer and a box of paper under my arm, billfold lighter as well, I sure hope this works...
Once I had the printer set up, I ran off a sheet of the timer circuits, cut one out, and warmed up my iron. I clean the copper side of the board with a mild abrasive pad to clean it and slightly rough up the copper surface. Dry it, and don't touch the copper surface before applying the transfer. I'm using a sheet of transfer release between the iron and the paper, I don't know if that's needed, but it seemed like a good idea. I held the heat on the transfer for about 1 minute, then dropped the board into warm water. After about 30 seconds I couldn't resist taking a look at the board. To my utter amazement, the paper peeled right off, leaving the toner on the copper with flawless traces.
A little light rubbing with a soft sponge removed what little paper that had stuck to the toner transfer. I've been using ferric chloride to etch the boards once printed, although there are other chemicals that could be used. About 1/4" solution in the bottom of a plastic or glass container is all that's required. Some agitation is needed to keep fresh solution moving over the copper, in about 15 or 20 minutes the newly made PCB is then rinsed in fresh water. To clean the toner/resist off the traces, I found acetone works the best. I use a Q-tip and the toner brushes right off.
Drilling the tiny holes through the board proved most challenging. I had a couple of small high speed steel drill sets that do work. But it's slow going and the bits break or bend easily. I've got a new set of carbide bits on the way now, which are designed to drill pcb's, while brittle, they should work better. I'm going to set up my high speed rotary tool in a drill press for more precision drilling.
Click Here for a JPEG file of the timer circuit. You can print this out at 1:1 size and should fit on a 1.5"x1.5" board. Just make sure you use a photo editing program and print it actual size.
My original timer page is Here.
The timer can be purchased as a kit from the Products Page.
Instructions on assembling the timer kit are Here.
