A while ago (in sixth grade) I built a rocket launch controller exclusively out of 4000 series chips and 555 timer. It was all on a breadboard and pretty messy. Now, in ninth grade, I've decided to get it back together, but this time on a PCB. But wait, there's more! I'm etching it myself, so it has to one-sided. Yes, there will be some jumpers, and the 555 will be replaced by an ATTiny for controllability and simplicity, but the displays and such will all be discrete. The first part I'm etching is the ATTiny and 4017 circuit. It will drive a bargraph display. Later, the divide-by-ten output of the 4017 will drive a
|Sorry for the poorly drawn lines...|
I drew up the first part of the circuit (from the clock to the bargraph) on Fritzing, my favorite PCB editor. I exported it to a PDF and printed in on a rather ancient laser printer. Now, if you're going to replicate this, here's some stuff to know. In this etch, I used some 16 mil traces, much smaller than I've used before. I've had good luck with 24, 32, and 48 mil traces, but I've never tried 16. So it might not work. Also, my printer has an option that controls how much toner goes on the paper. I found it in the print menu, under Preferences, Advanced. I set everything to "TonerSaver Off" and print quality Dark. You want as much toner as you can get. For paper, I used typical Staples Photopaper. Other people swear their lives on magazine paper, but I haven't tried this. This is what my printout looked like:
|There are two printer discrepancies in the printout,|
a litte north-east of the center.
When that's done, it's time for the actual transfer. This is the most exciting/tedious part, besides the actual etch. This part basically consists of pressing a hot clothes iron over the paper layered on top of the board so that the toner adheres to the board. Later, during the etching process, the toner acts as a resist so the parts of the copper covered with toner don't get dissolved. The first step is to heat up the clothes iron (I say this because there is also a soldering iron in my house) and align the printout with the board. Set the iron to its hottest setting. This is "Linen and Cotton" for me. Also, you obvious want the toner side of the paper matched up with the copper side of the board. You will also want a bowl of water on hand. Once the iron is heated up, lay the board with paper on top on a flat surface (for me a wooden board) and push down really, really hard for about thirty seconds. This gets most of the toner to stick so it should stay in place.
|In the basement lab, ready for transfer!|
|Pressing really, really hard.|
|Nicely transfered board, sitting in the water.|
|Saturation moving in.|
|Paper lifting off.|
|I gently pulled some of the paper of, revealing |
the copper and toner
|A nicely transfered (and shiny) board.|