A student in my class came in one day holding the pieces of her cell phone. She'd dropped it in the parking lot where it was squashed like a bug before it could be retrieved. Holding the bits in her hands she displayed it to classmates with obvious pleasure. "Look," she said, "it's got a circuit board inside just like we make in class."
I'd like to think the pleasure was in discovering what we'd been doing is a reflection of how electronic devices are made but she also allowed she now had the excuse she'd been looking for to get a new phone.
The point, though, is that part of the experience of understanding programmable devices is knowing what a circuit board is and how it works. It's for this reason that for many years now students make their own for at least one integrating project. An "integrating" project is one that combines the learning of several lessons.
We learned the hard way that most advice for how to make your own circuit boards doesn't work very well. It tends to focus on temperature control, special tools for chemical management, and techniques for agitating boards in both developer and etching solutions. Meanwhile, issues of concern for naïve students with few hands-on skills are not addressed.
We believe any DIY system for making circuit boards must include the following:
- Safety. For this reason we require ventilation, gloves, and splash goggles.
- Simplicity. The steps have to obvious - expose, develop, wash, etch, wash, drill, solder.
- Minimal demand for special skills. Assume students have no experience with chemical processes, operating a drill press, or soldering.
- High likelihood of success. This is the single hardest goal to achieve. For this we make traces wide, and soldering pads oversized when we can. We also choose trace routings to match prototyping over minimizing board size. And drilled holes are larger diameter than we might like in order to reduce breaking of drill bits. Small modifications of soldering procedure such as folding leads flat against the trace before soldering compensate for this.
- Minimal cost. We like to use an electric kettle from Target for heating water. This is where we also get the plastic tub for the hot water bath and the light-weight plastic food container to float on top. The container, in turn, holds the circuit board to be etched and just enough ferric chloride to cover the board.
The specific steps we follow are shown in How-To #5, How to Make a Circuit Board.
In order to optimize student success I've found manually laying out a board provides better results than letting a tool make the initial layout suggestion. In fact, while I’m partial to Fritzing many of our boards were laid out using Microsoft Visio. Visio is, in my opinion, one of Microsoft's best design tools and I honestly don't know why it doesn't receive more promotion.
Even when I begin with Fritzing I usually begin with the board layout, edit the resulting schematic, and leave the breadboard view an unorganized mess. It's just not needed.