Fab Academy Week 5 - Electronics Production
The second step involves soldering all the components onto the board. This is called “stuffing” the board, and the placement and selection of components is determined by the schematic available on the Fab Academy website. There are transistors, capacitors, resistors, diodes, a crystal, an actual chip called “attiny44a”, and a mini USB header. All of these pieces are soldered onto the board using tin solder. In addition to the components, there are two solder “bridges” which temporarily link different parts of the boards to each other. These bridges are used to load the initial firmware onto the board, and then must be removed afterwards in a second soldering operation. More on this later. Maybe.
The actual soldering method is pretty easy provided you prep your workspace properly. One thing that helped me was to raise the work surface closer to eye level by setting a small footstool on top of the table and using it as my work surface. The soldering is done with a tin-based solder and an electrically hearted soldering Iron, set to 700 degrees Fahrenheit. The method that worked best for me was to dip the end of my solder wire into the flux gel so that there’s just a tiny bit on the tip, then touch the heated element of the iron to the area of copper I wanted to solder to heat it up. While the copper is heating up, I tentatively tap the end of the solder wire onto the surface so that some of the flux flows off of the solder wire and onto the copper surface. As the copper heats up, the flux liquifies and spreads across the copper. When the copper is at just about the right temperature, the flux will start to smoke a tiny tiny bit, which is when I touch the tip of the solder wire to the surface a second time and if I’m lucky a tiny bit of it will flow onto the copper. If it doesn’t flow, I can touch it directly to the tip of the soldering iron, and it will usually bind partially to the copper and partially to the soldering iron. I then remove the soldering iron and use a damp sponge to wipe off any excess solder still clinging to the tip.
Once this initial dab of solder is in place, a component (such as a resistor, capacitor, etc) can be laid down on top of it and held in place with tweezers while the soldering iron is placed onto the connection point which raises the temperature of the solder and causes it to flow out from under the component and bind the component to the copper.
I don’t know anything about electronics, so this whole process quickly turned into a game of matching colors and shapes. I looked at the sample boards and the images on the website, and then rummaged through our local Fab Lab’s box of components until I found pieces that looked like the ones in the example. Then I soldered them into the corresponding spots on my own board. Once everything was in place, I plugged the Fab ISP into my computer’s USB port. The fact that no smoke issued from the device, and no error messages appeared on my computer, were indication enough that I was at least somewhat on the right track.