Week 3
Electronics Production

# Printed Circuit Board (PCB) Milling

It seemed like a straighforward, 10-minute job: Taping the board, screwing in the end mills, and calculating the origin coordinates. NOT SO. Three circuit boards and 1.5 hours later, I finally had a product on which to solder the electrical components.

Lessons learned:

• When preparing to print, raise the Z coordinate to screw in the end mill. Then, lower the Z coordinate and release the end mill so that the tip of the end mill taps the surface of the board. The tip should rest snugly on the board to create visible traces without cutting through the board.

• When adjusting the coordinates, calculate and eyeball the position of the mill to prevent off-roading. During my second attempt, the end mill started tracing a few millimeters further from the border, resulting in an off-center print. Since I was unsure whether the traces would fit onto the board, I canceled the job and re-started on a fresh one. This time, I raised the Z coordinate for "Jog to Origin" to increase the elevation of the end mill when lifting and shifting, thus preventing surface scratches. By setting precise origin coordinates and verifying the end mill position with a visual scan, I completed the PCB milling.

• Step 1: Load the traces and interior files for printing. Set and calculate origins for the end mill.

Step 2: Send files to print, switching from 1/64 to 1/32 for the end mill to create the traces and interior, respectively.

Step 3: Practice to make perfect: Adjust and tighten the end mill to print at the right depth. Re-calculate origins to center traces on the board and ensure space for the interior. Origins on the final attempt: x=110, y=10, z=5, where jog to origin was z=10.

Step 4: Feel accomplished for deceptively simple project.

# Soldering Board Components

After creating the PCB, I soldered the electrical components. I felt like a first-grader trying to control an outpour of Elmer's glue. It was challenging to get the right amount of solder onto the trace and component without frying the board and/or creating all those hershey kisses - mounds of solder that would need to be removed or flattened with a soldering braid.

Lessons Learned:

• Be flexible with technique! When I started soldering, I placed the iron tip on the trace and heated the solder to create an adhesive for the component. However, I couldn't transition the solder from the tip of the iron onto the board. Instead, the iron started to make the board crispy, slightly lifting one of the traces. Oops. Fortunately, I was able to rectify the situation and hold down the trace with more solder: This time, I learned to heat the solder with the iron tip without touching the board; then, I tapped the iron tip onto the trace, which allowed me to control the solder and prevent mounds of adhesive from accumulating. After positioning a component on the solder, I reheated the solder to make it stick. For surface mounts and more delicate components, I switched to the irons with a finer tip and focused on structural integrity, pinning one or two ends of the component onto the board. Then, I soldered the remaining pins. I'm sure I probably broke a couple of rules when it comes to best practices for soldering, but experimenting with technique enabled me to adapt to the components and overcome my lack of experience.

• De-solder excessive solder: For one surface mount, I pre-maturely soldered all the traces, deliberately creating tiny hershey kisses so that I could reheat the solder and glue the component onto the board more easily. Turns out, I shouldn't have done that, so I course-corrected by learning how to de-solder with the copper solder braid. By resting the solder braid on the excess solder and placing the iron tip on the braid, I removed and/or flattened unwanted adhesive. To de-solder more effectively, I put some solder on the braid to increase heat transfer.

# Programming the PCB

With the components soldered, I proceeded to program the PCB, which would result in a device that can program other devices. However, I encountered an error when entering the "Make Fuse" command: "Double check connections". So, I re-examined my board, finding that I failed to solder some of the components to the traces. I realized that even if the component was securely fastened to the board, with one or two ends, all of the pins on a component needed to be connected to the traces with solder in order to create an electrical connection. I re-soldered the components that I had missed, but kept generating the same error. So, I'm trouble-shooting again.