Electronics Production¶
Goals¶
Group assignment:
- Characterize the design rules for your in-house PCB production process: document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling.
- Document the workflow for sending a PCB to a boardhouse
- Document your work to the group work page and reflect on your individual page what you learned
Individual assignment:
- Make and test a microcontroller development board that you designed
Prior Knowledge¶
Projected Timeline¶
- Wednesday
- Start group assignment
- Start individual assignment
- Thursday
- Finish group assignment
- Friday
- Work on individual assignment
- Saturday
- Document
- Sunday
- Document
- Monday
- Finish individual assignment
- Tuesday
- Plan for next week
Actual Timeline¶
- Wednesday
- Start group assignment
- Finish group assignment
- Start individual assignment
- Thursday
- Work on individual assignment
- Friday
- Work on individual assignment
- Start and finish group
- Saturday
- Work on individual assignment
- Sunday
- Work on individual assignment
- Document
- Monday
- Work on individual assignment
- Tuesday
- Finish(?) individual assignment
Process¶
Milling¶
While I’ve done this process, I needed a slight refresher in details such as settings and bit changes. Conard Hull helped me out with the initial mill.
Export Gerber files¶
I used the Gerber feature in Fabrication Outputs to export the files to the Fab Lab’s Google Drive folder. I also generated drill files and considered that the main distinction between PTH and NPTH was the depth of the cut into the copper. We favored PTH in my freshman engineering class, which determined my choice. I chose the front cut, edge cut, and PTH hole file and exported them to the Fab Lab’s Google Drive folder. I could access the files on the milling computer after.
Prepare and Mill¶
I measured the dimensions of the copper sheet using calipers, which were 115127.2.7 millimeters. After taping the sheet to the surface and jogging the machine, I generated the Gcode. To follow our lab procedure, I changed the trace depth setting to 1.5 mm. I entered the 1/100th bit instead of 1/64th, as Conard explained that his boards typically worked with this substitution. However, when milling, I realized that this would not translate to smaller boards. Mr. Budzichowski informed me that the circuit would not work with the current wire spacing and component placement.
At this point it also occured to me that I never milled the silkscreen layer with text and images. I now figured that this was beyond the scope of the circuit. Still, I found the KiCad experimentation beneficial.
Note: for the bits we were given, each measurement corresponds to a color. - Engraving: Multicolor - White: 1/16 - Green: 1/32 - Purple: 1/64
Re-Mill¶
Mr. Budzichowski explained my issues with the limited amount of circuit space and the proximity of wires to components. After correcting these changes, I exported the updated PCB.
After re-doing the milling process, the board milled successfully. The wires were spaced properly with a layout that confused me at first, as I was not used to surface-mount pads, although I quickly adapted by referencing the PCB schematic.
Solder¶
Since I’m inexperienced in surface-mount soldering, the process took longer than intended. Still, there were no issues and the layout turned out clean and workable.
Of course, it then turned out that I cannot use headers when the rest of the board is surface mount. Or I - can - but really ought not to, because I somehow managed to melt it to the point that I could not remove the solder. I plugged it and the Arduino port simply didn’t connect, I presumably fried it.