[0] Overview
Up until this point, I've only worked with breadboards ith less complex circuts and never used a soldering iron before. So when I saw that we were not only soldering but milling a PCB board, I was very excited for this section of the course. Initially, we went over how PCBs are manufactured (chemically and physically), and then finalized on operating the Roland milling machine. For this week, I milled the 5V ATMEL SAMD11 board on the FAB website.
This week's assignments:
(1.) make an in-circuit programmer that includes a microcontroller
(2.) mill and stuff the PCB
(3.) test if it works
[1] Group Assignment
We are using a Roland SRM-20, with two bit sizes: 1/32 and 1/64.Before we start working on the machine, we had to characterize how well it mills and understand its limits.
Group
[2] SAMD11 Traces
[3] PCB Milling
Once I set up the 1/64 bit, I started to mill the PCB. I had issues with getting contact to the PCB but ultimately was able to fix that and make clean cuts.
To clean up the PCB, I used a knife to remove all the copper surrounding the edges of the board and those close to the pcb components, tp [revent capacitance and shorting. Afterwards, I used grit 1600 sandpaper to smoothen the the circuit edges and the usb mount. Lastly, I cleaned up my fingeroil that may have gotten on the pcb using isopropanol (it's also really good to get rid of extra flux).
[4] 'Shopping' List
Once I had the milled board, it was time to get all the components to fabricate the board. I scoured thorugh the lab and found the pieces, which I labeled on the scrap piece of plywood. One thing to note is that the microcontroller is directional, so I just had to be careful of putting it in the right orientation or else the hot air gun would need to come out. In addition, the pieces are much tinier than I expected to be working with! I remember struggling to pick these up when I was first practicing with Nathan during section.
[5] Soldering
I soldered the last components onto the board and voila! My very first PCB!
[6] Testing the Board
Yay! Now that I have a board, what now? Even though this is for two weeks in ahead, I wanted to look into how to program these. With the help of Nathan, we programmed my board and got it to read as a bootloader/programmer for other chips I make in the future! This part of bootloading is something I'm still not sure, and I might try other types of chips in the future like the ATTINYs or ATMEGA 238 that have a simpler process.
[7] Takeaways
Now the soldering is nowhere near perfect, but all the connections work! Ideally, you want the connections to have a shiny reflectance, so as I get better with soldering I'll be sure to use the correct amount to get an optimal connection.