Lab Visit + THE DEVBOARD WORKS NOW WOHOOO

After inhaling a mole of lead-based solder fumes, I finally got the devboard to work!!! It’s my first ever PCB so I’m really stoked!!

I visited my friend’s lab at the university where he works and we were able to debug and fix the devboard in a few hours. Unfortunately, I remembered that I had to record the whole thing in lapse in the last 20 minutes, but I guess that’s just karma for taking 9 hours ( ) to hand solder/debug a PCB in my last devlog (yes ik i suck).

Issues

My previous attempt at soldering failed because I set the temperature of my hot air gun too low, and I overestimated surface tension’s effect on my hot plate. I used a high-res microscope at the lab and saw that most of the QFN components were only partially soldered. I could quite literally see a tiny gap between the two pads. Another thing I saw was some obvious bridging, which I quickly fixed with a soldering iron.

One of my biggest takeaways from the lab was that THE TYPE OF SOLDER FLUX MATTERS!!! I previously used some generic $14 flux from Amazon, but it was so bad that even some of the most powerful ultrasonic flux cleaners couldn’t get it off easily. It was also so thick that even the infrared lamp couldn’t get the RP2040 to stick down. My friend used (and recommended) water-soluble flux, which makes it easy to clean off without messy isopropyl alcohol.

I ended up salvaging the parts from my old PCB to build a new one from scratch. I learned how to solder QFP packages, 0603s, and even 0402s with an iron. In the end, a soldering iron is THE BEST way to guarantee that your components are soldered down, especially when verified with a microscope. I also learned how to solder using an infrared lamp and hot air (properly, this time).

Results???

Right as I finished soldering the last component, I connected it to my computer and held down bootselect….and IT WAS DETECTED AS A MASS STORAGE DEVICE!!! I was so excited at this time that I finally rekindled my motivation to keep building more of these PCBs (I was pretty close to giving up on PCB-related projects ngl). Anyway, right before leaving, I put it in the ultrasonic washer they have for PCBs (which is just a tiny container with water and ultrasonic waves being fired it at from all directions to take the flux off. I’m currently waiting until tomorrow for it to air dry, and then I’ll incorporate it in the robot!