The time had come for the moment of truth. This is where the rubber meats the road, as the old adage goes. It was time to solder the motor leads. Soldering is a skill I acquired in my youth. My father and grandfather both worked with electronics and as a result, I had many opportunities to solder as a child. The problem was, it has been at least 20 years since I last soldered. I was seriously out of practice and worse still, I’ve never had to work on such micro-electronics before. There’s so much packed onto that tiny crazyflie printed circuit board (PCB). I had only ever soldered things I could actually see with my naked eye!! This was going to be an adventure.
To help me remember my skill (and not screw up on the crazyflie PCB), I decided to try to my hand at soldering a six dollar electronics kit. I found this one on Amazon. It’s a quaint little flashing LED kit. It’s got enough solder points to provide some practice, it’s cheap enough to buy a few (if needed), and it might be cool to play with after I put it together. I figured it would do well and I wouldn’t care too much if I screwed it up.
Of course, as things go, this exercise was also a great excuse to buy some good soldering equipment. I had a pretty good iron already but it wasn’t suited for micro-electronics. After all, there was no temperature control, it wasn’t ESD safe, and I didn’t have any “special” tips for it. I guess it was time for me to start looking at soldering stations instead… 😉 If I was going to do this, after all (goes my logic), shouldn’t I do it right!? So, the six dollar Amazon electronics kit purchase became a $180 shopping spree but it made me happy (and it’s close enough to my birthday anyway).
With all the equipment a professional could need, I proceeded to solder the little flashing LED kit and was pretty pleased with my results. It was easy though… Super easy. It was human sized, not nano like the crazyflie PCB. I was nervous. That didn’t help me to steady my hands at all!
The crazyflie PCB was so small I had trouble seeing the holes for the motor leads. Maybe my eyes are just getting old. In any case, the first thing I did was put the PCB on some helping hands under a magnifier lens. That made it much easier to see but much harder to work with. With a small magnifier lens, you have the tendency to want to close one eye but that throws your depth perception off and you need good depth perception when soldering. So with both eyes open I started to study the front and back of the PCB. Oh, and yes, that is a Raspberry Pi in the background. Eventually it will become ground control for crazy flying, I hope…
I bought a special angled micro tip for the soldering iron in the hopes that it would make soldering the tiny motor lead wires on the tiny solder pads easier. I mounted it on the soldering iron and tinned the tip with some good 60/40 tin/lead solder (I wasn’t about to use the higher heat silver solder on such a delicate operation – leaded solder flows so much better and, as a result, is so much more forgiving to work with). With the tip ready to go and the PCB mounted in the helping hands, I calmed my nerves, reminded myself to take it slow, and proceeded to solder.
The first motor was nerve wracking because I truly had never worked with anything this small. I was pretty sure I got it soldered but it was quite hard to see for certain. I used a little magnifying lens on my Swiss Army knife under the magnifying lens of my helping hands jig. That made it much easier to check my work. After both leads were soldered, I pulled the PCB from the alligator clips and tested the connections by applying power from a USB cable — much like I had done in my original hardware testing. The motor worked!! Whew. Ok, one down, and three more to go.
I remembered I needed to alternate the black and white motor leads per the assembly instructions and so proceeded to solder and test each motor as I went along. On the third motor, my solder looked a little sloppy. I was worried I’d bridged the connections and would have a hell of time fixing it back up. Once I ran the test though, the motor was working just fine and I was certainly relieved! On close inspection, I think it was a bit of flux reflecting the light that made it appear there was a solder bridge. My eyes must be getting old! This work is hard for me to see. After the last motor was soldered and tested, I sighed a sigh of relief and turned off my new Hakko iron. I was glad to have bought it. The thing served me quite well.
The assembly instructions provided on the bitcraze wiki were great. I essentially followed them verbatim. Were it not for my own fear of failure, this could have been a pain free process! I’ll try to remember that next time…