Last night was the PCB assembly party, in which 20 units went from bare boards and components to assembled boards. Some crucial components were missing from the BOM so we weren’t able to call them complete, but that was my fault. In fact, I had them, but on a test unit I had pre-assembled they kept failing, so I didn’t want to risk continuing to use the faulty components and instead sourced a different component from Mouser). But the vast majority of the pieces were placed last night. It took about 10 people, who contributed for varying amounts of time. Some stayed as long as 10 hours.
We learned a lot and developed some new methods, and people became very comfortable with SMT assembly. The first part of our setup included placement of the LEDs. Because these need to be a cleaner finish with the solder because they are externally visible, we used solder paste and baked the boards on a hot plate. This was an interesting stage because the heating of the board was such that the board warped almost immediately as the bottom of the board got hot and expanded but the top didn’t expand to compensate. We adjusted our methods to compensate, only doing half the board at a time, and holding it flat as it baked. This process worked well, and soon all the fronts were done. By soon, I mean it took approximately 4 hours to do all the fronts.
The backs were all hand soldered, and the microcontrollers were the most challenging, requiring a microscope and very careful hand for hours. This will hopefully be the only batch; in the future the boards will be done in bulk on automated machines.
The party was fueled by pizza and beer, which in retrospect were poor choices because of the effects of pizza fingers and manual dexterity, but it was a good time, and many hours were saved by many cool people, some of whom went from never having done surface mount work to being experts in a matter of hours.
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