Hello, welcome back to the factory. This time around we are assembling a full panel, putting it through the reflow oven to solder, and then electrically testing the finished product. There's not much point in being coy about this anymore, this is just a little display module, a string of individually addressable WS2812B LEDs with some friendly connectors for say banana plugs or crocodile clips you could clip on in either orientation. Anyway, let's get to it.

Picking up where we left off in the last video, first we stencil solder paste onto the panel using the stencilling machine. This deposits a controlled amount of solder paste exactly where it's needed. We queue up the pasted panels on this input conveyor. This gives us room for about three or four panels plus one in the machine.

Panels are ingested one at a time into the pick and place machine. The gantry has a probe that extends down to stop the panel at the right spot. The tracks lock the panel into place, and the vision system picks up some optical alignment marks on the first PCB. This helps the machine account for any small translation or rotation of the panel on the tracks.

After a nozzle picks up a component, it flies back and forth over another vision system. A camera takes a picture of the component, and if it happens to be offset or rotated, the machine compensates as necessary. You can see in this graphic a crosshair indicating the center of the nozzle and also the center of the component. The vision system also measures the component's dimensions to make sure it hasn't rolled onto its side. This isn't really a problem for these large LEDs, but it's really something to watch out for the smaller parts.

Once all the components are placed, the tracks unlock, the populated panel is passed out of the machine, and the whole cycle begins anew with the next panel. The populated panel exits the machine and rides down another conveyor, where we can perform some inspections or manual operations if necessary, before then entering the reflow oven.

The reflow oven is basically a fancy pizza oven. It takes the panel through a tightly controlled temperature profile, which melts the solder paste, adhering the components to the board. The soldering process does leave behind some residue. Now we're still in the process of figuring out what method works best for us, but in general, it's some process of a solvent bath followed by drying.

Depanelizing is pretty straightforward. I just snap off the V-cut rails, and here most of the PCBs are routed out, except for these local spots called mouse spots or stamp holes.

Finally, we need to do some quality control. For that, I whipped up this test jig. That's just basically a custom Arduino shield. These standoffs align with holes in the panel or in the PCB, and they register the design into the jig. These springy pogo pins deliver power and also pass a signal from the Arduino to the board that drives the LEDs in a test pattern. That test pattern just cycles through red, green, and blue repeatedly, and that's enough to show that the LEDs are powered, drivable, and that they also retransmit the signal that passes into them.

And there you have it, our first finished product. I thought this was a good first go because it only uses one unique part, and who doesn't like blinky lights? These factory videos are a bit different from our usual style. Let us know your thoughts, whether you like them, whether you don't like them, if you have some feedback. If you have any experience with pick and place machines or electronics assembly, we'd love to hear from you. The best place for technical stuff is on our forums. Until next time, thanks for watching.