The bottom plate has most of the assembly instructions on it, but since this guide is using the KB2040, the instructions have been slightly edited.
Modified assembly instructions:
Diode and Resistor Lead Bending Tool:
Center your component in the cutout rectangle and align leads with the notches. Then, whiile holding the component leads against the PCB, bend the lead ends into the notches to an angle of 90°.
BOM:
U0: [Adafruit KB2040]
J0, J1: 12 Pin Headers (usually come with Pro Micro)
D0-D9: Switching Diodes (ex. 1N4148)
D10: 3mm LED
R0: 1k Ohm Resistor
K0-K9: Cherry MX compatible or Alps Keyswitches
12x M2 screws
6x M2 spacers
Build Steps:
1. Solder the Diodes and Resistor:
- Use the Lead Bending Tool above to bend the leads
- Solder the Diodes with the marked side of the diode oriented with the markings on the silkscreen.
2. Solder the LED:
- Anode (positive) lead is usually longer than the Cathode (negative) lead.
- Positive side is marked with a '+' on bottom of the PCB, make sure to solder the Anode (positive) lead in that hole.
3. Solder the [KB2040] Headers:
- On bottom side of PCB, place headers in the correct rows (middle for Micro USB [or USB-C on KB2040], outer for Mini USB model)
- Hold these in place while flipping over the PCB, and place on a flat surface, keeping them as straight as possible while soldering. Placing the [KB2040] on them loosely can help with alignment.
- Solder the header pins to the pads on the top side of the PCB.
4. Solder the Switches:
- Place the Switches in their locations on the top of the PCB.
- Flip over the PCB and solder the Switch leads to the pads on the back of the PCB.
- After soldering, clip the leads on K1 and K4 shorter to prevent them from touching the Pro Micro.
5. Solder the [KB2040]:
- Place the [KB2040] on the headers, flipped with the chip-side facing the PCB and the USB port protruding slightly over the PCB edge.
- Solder the [KB2040] to the headers and then clip the ends of the headers short.
*Optional: Solder a Piezo Buzzer to the 'Buzzer' Pads for audio output
[6]. Connect top and bottom PCBs with the M2 Screws and Spacers.
This is a diode bender. I didn't realize this until after building it, so you definitely don't need to use it, but it makes things much easier.
After you're done, it should look something like this. I used ALPS SKCM Orange switches, which don't have the same fixing posts as some MX-style switches do. My advice for getting them straight would be to solder them in then heat up one pin at a time and rotate or move the switch a little bit at a time until it's straight.
