Fabrication
& Assembly
From raw FR1 copper stock to a finished product. The fabrication process involved precision CNC milling, surface mount soldering, and 3D printed enclosure design.
01 · PCB Fabrication
The PCB was milled on a Bantam Tools Desktop CNC Milling Machine using FR1 single-sided copper stock.
- Traces: 1/64" flat end mill.
- Holes & Outline: 1/32" flat end mill.
- Clearance: 0.2mm minimum trace clearance.
The Process
- CAM Setup: Imported Gerber files into Bantam Tools software. Configured tool paths for traces, holes, and outline.
- Fixturing: Secured FR1 stock to the spoilboard using double-sided Nitto tape.
- Milling: Started with 1/64" end mill for very fine and detailed traces, then switched to 1/32" for larger traces, drilling holes, and cutting the board outline. Total run time was approximately 15 minutes per board.
- Post-Processing: Deburred edges with a Scotch-Brite pad and washed with soap and water to remove dust.
02 · Assembly & Soldering
All components were hand-soldered. The design uses a mix of through-hole (headers, terminals) and surface mount (resistors, capacitors) components. The assembly process required careful attention to component placement and creative solutions for mounting breakout boards.
Component-by-Component Assembly Process
1. Raspberry Pi Pico W
Soldered the Pico W directly to the PCB using a temperature-controlled soldering iron and leaded solder. The digital microscope display was invaluable for reviewing solder joints in real-time, ensuring clean connections without bridges between pins.
2. HUB75 Connector
For the HUB75 connector to the LED matrix, I used two rows of 8-pin header pins—one row on top and one on bottom. This dual-row approach provided excellent mechanical stability for the high-density connector that carries 16 data and control signals.
3. MAX98357 I²S Audio Amplifier
The I²S amplifier breakout board was mounted on header pin "stilts" above the PCB surface. This elevated mounting approach was necessary because the board's layout footprint in Fusion 360 accounted for the breakout board's physical dimensions. The stilt mounting also improves airflow around the Class-D amplifier.
4. ICS-43434 I²S MEMS Microphone
The I²S microphone breakout board used the same header pin stilt technique as the amplifier. This keeps the microphone elevated and oriented properly for optimal audio pickup while maintaining electrical connectivity to the PCB traces below.
5. Power Connector
The power connector was fashioned from thick header pins with a plastic side sleeve. Due to the single-sided PCB design with traces on top, the connector had to be inserted from below the PCB front.
This awkward bottom-mounting will be corrected in the boards I've ordered from JLCPCB.com. With professionally manufactured boards, the vias come anodized (plated through-holes), allowing power connectors to be mounted on top of the PCB with headers soldered cleanly at the bottom—the proper way.
6. 5V Power Jack
The 5V power housing was a standard component that Anthony Pennes ordered for me. This replaced the earlier prototype's unstable hanging power lines with a proper barrel jack connector, making power connection much more reliable and professional.
03 · Enclosure Design
The enclosure was designed in Fusion 360 to house the 64x64 Matrix, the PCB, and the speaker. A critical aspect of the design was precisely positioning mounting points for both the PCB and the LED display.
Fusion 360 Design Process
The enclosure design started by importing the PCB outline from the Eagle/Fusion board file. This allowed me to:
- Import PCB Outline: Imported the .brd file directly into Fusion 360, which automatically extracted the board dimensions and mounting hole positions.
- Create Mounting Pads: Projected the mounting hole locations onto the enclosure base and created raised pads with integrated screw bosses for M3 screws. These pads provide structural support and ensure the PCB sits level.
- LED Display Integration: Repeated the same process for the Waveshare 64×64 LED matrix panel, creating four mounting bosses that align with the panel's mounting holes.
- Clearance Verification: Used section views to verify component clearances, especially around tall components like the HUB75 connector and power terminals.
Design Goals
- Compactness: Minimize volume while fitting all components.
- Precision Mounting: Accurate screw boss placement for both PCB and LED display using imported outlines.
- Acoustics: Ported chamber for the 3W speaker to enhance bass response.
- Modularity: Snap-fit design for easy access to internals.
Manufacturing
- Printer: Prusa i3 MK3S+
- Material: PLA (Matte Black)
- Layer Height: 0.2mm
- Infill: 20% Grid
- Support: None required due to careful orientation
Importing the PCB board file directly into Fusion 360 ensures mounting holes are positioned with sub-millimeter accuracy. This eliminates the need to manually measure and transfer dimensions, which is error-prone. The technique works for any Eagle or Fusion 360 electronics design.
04 · Final Integration
The final assembly brought everything together. The PCB mounts to the back of the LED matrix using M3 standoffs. The speaker is press-fitted into the enclosure, and the entire unit snaps together.
