The focus this week was on electronics production: understanding PCB fabrication methods, defining design rules, and fabricating a working microcontroller development board.

• PCB methods: reviewed dead bug, etching, and machining approaches to PCB fabrication.
• Machining workflow: practiced tool selection, fixturing, zeroing, and post-processing steps like deburring and cleaning.
• Vinyl cutting: studied how vinyl cutters can also produce flexible copper circuits.
• Development board: made and tested a microcontroller board (Quentorres) using the XIAO RP2040 with a button input and LED output.

Week 04 assignments and links

These are the pages related to my Week 04 electronics production work.

• CNC cutting, MCU development board making and testing (Quentorres)
• Group Assignment Week 04
• Group Assignment Week 04 (ChaiHuo Lab page)

PCB fabrication methods

There are several ways to fabricate PCBs, each with different tools, materials, and constraints.

• Dead bug method: components are glued upside down and wired directly, useful for quick prototypes.
• Etching: removes unwanted copper chemically from a board to leave traces.
• Machining: uses CNC milling to remove copper and outline boards; this was the main method used in the assignment.

Machining details

Machines

Different labs use a variety of CNC machines for PCB milling, each with its own workflow and settings.

Tools

• 1/64 inch mills for fine traces.
• 1/32 inch mills for cutting outlines.
• V-bits and tapered bits for specific trace widths or engraving.

Fixturing and underlay

• Fixturing: holds the board firmly so it does not move during milling.
• Underlay: protects the machine bed and allows drilling through without damage.

Zeroing

Zeroing sets the starting point of the mill and is critical for accurate depth and alignment.

• Mounting the tool.
• Lowering to the surface.
• Probing using a tool or sensor.

Set-screws, collets, lifetime

• Choose the correct mill and collet for the job.
• Monitor tool lifetime so worn mills do not ruin boards.
• Deburr traces to remove burrs and clean the board after machining.

Vinyl cutter and PCB materials

Vinyl cutters can be used not only for stickers but also to cut copper for flexible circuits.

Vinyl cutter

• Cuts designs derived from images or vector files.
• Can cut thin copper layers for flexible circuit applications.
• Results are flexible and can fit many different form factors.

PCB materials

Rigid

• FR4 (epoxy glass).
• FR1 (phenolic paper).
• Garolite.

Flexible

• Kapton, Pyralux.
• #1 epoxy film, #1126 copper tape.

High-frequency

• Teflon.
• Glass.

Copper thickness

• 0.5 oz: 17.5 µm copper.
• 1.0 oz: 35 µm copper.
• 2.0 oz: 70 µm copper.

Board houses and layers

• Board houses in Shenzhen can fabricate PCBs at low cost.
• Typical design rule for traces and clearances is 5 mils.
• Layer options include 1, 1.5, 2, 2+, 4, and higher layer counts.
• Rivets can be tricky at very small sizes and may cause cross-connections on 2-layer boards.
• Many devices use 4-layer boards, while phones often use 6 layers.

Components, assembly, and CAM

Beyond fabrication, electronics production also involves selecting components, assembling boards, and preparing files for services.

Components and sourcing

• Use Octopart to search for components and access datasheets.

Breadboards

• Breadboards are good for beginners but are not very aesthetic for final projects.

Assembly and soldering

• Soldering and wiring are needed to assemble the board.
• Aim for smooth, non-lumpy solder joints.
• Hold the solder slightly after applying heat to let the joint set properly.

Rework and desoldering

• Stuffing and desoldering techniques are important so components can be reworked if needed.

CAM and file formats

• Gerber is the standard format for CAM when sending boards to fabrication houses.

Machine cutting workflow

Digital fabrication of PCBs often starts from images or vector files and goes through a CAM pipeline.

1. Use PNG or SVG images for lossless resolution when preparing machining files.
2. Convert PNG or SVG files using mods, choosing an appropriate mill (for example a V-bit, 1/64, or 1/32).
3. Set the relevant parameters and preview the toolpaths and cutting traces before machining.

Quentorres development board

For the individual assignment I made and tested the Quentorres microcontroller development board.

• Uses the XIAO RP2040 as the main microcontroller.
• Includes a button as a simple input and an LED as a simple output.
• The design is CNC-machined and documents the full electronics production workflow.

Evidence (images)

Replace these placeholder images in images/week4/ with your own photos and screenshots.

Machining setup

Fixturing, underlay, and zeroing the board before milling.

Milled PCB

Traces after machining, deburring, and cleaning.

Quentorres assembled

XIAO RP2040 board with button input and LED output.

Vinyl-cut copper

Flexible copper circuits cut on the vinyl cutter.

Next step

With PCB production skills and a working development board, the next weeks will build on embedded programming and integration with sensors, actuators, and final project ideas.

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