Week 4
Electronics Production

The focus this week was on electronics production: understanding PCB fabrication methods, defining design rules, and fabricating a working microcontroller development board. [file:3]

• PCB methods: reviewed dead bug, etching, and machining approaches to PCB fabrication. [file:3]
• Machining workflow: practiced tool selection, fixturing, zeroing, and post-processing steps like deburring and cleaning. [file:3]
• Vinyl cutting: studied how vinyl cutters can also produce flexible copper circuits. [file:3]
• Development board: made and tested a microcontroller board (Quentorres) using the XIAO RP2040 with a button input and LED output. [file:3]

Week 4 assignments and links

These are the pages related to my Week 4 electronics production work. [file:3]

• CNC cutting, MCU development board making and testing (Quentorres) [file:3]
• Group Assignment Week 4 [file:3]
• Group Assignment Week 4 (ChaiHuo Lab page) [file:3]

PCB fabrication methods

There are several ways to fabricate PCBs, each with different tools, materials, and constraints. [file:3]

• Dead bug method: components are glued upside down and wired directly, useful for quick prototypes. [file:3]
• Etching: removes unwanted copper chemically from a board to leave traces. [file:3]
• Machining: uses CNC milling to remove copper and outline boards; this was the main method used in the assignment. [file:3]

Machining details

Machines

Different labs use a variety of CNC machines for PCB milling, each with its own workflow and settings. [file:3]

Tools

• 1/64 inch mills for fine traces. [file:3]
• 1/32 inch mills for cutting outlines. [file:3]
• V-bits and tapered bits for specific trace widths or engraving. [file:3]

Fixturing and underlay

• Fixturing: holds the board firmly so it does not move during milling. [file:3]
• Underlay: protects the machine bed and allows drilling through without damage. [file:3]

Zeroing

Zeroing sets the starting point of the mill and is critical for accurate depth and alignment. [file:3]

• Mounting the tool. [file:3]
• Lowering to the surface. [file:3]
• Probing using a tool or sensor. [file:3]

Set-screws, collets, lifetime

• Choose the correct mill and collet for the job. [file:3]
• Monitor tool lifetime so worn mills do not ruin boards. [file:3]
• Deburr traces to remove burrs and clean the board after machining. [file:3]

Vinyl cutter and PCB materials

Vinyl cutters can be used not only for stickers but also to cut copper for flexible circuits. [file:3]

Vinyl cutter

• Cuts designs derived from images or vector files. [file:3]
• Can cut thin copper layers for flexible circuit applications. [file:3]
• Results are flexible and can fit many different form factors. [file:3]

PCB materials

Rigid

• FR4 (epoxy glass). [file:3]
• FR1 (phenolic paper). [file:3]
• Garolite. [file:3]

Flexible

• Kapton, Pyralux. [file:3]
• #1 epoxy film, #1126 copper tape. [file:3]

High-frequency

• Teflon. [file:3]
• Glass. [file:3]

Copper thickness

• 0.5 oz: 17.5 µm copper. [file:3]
• 1.0 oz: 35 µm copper. [file:3]
• 2.0 oz: 70 µm copper. [file:3]

Board houses and layers

• Board houses in Shenzhen can fabricate PCBs at low cost. [file:3]
• Typical design rule for traces and clearances is 5 mils. [file:3]
• Layer options include 1, 1.5, 2, 2+, 4, and higher layer counts. [file:3]
• Rivets can be tricky at very small sizes and may cause cross-connections on 2-layer boards. [file:3]
• Many devices use 4-layer boards, while phones often use 6 layers. [file:3]

Components, assembly, and CAM

Beyond fabrication, electronics production also involves selecting components, assembling boards, and preparing files for services. [file:3]

Components and sourcing

• Use Octopart to search for components and access datasheets. [file:3]

Breadboards

• Breadboards are good for beginners but are not very aesthetic for final projects. [file:3]

Assembly and soldering

• Soldering and wiring are needed to assemble the board. [file:3]
• Aim for smooth, non-lumpy solder joints. [file:3]
• Hold the solder slightly after applying heat to let the joint set properly. [file:3]

Rework and desoldering

• Stuffing and desoldering techniques are important so components can be reworked if needed. [file:3]

CAM and file formats

• Gerber is the standard format for CAM when sending boards to fabrication houses. [file:3]

Machine cutting workflow

Digital fabrication of PCBs often starts from images or vector files and goes through a CAM pipeline. [file:3]

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

Quentorres development board

For the individual assignment I made and tested the Quentorres microcontroller development board. [file:3]

• Uses the XIAO RP2040 as the main microcontroller. [file:3]
• Includes a button as a simple input and an LED as a simple output. [file:3]
• The design is CNC-machined and documents the full electronics production workflow. [file:3]

Evidence (images)

Replace these placeholder images in images/week4/ with your own photos and screenshots. [file:3]

Machining setup

Fixturing, underlay, and zeroing the board before milling. [file:3]

Milled PCB

Traces after machining, deburring, and cleaning. [file:3]

Quentorres assembled

XIAO RP2040 board with button input and LED output. [file:3]

Vinyl-cut copper

Flexible copper circuits cut on the vinyl cutter. [file:3]

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. [file:3]

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