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9. Electronics Production

Week Assignment

Group assignment:

  • Characterize the design rules for your in-house PCB production process: document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling.
  • Document the workflow for sending a PCB to a boardhouse
  • Document your work to the group work page and reflect on your individual page what you learned

Individual assignment:

  • Make and test a microcontroller development board that you designed

Learning outcomes

  • Described the process of tool-path generation, milling, stuffing, de-bugging and programming
  • Demonstrate correct workflows and identify areas for improvement if required

Have you answered these questions?

  • Linked to the group assignment page
  • Documented how you made the toolpath
  • Documented how you made (milled, stuffed, soldered) the board
  • Documented that your board is functional
  • Explained any problems and how you fixed them
  • Uploaded your source code
  • Included a ‘hero shot’ of your board
Basic Defitions of the Electronic Production

These recources give Comprehensive Guides to PCB Fabrication, Machining, Materials, Assembly, and CAM

PCB Manufacturing Process: A Comprehensive Guide|mktpcb.com

PCB Assembly - A Comprehensive Guide|nextpcb.com

PCB Manufacturing Process|protoexpress.com

The Ultimate Guide to PCB Assembly: Everything You Need to Know|camtechpcb.com/

These guides cover all aspects of PCB manufacturing, from fabrication and machining to materials, assembly, and CAM.

1. PCB (Printed Circuit Board) Fabrication

Dead Bug Circuits A prototyping method where ICs and components are mounted upside down, with their leads bent upward for easy soldering or wire-wrapping. Often used in RF circuits, quick modifications, and space-limited setups.

Etching A chemical process used to remove excess copper from a PCB, forming circuit traces.

  • Set-up, Feature Size, Batch
  • Set-up – Preparing materials, chemicals, and the workspace for PCB fabrication.
  • Feature Size – The smallest trace width, spacing, or hole size that can be reliably manufactured.

Batch – The number of PCBs processed simultaneously, influencing cost and efficiency.

Lithography, Transfer, Print

  • Lithography – Using photoresist and UV light to define circuit patterns on a PCB.
  • Transfer – Methods for applying designs onto the PCB, including toner transfer, inkjet printing, and direct exposure.
  • Print – Screen printing or direct PCB printing for circuit traces.

Ferric/Cupric Chloride, Ammonium/Sodium Persulfate

  • Ferric Chloride (FeCl₃) – A widely used but highly corrosive etchant, producing stains and hazardous waste.
  • Cupric Chloride (CuCl₂) – Recyclable etchant that requires acidic regeneration.
  • Ammonium Persulfate (NH₄)₂S₂O₈ – Clear etching solution that provides precise etching but degrades over time.
  • Sodium Persulfate (Na₂S₂O₈) – A similar alternative with slightly longer shelf life.

Citric Acid, Peroxide

  • An eco-friendly etching alternative using hydrogen peroxide, citric acid, and salt.
  • Less toxic and safer for small-scale PCB manufacturing.

SDS (Safety Data Sheet)

  • A document detailing chemical hazards, handling precautions, and emergency procedures.

Water Consumption - The amount of water used for PCB rinsing, cleaning, and cooling in the etching process.

Waste - Disposal of etchants, metals, and other residues following environmental regulations.

2. Machining

Finish

  • The final surface quality of the PCB after machining, influencing solderability and electrical performance.

Machines

  • CNC routers, milling machines, and laser cutters used for PCB drilling, routing, and engraving.

Tools

  • Various drill and milling bits used for PCB machining.

0.010”, 1/64”, 1/32” (Drill or Mill Bit Sizes)

  • 0.010” (10 mils) – For ultra-fine engraving and micro-traces, fragile but precise.
  • 1/64” (15.6 mils) – Standard for cutting isolation paths, balancing durability and precision.
  • 1/32” (31.25 mils) – Used for cutting large traces and board outlines.

V-bits, Tapered Bits

  • V-bits – Conical bits used for engraving fine details.
  • Tapered Bits – Provide angled cuts and depth control for intricate patterns.

Fixturing

  • Securing the PCB in place during machining to prevent movement.

Underlay - A protective material under the PCB to prevent damage to the machine bed.

Zeroing - Calibrating the tool’s starting position to ensure precise cutting depth and alignment. - Mounting, Lowering, Probing – Steps involved in tool calibration.

Set-screws, Collets

  • Tool-holding mechanisms that secure the cutting bits in CNC machines.

Lifetime

  • The durability of tools depends on cutting speed, material, and usage frequency.

Deburring

  • Smoothing rough edges after drilling or milling.

Cleaning

  • Removing dust, debris, and residue from machined PCBs.

Climb vs Conventional Milling

  • Climb Milling – Produces smoother cuts, less tool wear.
  • Conventional Milling – Offers better control on harder materials.

Nesting

  • Arranging multiple PCB designs on a single sheet to optimize material usage.

Registration

  • Aligning PCB layers accurately to prevent misalignment.
3. PCB Materials

Rigid PCBs

  • FR4 (Epoxy Glass) – The most common PCB material, strong and flame-resistant.
  • FR1 (Phenolic Paper) – Cheaper alternative, good for single-layer PCBs.
  • Garolite – High-strength fiberglass-based PCB material.

Flexible PCBs

  • Kapton, Pyralux – Flexible, heat-resistant polymer substrates.
  • Epoxy Film, #1126 Copper Tape – Adhesive-backed materials for flex circuits.

High-Frequency Materials

  • Teflon (PTFE) – Low-loss dielectric for RF and microwave applications.
  • Glass – Used in high-performance, high-speed circuits.

Copper Thickness

  • 0.5 oz (17.5 µm) – Used for low-power applications.
  • 1.0 oz (35 µm) – Standard thickness for most PCBs.
  • 2.0 oz (70 µm) – For high-power circuits requiring better conductivity.
4. Assembly

Soldering

  • The process of joining components to the PCB using molten solder.

Iron Station, Fume Extractor, Burns

  • Iron Station – Controls temperature for precise soldering.
  • Fume Extractor – Removes toxic flux fumes.
  • Burns – A common hazard in manual soldering.

ROHS - Restriction of Hazardous Substances compliance, limiting lead and other toxic materials in electronics.

Types of Solder

  • Lead-Free Wire/Paste SDS – Environmentally friendly but requires higher temperatures.
  • Leaded Wire/Paste SDS – Easier to work with but contains hazardous lead.
  • Low-Temp Wire/Paste – Used for sensitive components to prevent damage.

Eutectic, Tinning, Wetting

  • Eutectic Solder – Melts and solidifies at a single temperature.
  • Tinning – Pre-coating metal surfaces with solder for better adhesion.
  • Wetting – Ensures solder flows and bonds properly.

Soldering Methods

  • Manual, Drag, Wave – Different techniques for applying solder.

Common Soldering Issues

  • Cold Solder Joints – Weak connections due to improper heating.
  • Solder Bridges – Unintended connections between pads.
  • Checking Joints – Inspecting soldered connections for defects.

Reflow Soldering

  • Stencil – Used for applying solder paste before component placement.
  • Hot Air, Hot Plate, Oven, IR – Different heating methods for reflow soldering.

Magnifying - Used for inspecting small solder joints for quality assurance.

5. CAM (Computer-Aided Manufacturing)

Formats

  • Gerber/RS-274X – Standard file format for PCB manufacturing.
  • PNG Resolution – Used for viewing PCB layouts in image format.

Software

  • FlatCAM, pcb2gcode – Converts Gerber files to CNC machine code.
  • gerber2img, gerber2png – Tools for visualizing PCB layouts.

Trace Width

  • Defines circuit paths and spacing requirements in PCB layouts.