Skip to content

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

Studied Topics

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.

Group and Individual Assignment

For our group assignment on electronic production, we completed all stages end to end: first, we designed the circuit board by capturing the schematic, selecting footprints, defining the stack-up, running ERC/DRC, and exporting Gerbers and a BOM; next, we “printed” (fabricated) the PCB by transferring copper patterns, drilling vias and mounting holes, routing the outline, and adding fiducials for accurate placement; then we soldered the board by applying paste, placing SMD parts for reflow, hand-soldering through-hole components, and inspecting polarity and joints under magnification; finally, we debugged by running continuity and power-on tests, reworking bridges or cold joints, replacing any misaligned parts, and feeding those lessons back into revised footprints and routing so the next build is more reliable and repeatable.

We had made the Electronic Production of all stages.

1. Designing Circuit Board

Process Demonstration

In schematic part, we picked up the Microcontroller, ESP32-WROOM-32U , boot/reset control, a UART header for programming, a few GPIO break-outs, and three indicator LEDs around it. Two LEDs (L1, L2) each have a series resistor (R1, R2, 1206 package). Headers labeled SV1 / SV2 / SV3 break out several GPIO pins (e.g., IO1…IO10 etc.) plus power/ground for hooking up sensors/actuators.

This PCB places an ESP32-S3 module in the center with a large ground/thermal pad, surrounded by BOOT/RESET switches at the top, two LED-resistor pairs at the bottom, and a 1×6 FTDI/UART header on the right.

in KiCad opened File → Fabrication Outputs → Gerbers… to generate the manufacturing layers for our board. In the Gerber dialog, we selected the layers we need (F.Cu/B.Cu, F.SilkS/B.SilkS, F.Mask/B.Mask, Edge.Cuts), set the plot format, then clicked Plot; next opened Generate Drill Files… to create the Excellon drills. Finally, zip the Gerbers + drills and inspected them in Gerber Viewer to verify registration, holes/slots, and polarity before sending to a board house or milling workflow.

We used Gerber2PNG to turn your KiCad Gerbers into a 1-bit PNG for PCB milling. Here in the Gerber, the white areas are copper to be kept (pads/traces), the black is what the is t be removed.

2. Printing Circuit Board

Process Demonstration

We used modsproject.org and opened programs →to switch G-code to mill 2D PCB, then it read png and loaded the 1-bit PNG of top copper (1000 DPI)

Then we changed the V-bit values to match tool: here a 30° V-bit with 0.1 mm tip, 2 offsets, 0.5 stepover, feed 4 mm/s This selected values gaved cut width ≈ 0.304 mm (12 mil) and cut depth ≈ 0.382 mm.

In mill raster 2D, we set the tool diameter = 0.3048 mm, cut depth = max depth = 0.382 mm, offsets = 2, stepover = 0.5, climb direction, then set origin/jog/home, previewed the toolpath, and saved G-code—zero Z on the copper, run an air pass, and mill.

Toolpath preview shows Blue lines which are isolation passes, red lines are rapids; we generated 2 offsets around every white copper region so traces stay insulated.

We picked Cutters: 30° V-bits with 0.1 mm tip (used for isolation).

On Workholding: FR-1 board taped down to a flat MDF spoilboard with double-sided Nitto tape for full-surface support.

The we setuped the Desktop CNC with dust extraction; MDF spoilboard installed and squared. V-bit mounted, XY zero set to the board corner; Z zeroed on copper using the paper-touch method.

Our board showed poor result as it made uneven isolation widths, ragged edges, and patches of copper left behind. It showed that spoilboard was not perfectly coplanar, so the V-bit cuted too deep in some areas and barely touches in others. a V-bit at~0.38 mm made huge, blowing out traces and leaving torn copper. Tool width/DPI in mods didn’t match, so paths were spaced wrong; chips weren’t cleared between passes.

3. Soldering Circuit Board

Process Demonstration

We assemblied the milled PCB, ESP32-S3 module, SMD passives, LEDs, buttons, and headers—with the board in a PCB vise.

At first, we made the afe soldering plan that worked well for milled boards. We scrubed copper lightly (Scotch-Brite/eraser) and then wiped with IPA, inspected for shorts/opens and fluxed the pads.

The sides of ESP32 module were soldered first.

4. Fixing problems and doing again

Process Demonstration

As our first attempt was failed so we decided to redo and made changes:

We changed the cut depth = max depth = 0.10 mm (vs. 0.38 mm before) with a 30°/0.1 mm V-bit → effective tool width ≈ 0.305 mm (12 mil) and kept 2 offsets and 0.5 stepover. Its path order corrected forward, climb cut.

We verified with a small trace/space coupon, then milled the full board.

Then we checked the house rules and got better results as it demonstrated reliable trace/space ≥ ~0.30 mm (12 mil), and the isolation looked uniform with sharp corners.

We used 1000 DPI PNGs, set tool diameter in mill raster 2D to the calculator’s width (≈0.305 mm) and prefered shallow passes (0.10–0.15 mm) with more offsets instead of deeper cuts. It kept the board very flat and Z-zero on copper.

The module soldered again on a new board.

We satisfied with quality of the board and then coded.

From Vimeo

CODE: 

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"

#define LED1 25
#define LED2 32
#define LED3 33
static void init_hw(void)
{
gpio_config_t io_conf = {0};
io_conf.intr_type = GPIO_INTR_DISABLE;
io_conf.mode = GPIO_MODE_OUTPUT;
io_conf.pin_bit_mask = (1ULL<<LED1) | (1ULL<<LED2) | (1ULL<<LED3);
gpio_config(&io_conf);
}

void app_main(void)
{
init_hw();

while (1) {
gpio_set_level(LED1, 1);
gpio_set_level(LED2, 0);
gpio_set_level(LED3, 0);
vTaskDelay(pdMS_TO_TICKS(200));

gpio_set_level(LED1, 0);
gpio_set_level(LED2, 1);
gpio_set_level(LED3, 0);
vTaskDelay(pdMS_TO_TICKS(200));

gpio_set_level(LED1, 0);
gpio_set_level(LED2, 0);
gpio_set_level(LED3, 1);
vTaskDelay(pdMS_TO_TICKS(200));
}
}

Learning outcomes

This week’s topic was completely new to me, so I needed to build a foundation in electronics production. I studied comprehensive guides covering PCB fabrication, machining, materials, assembly, and CAM, which together map the entire manufacturing workflow. These resources explained how designs move from files to finished boards—through patterning copper, drilling and routing, choosing the right laminates, and soldering components. They also highlighted practical checks like DFM/DFT and CAM reviews that prevent costly errors and ensure reliable results. I learned why stack-up choices, copper weight, and tolerances matter, and how panelization and fiducials improve yield. Overall, the guides gave me a clear, end-to-end view of PCB manufacturing and the key decisions that influence quality, cost, and lead time.