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.

Individual Assignment For individual assignment on electronic production, I prepared PCB Design to print circuit board by making circuit traces and molding. Schematic design prepared in previous week was processed for the next stage to do PCB design to cut by usingused an SRM-20 milling machine to cut it from a PSB board. Production process undergone in the following stages:

PCB Preperation Processs
Schematic Design Export to the Gerber and the Drill Files
Conversion of images into G-code: PNG or SVG conversion into Mods toolpath generation
CNC milling machine (SRM-20) setup and tool preperation
PCB milling process: tracing, drilling and outline
Soldering and assembling smd components on board
Key challenges and Learning outcomes

1. PCB Preperation Processs

I had two schematic designs: one is ESP32-WROOM-32U and another is ESP-12E

1a. Working with PCB Editor on the ESP32-WROOM-32U schematic

My short description of first experience: In schematic part, I 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.

I switched schematic to PCB Editor where 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.

After finishing the PCB layout, the file on fabrication output was sent to Gerber file, which edited the schematic to fit the production requirement.

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.

1b. Working with PCB Editor on the ESP-12E schematic

Detailed explanation of my second experience as I found that It is neccesary to show all important steps.

I decided to use the ESP-12E for the final project, so PCB production was processed.

After finishing the schematic design and fixing all errors with ELECTRICAL RULER CHACKER, i switched to PCB editor, which gave me two immediate errors related to the footprints of SWITCH and PINHEADER.

After fixing the errors, PCB editor brings together all schematic components and put to left bottom conner of PCB Editor and here the carefull work began. Simple, the schematic design might not be converted to BCB Board.

By clicking BOARD SETUP, first, open BOARD EITOR LAYERS and PHYSICAL STACKUP to set board configuration.

then with DRAW LINES located on left panel, square outline of PCB board was created and all component brought inside of the square and connected with wires.

by clicking VIEW and then 3D VIEW, I can see all possible direction of pinheaders. In my case, I found my mistake that PCB layer was difined as two layer PCB board; however, I have one layer connection. In my first experience I did not relise this mistake.

So I changed footprint side from BACK to FRONT.

Then I changed tracing width from 0.2mm to 0.4 mm and selected front layer - F.CU

Another important step in preparing the PCB board is that all component must be in SMD form, so by clicking on each component, in PAD PROPERTIES, pad type must be changed from THROUGH-HOLE to SMD.

After all changes made to PCB Board design, I got this beutiful ESP-12E PCB.

2. Schematic Design Export to the Gerber and the Drill Files

The next steps were to make FABRICATION OUTPUTS in the form of GERBER and DRILL FILES At first, the PLOT and then the GENERATE DRILL FILES were done

THE GERBER FILES were created in the same way and properly saved.

Three files (traces, drills, and outlines) were converted PNG FORMAT by using GERBER2PNG website where all files were uploaded and converted and downloaded.

In MODSPROJECT, go to the G-CODE and select MILL 20 PCB.

3. Conversion of images into G-code: PNG or SVG conversion into Mods toolpath generation

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

Then, by using MODSPROJECT.ORG, the PNG files were uploaded to set the tool parameters. This show immediate upload for all part of MODS where configuration shows primary values of a V-bit calculator

As files were in PNG format, PNG read shows further detail. This is my favority program as it simplified the communication with milling machine.

In particularly in a V-bit calculator, tip diamer’s value was changed from 0.0039 to 0.1.

toolpaths were generated by using the “mill raster 2D” process. As a result the G-code was exported.

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.

4. CNC milling machine (SRM-20) setup and tool preperation

SRM-20 Milling Machine YU Fab Lab had new SRM-20 Milling Machine, which considerable changed the quality of milling process. The SRM-20 is a desktop milling machine using the rotary tools to cut traces and drill holes.

Then I 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.

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

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

5. PCB milling process: tracing, drilling and outline

PCB Milling Process starts from uploading files for tracing, drilling and outline.

Before milling, as primary important step, the zeroing of the Z distance of V-Bit is made.

Despite all configuration set, due to the difference in the milling speed for tracing, drilling and outline, V-bit got broken. In my case I experienced twice.

Despite all experienced the failure in cutting outline, I had perfectly milled board.

6. Soldering and assembling smd components on board

Process Demonstration

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

At first, I made the safe 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.

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.

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));
    }
    }

7. Key challenges and Learning outcomes

As there was the first failure 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.

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.

Key definition

Being familiar with key definition is important, in my case, English is not my primary language, so I have to have them.

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.