Week 08
Electronics Production

Assignment

Group Assignment

The group assignment was to characterize the design rules for our in-house PCB production process and submit a PCB design to a board house.

Individual Assignment

The individual assignment was to make and test an embedded microcontroller system that I designed.

Introduction

Electronics production is the process of fabricating and assembling printed circuit boards. Compared with using a breadboard, a PCB provides a more stable, compact, and repeatable way to connect components.

For my individual assignment, I designed a custom development board based on the Seeed Studio XIAO ESP32C3. The board includes an onboard LED connected to D3, a slide switch, two servo connectors, a serial communication header, and an external power input. The purpose of this board is to create a small embedded system platform for later Fab Academy assignments.

Group Assignment

PCB Design Rule Test

For the group assignment, we characterized the design rules of our in-house PCB production process. We used a test pattern with different trace widths and spacings to understand the minimum reliable dimensions that could be produced with our PCB milling machine.

We then prepared the milling parameters, including spindle speed, feed rate, cutting depth, and toolpath strategy. These parameters directly affect the quality of the traces and the depth of the cut.

Group Result

From this test, I learned that PCB design rules are not only software settings. They depend on the machine, the tool, the material, the flatness of the board, and the accuracy of zeroing. Even if very thin traces can be drawn in software, they may not be reliable in the actual fabrication process.

Based on the milled test board, wider traces and clearances were more stable, while very thin traces became fragile or were not isolated cleanly. Therefore, for my own board, I avoided extremely narrow traces and kept enough clearance between pads and routes.

Submitting a PCB Design to a Board House

The second part of the group assignment was to submit a PCB design to a board house. Since I designed my board in LCEDA-Pro, I used the integrated JLCPCB layout ordering workflow. This allowed me to submit the layout directly from the same design environment.

I did not need to complete the payment process for this assignment. The purpose was to verify that the PCB design could be submitted to a professional board-house platform and checked as a manufacturable layout.

This step also helped me compare in-house milling with board-house production. Board houses can provide solder mask, silkscreen, plated holes, and more stable manufacturing tolerances, while in-house milling is faster for local prototyping.

Individual Assignment

Board Concept

My board was designed as a compact XIAO ESP32C3 development board. I wanted it to support several basic functions that would be useful for later assignments: LED output, switch input, servo output, serial communication, and external power.

• XIAO ESP32C3 microcontroller module
• LED connected to D3
• Slide switch connected to the power line
• Two 3-pin servo connectors
• TX / RX / GND serial communication header
• 5V external power input
• 3V3, 5V, and GND expansion headers

Schematic Design

I designed the schematic in LCEDA-Pro. The XIAO ESP32C3 is the main microcontroller. Around it, I added headers, servo connectors, a slide switch, power input, and an LED circuit.

The LED circuit is connected from D3 through a current-limiting resistor to GND. Therefore, when D3 is set to HIGH, the LED should turn on.

BOM and Component Source

I checked the bill of materials directly in LCEDA-Pro. Most of the components were selected from LCSC, the component supplier integrated with LCEDA-Pro and JLCPCB. The BOM table helped me check component names, designators, package types, supplier information, stock, and estimated unit prices before fabrication and assembly.

Estimated BOM Cost

Based on the BOM generated in LCEDA-Pro, I estimated the cost of the main peripheral components used on the board. The table below does not include PCB fabrication, shipping, or the XIAO ESP32C3 module itself, because the XIAO module price was not included in the BOM list shown in LCEDA-Pro.

The estimated cost of the peripheral components is about RMB 2.29, excluding the XIAO ESP32C3 module, PCB fabrication, and shipping. The PCB fabrication was prepared through JLCPCB in China, while most electronic components were sourced from LCSC.

This BOM check was useful because it connected the schematic design with real component availability and cost. It also helped me confirm that the selected packages matched the footprints used in the PCB layout.

PCB Layout and DRC

After finishing the schematic, I moved to PCB layout. I placed the XIAO module in the center of the board and arranged the connectors around it. The LED and resistor were placed on the left side, while the power input and slide switch were placed on the right side.

Before fabrication, I used the DRC function to check the design. The result panel showed “All (0)”, which means no design rule errors were detected before exporting the board.

PCB Fabrication

After finishing the PCB layout, I prepared the milling file and fabricated the PCB using the in-house CNC milling process. The copper board was fixed firmly to the machine bed, and the tool height was carefully zeroed before cutting.

During fabrication, I noticed that milling quality was affected by cutting depth, board flatness, and toolpath settings. If the cutting depth was too shallow, copper was not fully isolated. If it was too deep, traces became rough or fragile.

Soldering and Assembly

After milling the PCB, I assembled the board manually. Some components, such as the resistor, LED, and slide switch, were surface-mount components. Compared with through-hole parts, SMD components require more careful alignment because the pads are smaller and the component orientation is more important.

After soldering, I inspected the board visually. I looked for solder bridges, cold solder joints, missing connections, and incorrect component orientation. This step was especially important because small soldering mistakes can prevent the board from working even if the schematic and layout are correct.

Continuity Test

Before programming the board, I used a multimeter to check the continuity of important traces. This helped me confirm that the milled traces were connected correctly and that there were no unexpected short circuits between power and ground.

Programming the Board

I programmed the board using Arduino IDE. First, I installed the ESP32 board package and selected XIAO ESP32C3 as the target board. Then I selected the correct serial port from the Tools menu.

During this process, I learned the difference between compiling and uploading. “Done compiling” only means the code has been compiled successfully, while “Done uploading” or “Hash of data verified” means that the program has actually been written to the board.

Testing the D3 LED

The first functional test was to control the LED connected to D3. In my circuit, the LED is connected from D3 through a resistor to GND, so D3 should be set to HIGH to turn the LED on.

#define LED_PIN D3

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  delay(1000);

  digitalWrite(LED_PIN, LOW);
  delay(1000);
}

Troubleshooting and Debugging

Debugging means finding and fixing problems in both the software and the physical circuit. In electronics production, a board may fail because of code, upload settings, pin definitions, soldering, component orientation, or broken traces. Therefore, I checked the problem step by step instead of assuming that it was only a software issue.

One issue I encountered was related to the pin name. I first tried to define the LED pin as A3, but Arduino IDE returned a compilation error. The error message suggested that A3 was not declared in this scope and asked whether I meant D3. This helped me understand that the board package expected the pin to be written as D3 instead of A3.

I also encountered an upload issue. Arduino IDE showed that the sketch had compiled successfully, but the upload failed because the selected serial port was no longer available. I solved this by unplugging and reconnecting the XIAO ESP32C3, then selecting the new serial port from Tools > Port.

After correcting the code and selecting the correct port, I checked the hardware side when the LED did not respond immediately. I inspected the LED orientation, resistor soldering, D3 trace, and GND connection. This helped me understand that debugging an embedded system requires checking both the software and the physical circuit.

Reflection

This week helped me understand electronics production as a complete workflow. Before this assignment, I mainly thought of PCB design as drawing traces on a screen. After going through the process, I realized that PCB production is closely connected to fabrication limits, component packages, soldering quality, and testing methods.

The most important lesson for me was that debugging should happen step by step. When the board did not work immediately, I needed to separate possible problems: schematic design, PCB layout, DRC, milling quality, soldering, serial port selection, code upload, and pin definition.

Overall, this assignment gave me a much clearer understanding of how to design, fabricate, assemble, program, and test a small embedded microcontroller system.