Week 8: Electronics Production

Week 8 Assignment:

1. Group Assignment

   1. Characterize the design rules for your in-house PCB production process
   2. Submit a PCB design to a board house

2. Individual Assignment

   1. Make and test an embedded microcontroller system that you designed

3. Extra credits:

   • Make it with another process

Notes from the Lecture

• Design rules: what is the actual spacing, how close can it be together. and how skinny can you make a trace and it still survive.

• end mill

• material
• fixturing -> to hold the position. one way to do it is with tape underneath, another way is with clamps. with clamps -> make sure it doesn’t bow/no bending -> stress the board and can break end mills. MAKE SURE THE BOARD STAY FLAT

top to bottom

- materials
- underlay -> sacrifical layer. it must be flat, or else it will be a problem: your board won't be uniform. you periodically need to replace the underlay.
- moving bed

PCB Materials

- FR4 -> a glass fiber in epoxy metrics. this is hazardous for machining, we don't do it inside the labs
- FR1 -> copper with phenolic materials, safe and no hazard
- garolite
- copper -> usually we use 1.0 oz: 35 um

GROUP ASSIGNMENT

PCB Production

(18 Mar 2026) This week, I explored different ways to produce a PCB. While waiting for the new CNC milling machine to arrive, I tried vinyl cutting and laser cutting, but they did not turn out as planned…

CNC Milling

18 Mar 2026 - The CNC milling machine is not working, so we are still waiting the new one to arrive.

(22 March 2026) The new CNC milling just arrived, but not yet set up.

Vinyl Cutting

Failure

(18 Mar 2026) I made several attempts, but they all failed. The blade was already dull, so I asked my instructor to purchase a new 60° blade.

1. I used conductive gray paper as the material:

   

   First, I saved my PCB design in KiCad as an SVG file.

   Go to: File → Plot

   

   Then, this window will appear:

   

   I opened the SVG file, arranged the design, and converted it to a PNG file:

   I also added some text and a logo:

   I tried to cut the PCB design using a Cricut Explorer on this material, but all attempts failed. Regardless of whether I used low or high settings, the results were unsuccessful—the paper kept curling up as shown below:

   I tried different cut settings:

   I also tried mirroring the design and cutting it on the other side of the paper:

   However, all attempts failed.

2. Therefore, I tried using a different material and found copper tape:

   

   My design dimensions were 7 × 7 cm, but the copper tape width was only 6 cm. Therefore, I needed to adjust my design to fit the tape. Here is the updated design:

   

   I referred to Eduardo Chamorro’s documentation, where he used a PVC sheet as a base and placed copper tape on top. Inspired by this, I tried a similar approach.

   I placed the copper tape on top of a PVC sheet and cut it:

   

   However, I was not able to remove the unwanted copper tape from the PVC sheet.

   

3. I also tried the same method using conductive gray paper on a PVC sheet. This time, I successfully cut it and performed the weeding process:

   

   However, when I tried to solder the gray paper material, it melted…

   

Even though I did not succeed in producing a PCB using the vinyl cutter, I learned a new skill: WEEDING.

Laser Cutting

Failure

(18 Mar 2026) We checked it with multimeter, all of the parts of the board is connected. It might be because the laser cut was not deep enough to remove the copper surface.

Please refer to Timothy’s documentation.

Submit a PCB design to a Board House

on 16 March 2026, I submitted my PCB design to JLCPCB. Since I am based in Shenzhen, I wanted to try ordering from the China website, but I was not able to sign up because I do not have a Chinese phone number.

1. Before going to the JLCPCB website, I first prepared the Gerber files (.gbr) in KiCad:

   Go to:

   File → Fabrication Outputs → Gerbers (.gbr)

   

   Then, this window will appear:

   You can choose which layers you want to export. I selected the following layers: F.Cu, B.Cu, F.Paste, B.Paste, F.Mask, F.Silkscreen, B.Silkscreen, F.Mask, B.Mask, Edge.Cuts

   

2. Next, I opened the JLCPCB website and uploaded the Gerber files.

   

3. Then, I selected the specifications:

   • Base Material: FR-4
   • Layers: 1
   • Dimensions: 7 x 7 cm (according to your design)
   • PCB Qty: 5 (minimum quantity is 5)
   • Product Type: Industrial/Consumer electronics
   • Different Design: 1
   • Delivery Format: Single PCB
   • PCB Thickness: 1.6mm
   • PCB Color: Green
   • Silkscreen: White
   • Material Type: FR4 TG135
   • Surface Finish: HASL (with lead)
   • Confirm Production File: Yes

   

   

   

   Once everything was correct, I made the payment. Here is the cost breakdown:

   Description	Price
   5 Circuit Board	USD $3.14 (€2.73)
   Shipping	USD $2.04 (€1.77)
   Discount	-USD $2.04 (€1.77)
   Grand Total	USD $3.14 (€2.73)

   

   The order has been placed:

   

   We can check the detailed production progress in the Order History tab:

   

   Since I selected Confirm Production File, I received an email the next day to confirm the production files. After confirming, production started.

   

(22 March 2026) My first PCB board from JLCPCB has arrived!

INDIVIDUAL ASSIGNMENT

Make and Test an Embedded Microcontroller System

(18 March 2026) Since I have not yet succeeded in producing the PCB board, I have not completed building and testing an embedded microcontroller system.

(23 March 2026) My PCB board from JLCPCB just arrived yesterday, so I tried to build and test the embedded system using it.

1. First, I used solder paste to hold the components on the PCB. I applied a small amount of solder paste and placed the components on top. I started with the buttons to practice because they are slightly bigger than the other components (resistors and LEDs).

   

   Info

   To preserve its quality and usability, solder paste should be stored in the fridge after use.

   

   I placed the PCB directly on the soldering hot plate while it was turned off, so I wouldn’t have to move it later (to avoid components falling off after placement). Another benefit is that the height makes it easier to assemble the components.

   

   I finished applying the solder paste and placing the buttons:

   

2. Next, I turned on the soldering hot plate. It heats up and melts the solder paste, allowing the solder to hold the components in place. You can see the heating process in the video below:

   After finishing the buttons, I also assembled the other components (resistors and LEDs).

   

3. I uploaded the code to the XIAO ESP32C3 microcontroller that I wrote in Week 6 (generated by ChatGPT):

   // LED pins
   const int led1 = D0;
   const int led2 = D1;
   const int led3 = D2;
   const int led4 = D3;
   const int led5 = D4;
   
   // Button pins
   const int button1 = D9;
   const int button2 = D8;
   const int button3 = D7;
   const int button4 = D6;
   const int button5 = D5;
   
   // LED states (remember ON or OFF)
   bool ledState1 = false;
   bool ledState2 = false;
   bool ledState3 = false;
   bool ledState4 = false;
   bool ledState5 = false;
   
   // Previous button states
   bool lastButton1 = HIGH;
   bool lastButton2 = HIGH;
   bool lastButton3 = HIGH;
   bool lastButton4 = HIGH;
   bool lastButton5 = HIGH;
   
   void setup() {
   pinMode(led1, OUTPUT);
   pinMode(led2, OUTPUT);
   pinMode(led3, OUTPUT);
   pinMode(led4, OUTPUT);
   pinMode(led5, OUTPUT);
   
   pinMode(button1, INPUT_PULLUP);
   pinMode(button2, INPUT_PULLUP);
   pinMode(button3, INPUT_PULLUP);
   pinMode(button4, INPUT_PULLUP);
   pinMode(button5, INPUT_PULLUP);
   }
   
   void loop() {
   
   // ----- BUTTON 1 -----
   bool currentButton1 = digitalRead(button1);
   
   if (lastButton1 == HIGH && currentButton1 == LOW) {
       ledState1 = !ledState1;          // TOGGLE
       digitalWrite(led1, ledState1);
       delay(200);                      // debounce
   }
   lastButton1 = currentButton1;
   
   // ----- BUTTON 2 -----
   bool currentButton2 = digitalRead(button2);
   
   if (lastButton2 == HIGH && currentButton2 == LOW) {
       ledState2 = !ledState2;
       digitalWrite(led2, ledState2);
       delay(200);
   }
   lastButton2 = currentButton2;
   
   // ----- BUTTON 3 -----
   bool currentButton3 = digitalRead(button3);
   
   if (lastButton3 == HIGH && currentButton3 == LOW) {
       ledState3 = !ledState3;
       digitalWrite(led3, ledState3);
       delay(200);
   }
   lastButton3 = currentButton3;
   
   // ----- BUTTON 4 -----
   bool currentButton4 = digitalRead(button4);
   
   if (lastButton4 == HIGH && currentButton4 == LOW) {
       ledState4 = !ledState4;
       digitalWrite(led4, ledState4);
       delay(200);
   }
   lastButton4 = currentButton4;
   
   // ----- BUTTON 5 -----
   bool currentButton5 = digitalRead(button5);
   
   if (lastButton5 == HIGH && currentButton5 == LOW) {
       ledState5 = !ledState5;
       digitalWrite(led5, ledState5);
       delay(200);
   }
   lastButton5 = currentButton5;
   }
   

   4. Then, I soldered the XIAO ESP32C3 onto the PCB. (I worked on another PCB where I did not place the SW1 button initially, because I had made a mistake: the SW1 button slightly blocked access to the USB-C port.)

   After confirming that the code worked properly, I placed the SW1 button on the board. This time, I tried using a hot air gun, but I found that the soldering hot plate is more convenient.

4. After placing the final button, I connected the board to a battery to test how it worked:

   It ran smoothly! 🙂

My Mistake

I placed the XIAO ESP32C3 microcontroller in the middle, and the button “SW1” slightly blocks access to the USB-C port. It still works, but next time it would be better to place the microcontroller on the side so it’s easier to plug in the USB-C cable.