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8. Electronic Production

This week, I explored electronic production by milling and soldering a PCB.

I am going to be producing the PCB which I designed in Week 6: Electronics Design.

Part 1: Understanding

What is a PCB?

A PCB is an electronic assembly that uses copper conductors to create electrical connections between components. Its structure includes conductive features like copper traces, pads, and planes, laminated between insulating materials. The board is plated, covered with a non-conductive solder mask, and often printed with a silkscreen legend for component identification.

PCB Structure

Types of PCBs

  • Single-sided: Components mounted on one surface; the back is typically a full copper ground plane coated with solder mask.
  • Double-sided: Components on both surfaces with traces carrying signals between them.
  • Multi-layer: Multiple conductor layers, possibly including internal signal or plane layers; can be single or double-sided.
  • Rigid: Fabricated on rigid materials like FR4-grade epoxy resin-impregnated fiberglass.
  • Rigid-flex: Combines rigid sections connected by flexible polyimide ribbons, suitable for designs requiring movement.
  • Flex: Entirely flexible, made of polyimide ribbons without rigid materials.
  • Metal core: Features a metal core (usually aluminum) for increased rigidity and heat dissipation.
  • Ceramic: Used in applications requiring high thermal conductivity to dissipate large amounts of heat.

Machine in our Fab Lab

Our fablab has two machines Roland SRM 20 and Protomat E44. Fo this week I used Roland SRM 20 for the production of my pcb. Link to know more about the machine

Roland SRM-20 is a compact, desktop CNC milling machine used for PCB fabrication, prototyping, and engraving. It’s designed for precision prototyping and PCB fabrication.

Part 2: Developing the board

Understanding V-Panel

V-Panel is the software used to control the Roland SRM-20 milling machine. It helps move the machine, set the starting point (zero position), and start or stop the milling process.

How to install it?

To operate the Roland SRM-20 milling machine, I needed to install the VPanel software, which serves as the control interface for the machine. To download VPanel, I visited the official Roland DG. From there, I searched for “SRM-20” and navigated to the product page. Link to download the software.

After clicking on the link on the website the below page appears. Click on the software

Scroll down and click on V-panel for SRM-20 and then install it

Main Functions of V-Panel:

  • Manual Control: Move the milling head along the X, Y, and Z axes to set the origin (zero position).
  • Spindle & Speed Control: Adjust the spindle speed and feed rate for accurate milling.
  • Depth & Tool Adjustments: Set the cutting depth and change tools as needed.

Strart your process by setting the origin of the tool bit.

Stick a double sided tape on your copper plate and Stick the plate on the pink surface that is the Machinable wax. Make sure that the copper plate is firmly stuck on the surface

Why machinable wax?

Machinable wax is used in PCB milling since wax is soft and easy to mill, it prevents damage to tools and helps avoid material waste.

Once this is done its time to insert the milling tool. With the help of Akhilesh sir I installed a 0.2 mm conical bit into the milling machine for engraving. We use allen keys to insert the bit and lock it.

Now with the help of the Vpanel software you need to set the origin. I set the XY origin first and then adjusted the Z- axis.

So there are two methods of setting the Z-axis. You can change the cursor step to 1 in V-Panel and lower the tool until it just touches the surface. But this method is risky because PCB milling bits are fragile and can break easily.

The second method is the one which I did. Instead of using V-Panel I manually Loosen the bit slightly using an Allen key hole it tightly and slowly moved it lower until it just touches the copper surface and then hit on set origin in the software.

Leraning: I forgot to set the Z-axis and started milling. I tool bit hovered above the copper. So i paused the machine and set the correct Z-origin, and restart the job.

Once the origin is set we hop on to Coppercam software.

Error encountered

I worked on my board outline because I initially exported it as an SVG file, but it needed to be in DXF format for proper processing in CopperCAM. Since CopperCAM does not recognize SVG files correctly for defining the milling contour, I had to re-export the outline in DXF format from my design software.

After fixing this, the software properly detected the board edges, and I was able to proceed with generating the toolpath for cutting the PCB outline.

Learning: CopperCAM does not support SVG for outlines, so always exporting the board design in DXF ensures proper recognition of the cutting path.

Understanding CopperCam

CopperCam is used to set the cutting parameters. Once this is done a G-code is generated and sent to VPanel to start the milling process.

How to install the software?

To install CopperCAM, refer this link: CopperCam. Now click on the download button and download it.

After setting the bit position in VPanel, you need to import Gerber files of the PCB design in the CopperCam software.

Understanding Gerber Files

When we export our PCB design to make it ready for milling or manufacturing, we get a set of files called Gerber files. Each file gives different instructions to the machine — like where to cut, drill, or place components. At first I was confused about which files to import for milling.

Here’s what you actually need:

For a single-sided PCB:

  • Top layer file (.gtl): This is the file with the copper traces on the top side of your board.

  • Drill file (.drl or .txt): This tells the machine where to drill holes for the components.

  • Cutout file: This defines the edges and shape of your PCB.

For a double-sided PCB, you also need:

  • Bottom layer file (.gbl): This contains the copper traces for the bottom side.

Other files like silkscreen (text and labels) are typically not needed for this milling process. These are mainly for advanced PCB manufacturing and assembly, not for the basic milling I was doing.

Importing Files

You start off by imported the top layer file (engraving) by clicking on the new project

We choose the top engraving layer first as, the process of engraving requires only a single but and in the drilling and milling (cutting the outer body) requires the flat end bit.

The bits we used:

  • 0.2 mm conical for engraving
  • 0.8 mm flat end mill for drilling and cutting out counters

The first image is of the Engraver GB471 ( Size: Ø0.20×30°×3×3.00mm) which is used for engraving and the second image is of the 2F Endmill E2661 (Size: Ø0.800 mm) which is used for cutting and drilling

You can set one pad as a reference and aligne the drill holes accordingly.

Once this is done you can trace the track contours and set the board outline as the card contour.

Learning: I added my logo in CopperCAM, but it was not engraved because it was not recognized as a milling path. I realized that CopperCAM does not automatically generate toolpaths for logos unless they are properly vectorized or defined as an engraving operation. Next time, I will convert the logo into a proper vector file.

Make sure to use the vacuum to remove the dust.

Once the engraving was done I changed the bit to 0.8 mm end mill for the drill file

Soldering & Final Adjustments

After milling the PCB, the next step is soldering the components onto the board.

Before starting, I cleaned the PCB with isopropyl alcohol to remove any dust or grease. This ensures that the solder sticks properly to the copper pads. I also gathered all the required components, a soldering iron, lead-free solder wire, and tweezers for handling small parts.

I started with the smallest components first, such as resistors to make soldering easier.Using tweezers, I carefully placed each component on the corresponding pads. The solder paste helps hold them in position. I used a hot air gun to melt the solder paste. I set the temperature and moved the gun in circular motions to heat the board evenly. As the paste melted, the solder flowed and secured the components in place.

Once all components were soldered, I checked the joints to ensure there were no cold joints (dull or cracked solder), solder bridges (unwanted connections between pads), or missing connections. I used a multimeter in continuity mode to check for proper connections.

Part 3: Making the SMD board

In this part, I produced the second PCB I had designed in Week 6 — a version using SMD (Surface Mount Devices).

Milling the PCB

Just like the through-hole version, I used the Roland SRM-20 and CopperCAM for milling the board and follwed the same process of milling the board.

I began by attaching the copper board onto machinable wax using double-sided tape. Then, I inserted a 0.2 mm conical bit for engraving and set the XY and Z origin using VPanel. I adjusted the Z-axis manually by gently lowering the bit to just touch the surface.

In CopperCAM, I imported the Gerber files After engraving the traces, I switched to a 0.8 mm end mill for drilling and cutting the outline.

I made sure to vacuum the dust between each step to keep the board clean.

Final milled PCB

For soldering, I carefully placed the SMD components using tweezers. This is what my final PCB looks like after soldering

Error: I selected the wrong schematic for the push button which is why I placed the tactile push button diagonally to complte the connection

I mostly used hand soldering for assembling my PCB, as it gave me more control over the process, especially for larger SMD components. The precision of hand soldering allowed me to ensure clean solder joints and quickly fix any mistakes. However, it was a bit time-consuming, and sometimes I struggled with small components or fine pins, which led to bridges that required rework.

For the more densely packed sections of the board, I decided to try hot air reflow. This method was much faster and worked well for smaller SMD components, giving me a cleaner finish. However, I did have some issues with parts shifting or tombstoning, where components would lift off the board. This happened because I hadn’t quite perfected controlling the airflow and temperature.

In the end, I found hand soldering to be better for most of the work, especially when I needed precision and flexibility to fix mistakes. Hot air reflow worked best for densely packed, small components, where speed and cleanliness were more important. Both techniques had their challenges, but using them together, depending on the component size and placement, gave me the best results.

Fixing bridges

To fix the bridges, I used a copper wick and heated it to remove excess solder, which worked well to clear up any issues.

How to use it?

To use copper wick for solder removal, place the wick over the excess solder and heat it with the soldering iron. The solder will melt and be absorbed into the wick. Hold the iron for 5-10 seconds, then remove the wick and iron. Repeat the same procedure if needed.

Note: Avoid overheating to protect components.

Debugging and testing

Finally, I checked all solder joints for bridges and used a multimeter in continuity mode to ensure all connections were working correctly. To do this pull the dial to the connectivity symbol.

Once this was done I tested the pcb by running a basic led bink code.

Code

int powerPin = D7;

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

void loop() {
  digitalWrite(powerPin, HIGH); // ON
  delay(1000);                  // Wait 1 second
  digitalWrite(powerPin, LOW);  // OFF
  delay(1000);                  // Wait 1 second
}

Exercise files

Below are the files for:

EasyEDA file

EasyEDA file for SMD

Testing code