Samrudhi Rovalekar - Fab Academy

Assignment Brief:

Characterize the design rules for your in-house PCB production process.
Submit a PCB design to a board house.
Design, fabricate, and test a microcontroller development board.

New Week

I am a newbie in electronics design and production. You can refer to my Week 06 documentation to understand my attempts and struggles in building a circuit and designing a board. I designed one half of the electronics for my Final project which is mostly a pinout structure of the RP2040. In this week I worked on working on electronics production—fixing errors, refining the design, and ensuring proper connections. Debugging, tracing faulty connections, and optimizing the layout are part of my current process.

Electronics Production

Electronics production is the process of manufacturing electronic devices by assembling and integrating electronic components onto a circuit board. It involves designing, fabricating, assembling, and testing circuits to ensure they function as intended. This process can range from small-scale prototyping to large-scale industrial manufacturing. wokwi

What is a PCB?

A Printed Circuit Board (PCB) is a flat board made of insulating material (like fiberglass) with conductive copper tracks that connect different electronic components. Instead of using traditional wiring, a PCB provides a structured layout for electrical connections, making circuits more compact, reliable, and easier to manufacture.

Key Parts of a PCB:

Substrate (Base Material): Usually made of FR4 (fiberglass-reinforced epoxy resin) for strength and durability.
Copper Layer: Thin layers of copper act as electrical pathways connecting components.
Solder Mask: A protective layer that prevents short circuits and oxidation of copper traces.
Silkscreen: Printed labels on the PCB surface that indicate component placement and reference designators.

Types of PCBs:

Single-layer PCB: Has a single copper layer, used in simple circuits.
Double-layer PCB: Copper traces on both sides, allowing more complex designs.
Multilayer PCB: Multiple stacked layers, used in advanced applications like computers and communication devices.

PCB Design and Manufacturing Process:

Schematic Design: Creating a circuit diagram using software like KiCad, Eagle, or Altium. Refer to my Week 06 documentation
PCB Layout: Converting the schematic into a physical board design with component placements and copper traces. You can refer to my documentation
Fabrication: The PCB is manufactured using processes like etching, drilling, and applying solder masks.
Assembly: Components are soldered onto the board using surface-mount (SMT) or through-hole (THT) techniques.
Testing & Debugging: Checking for connectivity issues, short circuits, or faulty components.

Riidl Fablab: Roland SRM 20

Our Riidl FabLab has two machines for electronic production that are, Roland SRM 20 and Protomat E44. We used Roland SRM 20 for the production of our PCB. To know more about Roland SRM 20 Click here..

The Roland SRM-20 is a compact desktop CNC milling machine designed for precision prototyping, PCB milling, and small-scale machining. It’s designed for precision prototyping and PCB fabrication. The SRM-20 is widely used in engineering labs, maker spaces, and educational institutions for rapid prototyping and custom circuit board manufacturing.

Features of Roland SRM-20

The ProtoMat E44 is an entry-level PCB milling machine used for rapid prototyping of printed circuit boards (PCBs) without chemical etching. It precisely engraves copper layers, drills vias, and cuts board outlines with high accuracy. The machine supports single- and double-sided PCBs and is ideal for small-scale production, research labs, and educational purposes. It features automatic tool change, depth control, and a user-friendly interface. The ProtoMat E44 is commonly used for quick PCB fabrication, RF applications, and sensor prototyping. We used the SRM20 for the production of our PCB. Lets Deep dive in the process further. wokwi

Software: V-Panel for setting the origin.

The SRM-20 requires 2 software: V-panel for setting the X-Y-Z axis and origin before setting up the PCB board design.The Roland SRM-20 CNC machine requires VPanel to set the X, Y, and Z axis origins before milling. VPanel controls machine movement, spindle speed, and job execution. PCB design software like FlatCAM or Eagle is used to create toolpaths and generate G-code. You can refer to the PCB that I design for production in the documentation: Week o6 of Electronics design. After setting the origin in VPanel, the PCB design is loaded, and milling is initiated for precise fabrication. Lets understand every process in depth.

Now with the V-panel software, move and bring the tool bit to the closest of the surface of the copper plate. There are two ways of setting the origin or zero Z-axis here. One is change the cursor step on V-panel as *1 and the tool just touches the material set the zero axis. However, the precision in setting the bit in this manner is a bit risky as theses bits unlike the CNC Bits are a little fragile, and have a possibility of breaking.

We thus, went about with another method, where using the allen key we loosen the bit slightly from the collet> hold the sides of the bit with soft hands> Smoothly drop down the bit to the surface base> Make sure the bit doesn't drop down with force. Set the Zero axis on V-Panel software and SET ORIGIN. Now you can move the bit to any position but make sure the Z-axis is untouched.

Learning: I made an error by putting the bit extreme inside, the bit hand to be removed. The slipping the tool was insigthful. to understand the fragility of the tool. setting the origin and top layer is very important.

Software 2: CopperCam

After setting the bit position in VPanel, the Gerber files of the PCB design are imported into CopperCam. In CopperCam, cutting parameters are set, including tool selection, depth, and milling strategy. Once configured, the G-code is generated and sent to VPanel to execute the milling process for PCB fabrication. Lets understand the setting up of CopperCam now.

The two Drill bits that we use are:
0.2 mm conical for engraving
0.8 mm flat end mill for drilling and cutting out counters

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. We therefore import the engraving files before.

Learnings: I set the successive contours to 2. this made my contours layers very thin as a result of which, I faced a lot of difficulty while soldering.

As the option differs on every desired output like engraving, drilling and cutting. Other settings are, XY-xero point set to white cross, this is the origin point we set previoulsy. Z-zero point as circuit surface as to cut from base and finally "OK" when we have set the machine axis using the V-Panel.

Machine run

Once the engraving layer is done, we will have to change the tool bit for drilling and cutting the corners. For which firstly, we more the X and Y co-ordinates of the tool path away from the board using the V-panel. Make sure that the " Set origin Option" is untouched. Now on the SRM-20, change the output sequence to cutting> and cut.

Soldering AND Debuging!!!

Learnings: As I mentioned the countours that I set for the track was only 2, due to which the souldering process became very tough for me. The attention required to solder the XAIO board to the PCB, moved to not letting the soldering wire stick to the board excess copper wire. As a result of which, as I am new to soldering, some soldering wire got transferred to the copper plate which led to a mis-connection. Here, I used a suction pump for desoldering. to get rid of the mis-connection.

Note: The reason why I used an JSt pins as in through holes for soldering is by keeping in mind my Final Project. This PCB will be connected to elements like Servo and DC motors which will be farther away from the Board. Plus, there is going to be another PCB with SMD LED's on which will be connected to this board.

Post soldering all the JST connections through a through-hole soldering, along with an SMD soldering resistor. Spirit level

Debugging

Using a Multimeter to check if all the connections are working proper. How does the Mulitmeter work? For the connectivity symbol the multimeter will help you check the connectivity between two linkages. Wehn two points with connectivity are touched upon buy the multimeter, red and black pin wires, the number >0 signals to connectivity ans will give a beeping sound output.

Testing

Used the multimeter to check every point of connections refering to my schematic.

Now soldering the JST pin wires to the pin wires to the target components. A very big learning here was the mirror effect. As we PCB mill on the top surface, the through holes on the back surface become the mirror image of the above. Thus, if the 5V of a 3 Pin Jst wire is the top. It will move to the buttom because we have gone to the bottom surface which is the reverse of the engraving and drilling side. As I was using only JSt pins the over connections didn't make a big difference but I had to contantly turn over and check the wire configuration of my Easy Eda Circuit to solder the 5V pin hole of the PCB to the 5V pin of the Servo.