There are two types of assignments, one group and one individual.

Group Assignment :- Characterize the design rules for your PCB production process

During this week's group assignment, our focus was on Laser cutting and scanning. We formed three distinct teams to explore and conduct trials on the laser cutting machine. The primary objectives of the group assignment were as follows:

PCB Milling MAchine: Rolland SRM-20

• Comprehensive exploration of the PCB Milling machine and its specifications.
• Gaining insights into the technical details and capabilities of the machine.

Operational Knowledge:

• Acquiring practical knowledge on how to operate the machine effectively.
• Learning the step-by-step process of setting up and running the machine.

Safety Precationus:

• Understanding and implementing safety measures associated with operating the Machine.
• Emphasizing the importance of maintaining a secure working environment.

Optimization Parameters:

• Determining the optimum cut depth and min distance between two traces.
• Checking the diffrent end mills and observing its results: check the feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling

PCB Milling Machine

A PCB milling machine is a computer-controlled device designed for precisely cutting printed circuit boards (PCBs). Similar to a laser cutter, it employs a different method to achieve accurate results. Instead of a laser beam, the milling machine uses rotating cutting tools to remove material from the PCB substrate, creating circuit traces and patterns. This process is highly controlled and allows for the creation of intricate and customized circuitry. PCB milling machines are essential in the electronics prototyping and production process, enabling the quick and precise fabrication of PCBs without the need for chemical etching. At our Vigyan Ashram Fablab, we utilize the Rolland MonoFab SRM-20 PCB Milling Machine for experimentation and trials.

Rolland MonoFab SRM-20

The Rolland MonoFab SRM-20 is a versatile PCB milling machine equipped with advanced features for accurate and efficient PCB fabrication. Using computer-controlled precision, this machine precisely mills away the unwanted copper, creating intricate circuit patterns. It offers a user-friendly interface and is suitable for professionals and hobbyists alike. The SRM-20 streamlines the PCB production process, making it an indispensable tool for rapid prototyping and small-scale PCB manufacturing. A wide range of materials, including modeling wax, chemical wood, foam, acrylic, poly acetate, ABS and PC board can be precision milled using the SRM-20 small milling machine, allowing you to create realistic 3D prototypes that are virtually identical to production parts. Its capabilities extend to various materials used in PCBs, ensuring a clean and precise result.

Visit our Group assignment page here

PCB (Printed Circuit Board) fabrication

Printed Circuit Board (PCB) fabrication is a critical step in the electronics production process, serving as the foundation for assembling and connecting electronic components. PCBs are flat, rigid boards made of insulating material, typically fiberglass-reinforced epoxy, with conductive pathways etched or printed onto the surface to create a circuit.

The fabrication process involves several key steps, including design, substrate preparation, layering, etching, and finishing.

There are different types of PCBs, each catering to specific applications and requirements :

Single-layer PCBs: Suitable for simple electronics. Consists of a single layer of substrate. Conductive layer is present on one side of the substrate.

Double-layer PCBs: Allows for more complex circuitry compared to single-layer PCBs. Has conductive layers on both sides of the substrate. Widely used in a variety of electronic applications.

Multi-layer PCBs: Ideal for advanced electronic devices. Involves three or more conductive layers sandwiched between insulating substrates. Enables the creation of dense and intricate circuit designs. Offers enhanced performance and functionality for sophisticated electronics.

PCB Fabrication (Process, Material, Machine and Tools)

Etching for PCB Fabrication

Process:

Traditional etching involves using strong acids or mordants to cut into unprotected metal surfaces. Modern variants include microfabrication etching and photochemical milling, crucial for circuit board production.

Chemicals Used:

• Acetic acid (CH₃COOH)
• Citric acid (C₆H₈O₇)
• Hydrochloric acid/Muriatic acid (HCl)
• Hydrogen Peroxide (H₂O₂)
• Sodium chloride (NaCl)
• Copper sulfate (CuSO₄)

Precautions:

• Proper waste management to avoid environmental hazards.
• Avoid reusing etching solution for efficiency and cleanliness.
• Neutralize acid with sodium bicarbonate, precipitating copper for safe disposal.

Machining (Milling) for PCB Fabrication

Process:

Printed circuit board milling removes copper from a PCB sheet to recreate pads, traces, and structures according to a digital layout file. A subtractive, non-chemical process suitable for office or lab environments. Quality depends on milling accuracy, bit condition, and control, contrasting with the chemical etch process.

Material:

• FR1-Phenolic paper, a tough wood fiber and phenolic polymer board (FR-1 and FR-2).
• Epoxy film electrical tape with a thermosetting acrylic adhesive.
• Electronic components.

Machine:

PCB milling machines are akin to miniature, accurate NC milling tables. Controlled via serial or parallel port connections to the onboard controller. Examples include the Roland SRM-20, featuring precision three-axis machining for PCBs.

Tools:

Conventional endmills, especially flat end mills, are suitable for machining PCBs. Flat end mills provide consistent trace width and efficient material removal.

Categorizing PCB Components

Printed Circuit Boards (PCBs) are essential components in electronic devices, and they host various types of components that play specific roles in the circuit. Here are some common types of PCB components:

• 1.Resistors: Limit the flow of electric current.
• 2.Capacitors: Store and release electrical energy.
• 3.Inductors: Store energy in a magnetic field.
• 4.Diodes: Allow current to flow in one direction.
• 5.Transistors: Amplify or switch electronic signals.
• 6.Integrated Circuits (ICs): Complex assemblies of multiple components.
• 7.Connectors: Link different parts of the circuit.
• 8.Switches: Control the flow of current by opening or closing a circuit.
• 9.LEDs: Emit light when current passes through.
• 10.Transformers: Change the voltage level in a circuit.
• 11.Crystal Oscillators: Provide a stable frequency reference for timing.
• 12.Sensors: Detect changes in the environment and convert them into electrical signals.
• 13.Voltage Regulators: Maintain a constant voltage level in a circuit.

Through Hole v/s SMD Components

Printed Circuit Boards (PCBs) can accommodate electronic components in two main categories: Through-Hole Technology (THT) and Surface Mount Device (SMD) Technology. Each has its advantages and is suitable for different applications. Here's an overview of both:

Through-Hole Technology (THT):

Components: Through-hole components have wire leads that are inserted into holes in the PCB and then soldered on the opposite side.

Assembly Process: Manual assembly is common for through-hole components. The components are often larger and more spaced out, making it easier for manual soldering.

Strength and Durability: THT components tend to be more robust, making them suitable for applications where mechanical stress is a concern, such as connectors or components subjected to frequent plugging/unplugging.

Prototyping and Testing: Through-hole components are often preferred for prototyping due to their ease of use and reworkability.

Surface Mount Device (SMD) Technology:

Components: SMD components are smaller and have solder pads on the same side of the component, which is directly mounted onto the surface of the PCB.

Assembly Process: SMD components are typically assembled using automated pick-and-place machines. This allows for faster and more cost-effective mass production.

Space Efficiency: SMD components take up less space on the PCB, making them suitable for compact and miniaturized electronic devices.

High-Frequency Applications: SMD components are often preferred in high-frequency applications because the shorter lead lengths reduce parasitic capacitance and inductance.

Cost and Production: SMD components are generally more cost-effective in large-scale production due to automated assembly processes and reduced material usage.

In modern electronics, a combination of both through-hole and SMD components may be used on a single PCB. This is known as mixed-technology assembly. Through-hole components might be chosen for certain critical or high-stress parts, while SMD components are used for smaller, more densely populated areas of the board.

Individual Assignment

Tasks:-

• Operate PCB Milling

  Learn how to operate PCB milling milling for the fabrication process.




• Make an In-Circuit Programmer with a Microcontroller

  Create an in-circuit programmer that includes a microcontroller for programming tasks.




• Mill and Stuff the PCB

  Perform milling processes on the PCB and complete the assembly by placing components.




• Try Other PCB Processes

  Explore and experiment with various PCB fabrication processes beyond milling and stuffing.




• Program and Test the PCB

  Write code for the microcontroller, program the PCB, and conduct testing to verify its functionality.

To Operate PCB Milling Machine:

Make an In-Circuit Programmer with a Microcontroller

Mill and Stuff the PCB

Program and Test the PCB

Make an In-Circuit Programmer with a Microcontroller on Milling Machine

1. Create or Download the PCB Traces file

As we have not started with PCB designing week, I am taking a readymade file

Model Assembly in Fusion 360:

Actual Cutting and Joints

By incorporating parametric modeling into the design workflow, the ability to swiftly adapt to changes in material properties, laser cutting settings, and other parameters becomes a reality. This not only enhances efficiency but also ensures precision and accuracy in the final laser-cut components. Parametric modeling in Fusion 360 emerges as a valuable skill, offering a time-saving and versatile approach to design iteration and optimization.

Observation from actual Cutting

Observation of Cutting Cardboard: During laser cutting on corrugated cardboard sheets, I have noted a distinct difference in the outcomes based on the orientation of the cardboard. When the sheet is placed vertically, the laser cutting tends to cause the flutes to open up. However, when the cardboard sheet is positioned horizontally, a more favorable result is achieved, with the laser creating cross cuts that maintain the integrity of the flutes. This observation suggests that horizontal placement is preferable for achieving the desired cutting outcome on corrugated cardboard.

Vinyl Cutter

A vinyl cutter serves as an ideal entry-level device for crafting signs. It operates by directly cutting computer-designed vector files containing patterns and letters onto a roll of vinyl. The vinyl, mounted and fed into the cutter, is connected to the computer via a USB or serial cable.

Fablab VA Vinyl Cutter Deatils

Graphtec CE6000-60 Plus series Vinyl Cutter

Vinyl Cutter Assessories