How to Design a PCB Layout

A vivid understanding of electronics, PCB design software, and manufacturing processes are essentially required when designing a PCB layout. It is a difficult and time-consuming process, but with planning and attention to detail, a high-quality PCB that will meet the desired specifications can be designed.

The process begins with defining the functional requirements and specifications of PCB, then moves on to schematic capture, PCB layout, fabrication, and assembly. The first step involved in designing a PCB layout is determining the circuit’s functional requirements. After defining the functional requirements, a schematic diagram of the circuit is created using software such as EAGLE, Altium, or KiCAD. In this blog, we will learn about the whole procedure starting from the beginning of how to design a PCB layout.

Steps to Design PCB Layout

Following is a summary of the steps that are used one after the other in designing the PCB layout:

• Schematic Capture: The initial step is to use a schematic capture tool to create a schematic diagram of the circuit. It will help you visualize the circuit and understand how the components are connected.
• Component Placement: Once the schematic is complete, the components must be placed on the PCB layout. You should take into account the size and shape of the components, as well as the necessary space between them. You should also consider the flow of signals and power, and arrange the components logically.
• Routing: After you’ve placed the components, you’ll now have to connect them with traces. Traces are the copper lines that connect the components and carry signals and power. To reduce noise and interference, you should route the traces as effectively as possible.
• Ground Plane: A ground plane is a large copper area that acts as a reference point for all of the circuit’s signals. It also aids in the reduction of noise and interference. All of the component ground pins should be connected to the ground plane.
• Power Supply: This step involves connecting the power supply pins of the components to the power supply traces on the board. You must check that the power supply voltage and current ratings are correct.
• Design Rule Check: After you’ve finished the layout, run a design rule check to ensure that your design meets the manufacturer’s requirements.
• Generate Output Files: You must generate output files in the format required by the manufacturer once the design is checked. These files will be used to build the PCB.
• Fabricate: Fabricating the PCB by the manufacturer depends on the design once they receive the output files.

Schematic Capture in PCB Layout

The process of creating an electronic schematic diagram of a circuit design by using specialized software is known as Schematic Capture. It is the initial step in the creation of a Printed Circuit Board. It depicts the logical connections between the components and their functions, and how they are linked.

Before moving on to the PCB layout, schematic capture helps to visualize the circuit design and it ensures that the connections between components are correct. It also aids in the avoidance of errors and mistakes that can create problems with the final product. You can use tools like Altium Designer, Eagle, or KiCAD to place symbols representing various electrical parts, including resistors, capacitors, transistors, and integrated circuits, in your circuit design. You can also check PCB course to get a better understanding of the subject.

The step that follows the first one, is to join the components by connecting them with lines or wires that represent the electrical connections between them.

To sum it up, follow the steps below:

• Schematic capture creates an electronic schematic diagram.
• It is the first step in the creation of PCB.
• It ensures that the connections between the components are correct.
• It aids avoidance of possible errors.

Component Placement in PCB Layout

The process that is used to position electronic components on the PCB is known as Component Placement. Its goal is to create an efficient circuit board that will meet the electrical and mechanical requirements of the design in PCB layout. The following are some important component placement considerations:

• Orientation: The components must be oriented in such a way that they are simple to assemble and service. Components can be rotated to optimize space and accessibility.
• Signal Flow: When the components are placed, the flow of signals between them should be considered a priority. The signals should flow most directly and efficiently as possible to minimize noise and interference.
• Thermal Management: The thermal-sensitive components should be installed keeping thermal management in mind. It will entail leaving the room for heat sinks.
• Mechanical Constraints: When placing components, mechanical constraints such as board size, mounting holes, and connector locations should be considered.
• Assembly Process: The component placement should be optimized for the assembly process. This includes grouping components together that will be inserted at the same time or leaving enough space for the placement and soldering tools.
• Electrical Performance: The placement of components can also have an impact on the circuit’s electrical performance. Trace lengths should be kept to a minimum and high-speed signals should be routed in a controlled impedance environment.

Routing in PCB Layout

The process that involves connecting the electronic components on the PCB is known as Routing. It is a critical part of the PCB design process and requires careful attention to detail. The following are some crucial considerations for routing in PCB layout:

• The optimization of space and width of traces.
• To maintain signal integrity.
• Power distribution to minimize voltage drop and noise.
• The topology of the circuit should be considered.
• Component placement affects the routing of traces.
• The design rules should be followed.

Ground Plane in PCB Layout

A ground plane is a large, continuous copper plane on a PCB layout and is considered a part of the overall design. Its size, shape, and placement should be optimized to meet the electrical and mechanical requirements of the circuit design.

It should be connected to the ground pins of all components on the PCB and be clear of any signal traces that could interfere with the performance of the ground plane. The following are some of the benefits of a ground plane:

• It provides a low-impedance path.
• It acts as a shield and is used in EMI reduction.
• It enhances signal integrity by reducing the amount of interference.
• It simplifies the routing of signals.
• It helps in thermal management as it can dissipate heat.

Power Supply in PCB Layout

Power Supply is a critical component of PCB design, and it must be crucially considered in PCB layout. It is responsible for providing the necessary amount of voltage and current to the components. The following are the important considerations to remember when designing the power supply:

• It must be designed keeping the requirement of voltage and current in mind.
• The decoupling capacitors should be placed closer to the supply pins.
• Trace width should be determined based on the requirements of the components.
• It is effective for thermal management.
• It is a source of EMI and EMC considerations.
• The power plane is used to distribute power throughout the PCB.

Design Rule Check in PCB Layout

Design Rule Check or DRC helps prevent manufacturing defects and ensures that the PCB meets the requirements of the circuit. It is an automated process that is used in PCB layout for compliance with defined design rules. PCBs use it to identify and fix issues before manufacturing, which reduces the risk of costly errors and improves the overall quality of the final product. The following are the design rules that DRC checks in the PCB layout:

• The necessary distance between two copper features on a Printed Circuit Board.
• Minimum width and spacing of copper traces on current carrying capacities.
• Minimum drill size and annular ring to ensure proper connectivity.
• To ensure readability by complying with the silkscreen and legend on the PCB.
• To prevent solder bridges by ensuring the minimum size and clearance of solder masks.
• To ensure orientation by component placements.

Generate Output Files in PCB Layout

It is an important step in PCB design. The output files are generated from the PCB layout software and provide a set of files that are used by the manufacturer to create the actual PCB. The following are some of the key output files generated in the PCB layout design process:

• Gerber Files: The standard file format that is used to describe the solder mask, copper layers, and silkscreen.
• NC Drill Files: The files that provide the manufacturer with information about the placement and size of holes on the PCB.
• Bill of Materials: This provides a detailed list of all the components used in the PCB design.
• Assembly Drawings: These are used to display components on the PCB in an organized and concise way.
• 3D Models: These are utilized to offer a comprehensive three-dimensional depiction of the PCB design.

Fabrication in PCB Layout

The process of creating the actual PCB from the design files is known as Fabrication in PCB layout. This process involves a variety of steps, including panelization, imaging, etching, drilling, plating, and testing. After the PCB is fabricated and tested, it is ready for assembly, where components are mounted and soldered onto the board.

The following is an overview of the steps involved in fabricating a PCB layout:

• Panelization: In this step, multiple PCBs are laid out on a larger panel to optimize material usage and facilitate manufacturing.
• Imaging: This step is conducted by transferring the design onto the copper layers of the PCB.
• Etching: This step involves removing the unwanted copper from the PCB using an etchant solution.
• Drilling: In this step, holes are created in the PCB for components, via through-holes during the process of Drilling.
• Plating: This step involves depositing a thin layer of metal, usually copper, onto the drilled holes and copper traces.
• Solder masks and Silkscreen: The solder masks are applied to the copper traces and pads to protect them from oxidation in this step. The silkscreen is applied to provide additional information about the board.
• Testing: This is the final step where a series of electrical tests are performed to ensure that the PCB meets the design specifications.

Conclusion

Designing a PCB layout could be a complicated process and challenging for people who are new in this field. But if you plan, pay attention to component placement, and use good design practices, it will turn out to be a smooth task for you.