The Ultimate Guide to PCB Layout Design

Printed Circuit Board (PCB) layout design is the foundation of any electronic device, from simple gadgets to highly complex systems. PCB layout design is the process of arranging electronic components and routing connections on a board to create a functional and efficient circuit. The goal is to achieve the smallest possible footprint while maintaining signal integrity and ensuring thermal and electrical performance.

There is a lot that goes into any engineered circuit board design, from a basic printed circuit to a complex non rigid PCB. Any new electronic device will start as a block diagram and/or a set of electronics schematics. Once you have your schematics finished and validated, you can follow the steps below to create modern PCB designs and layouts. A well-designed PCB ensures optimal performance, reliability, and manufacturability. In this guide, we’ll explore the key aspects of PCB layout design, including best practices, important considerations, and steps to create an efficient PCB layout.

Steps Involved in PCB Layout Design

Step 1: Schematic Design Entry

Step 2: Define PCB Dimensions

Step 3: Synchronize Schematics to Your PCB Board Design

Step 4: Designing Your PCB Stackup

Step 5: Defining PCB Board Design Rules and DFM Requirements

Step 6: Component Placement

Step 7: Routing

Step 8: Add Labels and Identifiers

Step 9: Generate Design Output Files

Step 1: Schematic Design Entry

The first step is creating a schematic, a blueprint that defines how components are interconnected. Each component symbol is placed, and connections are drawn between them. The schematic serves as a reference for component placement and routing in the layout phase.

Step 2: Define PCB Dimensions

Before placing components, determine the size and shape of the PCB based on the device's physical constraints. Consider mechanical requirements such as mounting holes and connectors.

Step 3: Synchronize Schematics to Your PCB Board Design

All the tools in a CAD software work in a united design environment, where the schematic, printed circuit board layout, and BOM are interlinked and can be accessed simultaneously. To transfer schematics document information to PCB, Click on Design » Convert schematics to PCB.

Step 4: Designing Your PCB Stack-up

Stack-up is important to consider early on in the PCB design stage due to impedance, which refers to how much and how quickly electricity can travel down a trace. The stackup plays a role in how the mechanical engineer can design and fit the PCB into the device. Prior to placing components you should define the PCB layout (i.e. shape, layer stackup) using the Layer Stackup Manager, shown below.If you’re new to the printed circuit design world, most modern PCB board design concepts will start with a 4-layer board on FR4. If you’re working on a high speed/high frequency circuit board design, you can use the JLCPCB online impedance calculator tool.

Step 5: Defining PCB Board Design Rules and DFM Requirements

The number of PCB board design rule categories is extensive and you may not need to use all of these available rules for every design. DRC contains the information of:

1. Clearances between objects in the PCB layout, such as between traces and pads.

2. Copper or solder mask feature size limits

3. Routing rules, including trace width and length limitations that can be enforced on certain nets.

This is just a sample of the rules that can govern any PCB layout, but these rules are designed to help ensure a board is manufacturable at the required scale with your fabricator's standard capabilities.

Step 6: Component Placement

Component placement is a critical step that influences the overall performance of the PCB. Follow these guidelines:

• Group related components: Place components that work together, such as resistors and capacitors, close to each other.
• Prioritize critical components: Position components like microcontrollers, power regulators, and signal processors first.
• Consider heat dissipation: Ensure that heat-generating components have adequate space and access to heat sinks or ventilation.
  

Step 7: Routing

Routing involves creating the actual paths (traces) that electrically connect the components. Some key factors to keep in mind are trace width, minimize trace length and signal integrity. Routing is done on the basis of type of PCB, RF PCB has different requirements than a Power PCB. Sometimes we require impedance matching, no reflections and sometimes maximum current flow on the basis of which different routing schemes can be utilized.

Step 8: Add Labels and Identifiers

With the circuit board layout verified you are ready to add labels, identifiers, markings, logos, or any other imagery to your board. It is a good idea to include reference designators for components as this will assist in PCB board assembly. You can also add a company logo and part numbers using the image tools and text tools in the PCB Editor. These elements need to be placed in the Top Overlay or Bottom Overlay layers in the PCB layout.

Step 9: Generate Design Output Files

Before you create your manufacturer deliverables, it’s always a good idea to verify your circuit board layout by running a design rule check (DRC). If your board checks out, then you’re ready to release your manufacturer deliverables.

Once your board has passed the final DRC, you need to generate the design files for your manufacturer. The design files should include all the information and data necessary to build your board. For most manufacturers, you will be able to use a set of Gerber files as shown below; however, some manufacturers prefer other manufacturing file formats (IPC-2581 or ODB++). To know more details about these other PCB file formats visit this article.

Best Practices for PCB Layout Design

1. Optimize Component Placement:

Proper component placement can reduce routing complexity and improve signal performance. Position critical components like microcontrollers and power supplies first, followed by passive components such as resistors and capacitors.

2. Minimize Crosstalk and EMI:

High-speed signals are prone to crosstalk and EMI. To mitigate this Use ground planes to shield signals, Maintain distance between high-speed and low-speed signals. Avoid sharp angles and long parallel traces.

3. Keep Thermal Management in Mind:

Power-intensive components generate heat, which can affect performance and lifespan. To address this Position heat-generating components near heat sinks or allow airflow around them. Use thermal vias to distribute heat across multiple layers.

4. Verify Design Rules:

Each PCB manufacturer has specific design rules regarding trace width, spacing, and layer count. Ensure your layout complies with these rules to avoid manufacturing issues.

Power, Ground and Signal Trace Considerations

The above tips focused on best PCB practices that can be implemented in a design. You also need to route the power, ground and signal traces as per the design specification. Completing this step efficiently will help ensure your signals have a reliable path to travel to keep your board functioning properly. Here are three main factors to keep in mind:

1. Power and Ground Planes

One fundamental PCB layout design rule is to keep your power and ground planes internally within your board. Dedicated power and ground planes improve signal integrity and reduce noise. These layers distribute power evenly across the board and provide a return path for signals, minimizing ground loops and voltage drops. You should also keep your digital and analog grounds separate in a similar fashion. Try only to have analog lines cross your analog ground to reduce capacitive coupling.

2. Track Design

This step also involves connecting signal traces according to your schematic. You always want your traces to be as short and direct as possible. If you have horizontal trace routing on one side of the PCB, place vertical traces on the other side. Keep the impedance matching and reflection rules in mind while routing high speed lines.

For power design your board may require multiple nets with different currents, which will determine the net width you need. Using a trace width calculator can help with this step. Tracks that are around 10 mils thick can only take a current of around one Ampere, while a track that is 250 mils thick can carry as much 15 Amps with a 30 degree Celsius temperature rise.

3. Pad and Hole Dimension

You'll also need to determine pad and hole dimensions early in the PCB design process. As the size of the pads and holes decreases, getting the right pad-to-hole size ratio becomes more crucial. It’s especially critical when working with via holes. Shape of the PCB pads is also a crucial parameter. PCB footprints can vary according to the manufacturing process.

The Importance of Testing in PCB Design

Throughout the PCB design process, as well as the rest of the PCB manufacturing process, you should continuously check your work. Catching problems early on will help minimize their impact and reduce the costs of fixing them. Two common tests electrical rules check and the design rules check can be performed at early stages. These tests will help you solve many of the more significant problems you may encounter. Once you can pass your ERC and DRC tests without any problems, you should check the routing of every signal and compare your board to your schematic in detail.

Conclusion

PCB layout design is a critical skill that directly affects the performance, reliability, and cost of an electronic device. By following best practices such as optimizing component placement, maintaining signal integrity, and ensuring proper thermal management you can create a PCB layout that meets both technical and manufacturing requirements. Investing time in the design phase will pay off with better-performing, more reliable devices in the long run.

Whether you're a novice or an experienced designer, understanding the nuances of PCB layout design is key to creating high-quality electronics. With JLCPCB right tools and techniques, you can overcome the challenges and design efficient, cost-effective circuit boards.