How to Design a Complete PCB Layout? PCB Layout Engineer Must Know!

Each new revolutionary electronic gadget starts its life not with soldering iron sparks flying, but as a plain, simple concept - something as basic as an idea drawn on a napkin or software-simulated design. Actually making that idea into a physical and working unit is highly complex, and the critical bridge between the two is the Printed Circuit Board (PCB). The design and layout of components and traces on this board is PCB layout, and it's a fundamental skill for any electronics engineer.

This article will take you all the way along the process from a schematic diagram to the stage of manufacturing, giving you the capability to make your electronic idea a reality.

What a PCB Layout Engineer Should Know Before Designing

Before routing even one trace, a ton of preliminary work must first be done. A good PCB layout starts with the planning stage, where the logical circuit is established, and the physical limitations are defined. Rushing this stage is the most common cause of board rework, cost, and schedule overruns.

From Logic to Art: Schematic Capture and PCB Layout

The first step is schematic capture. This is the stage at which you have created the logical representation of your circuit in EDA software. This is the circuit diagram that shows all the components, and most importantly, how they are electrically connected using nets. The schematic is the absolute truth for the project and generates a critical file, called a netlist, that defines every single connection digitally that the PCB layout software needs to follow.

It is a common misconception that the schematic is nothing more than a rough drawing. The truth is, a neat, organized, and checked schematic is the single most important factor in completing a layout. The quality of your schematic capture and PCB layout is directly proportional; the EDA software will always reference the netlist in enforcing your electrical connectivity in the layout phase. If there is an error in your schematic, you will see that same error appear on the physical board in some form.

Creating a Layout-Ready PCB Layout Schematic

By design, a schematic that is intended for a simple layout goes beyond just a connection layout. A schematic should be considered a communication tool. Group related components logically on a single schematic page (for example, the power supply section, microcontroller section, and sensor inputs). Use descriptive net labels instead of the software's default net names for clarity (for example, 5V_IN is infinitely better than Net-C1-Pin1). For complex designs, hierarchical sheets allow breaking the design down into manageable, reusable blocks for easy schematic layout organization. The organization will transfer directly to the layout stage, allowing component placement to seem more logical.

Establishing Robust PCB Design Rules

After finalizing your schematic, you'll need to establish the physical rules and constraints for your board. The PCB design rules are input into your EDA tool and are essentially an automated assistant that helps you to avoid making mistakes that might make the board unproducible or unusable by the end user. The rules are a function of the physics of electricity and the capabilities of the manufacturer.

A few key rules include:

● Trace Width & Spacing: The width of the copper trace determines how much current it can carry. Wider traces can carry more current, while spacing between traces is important for electrical arcing (crosstalk). Several online calculators are based on the IPC-2221 standard that assist in determining these values.

● Clearances: This is the minimum distance between two different elements: trace-to-pad, pad-to-pad, and trace-to-board-edge..

● Via Sizes: Vias are plated holes that connect the different layers of your board. You can develop the rules for the drill size and annular ring (the copper pad surrounding the hole). The annular ring must be large enough to ensure a reliable connection post-drilling.

● Layer Stackup: For boards with more than two layers, you must define the order of signal, power, and ground planes. A typical 4-layer stackup (Signal-Ground-Power-Signal) is excellent for minimizing electromagnetic interference (EMI).

Defining these rules to match a manufacturer's specific capabilities is paramount. You can find all of JLCPCB's manufacturing capabilities online, but for complex designs, ensuring perfect alignment can be challenging. For a hassle-free experience, consider leveraging professional printed circuit board layout services where engineers handle this optimization for you.feel free for click to try JLCPCB Layout Service！

Choose Your EDA: The Best Free PCB Design Software

Your EDA software is your main workhorse. There are lots of choices, but typically they fall into one of two types of programs. There are free or relatively inexpensive tools that are perfectly suited for hobbyists or students, and professional-level suites of tools that are used for commercial engineering.

EasyEDA: The Easy Powerhouse

If you are looking for the best free software for PCB layout, EasyEDA will be one of your first choices. EasyEDA is a fully-featured, cloud-based tool that requires no installation. The best feature is its super-easy ecosystem. EasyEDA is directly connected to LCSC Components, which is a huge library of parts. That means your millions of parts before you start layout work have ready-to-go schematic symbols and PCB footprints. Once you're done with your layout, you can receive instantaneous quotes and order your board with one click from JLCPCB. This way, you can connect the parts and the manufacturing. JLCPCB provides a huge in-stock parts for PCBA Service.

Software Comparison: Making an Informed Choice

Ultimately, the best tool depends on the complexity of your project, your budget, and your workflow preferences. Both EasyEDA Standard as well as EasyEDA Pro offer the amazing flexibility of a cloud-based web app, as well as an optional desktop client that you can download. The main difference is in their feature set and the performance ceiling. The standard version is powerful for many projects, but EasyEDA Pro unlocks a set of professional features that are critical for modern electronics. It also offers professional features such as:

● Advanced Routing Engine: EasyEDA Pro has tools to route differential pairs and tune lengths, which is important in maintaining signal integrity in high-speed interfaces like USB, HDMI, or Ethernet.

● Improvements in Project Management: EasyEDA Pro also has better versioning and collaboration tools that make it better for small teams sharing projects.

● The Ultimate Ecosystem: Its fundamental advantage still lies in the native, uninterrupted link with LCSC's component library and JLCPCB manufacturing services. The "From Idea to Prototype" process works wonders. Sourcing and verifying component footprints are a prominent bottleneck in other EDA tools, such as Altium, for example. With EasyEDA Pro, you tap into a validated, massive library, reducing design time and costly footprint error risks.

EasyEDA Pro, however, is not targeted to compete with other PCB tools at the enterprise level. Altium Designer is the standard in the industry for large, enterprise-level design; it allows for design at a level that is critical for applications requiring compliance, simulation, and designing to a complete multi-board system. Altium truly shines in the following areas that separate it from EasyEDA Pro:

● Robust Simulation/Analysis: Altium has a fully integrated suite for Signal Integrity (SI), Power Integrity (PI), and thermal analysis; engineers can simulate and predict not only how a high-speed signal will perform but also how heat will dissipate before a board is ever manufactured, which is important for high-performance computing and RF applications!

● Circuit Board/Mechanical System Design: Altium is strongly developed to design entire electronic products and not simply circuit boards; it even includes tools to design harnesses and manage the routes/connections between multiple boards, all within one project to verify that everything will fit and connect correspondingly in the final assembly.

● Integrated MCAD Solutions: It has live, bidirectional co-design with mechanical CAD software like Fusion360; if an electrical engineer moves a part, then the mechanical engineer sees that part move in their 3D model and vice versa. This is imperative to products that are built to fit inside complex, custom-shaped enclosures.

● Full-Featured Design Rules: Altium has a rules engine that is far easier to implement queries, which allows for creating complex ruleset design rules.

Start Practice: A Simple PCB Layout Drawing Walkthrough

Theory is important, but there's no substitute for practice. Let's walk through the design of a simple 555 timer LED flasher circuit.

1. Schematic Entry:

○ Create the Schematic: First, let's lay out the circuit logic. In EasyEDA Pro, create a new schematic for the 555 astable multivibrator.

○ Find Your Components:

■ Main IC: Use the library search tool (Place > Device or the shortcut Shift+F). In the search bar, type NE555. You’ll see a list of options from the integrated LCSC component library. Select one that has a verified symbol and footprint.

■ Passive Components: For generic parts like resistors, capacitors, and an LED, you have two great options:

● For Speed: Grab them from the built-in 'Commonly Used' library.

● For Specifics: Search the LCSC library again to choose an exact part number you plan to order.

○ Add a Power Connector: This is a critical step! The VCC and GND symbols are just logical nets. To connect a real battery, you need a physical component.

● Go back to the library search (Shift+F) and look for a simple connector.  A 2-pin header is a great choice for soldering battery wires.

● Place this 2-pin connector on your schematic. Connect one pin to the VCC net and the other to the GND net. Now your logical power rails have a physical entry point to the board!

○ Connect Everything: Arrange the components on the schematic and wire them together according to the standard 555 timer flasher circuit diagram. Don't forget to add VCC and GND symbols to complete your power connections!

2. Convert to PCB:

Once the schematic is complete and checked, use the "Update/Convert Schematic to PCB" function. EasyEDA Pro will automatically create a new PCB file, placing all the component footprints - including your new power connector - into the PCB editor workspace with thin "ratlines" showing the connections.

3. Component Placement:

● Draw Your Board Outline: The very first thing you should do in the PCB editor is define the physical shape of your board. Select the "Board Outline" layer from your layers panel. Use the drawing tools (like rectangle, line, arcs, etc.) to create a closed shape for your board. For this simple project, a small rectangle is perfect.

● Place Components: Now, drag your components from the workspace onto the board outline you just created. A good strategy is to place connectors first (like your 2-pin power header near the edge), then larger ICs, and then group supporting components (like resistors and capacitors) close to the IC they are associated with. Rotate components to minimize the crossing of ratlines.

4. Routing:

● Trace Width Matters: Use wider traces for power and ground (e.g., 20-30 mil) to handle more current and reduce noise. Use narrower traces for general signals (e.g., 8-10 mil).

● Avoid Sharp Angles: Never use sharp 90-degree turns in your traces. Always use two 45-degree turns instead. This prevents potential manufacturing issues and is critical for signal integrity in high-speed designs.

● Keep Traces Short: Route connections as directly as possible to minimize noise pickup and signal degradation.

● Use Both Layers: Use the top layer (red) and bottom layer (blue) to your advantage. A common strategy is to run traces horizontally on one layer and vertically on the other. Use vias to switch between layers when a trace needs to cross another.

5. Copper Pour & Silkscreen:

How to Create a Copper Pour

For a robust design, it's excellent practice to fill the unused areas on both the top and bottom layers with copper pours connected to your GND net. This creates a large ground plane that provides excellent electrical shielding, helps with heat dissipation, and creates a low-impedance return path for signals.

I. Select the Layer: Start with the Bottom Layer.

II. Choose the Tool: Select the "Copper Pour" tool from the PCB Tools toolbar.

III. Draw the Area: Click at each corner of your board outline to draw a rectangle that covers your entire board. Right-click to finish drawing.

IV. Assign the Net: In the properties panel on the right, find the "Net" dropdown and assign the pour to your GND net.

V. Repeat for the Top Layer: Switch to the Top Layer and repeat the process to create another ground pour.

VI. Rebuild the Pour: This is a critical final step! After you finish routing or move a component, the pour will not update automatically. You must manually rebuild it by selecting the pour and choosing " Rebuild or pressing Ctrl + B”. Always do this as the last step before running your DRC.

Effective Silkscreen Design

The silkscreen is the text and symbols printed on the board, and a good one makes assembly and debugging much easier.

● Component Designators: Ensure every component's designator (R1, C1, U1) is clearly visible and close to the component it identifies. Don't let them overlap pads or vias.

● Polarity Markings: For components like diodes, LEDs, and electrolytic capacitors, add a clear polarity marker (e.g., a + sign or a diode symbol) on the silkscreen.

● Pin 1 Indicators: For integrated circuits (ICs), make sure there is a clear dot or number '1' on the silkscreen next to Pin 1.

6. DRC & Gerbers. Finally, run the Design Rule Check (DRC). This will automatically flag any violations of the rules you set up earlier. Fix any errors it finds. Once the board is error-free, use EasyEDA Pro's built-in 3D Viewer (Shortcut: 3). This is an incredibly powerful tool to visually inspect your board. Check for component collisions, verify silkscreen placement, and get a realistic feel for your final product.
Once you are satisfied with the 3D preview, click the "Generate Gerber" button. This will create the set of manufacturing files JLCPCB needs to build your board, or you can directly place an order from JLCPCB from its “Order PCB” button.

Conclusion

Now you have the full outline for how to create a PCB circuit board. We discuss the crucial connection between a clean circuit schematic and a successful layout, the significance of setting up strong design rules, and the hands-on component placement and trace routing. Designing your own PCB is an exciting task, but it does require some accuracy, technical know-how, and carefulness.

Ready to make your design real? JLCPCB is your go-to provider for leading PCB prototyping and assembly services. If you need assistance, and you want to be sure your design has the best chance of performing as intended while keeping costs down, our JLCPCB Layout service starts at just $20 now! Close to rates of $0.45 a pin, our designers and engineers can layout your design, so you can just keep innovating.

FAQs About PCB Layout Design

Q1: What is crosstalk, and how can I minimize it in my PCB layout?

A: Crosstalk is the unwanted coupling of a signal that occurs from one trace, called the “aggressor” trace, to an adjacent trace called the “victim” trace. This is one of the most significant contributors to noise in digital designs. To reduce crosstalk, there are a few ways that you can mitigate it:

1. Increase spacing: The farther apart the traces are, the weaker the coupling effect will be. A common rule of thumb is 3x the trace width as spacing between critical traces.

2. Use a ground plane: A solid ground plane located between signal layers provides excellent shielding.

3. Route orthogonally: When routing traces on adjacent layers, route the traces perpendicular to each other (horizontal on the top, and vertical on the layer below) and minimize, if possible, parallel runs.

Q: How do I determine the right number of layers for my PCB design?

A: A 2-layer board is adequate for simple circuits. You will need more layers (4, 6, etc.) when your design is really dense and you can't route everything on 2 layers, or when you need controlled impedance for high-speed signals (USB, Ethernet, DDR memory, etc.) that require a dedicated ground and dedicated power plane for signal integrity.

Q: What are some common mistakes to avoid in PCB layout for high-speed signals?

A: You'll start to notice common mistakes, like using a sharp 90-degree bump (which can create signal reflections), routing sensitive signals next to noisy power lines, or not providing a continuous, solid ground plane underneath the high-speed traces. Don’t forget that differential pairs also have to be matched for length and spacing.

Q: Can I get my PCB design reviewed before manufacturing?

A: Yes, a design review is critical. While you might be able to ask some friends/peers to check your design, or ask for some of the online communities to let you know if there are mistakes, there are also design review services, like JLCPCB Layout, as a good example. JLCPCB engineers not only take care of the board layout, but more importantly, they inherently check your design for manufacturability (DFM) to ensure that the board is capable of being built without issues. It can save the time and expense of having to manufacture a board again after the first run.

Q: What is the right way to manage analog versus digital grounds when designing a mixed-signal PCB?

A: Any embedded system that has sensors or ADCs will need to consider this. The typical approach is to have two separate ground planes (copper pours), one for analog (AGND) and the other for digital (DGND). Next, route all of your analog signals on the analog plane and any digital signal on the digital plane. Then, tie the two planes together at just one point - typically at the ground pin of the microcontroller or close by the power supply entry. This "star ground" layout will help prevent noisy digital currents from circulating through the sensitive analog ground plane and interfering with your readings.

Q: What is via stitching and when should I use it?

The term via stitching refers to the practice of placing a series of vias to interconnect parallel copper planes (i.e., top and bottom ground planes). This is done mainly for two reasons. First, it provides a ground plane with extremely low impedance, giving a more stable ground reference. Second, and equally important, it provides a "cage" around the interior signal layers, thereby containing and preventing electromagnetic interference (EMI) from radiating off the board. This is especially important around the edges of the circuit board and near high-frequency traces.