Seven Steps To Determine PCB Layout and Wiring

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Printed circuit boards (PCBs) are essential components in electronic devices that mechanically support and electrically connect electronic components. The PCB layout and wiring dictate the functionality, performance, and reliability of the overall system. Proper PCB design requires carefully planning the position and connections of components according to electrical and physical design rules.

Follow these seven key steps to determine the optimal PCB layout and wiring for your system:

Step 1: Define Requirements and Constraints

First, clearly define the requirements and constraints for your PCB design:

  • What are the key functions and features the PCB must enable?
  • What are the size limitations?
  • What components need to be included?
  • What is the target manufacturing technology (e.g. through-hole vs surface mount)?
  • What design rules and standards must be followed?
  • What electrical performance characteristics are needed (e.g. noise, EMI)?
  • What is the target cost?

Document all requirements to guide your design decisions.

Step 2: Create a Schematic Diagram

Next, draw a detailed schematic diagram mapping connections between components. The schematic should include:

  • All electronic components required
  • Component designators and values
  • Connection points between components
  • Grouping of components by function
  • Power supply, input, and output interfaces

The schematic defines the electrical connectivity that must be achieved with the physical PCB layout.

Step 3: Select Components

With the schematic defined, you can select specific component models to use on the PCB. Consider factors like:

  • Electrical performance – Does the component meet needs for voltage, current, tolerance, frequency response, noise, etc?
  • Physical size and packaging – Is the component suitable for the target PCB manufacturing process and board space constraints?
  • Cost – Does the component meet cost targets for your production volume?
  • Reliability – Is the component sufficiently robust and from a trusted supplier?
  • Availability – Can the component be procured reliably for your production schedule?

It is best to use standard, commonly available components where possible. Custom or specialized components can add cost and manufacturing risk.

Step 4: Plan Component Placement

With components selected, you can now plan the physical component placement on the PCB. Follow these tips:

  • Group related components – Place interconnected components close together to minimize track lengths.
  • Ensure accessibility – Ensure components that may require adjustments or servicing are accessible.
  • Balanced density – Spread components evenly across the board area to balance manufacturing stress.
  • Partition by function – Logically group components by stages like input processing, power supply, output drivers.
  • Consider heights – Ensure there is sufficient clearance over tall components.
  • Enable modularity – Plan for separate functional blocks if appropriate.
  • Allow for routing space – Leave sufficient space between components for routing traces.

Creating a visual layout map is helpful for planning. Iteratively adjust placement to optimize routing.

Step 5: Route Traces Between Components

With components placed, you can route the copper traces to connect them per the schematic. Aim for:

  • Short, direct connections – Use straight traces and minimize length.
  • Avoid obstacles – Route traces around components and keepouts.
  • Harness wide traces – Bring wide supply traces directly to pins.
  • Maintain separation – Keep high voltage traces away from low voltage and digital lines.
  • Utilize layers – Use multiple routing layers efficiently.
  • Balance trace lengths – Ensure matched trace lengths in precision circuits.
  • Minimize crossings – Route to avoid crossing traces or minimize crossing angles.

Follow all electrical and manufacturing design rules for trace width, spacing, drilling, etc. Use routing software to automate trace connections.

Step 6: Complete Physical Design Considerations

Finish the PCB physical design with these aspects:

Mounting provisions – Provide mounting holes, slots, or edges to secure the PCB. Consider mechanical stresses.

Test points – Include test points to probe key nodes or debug circuits.

Board outline – Define the board perimeter shape and dimensions. Consider production panelization requirements.

Connectors – Select and place connectors to interface with cables or other PCBs.

Markings and labels – Add component identifiers, ratings, warnings, board name, revision, etc.

Fabrication notes – Specify special instructions like surface finish, soldermask details, material requirements, etc.

Fiducials and tooling holes – Allow for manufacturing alignment and registration.

Thermal design – Ensure adequate heat dissipation for power components with pads, vias, or copper fills.

EMI/grounding design – Incorporate ground planes, shields, filtering, and other EMI reduction techniques.

Step 7: Validate the Design

Perform design validation through:

  • Design rule checks – Verify all spacing, widths, drill sizes, and other manufacturing requirements are met.
  • Electrical validation – Simulate and analyze signal integrity, power integrity, EMI, and thermal performance.
  • Mechanical validation – Model and analyze mechanical stresses, vibrations, shock, and thermal expansion.
  • Prototyping – Build and test prototypes to confirm functionality and refine the design.
  • Peer review – Have experienced engineers review the design and provide feedback.

Only proceed to fabrication once the design passes all checks, simulations, and prototyping tests.


Careful planning is imperative to implement complex PCB designs that meet rigorous electrical, mechanical, and manufacturing requirements. Sequencing through the steps of defining requirements, schematic capture, component selection, placement, routing, and validation helps achieve a successful PCB layout and wiring optimized for your application needs. Leverage the latest EDA software, simulation tools, and prototyping best practices throughout the iterative design optimization process. With diligence and cross-domain expertise, you can produce reliable, high-performance PCB designs ready for volume production.