Printed circuit board (PCB) design entails far more than just layout routing. To successfully transform concepts into manufacturable boards, engineers must methodically progress through a series of logical development steps:
1. Requirements Gathering
- Define design rules, specs and constraints upfront guiding all downstream efforts
2. Schematic Capture
- Build board schematics with target components defining connectivity
3. Component Selection
- Research suitable parts meeting functionality needs within parameters
4. PCB Layout
- Route traces obeying layout rules delivering nets between pads
5.Verification and Testing
- Validate designs through ERC checks, simulations and prototyping
This guide walks through considerations at each step culminating in assembled boards ready for deployment.
The first phase establishes core specifications, constraints and preferences dictating all subsequent design decisions through final testing validation gates.
- Functionality — Define essential operational capabilities
- Environment — Expected operating conditions
- Regulations — Applicable safety or EMI rules
- Size — Physical board dimensions and form factor
- Interfaces — External connectors required
- Testing — Validation methodologies to employ
- Budgets — Cost ceilings for BOM or fabrication
- Schedule — Project development pace and duration
As requirements evolve through early concept refinement, frequently revisit and update documentation keeping stakeholders aligned. Unexpected late stage alterations prove vastly more expensive to accommodate than early pivots.
With specifications set, schematic capture converts proposed architectures into symbolic representations defining circuit connectivity and component selection.
- Placement — Logically group associated functions
- Annotations — Layer metadata like reference designators
- Pages — Partition complex designs across sheets
- Buses — Declare bus structures with bus entries
- No Connects — Specify disconnected pins
- Wire Connections — Join interrelating nodes
Review results versus intended block diagrams and topology plans to ensure accurate translation from abstract concepts to concrete schematics.
- Libraries — Import manufacturer parts into databases
- Parametric — Filter by attributes to narrow large lists
- Ratings — Verify tolerances and electrical operation ranges suit needs
- Footprints — Assess physical dimensions and pinouts
- Alternates — Design in backups meeting key parameters
- Procurement — Check availability, lead times and budgets
Correct device selection greatly smoothes subsequent implementation stages. Strategically choosing parts with onboard programming firmware simplifies development.
- ERC — Electronic rules checking finds missing annotations and unconnected pins
- DRC — Design rule checking validates proper widths and spacing
- LVS — Circuit simulation contrasts schematic vs resulting netlist
- DFA — Manual review confirming assembly achievability
Address flagged issues before proceeding to layout routing to prevent costly backtracking.
With schematics and components finalized, board routing converts symbolic connective representations into physical trace geometries linking pads based on design rules.
- Board Outline — Dimension board shape and local feature keepouts
- Layer Stack — Define layer types and quantities
- High Speed — Plan impedance matched traces and constraint regions
- Components — Place parts with grouping and orientation considerations
- Nets — Name signal groups traced together post routing
- Power — Map power entrance and decoupling stratagems
Thoughtful preparations during floor-planning vastly simplify subsequent routing.
- Fanout — Propagate traces from pads obeying spacing/widths
- Escape — Route heavily trafficked zones first
- Review — Visually inspect post-routing to catch errors
- Tuning — Refine traces failing design rules
- Planes — Fill unused areas with ground/power planes
Iteratively route traces in order of criticality until all connections complete.
- Gibberish — Validate no dangling tracks or orphaned pads
- ECOs — Issue and integrate engineering change orders
- RC Extraction — Extract parasitic trace resistance/capacitance
- Generate Files — Export Gerber and drill files for fabrication
With all checks passed and data packages completed, PCB layout concludes ready for prototyping.
Prior to full production, engineers verify boards operate as intended through bench debugging and environmental testing:
Simulation
- SPICE — Simulate electrical performance with extracted netlist
- Thermal — Model heating dissipation across layout
- Signal — Assess EMI, resonance and transmission line effects
- Stress — Estimate reliability lifetimes under use conditions
Prototyping
- Visual — Inspect bare PCBs for flaws post fabrication
- Monitoring — Probe signals and performance data
- Debugging — Diagnose and correct malfunctions
- Environmental — Test in deployment contexts
- Compliance — Formally certify safety or wireless functionality
Iteratively resolving findings from intensive verification efforts qualifies designs before high volume manufacturing.
By progressing circuit designs through iterative phases spanning requirements, schematic capture, layout routing and intensive validations, engineers transform ideas into functioning PCBs ready for end product integration. Upfront planning and continual testing saves substantial costs and development time while ensuring reliable performance meeting specifications under application operating conditions. Adopting methodical design walkthrough best practices leads to successful printed circuit board implementations.
The first steps include building requirements documentation clarifying essential parameters, constraints and regulatory compliance needs providing the framework guiding all subsequent development decisions down selecting ideal components.
Library parts contain abstract behavioral models and parametric data representing components in schematics, while footprints define physical pad geometries and dimensions used for PCB population during layout.
EDA tools contain design rule checking functions validating trace geometry spacing and widths meet fabrication and functional specifications provided by engineers to enforce constraints.
The Gerber files specifying traces, drills along with bill of materials generating from EDA tools comprise the primary outputs supplied to manufacturers when completing PCB layouts to begin physical board fabrication.
Simulation allows modeled confirmation of electrical performance plus characterization of effects absent from pure schematic views like resonant behaviors or radiated emissions essential for high speed digital and analog layouts before committing costly fabrication iteration cycles.
