PCB Design & Layout

Printed Circuit Boards (PCBs) are the physical foundation of almost every electronic device. Studying PCB design takes you from prototype breadboards to professional, manufacturable products.

PCB Design Workflow

The PCB design process follows a structured flow from idea to manufactured board:

1. Schematic Capture

• Create a logical diagram of your circuit
• Select components with proper footprints
• Define net connections between components
• Run Electrical Rule Check (ERC)

2. PCB Layout

• Import netlist from schematic
• Define board outline and mounting holes
• Place components strategically
• Route traces to connect all nets
• Add ground/power planes
• Run Design Rule Check (DRC)

3. Manufacturing Files

• Generate Gerber files (layer artwork)
• Create drill files (NC Drill)
• Export BOM (Bill of Materials)
• Create pick-and-place files for assembly

PCB Layer Stackup

PCBs can have multiple layers. Understanding stackup is crucial for signal integrity and cost optimization.

Common Layer Configurations

• 2-Layer: Top signal/power + Bottom signal/ground. Cheapest, suitable for simple designs.
• 4-Layer: Top signal, Ground plane, Power plane, Bottom signal. Better for mixed-signal and moderate speed.
• 6+ Layers: Multiple signal and plane layers. Required for high-speed designs, DDR, etc.

Component Placement Guidelines

Strategic placement makes routing easier and improves signal integrity:

• Power Section: Keep power input, regulators, and bulk capacitors together
• Decoupling Caps: Place as close as possible to IC power pins
• Crystal/Oscillator: Keep very close to MCU, short traces
• High-Speed Signals: Minimize trace length, avoid vias where possible
• Analog/Digital Separation: Keep analog circuits away from noisy digital sections
• Connectors: Place at board edges for easy access

Routing Best Practices

Trace Width and Current Capacity

Trace width determines current-carrying capacity. Use an online trace width calculator based on:

• Required current (Amps)
• Acceptable temperature rise (typically 10-20°C)
• Copper weight (1oz = 35µm, 2oz = 70µm)
• Internal vs external layer

Signal Integrity Rules

• Avoid 90° Corners: Use 45° angles or curved traces
• Keep Traces Short: Especially for high-frequency signals
• Matched Length: For differential pairs and parallel buses
• Reference Planes: Ensure continuous ground/power plane under signals
• Via Usage: Minimize vias in high-speed paths

Power Distribution

Power Plane Design

• Use solid copper pours for power and ground
• Place decoupling capacitors with short vias to planes
• Consider multiple voltage domains (3.3V, 5V, analog)
• Use star-point grounding for sensitive analog circuits

Decoupling Strategy

• Bulk Capacitors: 10-100µF near power input
• Per-IC Decoupling: 0.1µF (100nF) at each IC power pin
• High-Frequency: Add 10nF or 1nF for fast-switching ICs

Design for Manufacturing (DFM)

Following DFM guidelines ensures your board can be manufactured reliably and cost-effectively:

• Minimum Trace/Space: Standard is 6mil/6mil, tighter requires advanced processes
• Minimum Via Size: 0.3mm drill is common, smaller adds cost
• Solder Mask: Ensure proper clearances around pads
• Silkscreen: Keep text readable (0.8mm+ height), avoid pads
• Panelization: Add mouse-bites or V-score for multiple boards per panel

Popular PCB Design Tools

KiCad (Free) Altium Designer Eagle EasyEDA OrCAD Fusion 360 Electronics

Manufacturing & Assembly

Choosing a Fab House

• Prototype: JLCPCB, PCBWay, OSH Park (small quantities, fast turnaround)
• Production: Evaluate based on quality, certifications (ISO, UL), and volume pricing

Assembly Options

• Hand Assembly: For prototypes and through-hole components
• Reflow Soldering: For SMD components, requires stencil and oven
• Turnkey Assembly: Fab house sources and assembles all components