PCB Design — Printed Circuit Board Design

PCB (Printed Circuit Board) design is the engineering process of creating the physical circuit board that mechanically supports and electrically connects electronic components using conductive copper traces, pads, and vias etched onto laminated substrate layers.

Why PCB Design Matters

The PCB is where a product’s schematic becomes a physical reality. Poor PCB design can cause:

• Signal integrity failures — Crosstalk, reflections, impedance mismatches in high-speed interfaces.
• Power delivery issues — Voltage droops, excessive noise, ground bounce.
• EMC non-compliance — Failing CE marking (EN 55032/55035) due to radiated or conducted emissions.
• Thermal problems — Overheating components, derating, reduced product lifespan.
• Manufacturing defects — DFM violations that increase scrap rates and cost.

PCB Layer Stack-Ups

Modern hardware products use multi-layer PCBs. The number of layers depends on complexity:

Critical PCB Design Disciplines

Signal Integrity (SI)

For high-speed interfaces (DDR5, PCIe Gen5, 112G SerDes, LVDS), signal integrity analysis ensures:

• Controlled impedance — Trace widths and stack-up tuned for 50Ω/100Ω differential.
• Length matching — Critical for DDR and parallel buses.
• Via optimization — Back-drilling, via-in-pad, anti-pad sizing.
• Crosstalk analysis — Spacing rules to prevent coupling between adjacent traces.

Power Integrity (PI)

Power Delivery Network (PDN) analysis ensures stable voltage supply:

• Decoupling capacitor placement — Optimized for target impedance across frequency.
• Plane resonance analysis — Identifying and damping PDN resonances.
• Voltage regulator module (VRM) design — Point-of-load regulators, power sequencing.
• Current density analysis — Preventing copper overheating on high-current paths.

Design for Manufacturing (DFM)

• Component placement — Automated assembly considerations (pick-and-place clearances).
• Panelization — Optimizing PCB panel layouts for production efficiency.
• Testability — Test point access for In-Circuit Test (ICT) and boundary scan (JTAG).
• IPC standards — IPC-2221 (general), IPC-6012 (qualification), IPC-A-610 (acceptability).

EMC & Compliance

• CE marking — EMC testing per EN 55032 (emissions) and EN 55035 (immunity).
• Shielding — Strategic ground planes, guard traces, shielding cans.
• Filtering — Common-mode chokes, ferrite beads on I/O interfaces.
• REACH & RoHS — Material compliance with EU environmental regulations.

PCB Design Workflow

1. Schematic capture — Component selection, circuit design, net assignment.
2. Component library — Creating/validating footprints, 3D models, and symbols.
3. Board outline & constraints — Mechanical form factor, mounting holes, connector positions.
4. Layer stack-up definition — Impedance targets, signal/power/ground plane distribution.
5. Component placement — Strategic positioning for signal flow, thermal, and manufacturability.
6. Routing — Trace routing with constraint-driven rules (impedance, length, spacing).
7. DRC/ERC — Design Rule Check and Electrical Rule Check.
8. Manufacturing output — Gerber files, drill files, BOM, assembly drawings.

PCB Design Tools

Related Terms

• FPGA — PCBs for FPGA systems require advanced stack-ups and high-speed routing.
• SoC — System-on-Chip devices require careful PCB co-design for power and thermals.
• IoT — IoT product PCBs must balance cost, size, antenna, and power constraints.