2.2 Infrastructure – Copper Traces and Via Architectures

Information travels through physical infrastructure. The copper traces on a board are the highways of the system, and their dimensions dictate the speed and volume of traffic they can handle. The connections between layers—vias—are the elevators that enable vertical integration.

Copper Traces: The Highways

• Etching Process: The board begins as a solid sheet of copper. Acid is used to dissolve the unwanted metal, leaving behind the specific pathways defined in the design files (Gerber).
• Impedance Control: High-speed data signals (like USB or 5G) require "smooth roads." The width of the trace must be controlled within tight tolerances (+/- 10%). Deviations cause signal reflections, leading to data corruption.

Vias: The Elevators

Vias connect the different floors of the PCB skyscraper.

• Through-Hole Via: Drilled from the roof to the basement. Reliable and cheap, but consumes space on every floor.
• Blind Via: Connects an outer layer to an inner layer (e.g., Floor 1 to Floor 3). Invisible from the bottom.
• Buried Via: Connects internal layers (e.g., Floor 3 to Floor 5). Completely invisible from the outside.
• Economic Trade-off: Blind and Buried vias (HDI Technology) allow for significant miniaturization (e.g., smartphones) but require sequential lamination cycles, often doubling the cost of the bare board compared to standard Through-Hole designs.

Final Checklist