5. Tracks and Pads

What Are Tracks?

Tracks (also called traces) are the conductive pathways that carry signals and power between components on a PCB. Think of them as the board's electrical road network.

Track widths vary depending on how much current they need to carry. For high-frequency signals, the width also affects impedance—so precise calculations are essential. Some components may also require spacing adjustments to reduce crosstalk, though this is rarely a concern in general-purpose designs.

What Are Pads?

Pads are small, exposed areas of copper where components are soldered. They serve two key roles:

• • Mechanical support - holding the component in place
• • Electrical contact - forming a conductive connection to the PCB's tracks

There are two primary types:

• • Through-Hole Pads: For traditional leaded components—soldered from the opposite side of the board.
• • Surface-Mount Pads (SMD): For components soldered directly to the PCB surface. No holes required.

You may also use vias—plated holes that connect copper layers in multi-layer PCBs:

• • Through-Hole Vias: Connect all layers from top to bottom
• • Blind Vias: Connect the outer layer to one inner layer
• • Buried Vias: Hidden entirely within the internal layers

Design Tips for Tracks and Pads

Designing a clean, reliable layout is part art, part engineering—like solving a puzzle where the reward is functional hardware. Here's how to get it right:

• • Check the component datasheets. Most layout errors trace back to overlooked details.
• • Keep trace direction consistent, especially for heat-sensitive or reflow-soldered components. This improves solder flow and reduces defects.
• • Use consistent pad sizes for fine-pitch parts like QFNs and BGAs. Uneven pads can cause poor solder joints or failed rework.
• • Match pad symmetry, especially under critical parts, to avoid tilting during soldering.
• • If you're working with controlled impedance traces, calculate the width precisely. Guesswork doesn't cut it here.