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PCB Design

Jose Jimenez edited this page Jan 4, 2021 · 2 revisions

General Notes on PCB Design

Components and Connections on a PCB

Component types

Two types of components that may be used on a PCB are through-hole and surface-mount (SMT). Through-hole components tend to be larger and require holes that go all the way through the PCB. Surface-mount components attach to the surface of the PCB and do not require holes through the board.

PCB connections

Components attach to the PCB through soldered connections to small copper areas called pads. These pads are connected by copper paths called traces (to make the "wire" connections between components). If a PCB contains multiple layers, it is necessary to use copper-filled holes called vias to make connections between the different layers.

Layers

PCBs typically consist of multiple layers to allow for a more organized structure. Generally, if a PCB has 4 or more layers, there is a dedicated layer for ground connections (GND) and another layer for power connections (VCC); the remaining layers are used for signal connections. Copper pours (i.e. filling a large portion of a layer with copper) are often used on the GND and VCC layers to help simplify the design process (can make the connection with a via, rather than a lengthy trace) and to avoid issues with grounding (e.g. ground loops).

Design Considerations

Trace width

Trace width is an important design consideration on a PCB. High currents require thicker traces in order to avoid issues with resistivity (note that a thicker trace reduces its resistivity, thus leading to problems with heat). Longer traces should also be made thicker for similar reasons. There are several online trace width calculators that may be used to determine the necessary width for a trace.

Signal separation

Digital signals (e.g. the clock) can interfere with analog signals and lead to unwanted changes. As a result, it is important to ensure these signals are kept separate. Long parallel traces (especially if a combination of digital and analog) should be avoided and their ground connections should be kept separate as well.

Micromouse PCB Design

The Micromouse will use a 4-layer design, with layers (in order from top to bottom) signal, GND, VCC, and signal.

Author: Brandon Cramer