PCB design software and the electronic components industry have come together to drive much of the terminology used by professional designers and engineers. For new designers and engineers, understanding the basic terminology involved in PCB design eases the curve involved in learning ECAD software and helps designers communicate with systems engineers, component vendors, and manufacturers.
The glossary shown here is divided up into two sections—one section covers terminology used in ECAD software and the other section covers terminology used to describe board construction and the physical layout of the board.
A CAD document showing the location of all physical elements that will appear on the finished PCB.
Functional drawings that illustrate the electrical connections between components.
Schematic design is sometimes called logic creation, referring to the use of logic components in DIP packages to perform logic operations before the advent of heavily integrated processors and microcontrollers.
Stands for “Simulation Program with Integrated Circuit Emphasis”; a simulation package that solves Kirchhoff’s laws for circuit diagrams using a numerical algorithm.
Functional drawings that illustrate the electrical connections between components. A CAD object that defines how a real electronic component is represented in schematic sheets and a PCB layout in ECAD software. All components include a schematic symbol and PCB footprint that are used to create schematics and a PCB layout, respectively. A component may also include a SPICE subcircuit for use in circuit simulations, and a 3D model for use in MCAD software.
A box with drawn leads that represent the physical leads on a component. The leads in a schematic symbol are used to make electrical connections in schematic sheets.
A CAD object that includes the land pattern, silkscreen outline, and package mechanical outline.
An ASCII-based simulation file that describes the electrical behavior of a component in SPICE simulations.
Component library or PCB library
A component library (or, simply, library) includes multiple components in a single file or set of files. Libraries are needed to create CAD documents in ECAD software, and the software will pull data from the libraries.
A graphical connection between two components that represents an electrical connection on a manufactured circuit board.
Nets in the schematic correspond to physical connections in the PCB layout
An alphanumeric code that is used to denote specific components in a PCB layout and schematic (example: U4 or C35). The letter prefix corresponds to a type of component and numbers are assigned to each type of component in series.
The general name given to an electrical connection between two components. This can be inclusive of all nets on the PCB, connectors, vias (see definition below), or other media used to make a physical connection in an electronic system.
A type of PCB where trace widths are very small (usually 4 mil or less) and layer counts tend to be very high (typically 12 or more). HDI PCB design normally requires the use of microvias (see definition below) to make connections between layers.
A practice where a design considers how the product will be fabricated and where fabrication constraints are used as design rules in ECAD software.
A practice where assembly constraints are considered during design and are defined in ECAD software as design rules.
Typically used for prototype design, this design practice emphasizes inclusion of features that enable the collection of electrical measurements and quality inspection.
The three terms above are sometimes lumped together into a larger idea known as DFX, or “design for X”, due to the application of these principles beyond manufacturing, assembly, and testing.
BOARD CONSTRUCTION AND PHYSICAL LAYOUT
When we refer to “board construction”, we’re not just talking about something that happens in manufacturing. ECAD software companies and designers use many of the same terms as manufacturers to describe the features in a CAD layout, as well as their corresponding features on a fabricated circuit board. Here are some of the important terms used to describe a physical PCB layout.
Copper pour, traces, vias, and reference designators in a KiCAD PCB layout.
A polygon is often called a polygon pour or copper pour. Filling in the empty space on a PCB with grounded copper provides shielding against EMI.
Refers to the size of pads, arrangement of pads, and package outline for a given part that should be designed onto a PCB. Land patterns for standard component packages are defined in the IPC-7351B standards (SMD components) and IPC-7251 standards (through-hole components).
The terms land pattern and PCB footprint are sometimes used interchangeably, but they are technically not the same thing. A component could have several allowable land patterns, but it will only have one footprint.
Refers to electronic components that are mounted to a PCB by placing leads into through-hole vias.
At Ultra Librarian, we care deeply about the success of all PCB designers and engineers, and we strive to provide resources to help new designers advance their careers. In addition to our glossaries, one of the resources we provide is a comprehensive electronics search engine that helps designers find the components they need. All Ultra Librarian users can access CAD models for components and verified 3D models that can be imported into popular ECAD applications. We also give users access to aggregated sourcing information from worldwide distributors.
These axial resistors are classic through-hole components