Background Theory > Dimensions

In electronic design, schematic dimension symbols are graphical representations used to annotate and indicate the physical dimensions, sizes, and spacing of components, PCB features, and other elements in a schematic diagram. These symbols help convey crucial information about the physical aspects of the circuit design and assist in ensuring accurate representation during the PCB layout phase.

Here are some common schematic dimension symbols:

•Horizontal and Vertical Lines with Arrows: These symbols represent dimensions for the length or width of components or PCB features. The arrows at the ends of the lines indicate the direction of the dimension measurement.

•Diameter Circle: This symbol is used to indicate the diameter of circular components or holes, such as vias or mounting holes.

•Radial Lines: Radial lines are used to denote the diameter of a circular component or pad.

•Horizontal and Vertical Lines with No Arrows: These symbols are used for indicating distances or clearances between components, traces, or other objects on the schematic.

•Double-Ended Arrow: This symbol represents the distance between two points or the spacing between two objects.

•Box or Rectangle with Dimension: This symbol is used to enclose a component or an area and annotate its dimensions.

•Grid-like Pattern: A grid-like pattern with dimensions shown on the schematic is used to represent an array of components or pins.

•Connector Pitch: This symbol denotes the pitch or spacing between the pins or terminals of a connector.

•Component Footprint Symbol: Some schematic symbols for specific components may include a representation of the physical package or footprint size.

•Reference Designator with Dimension: Dimension symbols may be placed adjacent to a component reference designator to indicate its size.

Schematic dimension symbols are typically accompanied by numeric values to indicate the actual measurement in the required unit (e.g., millimeters or inches). The symbols are placed alongside the relevant components, pads, traces, or areas they refer to, providing clarity about the physical aspects of the circuit design.

When using schematic dimension symbols, it's essential to ensure accuracy and consistency to avoid errors during the PCB layout and manufacturing stages. Properly annotated dimensions contribute to the successful realization of the electronic design and aid in meeting specific design requirements and constraints.