Aperture
Aperture turns up in 2 fields: PCBs, geosynthetics. Here is what it means to the people in each one.
Aperture in PCBs
Shape and size used to draw or flash a feature in Gerber data, named for the opening in a photoplotter's aperture wheel.
An aperture defines the shape and size, round, rectangular, oblong or custom, that a Gerber file uses to flash pads or draw traces. The name comes from vector photoplotters, where each aperture is a physical hole in a wheel that shapes the light exposing the film, listed in a separate aperture file. RS-274X embeds the definitions in the Gerber file itself, and stencil designers use the same word for each opening in a solder paste stencil.
"Stencil apertures on the QFN thermal pad should be a window pane at about 60 percent, not one big opening."
Aperture in geosynthetics
Open space between the ribs of a geogrid or between the strands of a woven geotextile.
Geogrid apertures are matched to the aggregate placed on them so particles strike through and lock in; too small and the grid acts like a slip sheet, too large and stone falls through without interlocking. Design rules tie aperture size to the coarser fraction of the aggregate grading. In woven geotextiles, aperture size and percent open area govern filtration.
"Aperture is two inches and they're bringing in three-quarter minus, that stone will just fall through."