A photoplotter is a specialized electro-opto-mechanical machine that exposes a latent image on a medium, usually high-contrast monochromatic (

black-and-white Black-and-white (B&W or B/W) images combine black and white in a continuous spectrum, producing a range of shades of grey. Media The history of various visual media began with black and white, and as technology improved, altered to color. ...

) photographic film, using a light source under computer control. Once the film has been exposed, it must be processed before it is ready for use. Photoplotters are used primarily for industrial production of printed circuit boards (PCB) and integrated circuit (IC) packaging. In the PCB industry, photoplotting is the first step of making photolithography masks for printed circuit boards. These masks are called ''photoplots'' and are limited in resolution by the technology in use; in 1998 photoplots with resolvable details of 2.5 µm or more were possible. Integrated circuits are made in a similar fashion utilizing ''

photomask A photomask is an opaque plate with holes or transparencies that allow light to shine through in a defined pattern. They are commonly used in photolithography and the production of integrated circuits (ICs or "chips") in particular. Masks are used ...

s'' with sub-micrometer feature sizes; photomasks are traditionally made by photoreducing photoplotter output. Other application of photoplotters include chemical milling and specialized graphic arts.

History

The first photoplotter was introduced by Gerber Scientific, Inc. in the 1960s. The company's file standard, the

Gerber format The Gerber format is an open ASCII vector format for printed circuit board (PCB) designs. It is the de facto standard used by PCB industry software to describe the printed circuit board images: copper layers, solder mask, legend, drill data, et ...

for PCB files, eventually became an industry standard for describing the printed circuit board images such as the copper layers, solder mask and legend. Early machines used a xenon flash lamp, and projected an image mounted in a rotating ''aperture wheel'' onto the photosensitive surface of the film or glass plate. The imaging head assembly traversed over the surface of the media without touching it to produce ''draws'' and ''flashes''. Draws are vectors or arcs created by continuous illumination as the imaging head moves over the photosensitive surface. A flash creates a single simple graphic in a location by shining light through an aperture of the appropriate shape at a fixed location. Modern photoplotters are generally raster-scan devices that use a

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fi ...

beam focused to one or more spots, modulated at multi- megahertz rates to form the image. The most recent development related to photoplotting is laser direct imaging (LDI) which utilizes a high-power laser or xenon lamp to directly expose photoresist on a coated substrate instead of exposing photographic film. This eliminates the handling of photographic film. The input of photoplotters is a vector graphics file, typically in

. Manufacturers of photoplotters include Gerber Scientific,

Orbotech Orbotech Ltd. a subsidiary of KLA Corporation and a technology company used in the manufacturing of consumer and industrial products throughout the electronics and adjacent industries. The company providing electronics reading, writing, and conne ...

and Ucamco.

References

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External links

* Ronald B. Webster
Variable Aperture Photoexposure Device
15 September 1970, 3 October 1972. Gerber variable shutter patent. Electronics manufacturing Plotters