A photoplotter is an electromechanical-optical machine that uses light to produce images on a medium. It is used to complete printed circuit board designs and can create photolithographic masks for integrated circuit manufacturing. Laser systems allow for more sophisticated designs, and the machine has undergone technological changes to become an invaluable tool in various industries.
A photoplotter is a device that uses light to produce an image on a medium. The electromechanical-optical machine was originally developed in the 1960s and allows processes that used to take up to 10 hours to be completed in minutes. Data instructions, commonly written in Gerber format, are used to drive the machine and draw the lines and shapes needed to complete printed circuit board (PCB) designs. 21st century laser systems allow for more sophisticated designs and work with complex CAD (Computer Aided Design) software.
In the most basic form of the photoplotter, images are exposed on black-and-white film by a computer-controlled light source. The film backing is then developed using a wash and dry process. Photolithographic masks for PCBs are made from a photoplotter and photomasks with sub-micrometer size features can be developed for integrated circuit manufacturing.
The vector photoplotter was a machine that overcame a major hurdle in the manufacturing of electronic components. It had a bright lamp which enabled the machine to project an image mounted inside a rotating wheel. The image was then transferred onto photosensitive film or glass. Shapes were drawn onto the surface using arcs called draws, produced by a continuous beam of light, while flashes were created by shining light at a fixed point. Information about the shape and size of lines, holes, and other image features was contained in the Gerber data.
Specific sets of this data are used by CAD software, but laser photoplotters often use numerical data to turn the laser on or off at specific time intervals. Other data formats have been developed for photoplotting with CAD or CAM software programs. A file can be used to store data, and the large size of most data storage systems are compatible with small and complex circuit design processes.
Laser photoplotter systems can focus beams to one or more locations. Laser beams can be modulated at high frequencies to form detailed images. A red helium-neon laser is often used, but diode lasers and red light-emitting diodes are also commonly implemented for laser phototracing. Some machines do away with photographic film altogether, and one system has a laser or xenon lamp that directly exposes a coated substrate to light. The photoplotter has undergone technological changes and is an invaluable tool in the PCB industry, graphic arts and chemical milling.
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