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How PCB files are transfered to circuit boards

2017-12-21 01:59  
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When you are done with a€?cleana€? period of task a€“ designing, drawing a circuit and tracing a PCB, you need to transfer a design to a real board. Here starts what I call a a€?messya€? part of design. When designing at home there are several options – to use prototyping boards or make PCB by yourself. In second option you have to transfer PCB image to board with copper layer. There are several methods of doing this: direct transfer with glossy paper where image is printed with laser printer or use more advanced ultraviolet exposure. This way PCB image is printed on paper or film directly from program window without keeping in mind about pcb file formats. Different situation iswhen fabricating professional PCB’s. Each company which fabricates PCB boards always announce what type of file formats they support. So if you are going to order a PCB better check with them in order to save your time.

The most common and standard format is so calledGerberfile format. Almost all layout tools are able to produce Gerber files. If you want to preview your generated Gerber files there is a nice free Gerber file viever(GCPrevue) from GraphiCode, Inc. (http:\\www.graphicode.com) which is free to use.

gerber_view.JPG

 

Or you can use another Free Gerber Viewer a€“ gerbv.

Same Gerber standard has many variations but here are two main:

Standard Gerber a€“ like RS-274-D which requires an external aperture list to define all the apertures in the design;

Extended Gerbger a€“ like RS-274-X which contains all aperture definitions within a file.

Mostly there Extended Gerber is used.

PCB manufacturers have to transfer image to PCB, They usually use a Photoplotter a€“ where they expose resist layer of circuit board with the image. Resist layer controls removal of copper during etching phase. A photoplotter simply draws an image with a light according to data in Gerber file. Photoplotter contain a special shaped apperture which controls a light passing through. Photoplotters can berasterorvector. Most of them are raster.

Other methods are exposing circuit board through very detailed transparent material or more time consuming is direct engraving.

 


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