Pcb Production

Written by Serena Berger
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A printed circuit board in its most basic form consists of a sheet of copper foil attached to a piece of plastic, known as the substrate. Circuits are formed by stripping away the copper, resulting in traces being left on the substrate. There are three common methods by which this process is performed, two of which remove copper from the attached substrate while the other directly applies a conductive material to the substrate.

Photoengraving requires the least hardware of the three approaches. Using a drafting program, the PCB is designed, and then a negative of the layout is created. On the negative, areas where traces occur are left blank, while the rest of the space is covered in black ink. Some designers are able to make these negatives simply by using a laser printer with an overhead transparency, while others use software packages.

The negative is then laid on top of the light-sensitive PCB substrate and exposed to a UV light. Parts of the negative that were black do not allow light to shine through, so the PCB will be unaffected in those areas. Traces, which are blank on the transparency, will allow light to shine onto the board so that they can be marked. A chemical solution is then used to remove the excess copper. The traces that appear on the PCB can then be plated with a metal such as tin to prevent oxidation from occurring.

Alternatives to Photoengraving

If you are designing a prototype and do not want to invest in milling or printing equipment, photoengraving may be an acceptable option. For bulk manufacturing, you are better off investing in hardware to automate the task. Two options are PCB milling, which removes copper from the substrate, or PCB printing, which applies traces to the substrate directly.


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