We use laser photoplotters in a temperature and humidity-controlled darkroom to make the films we will use later to image the PCBs. The photoplotter takes the board data and converts it into a pixel image. A laser writes this onto the film. The exposed film is automatically developed and unloaded for the operator. The films are ready now for the PCB fabrication process.
We have generated one film or phototool per PCB layer. Now the films are registered with each other so that the different layers of the PCB will be perfectly aligned. We do this by punching precise registration holes in each sheet of film. The operator puts the film on the table of the punch and then micro-adjusts the table until the targets on the film are exactly lined up with the targets on the film punch. She then punches each sheet of film with the registration holes which will fit onto the registration pins in our imaging equipment.
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