Marking print (alt. legend print or position print) is used to identify the type and position of components on the printed circuit board and for the transfer of information to the assembler or the service technician. When using fully automatic loading assembly machines for PCB assembly a marking print is not absolutely necessary, it is however still used in complex printed circuit boards in order to increase the positioning accuracy.
Usually the external contours, the component names and the polarity (in polarized components) are given by the marking print. It has its own layers in the CAD file of the printed circuit board, one per each side (TOP, BOT).
When creating the marking print / legend print, attention should be paid to an adequate text size and avoiding overwriting of pads and other copper surfaces (clipping). This error is usually resolved with the design rule check of the PCB manufacturer.
The PCB marking print can be applied by screen printing, (direct-) imaging/exposure or inkjet process.
