What is Master Drawing
A master drawing is a comprehensive document containing essential information regarding the design and fabrication of a printed circuit board. It is a crucial reference for the manufacturer and stakeholders involved in the PCB production process.
The master drawing encompasses various design requirements, such as silkscreen requirements, board detail and construction, marking requirements, conductor definition, bow and twist requirements, minimum spacing requirements, test coupon requirements, artwork configuration control, electrical test requirements, fabrication allowances, performance requirements, and solder mask requirements. It also includes a reference to CAD data, which aids in accurately translating the design intent.
The level of detail required in the master drawing depends on the PCB classification. For Class 1 PCBs, the board layout itself can serve as the master drawing, supplemented with additional manufacturing instructions and pertinent notes to facilitate the manufacturing process. However, for Class 2 and Class 3 PCBs, a separate Master Drawing is necessary.
In Class 2 PCBs, the master drawing should explicitly depict the physical dimensions of the board, including pattern features that are not referenced by hole size or location. It may also specify coating thickness, plating details, and incorporate quality conformance test markings if required.
Class 3 PCBs demand the most comprehensive documentation. The master drawing for Class 3 boards should include all the necessary details, which are not explicitly provided in the given context. This likely encompasses specific requirements unique to Class 3 PCBs, as well as details of the manufacturing processes involved, such as drilling, plating, and etching.