说明：  1、规范PCB的设计流程；2、保证PCB设计质量和提高设计效率；3、提高PCB设计的可生产性、可测试性、可维护性。
(1, standardize the design process of PCB; 2, to ensure the quality of PCB design and improve the design efficiency; 3, improve the PCB design of the production, testability, maintainability)