With the continuous development of SMT (Surface Mount Technology) and the introduction of new generation SMD (Surface Mount Devices), such as QFP, QFN, CSP, BGA (especially MBGA), make electronic products more intelligent and miniaturized. And promote the PCB industry technology, a major reform and progress.The rapid development of these processing technology, prompted the PCB design has gradually to the multi-layer, high-density wiring direction. Multi-layer printed circuit board with its design flexibility, stable and reliable electrical performance and superior economic performance, is now widely used in the production of electronic products.

Multi-layer PCB and single-panel, double-panel The biggest difference is that the internal power supply layer (to maintain the internal layer) and ground plane, power and ground network mainly in the power layer wiring. However, multi-layer board wiring is mainly to the top and bottom of the main, supplemented by the middle of the wiring layer. Therefore, the design of multi-layer board and double-panel design method is basically the same, the key is how to optimize the wiring of the inner layer, so that the circuit board wiring is more reasonable, better electromagnetic compatibility.

Multi-layer PCB shelf life in the IPC is defined, the surface process is anti-oxidation, not demolition of vacuum packaging, half a year to use finished, demolished the vacuum packaging in twenty-four hours, and is the temperature and humidity control environment , The board is not used in the next year to use the packaging, opened within a week should be finished finished film, the same to control the temperature and humidity, gold plate equivalent to tin plate, but the control process than tin plate strict.