Multi-layer PCB is "core main force" in communication, medical, industrial control, security, automobile, electricity, aviation, military, computer, computer around the field, product functions are getting higher and higher, PCB is getting more accurate, then relative to production difficulty It is also getting bigger and bigger. 1. Inner-layer line making difficult point multi-layer circuit has a variety of special requirements, thick copper, high frequency, high TG value, which is increasingly controlled to the inner layer wiring and graphic size. For example, the ARM development board has a very multi-impedance signal line, ensuring that the integrity of the impedance increases the difficulty of production of inner line. The inner layer signal line is much, the width and spacing of the line are basically around 4 mil or less; the plate-layer multi-core plate is easy to wrinkle, and these factors will increase the production of the inner layer. Suggestion: Line width, line spacing design in 3.5 / 3.5mil or more (there are no difficulty in production production). For example, a six-layer board, it is recommended to design a fake eight-layer structural design, which can be 4-6MIL line width 50OHM, 90OHM, 100OHM impedance requirements. 2, the inner layer is difficult to point the number of layers of multi-layer layers, and the inner layer is also getting higher and higher. The effect of Philippine's environmental temperature and humidity will have a rising shrinkage, and the core board will have the same rising shrinkage, which makes the inner intercommunication point accuracy more difficult to control. Recommendation: This can be given to the reliable PCB manufacturing plant. 3. Difficulties of the pressing process and the superposition of the PP (version of the solid sheet), which is prone to layers, skateboards, and stereotype residues when pressing. In the inner structure design process, it should be considered in consideration of the dielectric thickness of the layer, flow collactance flow, and heat resistance and other aspects of heat resistance, and the corresponding press structure is reasonably designed. Recommendation: Harcasle the inner layer is uniform, paved in a large area in the same area, paved the copper balance with PAD. 4. Difficulty multi-layer plates produced by drilling use high Tg or other special sheets, and different material drilling roughness is different, and the difficulty of removing endogenous gums is increased. High-density multi-layer panel density is high, low production efficiency is easy to break the knife, between different networks, and the edges of the hole will lead to the problem of CAF effect. Suggestion: Different networks of hole edge spacing ≥ 0.3mm