As the name suggests, a multi-layer circuit board can be called a multi-layer circuit board with more than two layers. I have analyzed what is a double-sided circuit board before, so the multi-layer board has more than two layers, such as four layers and six layers. Eight floors and so on. Of course, some designs are three-layer or five-layer circuits, also called multi-layer PCB circuit boards. For conductive traces larger than two-layer boards, there is an insulating base material between the layers. After each layer of wiring is printed, it is laminated to overlap each layer of wiring. Then drill holes again, and the conduction between the lines of each layer is realized by the via holes. The advantage of the multi-layer PCB circuit board is that the circuit can be distributed in the multi-layer wiring, so that more precise products can be designed. Or smaller products can be realized by multi-layer boards. Such as: mobile phone circuit boards, micro projectors, voice recorders and other products with relatively large volumes. In addition, multi-layer can increase the flexibility of design, can better control the differential impedance and single-ended impedance, as well as the output of some signal frequencies.

Multilayer circuit boards are an inevitable product of the development of electronic technology in the direction of high speed, multi-function, large capacity and small volume. With the continuous development of electronic technology, especially the extensive and in-depth application of large-scale and very large-scale integrated circuits, multilayer printed circuits are rapidly developing in the direction of high density, high precision, and high-level digitalization. Fine lines and small apertures have appeared. , Blind and buried holes, high plate thickness and aperture ratio and other technologies to meet the needs of the market. Due to the need for high-speed circuits in the computer and aerospace industries. It is required to further increase the packaging density, coupled with the reduction of the size of separate components and the rapid development of microelectronics, electronic equipment is developing in the direction of shrinking volume and reducing quality; single and double-sided printed boards are no longer possible due to the limitation of available space. Achieve a further increase in assembly density. Therefore, it is necessary to consider using more printed circuits than double-sided boards. This creates conditions for the emergence of multilayer circuit boards.