A PCB board is a printed circuit board. A multilayer PCB is also a multilayer circuit board, also called a multi-substrate board.

The increased density of integrated circuit packages leads to a high concentration of interconnections, which makes the use of multisubstrate necessary.Unexpected design problems such as noise, stray capacitance, crosstalk, etc. have arisen in the layout of printed circuits.Therefore, PCB design must focus on minimizing the length of signal lines and avoiding parallel lines.Obviously, in a single panel or even a double panel, these requirements cannot be answered satisfactorily due to the limited number of crossings that can be achieved.In the case of a large number of interconnection and cross requirements, the board to achieve a satisfactory performance, the board layer must be expanded to more than two layers, so there are multilayer PCB board.Therefore, the original intention of making multilayer circuit boards is to provide more freedom for complex and/or noise-sensitive electronic circuits to choose suitable routing paths.A multilayer circuit board has at least three conductive layers, two of which are on the outer surface, and the remaining layer is synthesized in an insulating plate.The electrical connection between them is usually made through a hole in the cross section of the circuit board.Unless otherwise specified, multilayer printed circuit board, like a double panel, is typically a plated through hole plate.

A multi-substrate is fabricated by stacking two or more circuits on each other with reliable pre-set interconnections. Since drilling and electroplating have been completed before all the layers have been rolled together, this technique has violated the traditional manufacturing process from the beginning. The innermost two layers are made up of traditional double panels, while the outer layers are different, they are made up of separate single panels. Before rolling,the inner substrate will be drilled, through-hole plated, patterned transferred, developed, and etched. The outer layer to be drilled is a signal layer that is plated in such a way as to form a balanced copper ring at the inner edge of the through hole. The layers are then laminated together to form a multi-substrate that can be interconnected using wave soldering (between components).

Rolling may be done in a hydraulic press or in an overpressure chamber (autoclave). In the hydraulic press, the prepared material (for pressure stacking) is placed under cold or preheated pressure (high glass transition temperature material is placed at a temperature of 170-180 °C). The glass transition temperature is the amorphous region of the amorphous polymer (resin) or portion of the crystalline polymer that changes from a hard, relatively brittle state to a viscous, rubbery temperature.

Multi-substrate is put into use in professional electronic equipment (computers, equipment), especially in the case of weight and volume overload. However, this can only be achieved by increasing the cost of the multi-substrate in exchange for space increase and weight reduction. Multi-substrate is also very useful in high-speed circuits, which provide designers of printed circuit boards with more than two layers of boards to route wires and provide large ground and power areas.

What are the advantages of multi-layer PCB boards?

The multi-layer circuit board is as the name suggests that more than two layers of boards can be called multi-layer. Before you analyzed what is a double-sided board, then the multi-layer board is more than two layers, such as four layers, six layers, eight layers and so on..Of course, some designs have three or five layers of circuit, also called multilayer PCB.The conductive trace diagram is larger than the two-layer board. The layer is separated from the layer by an insulating substrate. After each layer is printed, the layers are overlapped by pressing. After drilling, the vias are used to achieve conduction between each layer of the line. The advantage of a multi-layer PCB board is that the lines can be distributed in multiple layers of wiring, allowing for the design of more sophisticated products. Or smaller products can be achieved with multi-layer boards. Such as: mobile phone circuit boards, micro projectors, voice recorders and other volumetric products.In addition, multiple layers can increase the flexibility of design, which can better control differential impedance and single-end impedance, as well as better output of some signal frequency.

Multi-layer printed circuit is rapidly developing towards the direction of high density, high precision and high level digitization.Because of the need for high-speed circuits in the computer and aerospace industries.It is required to further improve the packaging density, and with the reduction of the size of the separated components and the rapid development of microelectronics, the electronic equipment is developing towards the direction of reduction in size and quality.Due to the limitation of available space, it is impossible to improve the assembly density further.Therefore, it is necessary to consider using more printed circuits than the number of double panel layers.This has created the condition to the multilayer pcb circuit board appearance.