What is a multilayer PCB?

In simple terms, a multilayer board is a printed circuit board with more than two layers and at least three layers of conductive material or copper. When looking at a multilayer PCB, the top and bottom layers look similar to a double-sided PCB, but they have more layers on both sides of the core. The layers are interconnected through copper plated vias and there can be more layers, we have witnessed up to 40 layers. Active and passive components are placed on the top and bottom layers of a multilayer PCB, while the internal stacked layers are used for routing.

As multilayer PCBs can accommodate more electronic components, they are widely used in modern electrical appliances, with the number of layers ranging from four to twelve. Several applications such as smart devices require four to eight layers, while smartphones can use up to twelve layers. When manufacturing a multilayer PCB, designers will choose an even number of layers instead of an odd number of layers, because laminating an odd number of layers makes the circuit complex and the cost will also be high.

Why we need it:

Cause the increased concentration of integrated circuit package leading to a high concentration of interconnect lines, It makes it necessory to use the multiple substrates.

Unpredictable design issues such as noise, stray capacitance, crosstalk, etc. occur in the layout of the PCB. Therefore, the design of PCB must focus on minimizing the length of the signal line and avoiding parallel paths.

Obviously, due to the limited number of crossovers that can be achieved in a single-side, even in a double-side board, these requirements cannot be satisfied.

In the case of a large number of requirements in interconnections and crossovers, to achieve a satisfactory performance, the board must be expanded to more than two layers, so a multilayer PCB board is manufactured.