With the improvement of PCB technology and the increase in consumer demand for faster and more powerful products, PCB has changed from a basic two-layer board to a board with four, six layers and up to ten to thirty layers of dielectric and conductors. . Why increase the number of layers? Having more layers can increase the power distribution of the circuit board, reduce crosstalk, eliminate electromagnetic interference and support high-speed signals. The number of layers used for the PCB depends on the application, operating frequency, pin density, and signal layer requirements.

By stacking two layers, the top layer (ie, layer 1) is used as a signal layer. The four-layer stack uses the top and bottom layers (or the 1st and 4th layers) as the signal layer. In this configuration, the 2nd and 3rd layers are used as planes. The prepreg layer bonds two or more double-sided panels together and acts as a dielectric between the layers. The six-layer PCB adds two copper layers, and the second and fifth layers serve as planes. Layers 1, 3, 4, and 6 carry signals.

Proceed to the six-layer structure, the inner layer two, three (when it is a double-sided board) and the fourth five (when it is a double-sided board) as the core layer, and the prepreg (PP) is sandwiched between the core boards. Since the prepreg material has not been fully cured, the material is softer than the core material. The PCB manufacturing process applies heat and pressure to the entire stack and melts the prepreg and core so that the layers can be bonded together.

Multilayer boards add more copper and dielectric layers to the stack. In an eight-layer PCB, seven inner rows of the dielectric glue the four planar layers and the four signal layers together. Ten to twelve-layer boards increase the number of dielectric layers, retain four planar layers, and increase the number of signal layers.