Multi-layer printed circuit boards were made to simplify and optimize the connection layout of double-sided dielectric plates. Increased integration of microcircuits, the provision of a significant number of interlayer connections, as well as the implementation of cases with many wires — all this was the primary reason for the production and intensive development of MPCB technologies.

As models and technological requirements become more complex, not only the quality but also the total number of layers has increased. As a result, advanced multi-layer printed circuit boards can have 30−32 layers.

MPCB are used in high-frequency devices with a regulated impedance of signal circuits and an acceptable level of electromagnetic interference.

Among the basic materials of multi-layer printed circuit boards there are:

— Rogers of Ro4003 and Ro4350 series.
— Fiberglass FR4 KingBoard [KB-6160] with a thickness of 0.25−0.8 mm or [KB-6167F] with a thickness of: 0.25−0.71 mm.
— Prepregs KingBoard [KB-6060] ([KB-7628], [KB-2116] or [KB-1080]) and [KB-6067].

The combination is possible among the basic materials. For example: the application of polyimide (PI) in flex-rigid printed circuit boards with fiberglass FR-4.

The basis of the design — alternating thin dielectric layers in combination with elements of topology. When producing, the layers are combined into a single, integral multi-layer plate.

Electrical connections, depending on the pressing technique, may have both vias of the reach-through type and interlayer transitions:
— External layers on internal — blind;
— Internal layers — hidden.

Any multi-layer PCB design consists of 2 elements:
— Core — dielectric foil-coated layer on both sides of considerable thickness.
— Prepreg — dielectric foil-coated layer on one side or not foil-coated layer of small thickness. It acts as a connecting intercore layer.

— External
Another name is mounting. Layer essence: installation of components and realization of connections between the elements located in close proximity of board.

— Power layers
They are presented in the form of solid polygons. They have minimal current resistance and low induction. They contribute to the shielding of signal layers.

— Signal
They allow making electronic connections between components. Feature: significant indicators of the density of communication lines.

— Heat conductive
They remove and distribute heat excess of the components of the circuit with increased technological values of heat generation.

— Layer-by-layer build-up.
— Pairwise pressing.
— Combination of methods.

The main method is pairwise pressing of nuclear blanks — thin double-sided boards of a certain topology. The method is implemented using fiberglass liner.

Layer-by-layer build-up/metallization of the core holes (through type) is performed by a subtractive chemical method. Photoresists are used as a protective coating.