PCB structure

The choice of the number of layers determines the physical ability to conduct the required number of printed conductors and the manufacturability of the board. Single-layer boards have limited switching capabilities, but the highest manufacturability. As the number of conductive layers increases, the first indicator increases, the second decreases, and the absolute values ​​of the labor intensity of manufacturing are highly dependent on specific technological processes. Introduction of hinged jumpers reduces manufacturability, so their number on the board should not exceed 5 ... 10% of the total number of connections, therefore even in this case single-layer boards often do not meet modern requirements and are applicable only to simple RFEs.

For IET installation, relatively technologically advanced two-layer boards are preferred, which, in the absence of restrictions on size, speed, reliability, etc., make it possible to realize electrical circuit diagrams of high complexity.

Multilayer boards provide: increased switching capabilities; reducing the length of the connecting lines: placing the elements of the conductive pattern in a homogeneous dielectric medium, which weakens *** the influence of external influences; possibility of placement of shielding layers inside the MPP. When assessing the possibilities of multi-layer printed wiring, it should be borne in mind that multilayer boards have a high cost, low manufacturability and reliability. The approximate number of layers N _SL for the selected density of the printed pattern, which can be characterized by the step of the printed conductors,

(16.4)

where b , s is the width of the conductors and the distance between them; M - the average number of involved findings IC; H - the side of the board on which the connector is installed; n _x , n _y - the number of columns and rows of IC.