the inner copper layers are protected by the adjacent substrate layers. The soldering mask soldermask is made of a fluid substance like an ink imprimata placa and is applied in a thin layer similar to varnish on the entire surface of the printed circuit less on the soldering pads and it also has a role
need for multilayer printed circuit boards with more than two, four and especially more than six layers of copper has been concurrent with the adoption of surface mount technology. "Through holes" components are assembled by their placa imprimata legs passing through the board and glued to the pads on
a multi-layer board, an internal layer may be mostly solid copper to act as a ground plane for shielding and power return. For microwave printed circuits, transmission lines can be laid out in a planar form, such as stripline or microstrip, with dimensions carefully controlled to ensure imprimata placa consistent impedance. In