Services

etc.; each layer of copper is etched and any internal sleepers (which will not extend to both outer surfaces of Services the finished multilayer board) are plated before the layers are laminated together. FR-4 epoxy glass is the most common insulating substrate. Flexible-Rigid printed circuits are boards that bring in a

paths. In a multi-layer board, an internal layer may be mostly solid copper to act as Services 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 consistent impedance.

insulation. For a multilayer printed circuit with a specific stack-up, it must be taken into account that the internal tracks with controlled impedance are shielded by copper planes and for this reason only the thickness of the insulation between layers and tracks Services and the track thickness must be taken into account.