Layer Configuration
Arrangement of copper and dielectric layers in a multilayer circuit board defines the electrical and mechanical foundation of the assembly. A well planned stackup design balances the need for signal routing space with the requirements for power distribution and thermal management. This configuration determines the overall thickness of the board and the distance between the signal traces and their reference planes.
Designers specify the material type and the thickness for every layer in the sequence.
Impedance Control
Spacing between the signal layers and the ground planes is the primary factor that sets the characteristic impedance of the transmission lines. During the stackup design, engineers calculate the necessary dielectric heights to achieve specific impedance values like fifty or one hundred ohms. Using standard material thicknesses helps to keep the manufacturing costs low and ensures that the materials are readily available.
Minor adjustments to the trace widths are made later to fine tune the electrical performance.
Production Yield
Symmetry in the arrangement of the layers prevents the board from warping or twisting during the high temperature lamination and soldering processes. A poor stackup design can lead to manufacturing defects such as delamination or registration errors between the layers. Fabricators review the proposed layer order to ensure that it is compatible with their pressing equipment and chemical processes.
Final approval of the design is granted after verifying that the mechanical and electrical goals are met without compromising the manufacturability.
