We need to work with your preferred fabricator to create formal stackups.
Please provide a email contact for your preferred fabricator. We can work with your fabricator to design formal stackups and keep you in the loop (on the email threads).
The overall board thickness, choice of materials (glass and resin) and the material Dk (dielectric constant) will determine precise trace widths and spaces for controlled impedance.
The ideal material for high-speed designs will have low a Df (dissipation factor) to minimize signal attenuation. The length of the traces should be considered when selecting the materials. If traces are short and wide then Df will not be a significant factor. Low Df material is typically used on a high speed back planes and RF designs. Note low Df materials are more expensive.
To maintain manufacturable trace widths as layer count increases where overall board thickness is ~80 mils or less the Dk needs to be lower than what is typically found on popular FR4 materials like 370HR. FR408HR and GETEK are a popular choices for low Dk materials.
Fabricators prefer plated holes (vias) sized with 10:1 or less aspect ratio. Where the aspect ratio is the overall board thickness divided by the drill hole size.
Note drill/pad sizes 8/20mil (0.2/0.5mm) are needed to allow for routing diff pairs or two signal traces between the vias under 1mm pitch BGA and routing one trace between the vias 0.8mm pitch connectors.
That's it !
