A stackup lists every layer of a board from top to bottom: copper layers with their function and weight, and the cores and prepregs between them with glass style, thickness and dielectric constant. It sets finished thickness, the impedance of every routed layer, crosstalk, plane capacitance and how symmetric the board is, since an unbalanced stackup warps. Designers propose one, and the fabricator confirms or adjusts it to the materials it actually stocks.
Send the stackup to the fab before routing starts, I don't want to redo every impedance after they swap the prepreg.
Keep the stackup mirrored about the center, copper weights and dielectrics alike, or the board bows coming out of the press.
Also heard as
- layer stack
- stack-up
- build-up
- lay-up
Related terms
Core
Fully cured laminate with copper on both sides, etched into inner layers and bonded with prepreg into a multilayer.
Prepreg
Glass cloth soaked in partly cured resin, used as the bonding layer that glues cores together in a multilayer board.
Impedance control
Designing and building traces to a target impedance, such as 50 or 100 ohms, within a set tolerance.
Dk
Dielectric constant: how much a board material slows signals and sets trace impedance, relative to vacuum.