stackup

Stackup is a term used in engineering and manufacturing to describe the arrangement and cumulative properties of layered structures. In electronics, a PCB stackup refers to the order, thickness, and material properties of the board's layers: copper foils, dielectric laminates, prepregs, and coverlays. The stackup determines controlled impedance, signal integrity, thermal performance, and mechanical strength. Common parameters include copper weight (for example 1 oz or 35 µm), dielectric constant, and overall board thickness. Designers select materials and layer counts to meet impedance targets (such as 50 ohms) and to fit routing needs. Multilayer boards may include core and prepreg layers, blind or buried vias, and different copper thicknesses in different regions. Fabrication notes specify the precise stackup to ensure consistent impedance and manufacturability; manufacturing tolerances for each layer thickness and flatness influence the final electrical performance.

In tolerancing, the term stack-up refers to the cumulative variation of dimensions across an assembly. Worst-case stack-up analyzes the maximum possible deviation by summing prescribed tolerances; statistical approaches, such as root-sum-square methods, estimate the probability distribution of the total variation. Tolerance stack-up analysis is used in mechanical design and is guided by standards such as ASME Y14.5 for geometric dimensioning and tolerancing.

Other uses: the term is sometimes used more broadly to describe a technology stack in software, or as a brand name in certain contexts, but the engineering sense described above is the primary meaning.