Differential Phase Skew Control through Glass Cloth Weave Flattening and Alignment
Differential phase skew control requires spread-glass fabrics or off-axis routing to eliminate local micro-scale dielectric variations across high-speed traces.
Stackup Drawing Notes
Engineering Specification
Written instructions on a fabrication print define the materials, tolerances, layer order and construction methods required to build a multilayer printed circuit board. Stackup drawing notes provide the essential details that are not captured by the electronic data files alone. These comments are legally binding parts of the contract between the designer and the fabricator.
Detailed Requirement
Detailed stackup drawing notes specify the exact dielectric thickness, copper weights, copper types and resin types for every layer of the board. They define the controlled impedance requirements including the target values and the permitted tolerance of ten percent or less. The notes also call out the required surface finish such as ENIG or OSP and the type of solder mask to be applied.
Any requirements for backdrilling, via filling or edge plating must be clearly stated to avoid manufacturing delays. If there is a conflict between the digital layout and the written notes, the notes usually take precedence. Clear communication in this section prevents costly scrap and ensures the finished board meets the electrical performance goals.
Reviewing Compliance
Reviewing the stackup drawing notes is the first step for a quality engineer during the incoming inspection process. Each board is measured against these specifications to verify that the physical construction matches the design intent.