Meaning
Printed circuit board design constraints define the vertical arrangement and electrical properties of conductive layers and dielectric cores. Altium stack-up rules automate the verification of these physical structures against manufacturing capability limits and signal integrity requirements during the layout phase. These parameters dictate the specific copper thickness, dielectric constant, and relative spacing allowed for multi-layer board fabrication.
Fabrication Compliance
Board houses maintain specific tolerance ranges for the etching of copper and the pressing of prepreg materials. Designers program these tolerances into the software to flag instances where a proposed trace width or clearance falls outside the acceptable processing capability of the manufacturer. Automated checks prevent the export of board files that would require rework or suffer yield loss during the etching process.
Impedance Control
High speed signals rely on controlled transmission line dimensions to prevent reflections and maintain data integrity. These settings calculate the required trace geometry for single ended and differential pairs based on the distance to the reference plane. Consistent adherence to these values allows the software to generate output files that match the electromagnetic performance targets of the final hardware assembly.
Material Interaction
Dielectric materials exhibit temperature sensitive characteristics that affect the propagation delay of signals traveling through inner layers. Changes to the thickness of these substrates necessitate recalculations of all associated geometric constraints to ensure the board maintains its intended operating frequency and thermal performance. Proper configuration of these variables prevents signal degradation caused by impedance mismatches.
