Boundary Scan Coverage and the Faults It Never Reaches
Boundary scan isolates structural opens and shorts on compliant nets, requiring hybrid physical probe testing to catch unmapped passives and dynamic failures.
Non-Boundary Nets
Net Routing
Unrouted copper regions crossing multiple schematic sheets without an explicit board edge restriction are non-boundary nets that require careful clearance validation during printed circuit board layout. Automated design rule checks flag these floating traces when distance thresholds drop below manufacturer tolerances during inner layer routing. Fabrication shops evaluate copper pour margins against drill tolerances to prevent shorts caused by laminate shifting.
Subsequent electrical testing verifies continuity across distributed ground planes.
Routing Constraint
Minimum annular ring requirements govern trace spacing near mechanical fastener holes. Etching tolerances dictate how close signal paths approach routing margins before copper delamination occurs during thermal shock testing. Automated optical inspection systems capture dimensional drift along milling paths by comparing photoplotter data against etched boards.
Assembly Clearance
Stencil aperture design accounts for solder paste spreading near unrouted copper boundaries to prevent bridging defects during reflow soldering. Component placement machines halt operation when fiducial markers indicate board warping near unrouted edges. X-ray inspection confirms void percentages remain below acceptable thresholds beneath bottom terminated packages situated near board cutouts.
Thermal cycling exposes mechanical stress points along unrestricted copper traces.