Minimum electrical clearance between conductors for a given voltage, from IPC-2221 Table 6-1. Shows the selected case and all categories at once: internal layers, external layers with and without coating, above 3050 m, and component leads.
Source. The values are the minimum conductor spacings of IPC-2221C (2023) Table 6-1 for DC or AC peak voltages in nine bands up to 500 V. Above 500 V the table gives a spacing per volt that is added to the 500 V value: for example B1 at 600 V is 0.25 mm + 100 V × 0.0025 mm/V = 0.50 mm.
Categories. B1 internal conductors; B2 external uncoated up to 3050 m; B3 external uncoated above 3050 m; B4 external with permanent polymer coating; B5 external with conformal coating; A6 component lead with conformal coating; A7 and A8 component lead uncoated, below and above 3050 m.
Scope. IPC-2221 gives functional spacings. Products that must meet safety standards (IEC 62368-1, IEC 61010-1, IEC 60664-1) need creepage and clearance distances from those standards, which depend on pollution degree, material group, overvoltage category and insulation type, and are often much larger.
Not for safety. Mains-connected products must meet the creepage and clearance distances of the applicable safety standard, which are usually larger than IPC-2221 values.
The peak voltage, including any transients you expect in normal operation.
Minimum pad for a plated hole per IPC-2221, and a worst-case annular ring check for an existing pad.
Width a trace needs for a current, or the current a trace can carry, with IPC-2152 and IPC-2221.
Impedance of an outer-layer trace over a plane, with solder mask or embedded, and width for a target impedance.
Impedance of an inner-layer trace between two planes, symmetric or offset, and width for a target.
Differential, odd, even and common-mode impedance of edge-coupled microstrip and stripline pairs.
Impedance of a coplanar waveguide, with or without a ground plane underneath (grounded CPW).