netclass-via-drill

Remedy ¶

Enlarge the via drill to the size its class declares, or amend the class if the smaller drill is intended. The class carries an assumption about current capacity or plating, and one of the two has moved.

A net’s via is drilled smaller than the drill its own net class declares.

What this checks ¶

For each net class, the project’s net_settings states the via drill that class’s nets should use. This compares each net’s smallest routed via drill against that declared drill and reports the nets that fall short.

There is no number in this rule. The limit comes entirely from the design.

How it differs from hole-size ¶

hole-size asks can this be drilled, comparing via drills against a universal mechanical-drill floor (0.2mm). A finding there means the fab cannot make the hole, or will silently upsize it.

This rule asks is this what you asked for. A class’s declared drill is usually sized for the class’s current, or for the process quoted for the board. A via below it is often perfectly drillable, and still discards the reason the number was chosen.

Resolving the declared drill ¶

A net can belong to several classes at once, and a naive implementation goes wrong here.

KiCad does not pick one of a net’s classes and use it wholesale. It fills each constraint from the highest-priority class that states that constraint, and the Default class supplies whatever is left over. Default applies to every net, including nets in no class at all. Suppose a net’s high-priority class declares only a track width. The net still takes its via drill from the next class down, and a net in no class still has a drill to meet.

A rule could compare a net’s vias against every class the net belongs to. That would fail nets that correctly obey the winning class. This rule resolves the cascade first, then compares once, and the finding names the class that supplied the limit.

Sometimes none of a net’s classes, Default included, states a drill. That net has no limit to meet, and the rule reports that rather than a pass.

Hardware context (for software readers) ¶

• A via is a plated hole connecting copper on different layers. The drill is the hole diameter before plating.
• The declared drill matters because a bigger drill carries more current and plates more reliably. A class that declares one has usually been sized with both in mind.

Absence is not a pass ¶

The rule declares CapNetClassDefs. A design that declares no net-class definitions has no limit to compare against, so the rule reports not-applicable rather than running over zero comparisons and reading clean. Only a KiCad project read supplies definitions.

The rule reports a net with no vias as not-considered, since there is nothing to measure.