Checking Routed PCB Edge Perpendicularity Through the Board Thickness

A routed board can meet its top-view outline dimensions while binding in a close-fitting housing. The edge may lean, taper or vary through the thickness. An inspection that checks only the upper copper surface cannot fully describe a mechanical interface that contacts the entire board edge.

Identify the contact surface in the enclosure

Determine whether the housing locates against the top edge, bottom edge or a broad vertical face. Define the relevant width at those heights and specify perpendicularity only where the function requires it. Applying a tight edge-angle requirement to an entire board can add inspection cost without improving fit.

Eurocircuits explains how routed outlines are formed by the tool path. A two-dimensional path controls the planned contour, while the actual three-dimensional edge also depends on cutting and support conditions.

Investigate stack position and tool behavior

Where boards are routed in stacks, retain each sample’s stack position. Tool deflection, support and chip removal can produce different edge results at the top and bottom of the stack. Measuring only one convenient board can hide that pattern. Inspect external edges and internal cutouts separately when cutting direction or engagement differs. Identify the start and end of each routed segment so a short entry defect is not confused with taper along the entire edge.

• Measure edge position near both faces using an appropriate method.
• Record board orientation and stack position.
• Separate edge lean from loose fibers or burrs.
• Compare new and used tools before changing nominal dimensions.

Verify the fit without masking the cause

For example, widening a chassis slot may make a tapered board fit but leave an uncontrolled edge that still conflicts with a connector bracket. Compare the measured edge profile with the complete mating assembly. If the issue is tool deflection, correcting the machining process may preserve the intended mechanical dimensions.

Use the edge-burr inspection to distinguish removable projections from the underlying surface. Coordinate critical cutout geometry with corner-fit review. Acceptance should state which surfaces establish the board’s fit and how they are measured. A passing silhouette confirms the outline in one projection; it does not prove that every cross-section through the thickness occupies that same boundary.