What DRC checks
A CAD design-rule check compares the design with configured rules such as clearance, width, connectivity or component constraints. Its usefulness depends on whether the rules match the product and intended manufacturing process.
What DFM adds
Design-for-manufacturing review considers how the supplied data will be fabricated, assembled, inspected and handled. It can identify process-specific problems, ambiguous documentation and production constraints that were not represented in the CAD rule set.
Why passing one does not replace the other
A board can pass its CAD checks while using an unavailable material, an unsuitable via structure or an incomplete fabrication drawing. Conversely, manufacturing approval does not establish that the electrical circuit meets the product requirements.
Close findings through change control
Record each issue, the proposed resolution and who approves it. If geometry or stack-up changes, check the electrical and mechanical effects before releasing the revised output package. Do not leave the CAD source and manufacturing data at different revisions.