DFM for HDI PCB: close the gaps before fabrication

A drill file without unambiguous layer spans can leave the process sequence unclear. For the proposed HDI PCB construction, match every via family to start and stop copper layers and identify laser, mechanical, filled and capped structures. Confirm that dielectric depths match the current stack-up revision.

Check whether the same nominal hole is used across different depths. A geometry rule that works for one transition may not apply to another. The microvia tool computes a ratio and nominal land only; it does not certify plating or registration capability.

Inspect BGA pad neckdowns, copper-to-copper clearances, capture lands and plane anti-pads. Where a hole enters a component pad, specify the via-in-pad filling and capping requirements alongside the escape geometry. Evaluate both the desired route and the manufacturing tolerances. A trace passing a center-to-center pitch check may still fail near the via land.

Separate electrical clearances from process clearances. If a supplier requests larger lands, check whether the escape remains routable and whether reference-plane continuity changes. Record which CAD rules were adjusted and why.

Compare artwork, drills, stack-up, fabrication notes and netlist for one revision. Identify conflicting finish, copper, thickness or impedance-control requirements before the quote becomes an order. Send the same revision package with the PCB manufacturing request so the quotation and DFM review refer to one build.

Use the checklist output as a discussion brief. The actual DFM response should identify the affected feature, proposed change and owner approval. A checked browser box is not a substitute for that documented engineering review.