Comparing PCB fabrication parameters: hole diameters, copper weights, and structural combinations

PCB fabrication parameters constrain one another. Minimum holes, heaviest copper, and most layers may come from different materials/processes; their extremes cannot be combined into one board automatically. Submit complete stackups, hole groups, traces, and inspections for manufacturing review of the actual combination.

First clarify which object the parameter measurement targets

“Hole diameter 0.30 mm” may mean drill diameter or plated finished diameter. “Copper thickness 35 µm” may mean base or finished copper. “Board thickness 1.6 mm” also needs included layers and tolerances. With different definitions, identical quotation numbers may describe different deliverables. Align nominal values, finished targets, and tolerances first.

PCBWay's public capability page provides a third-party example of parameter categories. Its values/conditions describe only that supplier's public capabilities, not other companies' commitments. This page uses categories for RFQs and design review.

Calculate hole aspect ratio based on actual hole groups

Hole aspect ratio generally divides depth by drill diameter, but manufacturers may use different diameter definitions; confirm first. An engineering example uses 1.6 mm depth and 0.30 mm drill diameter, giving 1.6÷0.30≈5.33. At the same drill diameter through a 3.2 mm board, the ratio is about 10.67. The change affects drilling/metallization review, not independently proving feasibility or infeasibility.

Buried-via, blind-via, and laser-microvia depths follow corresponding substructures or interlayer distances, not full board thickness. Plating reduces hole diameter, but plated diameters cannot be compared directly with published ratios defined by drill diameter. List original inputs and formulas in RFQs for manufacturer review.

Why thick copper and fine lines must be evaluated together

Heavier copper demands greater attention to etching geometry, undercut, and pattern uniformity. Large inner-layer copper-height differences affect PP filling and post-lamination dielectric thickness. Applying thin-copper minimum spacing to heavy layers may cause local bridges, width deviations, or inadequate resin fill. Outer plating changes both surface copper and hole deposits and belongs in the same process review.

Engineering example: with a pad diameter of 0.60 mm and hole diameter of 0.30 mm, nominal geometric ring width is (0.60－0.30)÷2＝0.15 mm. This excludes hole-position, artwork-registration, and dimensional deviations and is not minimum remaining annular ring. Further pad reduction for escape space requires renewed finished-connection and acceptance review, not merely nonoverlap in CAD.

What should a combined specification table include

Identify unresolved critical items explicitly rather than letting manufacturers choose defaults. Submit design targets and adjustable ranges first, such as permitted dielectric or width adjustments, with designers approving final solutions. Capability confirmation should reference the combined-specification table revision.

Compare manufacturing routes first when comparing quotes

Identical layer counts do not imply identical processes. Sequential lamination, resin-filled/copper-capped vias, hybrid materials, backdrilling, special tolerances, and verification may change routes. Put inclusions, exclusions, and items requiring rereview in one table before comparing prices and lead times. Bare-board-only quotations cannot be ranked directly against those including coupons and special reports.

1. Send candidate manufacturers identical controlled packages, specification revisions, and quantity definitions.
2. Collect explicit confirmation of hole-group, material, and trace combinations; check for default substitutions.
3. Return engineering adjustments for design review; independently modified versions cannot still be called identical specifications.
4. Freeze final stackups and inspection scope before confirming production revisions and quotation applicability.

A screenshot of individual capabilities identifies only a candidate manufacturer. Confirm combinations before ordering to avoid discovering midway through prototyping that layers, holes, or pads must change.

How to handle combination review rejection

Break “cannot manufacture” into specific constraints: incompatible depth/diameter, heavy-copper/spacing conflicts, insufficient resin, difficult local tolerances, or inadequate inspection coverage. Map each constraint to an adjustable variable and effect. Design can compare larger holes, different via-layer pairs, local copper changes, more layers, or layout changes rather than demanding manufacture at independent limits.

Create an “original requirement—constraint reason—candidate change—electrical effect—approver” table, with before/after nets and layer sequences. First-article acceptance should inspect the same sensitive locations to confirm implementation. Passing tests covers only the verified combination; assess later thickness, material, or lamination changes anew.

Engineering confirmation should explain production-panel versus delivered-board relationships. Panel borders, tooling holes, coupons, and separation tabs occupy manufacturing space but may fall outside delivered outlines. Different panel utilization assumptions change unit pricing. Reconcile outlines, panel drawings, and delivery quantities; “per panel” and “per board” are not identical units.

For staged prototypes, record confirmed structures versus preliminary assessments. Before production, recheck material availability, methods, and repeatability without formally reopening every unchanged parameter. Effective combination reviews reduce guesswork and consolidate engineering adjustments in one controlled file set.

How should acceptance class and inspection scope enter comparisons?

Identical geometry under different acceptance requirements may need different manufacturing review and inspection. Specify standards/revisions, product classes, or customer supplements, plus actual inspection objects. “High reliability” cannot define hole, visual, impedance, or environmental requirements or establish quotation equivalence.

Determine representative hole groups/locations for cross-sections, electrical-test revisions, and whether coupons share delivery-board batches during review. Unspecified items may remain pending, but cannot automatically become the loosest or strictest interpretation after quotation. Actual tasks define inspection quantities and criteria.

Check received samples against approved combinations and inspection plans. If manufacturing recommendations changed holes or materials, confirm synchronized documentation before interpreting results. One compliant dimension does not verify every item; passing reports must trace to current board IDs and process revisions.

Frequently Asked Questions

Does passing DRC establish manufacturing approval?

It only establishes compliance with current design rules; their match to actual processes still needs confirmation. See Basic Design Rules.

What are capability-table extremes useful for?

for initial screening and review priorities, not complete order specifications. Ultimately return to Manufacturing Combination and Data Delivery Checklist.