When is HDI justified?
HDI can be useful when package pitch, routing congestion or mechanical volume prevents a simpler construction from meeting the design requirements. Demonstrate the need with an escape study and preliminary placement. Compare alternate packages, orientations or connectors before assuming that every congestion problem needs another buildup level.
If a conventional board already meets the size and electrical requirements, assess the practical benefit of changing. The decision should consider assembly and verification effort as well as bare board area and layer count.
Does HDI always reduce layers or cost?
It may reduce routing detours or enable a smaller outline, but neither total layer count nor cost is guaranteed to fall. Additional construction steps, special materials and evidence requirements can change the economics. Ask for comparable quotations using explicit alternative constructions.
State which constraint has the most value to the product: enclosure size, signal performance, available battery volume or assembly simplification. A board that costs more can still be the appropriate system choice, but the reason should be visible rather than assumed.
What should a supplier review before routing finishes?
Share package escape requirements, a preliminary stackup, proposed via spans and the critical mechanical envelope. Ask which features are established for the proposed process and which need adjustment. Resolve these questions before a dense layout depends on unsupported assumptions.
- Identify the specific constraint that motivates HDI.
- Compare a simpler construction with the proposed structure.
- Agree on material, via and impedance assumptions early.
- List the evidence required for the first manufactured build.
What makes a release package complete?
Ucamco's fabrication data guide emphasizes consistent, clearly interpretable design data. For an HDI release, use one controlled archive with the agreed copper, drilling, profile, drawing and construction information. Check that all files describe the same revision and coordinate system.
Complete means sufficient for the agreed job, not the largest possible collection of exports. Include clear acceptance and reporting requirements, identify open questions and define who approves changes. Remove obsolete alternatives from the active package while retaining them in internal history.
Adjacent-layer access, one connection at a time
Dielectric · geometry + material
Core or build-up dielectric
Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.
Common questions
Does a microvia reliability report guarantee the finished product?
No. It supplies evidence for a defined structure and test. Review its relevance to the board and assembly conditions, then complete the product's required verification.
What should I do if a supplier proposes changing the stackup?
Request a specific revised construction, compare affected design assumptions and approve it through change control. Update the drawing and source design where needed before manufacture.
References & further reading
Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.