Stacked microvias align successive interlayer connections vertically. Staggered microvias offset successive connections and join them with copper on the intermediate layer. The choice affects routing area, layer access and the physical interconnect structure. It should be explicit in the fabrication drawing.
Compare the actual route
Stacking can conserve lateral area where a dense package leaves few alternatives. Staggering requires room for the offset and connecting copper. That extra area can interact with neighboring signals or planes, so “use staggered vias” is not a complete design instruction without an achievable layout.
Neither arrangement should be assigned a universal reliability rating independently of the material, geometry and process. Compare evidence for the proposed construction and intended exposure. A qualified example with a different stack height or material may not represent the board being purchased.
Decision table
| Consideration | Stacked arrangement | Staggered arrangement |
|---|---|---|
| Lateral space | Concentrates the path in a smaller area | Requires an offset and connecting copper |
| Interfaces | Successive connections align through the structure | The route shifts across an intermediate layer |
| Routing review | Check access and surrounding clearances | Check that the offset does not block adjacent routes |
| Acceptance planning | Represent the demanding stacked structure | Represent the actual offset construction and process |
Ask for construction-specific evidence
IPC has warned that weak microvia interfaces can escape traditional inspection and appear after further thermal exposure. Use that concern to frame a suitable acceptance discussion; do not turn it into a claim that every stacked connection fails or that a staggered connection needs no validation.
An illustrative review can compare two fanout sketches under the same device: one aligned path and one offset path. Include pad sizes, clearance envelopes and reference copper. Ask the supplier to review both and explain which construction is supported by its current process evidence.
Control changes after approval
State whether alternative arrangements are permitted. A CAM change that moves a via or changes an aligned path to an offset one can affect more than manufacturability. It may change routing, electrical behavior or the structure represented in qualification evidence.
Keep the approved arrangement in the stackup and via schedule. If the product's assembly sequence or material system changes, review whether the prior evidence remains relevant. Use the reliability and microsection guides for the acceptance discussion and the stackup planner to communicate the architecture.
Continue the engineering review
- 2+N+2 HDI stackup design
- Microvia reliability and thermal exposure
- Microvia capture pads and registration
- HDI PCB engineering hub
Source checked October 2, 2026: IPC microvia reliability warning. Supplier literature is context, not a claim of this site’s equipment or capabilities.
Review your HDI requirements
Share the board revision, proposed stackup, quantity and open questions. Include the requirements discussed in this guide so the project review starts with the same assumptions.