https://protoexpress.wistia.com/medias/x5vo5u1tfc
This part of our webinar on via design and manufacturing highlighted important considerations when choosing between stacked and staggered vias for high-density interconnect designs.
Key points:
-
Stacked vias:
- Frequently used in HDI builds, especially with center cores.
- Typically involve a through-hole via that is conductively filled and capped, followed by stacked microvias.
- Enable greater space efficiency but are more complex to manufacture and require precise registration.
- Suitable materials are critical—flat glass or spread glass prepregs are recommended to ensure material consistency during laser drilling.
- Laser drilling consistency depends on uniform material properties, as the energy removes a fixed volume of material.
-
Staggered vias:
- Easier to manufacture since they don’t require filling.
- May be a better choice when cost or process simplicity is a higher priority than routing density.
Example shared:
- An 8-layer board with:
- Vias from layer 1 to 3, 1 to 4, and 5 to 8.
- Emphasis on maintaining an aspect ratio of 0.75, such as using a 6 mil drill for 5 mil dielectric layers.
- Design must balance:
- Drill size constraints
- Material stack-up and press-out thickness
- Controlled impedance requirements
- Available space
Clear communication with the fabricator is essential to ensure materials, stack-up, and via structures meet all performance and manufacturability targets. The interplay between these factors is critical in tight, high-performance layouts.
Watch the full webinar here.