The capability extract shows in thirty seconds what runs as standard and what carries a surcharge.
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To the data check →A through-hole blocks every layer it passes. A blind or buried via blocks only the ones it joins, which is how a dense multilayer finds routing space. The catch is that each of them needs its own drill and press sequence, and that is where the lead time goes.
A blind via starts on an outer layer and stops at an inner one. A buried via lives entirely inside the stack and is invisible from either surface. Both are drilled mechanically — unlike microvias — which puts a floor on their diameter but lets them span several layers at once.
The manufacturing reality is sequential lamination. Buried vias are drilled and plated in a sub-assembly, which is then pressed together with the rest of the stack, and any blind vias are drilled afterwards. Each sequence is a full drill, plate, press and inspect cycle. One extra sequence is a few days; three is a different product with a different price.
A buried via between layers 3 and 4 leaves layers 1, 2, 5 and 6 completely clear. In a dense design that is often what makes the routing close.
No laser, no dielectric depth limit — a buried via can span several layers in one hole, which a microvia cannot.
Removing the unused length of a through-hole removes its stub. Above a few GHz that stub is a real reflection, and backdrilling is the alternative.
| Parameter | Standard | Advanced | Note |
|---|---|---|---|
| Min. Ø, blind | 0.25 mm | 0.20 mm | Mechanically drilled to a stop layer |
| Min. Ø, buried | 0.25 mm | 0.20 mm | Drilled in the sub-assembly |
| Aspect ratio, blind | 0.8 : 1 | 1 : 1 | Depth to diameter — tighter than a through-hole |
| Layers spanned | 2 – 4 | 2 – 8 | Buried vias can cross several layers |
| Lamination sequences | 1 – 2 | 3 | Each adds days of lead time and a price step |
| Annular ring | ≥ 150 µm | ≥ 125 µm | Same standard as a through-hole |
| Registration | ± 100 µm | ± 75 µm | Sub-assembly to outer layers |
| Fill requirement | optional | required under blind | Buried vias under a blind via must be filled |
Guide values for pre-selection. Binding values are confirmed per project against your data.
The points below are what most often comes back as a query after data review. Settling them before layout freeze saves a loop.
The number of lamination sequences is a commercial decision made before routing. Discovering three sequences worth of buried vias after layout means either re-routing or a price the project did not budget for.
Buried vias between layers 3–4 and 5–6 can often share a sequence if the stack allows. Vias scattered across arbitrary layer pairs cannot, and each pairing costs a cycle.
If a blind via lands above a buried one, the buried via has to be filled and planarised first — otherwise the press pushes resin into the open barrel.
If the reason for a blind via is stub removal rather than routing space, backdrilling a through-hole is usually far cheaper than a lamination sequence.
Microvias are smaller, cheaper per hole and limited to one dielectric layer. Blind and buried vias are mechanically drilled, span more layers and cost a lamination sequence. Dense fine-pitch work uses microvias; layer-hungry backplane work uses buried vias.
Typically 20 – 40 % on the board price and several days of lead time. The exact figure depends on layer count, but it is never a rounding error.
Yes, and it is common in symmetrical builds. It does not necessarily add a sequence if both are drilled at the same stage of the build.
Plating chemistry has to enter and exhaust through one opening instead of two. That halves the exchange and limits how deep the hole can be relative to its diameter.
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