Due to the increasing complexity of design structures blind vias and buried vias are increasingly used in high-density circuit boards (HDI-PCB).
A blind Via connects exactly one outer layer with one or more inner layers.
A buried via is a via between at least two inner layers, which is not visible from the outer layers. This technology allows more functionality in less board space (packing density).
For cost reasons, we recommend avoiding an overlap of blind and buried vias in the layer build-up! For example, avoid blind vias from L1 - L3 and simultaneously buried vias from L2 - L4.
Blind vias are used to connect one outer layer with at least one inner layer.
The holes for each connection level must be defined as a separate drill file.
The ratio of drill diameter to hole depth (aspect ratio) must be 1:1 or larger.
The smallest hole determines the depth and thus the max. distance between the
outer layer and the corresponding inner layers.
Your advantage: Whether laser or mechanically drilled, we always use the best / cheapest technology suitable for the job!
| Aspect Ratio | Ø min. | Ø max. | Via Pad | Annular ring min.* | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Blind Via (mechanical) | Aspect Ratio | 1:1 | Ø min. | 200µm | Ø max. | 300µm | Via Pad | 400µm | Annular ring min.* | 100µm | |
| ⇒ as Special production | Aspect Ratio | 1:1.2 | Ø min. | 150µm | Ø max. | 150µm | Via Pad | 350µm | Annular ring min.* | 100µm | |
| Blind Via (laser) | Aspect Ratio | 1:1 | Ø min. | 100µm | Ø max. | 100µm | Via Pad | 280µm | Annular ring min.* | 90µm |
* circular
Buried vias are used to create connections of the inner layers, which have no contact with the outer layers.
The holes for each connection level must be defined as a separate drill file.
The ratio of drill diameter to hole depth (aspect ratio) must be 1:12 or larger.
The smallest hole determines the depth and thus the max. distance between the respective inner layers.
Generally: The larger you choose the annular rings on the inner layers, the more stable the connection.
| Aspect Ratio | Ø min. | Ø max. | Via Pad | Annular ring min.* | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Buried Via | Aspect Ratio | 1:10 | Ø min. | 200µm | Ø max. | 0.4mm | Via Pad | 400µm | Annular ring min.* | 100µm | |
| ⇒ as Special production | Aspect Ratio | 1:12 | Ø min. | 150µm | Ø max. | 0.4mm | Via Pad | 330µm | Annular ring min.* | 90µm |
* circular
Buried vias with a min. Ø of 150µm (0.150mm) can be filled galvanically.
