Blind holes and Buried holes in PCB manufacturing process

Holes, often called via holes or vias are needed within a PCB to connect the different layers together at different points. Holes may also be needed to enable leaded components to be mounted on the PCB. Additionally some fixing holes may be needed. There are a lot of people who are new hand in PCB industry can't tell the difference between blind via and buried via, china pcb manufacturer teach you how to distinguish the difference between them.

For blind via, these vias is finally plated over with copper. Via in Pad can save pcb spacing and also provides a direct conduit for heat transfer, you can put the PCB board against a source of light and see whether you can see the light coming from the source through the via or not. If you can see the light, then the via is thru-hole, otherwise the via is blind.

These kinds of vias in printed circuit board design is very useful, for example, if you don't have too much space for placing components and routing, blind via can help you a lot. You can put components on both sides and maximize the space. If the vias were thru-hole instead of blind, there would be some extra space used by the vias on both sides.

Now let us see the picture from left to right, the first via that we will see is thru-hole via or fullstack via, the second via begins on the top layer and ends on the second layer ( inner ), so we say that this is a one-two blind via, at last, the third via begins on the bottom layer and ends on the third layer, so we say that this is a three-four blind via. It is important to keep that in mind that this kind of vias are often manufactured in consecutive (L1 L2, L3 L4, Ln-1 Ln) layers. When compared to the thru-hole alternative, the price for blind via is high, this is its main disadvantage.

Buried vias are similar to the blind ones, but they begin and end at an inner layer different from blind vias. We can have a look at the below picture, the first one is full stack or a thru-hole, the second one is a one-two blind via, and the last one is a two-three buried via that begins at the second layer and ends at the third layer. Blind vias are often manufactured in consecutive(L1 L2) layers.

Blind and buried holes in PCB

Because of the difficult and technological process added by blind and buried vias, it is recommended that the PCB layouter try to avoid use them as less as possible, if it is in-evitable, then be prepared to pay much more money to your PCB supplier. China is now the world’s biggest PCB manufacturing base, Shenzhen as the biggest PCB city, you can always find reasonable PCB price there.