Blind Vias
Vias are barrel shaped vertical conductive holes that make connections between multiple layers of a PCB. IPC defines eight different types of vias, but the two most common are blind and buried. A blind via connects outer layers to inner layers and doesn’t go through the whole board, while a buried via is hidden beneath the surface of the layers and frees up space for routing without impacting traces and components on top and bottom layers. Both types work well for high-speed digital circuits.
To manufacture a PCB that has both blind and buried vias, the PCB maker needs to know how to handle them properly. Unlike through hole vias, which require whole-board electroplating and pattern plating for each layer, these types of vias are plated just once after the entire board has been laminated. Because of this, they’re usually more expensive than through-hole vias. But their benefits often outweigh the cost in demanding applications.
When drilling a blind via, it’s important to keep the drill depth at an appropriate level. If the hole is too deep, it could affect signal integrity and cause degradation or distortion. If it’s too shallow, it would result in an improper connection. The ideal depth is between 1.5 and 2. The PCB fabricator also needs to be careful when creating a blind via, as it’s possible for the copper connecting pad on the top side to overlap with the copper of the adjacent layer. In this case, the fabrication process needs to be adjusted so that the overlapping area is small.
Blind Vias – Can Blind Vias Be Drilled From One Side of the PCB Only?
The PCB manufacturer should also ensure that the height of the hole and the diameter of the hole are evenly matched, so that the via doesn’t percolate all the way through the PCB. The aspect ratio of the hole is also a consideration, and it’s best to use a value of less than one, as bigger diameters might not be compatible with some manufacturing processes.
In addition, the manufacturer should carefully place the vias. They can’t be placed near the edge of the board, as this could lead to cracks and shorts. They should also be careful when placing them in a high-speed environment, as they can cause signal interference.
Another issue when creating a PCB with buried and blind vias is the presence of bubbles during soldering. To reduce the likelihood of this, the manufacturer should use a smaller drill bit and make sure that it’s drilling through the pads instead of the board substrate. It’s also recommended that the manufacturer use a laser drill to minimize tool wear.
If you’re designing a PCB that requires blind and buried vias, it’s crucial to choose the right electronic contract manufacturer. The right partner will be able to provide excellent manufacturing, reliable products, and superior customer service. Click the button below to enter your custom PCB spec and get an instant quote. You can also call us if you have any questions. We’re always happy to help!
