Skip to main content

Blind and Buried Vias

LEARN PCB
PCB Manufacturing
PCB Assembly
PCB Design and Layout
PCB Basics
Vias, Drilling & Throughplating
Mechanics
Surface
SMD
Quality
SPECIFICATIONS
PCB Fabrication
STANDARDS & POLICY
PCB Ordering
Policy

Different types of vias can be drilled on a PCB stack-up. A via is implemented in a circuit board for providing electrical interconnection between its layers. The components and traces conduct signals through these vias, and hence they form the conducting channels through board layers. Blind and buried vias increase the connectivity and at the same time occupy very little space.

What are blind and buried vias?

blind-and-buried-vias-on-pcb.jpg
Blind and buried vias

Blind and buried vias are controlled depth vias commonly used in HDI boards. Here interconnection is established without consuming more space on the PCB, thus making more room for the increased wiring density. Since through-holes consume more board real-estate, the space available for wiring is reduced. Hence, blind and buried are preferred.

Blind vias

Blind vias start from an outer layer and terminate at an inner layer. These vias do not go through the entire board stack-up. They connect at least one inner layer of the circuit board with the outer layer. Top and internal layer or bottom and inner layer.  Once these vias are laminated, the other end will not be visible, and that is why they are called blind vias.

Buried vias

Buried vias are also called hidden vias since they are not visible when observed from the external layers. These vias are meant for connecting the inner layers of the circuit board. Therefore, space will be available on other layers for wiring.

The IPC standards suggest that the diameter of the blind and buried vias should be 6 mils (150μm) or less.

How are blind and buried vias created?

For drilling blind and buried vias, controlled-depth drilling methods are chosen.

The drilling process of controlled depth blind vias is quite similar to that of the through-holes. The only difference is that the drilling source is programmed to stop after one or two layers. Care should be taken to ensure that the drilled hole does not have any connection with the layers underneath it. Then the hole is copper plated and made conductive.

Before drilling buried vias, the inner layers are drilled first. Next, the other layers are pressed to complete the stack-up.

Important guidelines when designing a blind/buried vias

While placing vias in your PCB design, follow these guidelines:

  • These vias should always span an even number of copper layers.
  • Blind vias should always begin at the top/bottom layer of the stack-up

These vias when compared to conventional through-holes are very effective in increasing the space available on a board for component placement.

Sierra Circuits is
headquartered in Silicon Valley.
We welcome visitors at
our 70,000 sqft facility,
located at 1108 West Evelyn Avenue
in Sunnyvale, California.
Book a tour with an account manager today!
Let us introduce you to one of the most innovative communities of engineers and designers in the world.
We can help you plan your project from design to assembled board.

Manufacturing Equipment at Sierra Circuits

Our 70,000 sqft state-of-the-art campus in the heart of Silicon Valley contains the most advanced equipment required for the manufacture and assembly of your PCBs. Whether you’re looking for standard quick turn PCBs or boards with the tightest tolerances, made from exotic metals, there’s a reason Sierra Circuits leads the industry in quality and performance.

PCBs manufactured and assembled in the United States

Turn-times as fast as 1 day.

Sierra Circuits can manufacture your PCB and have it expedited to you within 24 hours.

Full turnkey boards, with assembly and components in as fast as 5 days.


Get an Instant, Itemized Quote

Talk to a Sierra Circuits PCB Expert today

24 hours a day, 7 days a week.

Call us: +1 (800) 763-7503
Email us: through our Customer Care form