types of vias in an HDI printed circuit board
The choice of via size, type, and location impacts the PCB’s manufacturing costs. Using smaller via holes, such as microvias, reduces the number of layers and materials used while providing better signal integrity. Via-in-pad, blind, and buried vias further enhance signal quality and increase the reliability of your circuit board. These features are all used in High Density Interconnect (HDI) printed circuit boards.
The smallest and most space efficient via hole is a microvia, which has a diameter of less than 150 microns. It is the most common via type in hdi printed circuit board. Microvias connect multiple layers of the PCB by copper plating. They are generally drilled in the shape of cones so that the sides can be easily copper plated. Unlike thru-hole vias, microvias cannot pass through more than two adjacent layers.
There are also buried and blind vias, which are mechanically drilled but do not appear on the surface of the circuit board. A buried via has a hole that goes through one or more internal layers of the PCB, and it requires additional fabrication steps to drill and plate it on these internal layers.
What are the types of vias in an HDI printed circuit board?
These types of vias are important for the assembly and performance of the circuit board. The shorter distance for signals to travel decreases internal noise, improving signal strength and clarity. Additionally, by eliminating stubs and reducing signal reflection, these vias reduce parasitic loads.
When using microvias in a complex design structure, the placement of these vias is critical. To prevent crosstalk, the PCB designer should use staggered or stacked structures instead of overlapping vias to increase reliability.
Staggered design structures are created by placing the vias with small offsets between layers, while stacked structures place them directly adjacent to each other. These types of layouts minimize crosstalk and improve signal stability while still allowing the circuit to operate at high speeds.
The type of stack-up you choose will also affect the production process and costs. For example, a 2+N+2 stack-up has two sequential build-up layers on each side of the core layer and adds four copper layers, making it N+4 layers. Alternatively, a 2-N+2 stack-up has two sequential builds and adds four copper layers, but it does not have stacked vias.
When it comes to choosing an HDI stack-up, it is important to choose the one that meets your circuit’s specific requirements. Sierra Circuits’ team of skilled engineers can help you select the best design for your next project. Contact us today to learn more about our high-speed PCB design and fabrication services. We’ll be happy to answer any questions you may have. Then, you can be confident that your product will perform as expected and provide the functionality you need. We’ll get your project on the road to success quickly and efficiently. With our fast turnaround and excellent customer service, you’ll have your finished product in your hands sooner than you might think! Then, you can rest assured your customers will be happy with the quality and performance of your circuit board.
