How HDI Board Design Handles Multi-Layer Configurations

HDI Board Design Handles Multi-Layer Configurations

With more powerful electronics and devices demanding greater functionality in smaller packages, PCB manufacturers have been forced to push the boundaries of what’s possible. One such innovation has been HDI, or high-density interconnect, which allows for more copper layers to be incorporated into a multilayer PCB while maintaining reliability and performance levels. However, this new level of connectivity means that designers need to think differently about how they layout components and route signals throughout the board. In this article, we’ll take a look at how HDI board design handles multi-layer configurations by using different techniques to increase signal routing density and reduce the number of vias required to connect them.

HDI boards are used in a wide variety of electronics, from IoT devices to industrial machinery. The technology is especially useful for avionics and military applications, where the reliability of electronic circuits is critical. The technology allows for more copper traces to be incorporated into the board, which translates into lower impedance and higher signal speed. It also enables engineers to use thinner multilayer boards than would otherwise be possible, which can save on space while still providing the necessary functionality.

The key challenge for hdi board is reducing the number of vias required to make the connections. This is made difficult by the fact that HDI circuit boards require smaller traces, which can result in more contact resistance and other issues unless carefully designed. To address these issues, manufacturers employ various techniques when producing HDI multilayer boards. These techniques include sequential lamination, blind vias, and buried vias.

How HDI Board Design Handles Multi-Layer Configurations

A key factor in HDI multilayer design is understanding the layer stack-up, or how the electrical & insulating layers are arranged and sequenced on the board. The different parts of the layer stack-up include prepregs, copper layers that conduct electricity, and vias that link the different layers together. Vias come in two types: through-hole and microvias. Through-hole vias predominate in regular HDI multilayer designs, while blind and buried vias are often employed in HDI designs that require more routing density.

Blind and buried vias are small, plated holes that run through internal layers but don’t pass through the outer layers of the PCB. They can be either stacked or staggered, and they can be filled with conductive copper or non-conductive dielectric paste. These vias are used to make contact with other layers without exposing them to the outside of the board, and they can impact signal performance based on their location and design.

As the design of HDI PCBs continues to evolve, new techniques are being developed to increase routing density and reduce the amount of copper needed for connection. For example, one popular method is called every-layer interconnect (ELIC). This routing style uses a technique known as extending microvias across the entire stackup to allow signals to route between any set of layers. This increases routing density and eliminates the need for stubs, but it does have some limitations that are important to keep in mind when designing an HDI PCB.