High Density Interconnect Materials

High density interconnect, or HDI, circuit boards have a much higher wiring density than traditional printed circuit board technology. This is achieved by using smaller vias, spaces, copper traces and pads. The result is a more compact product with improved functioning and signal transmission.

There are several considerations when designing and manufacturing an HDI PCB. The most important one is the core material, which can be FR4, metal or fiberglass. Surface finishes are also a key factor, with options including ENIG, HASL, immersion tin and gold. It is also important to consider the number of sequential laminations required, as this can have a significant impact on fabrication costs.

The most common type of high density interconnect uses a single layer of high-density interconnect, which can be referred to as 1+N+1. This structure has a single signal routing layer on the top and bottom, with N number of sequentially laminated buildup layers comprised of alternating dielectric and copper layers in between. These layers are drilled with a laser, then filled with a conductive material such as copper.

Types of High Density Interconnect Materials

Another option is 2+N+2 HDI, which utilizes two signal layers on the outer surfaces of the board, with N number of sequentially laminated builds in between. This structure allows for routing on four outer layers of the circuit board, and it is ideal for use with complex designs that require more than three signals.

There is a third option, 3+N+3 HDI, which has three signal layers on the outermost surfaces of the circuit board and N number of sequentially laminated builds in the middle. This configuration allows for routing on six outer layers of the circuit board. This is the most advanced form of HDI circuit board and is suitable for use in the most demanding applications.

When designing a high-density interconnect printed circuit board, it is critical to use the right materials for the job at hand. The choice of material will affect everything from the circuit board’s strength and rigidity to its thermal reliability. It is important to select a material that can handle the current and voltage levels of the circuit board.

Moreover, the choice of material will also impact how easy it is to fabricate the circuit board. For example, some materials may be more suitable for use with certain laser drilling technologies or soldering techniques.

Finally, it is important to note that high-density interconnect printed circuit boards require special equipment for assembly. This is because the small microvias in HDI circuit boards must be drilled with a laser and then filled and capped before being used. The process is time-consuming and costly, but it is the only way to achieve a high-quality, reliable circuit board. However, this expense is offset by the benefits of the technology, such as improved component placement and better signal functionality. The use of HDI circuit boards is expected to continue to grow as the technology advances and manufacturers need to create smaller, more compact devices.