HDI PCB stackup is a type of printed circuit board design that allows for more components and connections to be packed into a smaller board area. This is achieved by using a combination of smaller vias, thinner traces, and multiple layers of circuitry.

There are several different types of HDI stackup configurations, including:

1.1+N+1: This stackup has one layer of high-density interconnects sandwiched between two outer layers of standard circuitry.

2.2+N+2: This configuration has two high-density interconnect layers between the outer layers of standard circuitry.

3.3+N+3: This stackup has three high-density interconnect layers sandwiched between the outer layers of standard circuitry.

4.Any layer HDI: In this configuration, high-density interconnects are present in every layer of the PCB, allowing for even higher component density.

Each type of HDI stackup has its own advantages and disadvantages, and the choice of stackup configuration depends on the specific requirements of the PCB design. For example, the 1+N+1 stackup is more cost-effective and easier to manufacture, while the any layer HDI stackup offers the highest density and signal integrity.

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