An 8 layer immersion gold impedance HDI (High Density Interconnect) board is a highly advanced printed circuit board. It consists of eight layers of conductive materials and insulating substrates laminated together. The two-step structure provides increased routing density and allows for more complex circuit designs. The immersion gold finish offers excellent electrical conductivity and solderability, while also providing protection against corrosion. The impedance control feature is crucial for ensuring proper signal transmission and minimizing signal distortion in high-frequency and high-speed applications. This type of board is commonly used in advanced electronics such as high-performance computing, telecommunications, and medical devices where reliability and performance are of utmost importance.