The media thickness of HDI PCB is less than 50um mainly because its media thickness will affect the signal quality and performance of the circuit board.
In high-speed circuits, the characteristic impedance of signal transmission changes with the dielectric thickness of the transmission line. If the medium thickness is too large, it will lead to unstable signal transmission and increased signal loss. Therefore, in order to ensure the stability and integrity of signal transmission, the media thickness needs to be controlled at a low level.
In addition, micropore technology is required in the production process of HDI PCB, and the diameter and depth of micropores are limited by the thickness of the medium. If the thickness of the medium is too large, the processing difficulty of micropores will increase, and it will also affect the mechanical properties and reliability of the circuit board.
Therefore, reducing the thickness of the medium to less than 50um can make HDI PCB have higher performance and reliability, while also helping to improve the manufacturing yield of the circuit board and reduce costs.