With the development of miniaturization and high integration of VLSI and electronic components, multi-layer boards are often moving towards the direction of combining with high-performance circuits. Therefore, there is an increasing demand for high-density circuits and high line capacity, and also a stricter demand for electrical characteristics (such as the integration of Crosstalk and impedance characteristics). The prevalence of multi pin components and surface mount devices (SMD) has led to more complex shapes of circuit board patterns, smaller conductor lines and apertures, and the development of higher multilayer boards (10-15 layers) has become a trend. In the latter half of the 1980s, in order to meet the needs of small and lightweight high-density wiring and small hole trends, thin multilayer boards with a thickness of 0.4~0.6 mm gradually became popular. Complete the guide hole and shape of the part through punching processing. In addition, some products produced in small quantities and in various forms are photographed using photosensitive agents to form patterns.