Multilayer circuit boards generally refer to circuit boards with three or more layers, which require high quality and reliability. Mainly used in communication equipment, high-end servers, medical electronics, aviation, industrial control, military and other fields. In recent years, the market demand for multilayer circuit boards in applied communications, base stations, aviation, military and other fields is still strong. With the rapid development of my country's telecommunications equipment market, the market prospects for multilayer circuit boards are broad.

The average number of circuit boards has become an important technical indicator to measure the technical level and product structure of circuit board manufacturers. However, there are also many difficulties in the processing and production of multi-layer circuit boards. Compared with the characteristics of conventional circuit board products, multi-layer circuit boards have thickness, more layers, dense lines and vias, larger unit sizes, and thinner dielectric layers. Features. At the same time, the requirements for internal space, interlayer alignment, impedance control and reliability are more stringent.

Due to the large number of layers of multi-layer circuit boards, the alignment of layers at the customer's design side is becoming more and more strict. The alignment tolerance between layers is generally controlled at 75 microns, taking into account the larger design of the multi-layer circuit board unit size, the ambient temperature and humidity of the graphics transmission workshop, the misalignment stacking caused by the inconsistent expansion of different core boards, and the positioning method between layers , The degree of alignment between layers of multilayer circuit boards is more difficult to control.

Multilayer circuit boards are made of special materials such as high TG, high speed, high frequency, thick copper, and thin dielectric layers. This puts forward very high requirements for internal circuit production and graphic size control, such as the integrity of impedance signal transmission, which increases the difficulty of internal circuit production. The line width and line spacing are small, the number of open circuits and short circuits increases, the number of short circuits increases, and the pass rate is low; there are many signal layers in the thin line, and the probability of missing internal AOI detection increases; the inner core board is thin, which is easy to fold and cause poor exposure, and when etching Easy to roll; multi-layer circuit boards are mostly system boards, with a large unit size, and the cost of scrapping the finished product is relatively high.