PCB high-level circuit boards are generally defined as 10-20 or more advanced multilayer circuit boards, which are more difficult to process than traditional multilayer circuit boards and 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, market demand for high-level boards in the fields of communications, base stations, aviation, and military has remained strong.
With the rapid development of China's communication equipment market, the market for high-level boards is promising.
At present, PCB manufacturers that are capable of producing high-level circuit boards in China are mainly from foreign-funded enterprises or a few domestic-funded enterprises. The production of high-level circuit boards not only requires high investment in technology and equipment, but also requires the accumulation of experience of technical staff and producers.
The average PCB level has become an important technical indicator for measuring the technical level and product structure of PCB companies. This article briefly describes the main processing difficulties encountered in the production of high-level circuit boards, and introduces the control points of key production processes for multilayer circuit boards for reference.
1. Difficulties in alignment between layers
Due to the large number of layers in the high-level panel, users have increasingly higher requirements for the calibration of the PCB layer. Typically, the alignment tolerance between layers is controlled at 75 microns. Considering the large size of the high-rise board unit, the high temperature and humidity of the graphics conversion workshop, the dislocation overlap caused by the inconsistency of different core boards, and the way of positioning between layers, it makes the alignment control of the high-rise board more difficult.2. Difficulties in making internal circuits
The high-layer board uses special materials such as high TG, high speed, high frequency, thick copper, and thin dielectric layers, which places high requirements on the internal circuit production and pattern size control. For example, the integrity of impedance signal transmission increases the difficulty of manufacturing internal circuits.Small width and line spacing, open circuit and short circuit increase, short circuit increase, low pass rate; more thin wire signal layers, increase the probability of AOI leakage detection on the inner layer; thin inner core plate, easy to wrinkle, poor exposure, easy to curl when etching machine; High-level plates are mostly system boards, the unit size is large, and the cost of product scrap is high.
3. Difficulties in compression manufacturing
Many core boards and prepregs are superimposed, and are prone to defects such as slides, delamination, resin voids and residual air bubbles in stamping production. In the design of the laminated structure, the heat resistance, pressure resistance, glue content and dielectric thickness of the material should be fully considered to formulate a reasonable high-level sheet pressing scheme.Due to the large number of layers, the expansion and contraction control and the dimensional coefficient compensation cannot maintain consistency, and the thin interlayer insulation layer easily causes the interlayer reliability test to fail.
4. Difficulties in drilling
The use of high-TG, high-speed, high-frequency, thick copper special plates increases the difficulty of drilling roughness, drilling burrs, and decontamination. The number of layers is large, the total copper thickness and plate thickness are accumulated, and the drilling is easy to break; the dense BGA is many, and the CAF failure problem caused by the narrow hole wall spacing is easy to cause the oblique drilling problem due to the plate thickness.This article is proofed by a multilayer pcb circuit board, this article does not represent the views of this site.
