What is the difficulty in the production process of multilayer PCB circuit board?

High-level PCB is often defined as 10-20 layers or more advanced multilayer circuit boards. Compared with traditional PCB products, high-rise PCB has the characteristics of many thick plates, many layers, dense lines, many holes, large unit size, thin medium layer, and high requirements for internal space, interlayer alignment, impedance control and reliability; mainly used in communication equipment, high-end servers, medical electronics, aviation, industrial control, military and other fields. So, what are the difficulties in the high-rise PCB circuit board production process?

1. Difficulties in alignment between layers

Due to the large number of high-rise floors, users have increasing calibration requirements for PCB floors. Typically, the alignment tolerances between the layers are controlled at 75 microns.

2. Difficulty in internal circuit production

The high-rise panel adopts special materials such as high TG, high speed, high frequency, thick copper and thin dielectric layer, which puts forward high requirements for internal circuit production and graphic size control. Specific performance is in: line width line distance is small, open circuit short circuit increased, low qualified rate; fine line signal layer, inner layer AOI leakage probability increases; inner core plate is thin, easy to wrinkle, poor exposure, etch machine is easy to curl, etc.

3. Difficult points in compression manufacturing

Many inner core plates and semi-cured plates are superimposed, which are prone to skateboard defects, lamination, resin void, and bubble residue in stamping production. Due to the large number of layers, the expansion and shrinkage control and the size coefficient compensation cannot be kept consistent, and the thin inter-layer insulation layer easily leads to the failure of the inter-layer reliability test.

4. Difficulty in drilling and production

The use of high TG, high speed, high frequency and thick copper special plate increases the difficulty of drilling roughness, drilling burr and drilling decontamination.