High-precision multi-layer circuit board PCB proofing, four major production difficulties can not be ignored

Multi-layer PCB are used as the "core main force" in the fields of communications, medical treatment, industrial control, security, automobiles, electric power, aviation, military industry, and computer peripherals. Product functions are getting higher and higher, and PCB are getting more and more sophisticated, so relative to the difficulty of production Also getting bigger.

1. Difficulties in the production of inner circuit
Multilayer board circuits have various special requirements for high speed, thick copper, high frequency, and high Tg value, and the requirements for inner layer wiring and pattern size control are getting higher and higher. For example, the ARM development board has a lot of impedance signal lines in the inner layer. To ensure the integrity of the impedance increases the difficulty of the inner layer circuit production.
There are many signal lines in the inner layer, and the width and spacing of the lines are basically about 4mil or less; the thin production of multi-core boards is prone to wrinkles, and these factors will increase the production of the inner layer.
Suggestion: design the line width and line spacing above 3.5/3.5mil (most factories have no difficulty in production).
For example, a six-layer board, it is recommended to use a fake eight-layer structure design, which can meet the impedance requirements of 50ohm, 90ohm, and 100ohm in the inner layer of 4-6mil.

2. Difficulties in alignment between inner layers
The number of multi-layer boards is increasing, and the alignment requirements of the inner layers are getting higher and higher. The film will expand and contract under the influence of the temperature and humidity of the workshop environment, and the core board will have the same expansion and contraction when produced, which makes it more difficult to control the alignment accuracy between the inner layers.
Suggestion: This can be handed over to reliable PCB manufacturing plants.

3. Difficulties in the pressing process
The superposition of multiple core plates and PP (cured plate) is prone to problems such as delamination, sliding plate and steam drum residues during pressing. In the structural design process of the inner layer, factors such as the dielectric thickness between the layers, the glue flow, and the heat resistance of the sheet should be considered, and the corresponding laminated structure should be reasonably designed.
Suggestion: Keep the inner layer of copper spread evenly, and spread the copper in a large area without the same area with the same balance as PAD.