Do you know the production difficulty of multi-layer PCB proofing?

Multi-layer PCB board in communication, medical, industrial control, security, automotive, electric power, aviation, military, computer peripherals, and other fields as the "core body", product functions are more and more, traces are denser and denser, so relatively speaking, the production is more and more difficult.

The production of a multi-layer circuit board not only needs higher technology and equipment investment but also needs experienced production technicians, At the same time, to obtain the multi-layer circuit board customer certification, strict and cumbersome procedures, therefore, the entry threshold of the multi-layer circuit board is high, to achieve long industrial production cycle. Specifically, the difficulties encountered in producing and processing multilayer circuit boards are mainly in the following four aspects.

Four difficulties in the production and processing of multilayer circuit board

1. The production of the inner trace is difficult

Multilayer circuit has various special requirements such as high speed, thick copper, high frequency, high Tg value, etc., and the requirements for inner wiring and graphic size control are increasingly high. For example, ARM development boards have many impedance traces in the inner layer, which makes it more difficult to make the inner trace to ensure impedance integrity.

There are many signal tracks in the inner layer, and the width and spacing of the tracks are about 4 mil or less. Multi-core thin production of the sheet is prone to wrinkle, these factors will increase the production cost of the inner layer.

2. Difficulty in alignment between inner layers

With the increasing number of multilayer boards, the alignment requirements of the inner layer are also higher and higher. The film will expand and contract under the influence of ambient temperature and humidity in the workshop. The core board will also have the same expansion and contraction, which makes the alignment accuracy between the inner layers more difficult to control.

3. Difficulties in the process of suppression

The multi-core plate and PP(semi-cured plate) are superimposed together, and problems such as delamination, slippage, and drum residue are easy to occur when pressed together. The higher the number of layers, the lower and lower shrinkage control cannot be consistent with the size coefficient compensation. The thin insulation layer easily leads to the failure of the inter-layer reliability tests.

4. Difficulties in drilling production

The high Tg or other special plates are used in the multilayer board. The roughness of the drilling of different materials is different, which increases the difficulty of removing the glue slag in the hole. High-density multilayer board hole density, low production efficiency, easy to break the knife. Between different through predicaments, the edge of the hole is too close, which is easy to cause the CAF effect problem.

Therefore, in order to ensure the high reliability of the final product, the multilayer manufacturers need to carry out corresponding control in the production process.