It is widely known in the industry that there are single-sided, double-sided and multi-layer PCBs. For simple electrical appliances, a single-sided PCB can be used.

But with the advancement of the times, electronic products need to be updated, whether in function or volume. For multi-functional and small-volume electronic products, single-sided and double-sided PCBs cannot fully meet the requirements, and multi-layer PCBs are required at this time.

However, regarding the professional terms such as "single-sided, double-sided, and multi-layer PCB", although it is often said that many people in the industry only have a memory and a general concept, they do not have a specific understanding of the real thing.

So, what is the familiar PCB multilayer board?

Regarding PCB multilayer boards, there is no unified, better, and recognized definition standard in the industry.

So, what to do?

Don't worry, on March 10 this year, CPCA (China Electronic Circuit Industry Association) released an "Electronic Circuit Terminology" which said:

Multilayer printed board

multilayer printed board; MLB

Multilayer board: a printed board with three or more layers of conductive patterns.

Some industry know-hows for PCB hobbyists:

Multilayer boards are mainly composed of the following layers:

Signal Layers

InternalPlanes (Internal Power)

Mechanical Layers

Masks (solder mask)

Silkscreen (screen printing layer)

and System (system working layer)

The signal layer is divided into top layer, middle layer and bottom layer, which are mainly used for placing various components, or for wiring and soldering.

The internal power layer, also called the internal power layer, is dedicated to laying out power and ground wires.

The mechanical layer is generally used to place indicative information about board making and assembly methods, such as circuit board physical dimension lines, data sheets, via information, etc.

Soldermask also has a top and bottom layer, and pads or other objects placed on this layer are copper-free areas.

The silk screen layer is mainly used to draw the outline of the component, place the number of the component or other text information.

The system working layer is used to display information on violations of design rule checks.

No matter new or old users, no matter individuals or enterprises, they can enjoy 0 yuan proofing of multi-layer board, 2 times a month at NextPCB.

Talking about high multi-layer circuit board PCB proofing, what are some unknown production difficulties?

Multi-layer PCB is used as the "core main force" in the fields of communication, medical treatment, industrial control, security, automobile, electric power, aviation, military industry, and computer peripherals. The difficulty is also increasing.

At present, domestic PCB manufacturers that can mass-produce high-level multi-layer circuit boards often come from foreign-funded enterprises, and only a few domestic-funded enterprises have the strength of batch production.

The production of high multi-layer circuit boards not only requires high investment in technology and equipment, but also requires experienced production technicians. At the same time, the introduction of high-level multi-layer board customer certification is strict and cumbersome. Therefore, high-level multi-layer circuit boards. The entry threshold is high, and the industrialized production cycle is long.

Specifically, the processing difficulties encountered in the production of high-level circuit boards are mainly the following four aspects.

1.  Difficulties in making inner layers

The multi-layer board circuit has various special requirements of 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 many independent 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 easy to wrinkle, and these factors will increase the production cost of the inner layer.

2.  Difficulties in alignment between inner layers

The number of multi-layer boards is increasing, and the alignment requirements of the inner layer are also getting higher and higher. The film will expand and shrink under the influence of the temperature and humidity of the workshop environment, and the core board will have the same expansion and contraction, which makes the alignment accuracy between the inner layers more difficult to control.

3.  Difficulties in the pressing process

The superposition of multiple core boards and PP (prepreg) is prone to problems such as delamination, sliding plates and steam drum residues during lamination. If there are too many layers, the expansion and shrinkage control and size coefficient compensation cannot be consistent; if the interlayer insulating layer is thin, it is easy to cause the failure of the interlayer reliability test.

4.  Difficulties in Drilling Production

The multi-layer board is made of high Tg or other special boards, and the roughness of the drilling holes of different materials is different, which increases the difficulty of removing the glue residue in the holes. High-density multilayer boards have high hole density, low production efficiency, and easy to break the knife. Between different network vias, the edge of the hole is too close to cause the CAF effect problem.

In order to improve the high reliability of the products, NextPCB has made all-round efforts and taken multiple measures simultaneously—continuously purchasing high-precision equipment and high-quality materials, continuously optimizing the process level, and improving management capabilities. At present, the HDI boards produced by NextPCB have the smallest blindness. Pores have reached 75μm.

High reliability is NextPCB’s commitment and unswerving insistence. We align with the traditional manufacturers in terms of quality, and strive for a higher level of after-sales service. We are committed to providing high-reliability multi-layer board manufacturing services for our customers. Please check out our official website at NextPCB.net.