Mastering PCB Stack Design: Best Practices for Beginners

Printed Circuit Boards (PCBs) created a huge buzz and movement in the field of technology and changed many things in our world. Every day the world experiences new changes in electronic products, as devices become smaller and more efficient in performing many tasks.

Since PCBs were one of the main factors in the development and change of electronic products, it was necessary to develop means of designing these boards, which are considered the basic structure of any electronic device. The development of PCBs, in turn, has led to the production of a large number of embedded systems that have greatly contributed to changing our daily lifestyles. When we say upgrading PCBs, it definitely means increasing PCB layers.

What is PCB Stack?

Certainly, as is known, multi-layer PCB boards consist a number of layers, like sweet mould, placed on top of each other. That is, it is formed by stacking several layers together, and these layers are connected to each other. This process, in which layers are placed on top of each other in sequential manner, is called stacking, meaning stacking them one after the other.

The stacking process represents the basic structure of the PCB board design process in general because it contains the number of layers, so this process becomes more important and accurate, through which the thickness of the layers and the weight of each layer are clarified based on the requirements of all the integrated circuits that will be assembled in these layers. So, what is PCB stacking?

PCB Stack

In general, the principle of stacking PCB means arranging the layers that make up PCB in an organized and arranged manner, one after the other, to form PCBs that perform their functions with high performance and reliability. Therefore, the PCB stacking process must be carried out correctly and properly. If this process is correct and the layers are stacked properly and completely, a board will be produced free of defects that may in turn affect the final product. PCB stacking directly affects the reliability and operation of the board, such as electrical performance, signal integrity between layers, electromagnetic interference and thermal performance of the board.

Well-stacked layers reduce electromagnetic radiation and prevent noise interference, as well as signal transmission and impedance issues. It is certain that if the PCB stacking is not done properly, it will directly affect the electrical performance, thus increasing electromagnetic interference, noise and signal interference resulting in lower panel performance and reliability.

The PCB stacking design process must be carried out with high precision because the ability of the produced panel and its effectiveness in performance in general are determined.

How to design a proper PCB stack?

After knowing that stacking PCB play very big role in producing board with high performance and reliability, the next question on your mind will be: How to design a proper PCB stack?

The process of designing a PCB stack in general is to arrange the different layers of PCBs, which usually consist of conductive layer, an insulating material layer, and other additional components. As mentioned previously, the PCB stack design determines the thickness and weight of each PCB layer.

A typical PCB stack usually consists of copper layer, insulating layer, ground plane, and signal layer. As mentioned previously, the process of stacking these layers to produce a PCB directly affects the performance and reliability of the board produced. PCB stack can be designed from a single layer of signal layer and ground plane layer, or several complex layers.

Copper Layers Design

As it is known about this layer, it has two types: an inner layer and an outer layer. The inner layer works to provide communication between the internal elements of the board, and the outer layer of copper provides communication with external devices. One of the most important factors in stacking this layer is the thickness of the copper layer. The thicker it is, the stronger it is. When the copper layer is a thin layer, this may directly affect the performance of the electrical circuit and make it difficult to direct. Since increasing the thickness means increasing the cost, therefore the thickness must be determined according to the design and PCB stack requirements .

Insulation Layers Design

The insulating layer insulates the copper layers, thus avoiding any unwanted electrical contact. There are several types used to form this layer, such as FR-4 epoxy and glass epoxy, which are the most common types. The material is selected according to the required design characteristics. We find that RF-4 epoxy has thermal and electrical properties and is cheaper compared to glass epoxy, and we also find that the latter is of higher quality compared to the former. The thickness of the copper layers and insulation layers are the most critical part in PCB stack.

PCB Stack Layers

Design of Ground Plane Layers

These layers protect the electrical circuits on the board from signal interference and reduce noise and electromagnetic interference. They act as paths for feedback currents and thus lower the DC voltage on the components. This layer also works to balance the power between the board components. This layer usually consists of copper because it is cheaper and has less conductivity, but it is usually preferred to mix copper and nickel because it has better protection ability and is less susceptible to corrosion. So ground plane layers design is also important in PCB stack design.

Design of Signal Layers

The signal layer or conductive layer works to transmit electrical signals, providing single or multiple signal transmission. The selection is made based on the design requirements. If the application requires high-speed signals and higher power, this will certainly require a greater number of signal layers compared to applications that require lower speed.

The PCB stack design process is very important because it fundamentally affects the capacity and reliability of the board.

The above is a general explanation of the most common PCB stacking layers, so when designing any proper stack, the following considerations must be taken into account,

  • The design must include the Ground plane layer, as it is one of the most important factors that play an important role in designing the stack appropriately and soundly. As we mentioned, it works to reduce interference between signals and prevent radiation from high-speed signals. The presence of many ground planes in the design is also very useful for reducing radiation.
  • The presence of signal layers adjacent to the ground level layers ensures that no interference or noise occurs during signal transmission between the layers, as well as to ensure directing the current and reducing its resistance.
  • Taking into account the arrangement of the signal layers, the order of the signal layers must be clearly defined, as this contributes to reducing signal interference, ensuring effective signal routing, and ensuring signal integrity.
  • Choosing the materials that make up the layers, as they play a role in the quality of the layer. The choice must be based on the characteristics of this material, such as electrical, mechanical, and thermal performance, and other factors that can affect the overall performance of PCBs.

One of the strongest and most important reasons for producing high-quality electronic devices with strong and effective performance is designing the PCB stack properly. It is necessary to carefully check and ensure that the layers are not stacked randomly or without specifying the requirements and characteristics of the application to be designed. If there is any flaw in the design of the PCB stack, this in turn leads to failure in product performance.

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