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Multilayer PCB – the 21st century technology in PCB or PCBA industry


The term PCB stands for Printed circuit board and multilayer PCB is printed circuit boards made up of three or more conducting copper layers. Now a day’s multilayer PCB is used almost in all electronic components. Before this multilayer PCB technology, the PCB was simple in design but today companies are adding up to 56 layers of PCB.

For the simple electronics components, the PCB is single-layered, and when we talk about complex electronic devices like motherboards they consist of multilayers of PCB substrate over each other. The layers that made up multilayer PCB must be even in number and they may be 2,4,6,8 and up to 56. Multilayer PCB is complex in design and all the layers that made up a multilayer are compressed and form a single multilayer layer.

This article covers many important questions regarding multilayer PCB. Furthermore, the article describes the difference in designs of single and multilayer PCB and why PCB have layers.
PCB Multilayers

Why do PCBs have layers?

The answer to this question comes to mind from every newcomer in the industry. The use of layers in PCB like the use of Multilayers is of great advantage for electronics engineers and designers. This is because when we add layers the surface area of to design gets increased without increasing the actual size of the component.

Other advantages include the increase of power distribution capability on the board, it reduces the crosstalk, it mitigates the EM interference in the layers, and lastly, increases in the speed of electronic components by increasing the overall efficiency of the design.

How many layers can a PCB have?

The efficiency of a printed circuit board depends on the number of layers, and the number of layers in a PCB depends upon the type of application for which a PCB is designed. Commonly, there are even no substrates available. The boards that are widely available in the market are between (4 to 8) layers, but technically, nearly 100-layer PCB boards can be achieved.

Most large supercomputers use fairly multi-layer motherboards, but because such computers can be replaced by clusters of many ordinary computers, ultra-multi-layer boards have gradually fallen out of use. Because the layers in the PCB are tightly combined, it is generally not easy to see the actual number, but if we look closely at the motherboard, we can still see it.

Is there are a 3 layer PCB?

Three-layer PCB does not exist or it is rarely available in the market. You will find layers in plural numbers like 4 layers, 6 layers, and 8 layers. The other reason for the odd layer is that they create issues with circuit boards.

The four-layer board has one more layer of copper foil and adhesive layer than the three-layer board, and the processing cost is not much different. In addition, the four-layer board is easier to control than the three-layer board. Mainly in terms of symmetry, the warpage of the four-layer board can be adjusted. Controlled below 0.7% (ipc600 standard). However, when the size of the three-layer board is larger, the warpage will exceed this standard, which will affect the reliability of the SMT patch and the entire product.

Why Designers are using Multilayer PCBs?

multi-layer-printed-circuit-board-pcbDo designers have to save the overall space? The answer is no.There are many other reasons that designers prefer multilayer PCB over single layer.

Firstly, multilayer PCB have many advantages according to the designers as multilayer PCB is smaller in size. This is one of the great benefits of multilayer PCB. The multilayer PCB is much smaller than other PCBs and have much more increased functionality than other PCBs. This modern technology benefits electronic technology as the current trend is towards miniaturization of designs.

Secondly, multilayer PCB offers lightweight as compared to other PCBs, and due to these advantages. Lightweight equipment is liked by consumers all over the world due to its compact size.

Thirdly, multilayer PCB offers high quality and is of great quality when compared with single and double-layered PCB.

Fourthly, the equipment having multilayers results in increased durability. Multiple insulation layers are used in the PCB which do not allow them to trap heat. That’s why they offer high durability than single-layer PCB. Lastly, multiplayer PCBs offer high speed than other types of PCB and it increases the performance of hardware.

How are multilayer PCBs made?What are the materials used ?

Multilayer PCB is made with different materials pressed together. The prepreg and conductive materials are pressed together under very high pressure and temperature resulting in the making of Multilayer PCB. Under extreme heat and pressure using a hydraulic press, the prepreg starts to melt and results in the joining of layers. Then it cools down so that all the materials are fused properly. For the appropriate current run in PCB, the plated through holes must be correctly located and it needs the board layers be aligned.

The materials required for making of PCB boards are :
● Sheets of Prepeg
● Conducting copper substrate
● Inner layer core

How are multilayer pcb are connected?

To join the layers and prepreg, high pressure and temperature are applied. By applying a hydraulic press these materials join together. Leave the materials so that it cools down and solidifies. Then it’s a choice of engineers whether to choose the through-hole method or surface mount method to connect components on PCB.

What is the difference between single and multi-layer PCB?

single PCB -VS-multilayer PCBThe main difference between a single and multilayer is obvious. As a single layer, PCB uses only single base material, while multilayer PCB uses multiple layers.

If you want to distinguish the single layer or multi-layer. You can pick up the PCB and face it towards the light. The inner core is opaque( it is all black), then It is a multi-layer board. Otherwise, it is a single-sided or double-sided board. A single-sided board has only one layer of wiring and there is no copper in the hole. Double-sided is that there are lines on the front and back, and there are copper holes in the conduction holes.

What are types of PCB ?

There are different types of PCB which are listed above:
● Single Sided PCB
It is modest among all the types of PCB. Only one copper layer is used in it and one PCB substrate.
● Double-sided PCB
As the name suggests the double-sided PCBs have two conducting copper substances on both sides. It is widely used for different applications
● Multilayer PCBs
As the double-sided has two conducting layers, the multilayer PCB has more than two conducting layers such as 3, 4, and 8. This type of PCB is widely used in industries and there are many applications for multilayer PCBs.

i) Industries that make electronics appliances and consumers goods
ii) In the making of motherboards, computers, etc.
iii) Telecommunication equipment uses multilayer PCB such as BTS, BSC, Satellite, GPS, and transponders.
iv) It is used in the industrial machinery which makes goods.
v) Medical devices use multilayer PCB to perform multitasking. X-ray equipment and heart monitors and other equipment are made using multilayer PCB.

What are the classification methods for PCB?

There are several methods to classify printed circuit boards and assembly. One needs to look for the following things :
1.How many conducting layers are there
2.Which base material is used
4.Assembly type
5.Is it with or without core

You need to look for conducting layers. By these conducting layers of copper, a PCB can be further classified as a single-sided, double-sided, or multilayer PCB. Different material is used in manufacturing like copper and prepreg. There are two types of assembly types are there; surface mounting and through the hole.

The printed circuit board is the most important entity in electronics, and the PCB used in the past were limited to a single layer. But with the continuous update and development of the electronics industry, multilayer PCB has emerged and are widely used in many fields. At present, the number of layers has even exceeded 100. It is believed that with the development of technology in the future, the number of layers will exceed the limit and become more and more.



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