An Ultimate Guide To Multilayer PCB Manufacturing Process In 2021

Why Multilayer PCB Boards Have Great Demand in Modern Electronics?

Nowadays PCB boards are present in all electronic devices whether they are the smallest electronic gadgets or the most complicated equipment of the modern medical laboratory.

In fact, the construction of the most ultramodern aerospace vehicles has become possible only because of the multilayer PCB manufacturing process.

Today multilayer circuit boards have a great demand because they play the main role to make smaller, faster, and more powerful electronic devices.

Moreover, these are multilayer PCB boards that have made all the impossible possible.

Let’s start to know about multilayer PCB boards in detail!

What are they, in which applications they are used as well as what are their manufacturing processes?

What are the Most Common Types of PCB Boards are there?

Essentially, there are several types of PCB boards. Moreover, they have categorized on the basis of their number of layers, frequency as well as substrate used in them.

Generally, the most common types of PCB boards are;

But in this guide, we are going to discuss multilayer PCB boards and the multilayer PCB manufacturing process.

What is a Multi-layer PCB?

In fact, in multi-layer PCB boards, PCB manufacturers use more than two layers. It is totally different from the double-sided circuit boards as they have just two conductive layers of material.

On the other hand, in a multilayer board, there are at least three layers of conductive material. These multiple layers of conductive material are actually buried in the center of the material.

Today the multilayer PCB boards have opened up the new doors of a world of possibilities upon us. Actually, these boards have allowed engineers to manufacture more and more complex and smart electronic appliances.

Dreams that were just a dream in the past are only possible because of the multi-layer board. It is an ideal benefit that PCB manufacturers were not able to achieve by using double-sided boards.

MULTILAYER PRINTED CIRCUIT BOARD

MULTILAYER PRINTED CIRCUIT BOARD

How do I Know if My PCB is Multilayer Circuit Board?

You can easily know whether your PCB boards are multilayer or not because, in multilayer circuit boards, PCB manufacturers sandwich more than two insulation layers between the PCB copper layers in the multilayer PCB manufacturing process.

Moreover, you can also count the total number of layers of your PCB boards by inspecting them via blind vias or holes.

Why do PCBs Have Multiple Layers?

If PCB manufacturers want to construct PCB boards for complex electronic devices, they can easily add more and more circuits by adding more layers on a single board. Further, adding more circuits and layers on a board makes sure that there is a lot of space for more connections.

So, PCB boards have multiple layers for constructing highly advanced electronic gadgets.

Today all the modern and ideally smart electronic devices such as smartphones, the latest laptops, etc. have become possible just because of this level of complexity of the circuit boards.

Why Multilayer PCB Boards Have Become Extremely Popular in Modern Electronics?

Nowadays multilayer PCB boards have become extremely popular in modern electronics only because of their wide space for design integrity.

Usually, they have an ideally wide range of thicknesses and sizes in order to provide more space according to the needs of their expanding applications.

Have you ever noticed that multilayer PCB circuit boards often have an even number of layers? It is only because the odd number of layers may cause several issues in the circuit boards such as warping.

Basically, in multi-layer PCBs, even number of layers are highly cost-efficient to produce. Although these boards are present in variants ranging but the most common number of layers is from 4 to 12.

Typically, the majority of advanced electronic appliances need layers between four and eight.

But most applications such as the latest smartphones actually need a maximum of 12 layers for their high-grade performances.

MULTILAYER PRINTED CIRCUIT BOARD 1

Multilayer PCB Board

Why More than 12 Layers in the Multilayer PCB Manufacturing Process are Used?

Some highly professional PCB manufacturers also use more than 12 layers in the multilayer PCB manufacturing process.

PCB manufacturers often increase the number of layers up to 100 layers. Generally, they design so many layers altogether in order to boost the ability of their extremely complex electronic applications like aerospace.

But multilayer PCB boards with so many layers are usually rare because such PCB circuits are very cost-inefficient to produce. So, they are only used in highly complicated gadgets.

Come with us to know about the manufacturing process of multi-layer PCB boards!

What is the Multilayer PCB Manufacturing Process?

Basically, the overall process of manufacturing multi-layer PCB boards is simple and straight forward but PCB manufacturers need a high level of attention to construct them.

They also need to be deeply attentive because it is necessary to make sure that all layers are perfectly registered to all the required drilled holes. Further, if they don’t care about it then there are great chances of deformation stresses that can be produced by the pressure and heat as well.

Furthermore, in the multilayer PCB manufacturing process, PCB manufacturers always make sure that they have selected the correct materials. Additionally, they also make sure that the orientation of each and every sheet is correct.

They actually laminate core materials and alternating layers of prepreg altogether under extremely high temperatures. Further, they also have to use very high pressures in order to create multilayer PCB circuit boards.

Usually, this whole process helps to make sure that there is no air trapped between layers.

Moreover, all the conductors have completely encapsulated by resin as well as the additional adhesive that helps to hold all the layers together is perfectly cured and melted.

PCB manufacturers have a wide range of material selections from exotic ceramic to basic epoxy glass or Teflon materials.

What Special Equipment is Used in the Multilayer PCB Manufacturing Process?

Actually, PCB manufacturers use special equipment for pressing multilayers in the multilayer PCB manufacturing process. They usually need a specialized hydraulic press with special heated platens.

In the pressing process, PCB manufacturers squeeze all the books with a special pressure of 50 psi earlier to being heated to 350F at 350 psi for almost a minimum of one hour.

Hence, after pressing, they allow the whole assembly to cool down slowly before starting the remaining processing.

Inspection of Multi-layer PCB

Inspection of Multi-layer PCB

What is the Stackup of a Multilayer or a 4-Layer PCB Board?

4layer Stack Up

4layer Stack Up

The above figure ideally helps you to understand the stackup of a 4-layer PCB board.

Core material and prepreg are actually the same kinds of materials. While in a multi/4layer PCB board, the prepreg is not fully cured. So, it makes it more malleable as compared to the core.

In the next step, PCB manufacturers place the alternative layers into a lamination press. They usually apply greatly high pressures and temperatures to the whole stackup in order to completely melt the prepreg as it helps to join all the layers together.

It was the last step in the multilayer PCB manufacturing process. Hence, after cooling the whole stackup, manufacturers get extremely hard and solid multilayer boards.

What are the Popular Applications of Multilayer PCB Boards?

The lightweight, smaller size as well as highly improved design functionality, all these ideal features make the multilayer PCB circuits perfect to use in modern electronic gadgets.

Here are some most popular uses of multilayer PCBs so that you can deeply examine their role in all the latest advancements.

Let’s check out in detail!

In latest computer electronics:

In modern computers and laptops, electronic engineers always prefer to use multilayer boards as they help to save extra space and provide high-functionality.

Defense and military:

Essentially, multilayer PCB circuits have extreme durability, ideal functionality, as well as lightweight features. So, all these great qualities make these boards perfect to use high-speed circuits.

Hence, the defense industry is totally relying on these boards as their small size leaves extra room for other components to flourish existing functions.

In advanced automotive:

In this modern era, all the latest models of vehicles are using more and more electronic components. Hence, using the right types of components becomes highly essential in automotive design.

So, all automotive engineers are increasingly preferring to use multilayer PCBs over all other alternatives as they are small in size as well as relatively heat-resistant.

In several other applications:

Furthermore, multilayer PCB circuits are ideally used in aerospace, modern telecommunications, extremely advanced medical devices, and the healthcare industry.

These boards are not only beneficial to use in the science and research industry but even in home appliances and security requirements. Their uses are endless as they are almost present in all simple to complex electronic appliances.

For the manufacture of multilayer printed circuit boards in industry, four main methods are used:

  1. Layered build-up
  2. Open contact pads
  3. Pairwise pressing
  4. Electrochemical metallization of through holes.

Multilayer printed circuit boards

Fig. 10 Multilayer printed circuit boards manufactured by various methods:

 a – layer-by-layer build-up

b – Open contact pads

c – Pairwise pressing

d – Metallization of through holes

1 -Insulation

2 – Printed conductor

3 – Interlayer connections

4 -Output

5 – Printed circuit board

6 – Foil

7 – Fiberglass

8 -interlayer hole

What is the Method of Layer by Layer Manufacturing in Multilayer PCB Board?

The method of layer-by-layer build-up consists in the sequential application of insulation 1 (Fig. 10, a) and printed conductors 2. Interlayer connections 3 can go through the entire depth and connect any inner layers to each other.

An insulating varnish or epoxy resin is used as an insulating layer. The method is highly reliable and allows a high packing density. The number of layers can be more than six. The disadvantage of this method is the great complexity associated with the need to strictly adhere to the sequence of the operation.

What is Open Contact PADs Method?

The method of open contact pads consists in pressing blanks of insulation 1 (Fig. 10.6) with a pattern applied in the form of strips of copper foil, interlaced with layers of fiberglass. Pressing the printed layers of the board is carried out simultaneously.

Pins 4 from each layer of the board are folded outward. The method is simple and allows you to get a board with the number of layers up to 15. The disadvantage of this method is the low packing density.

The pairwise pressing method consists in pressing prefabricated double-sided printed circuit boards (Fig. 10, c). On one of the sides of a double-sided foil-clad dielectric, a drawing of a diagram of the inner layers of a multilayer printed circuit board 5 is applied in a combined way (the other side is completely covered with foil).

On each workpiece, between the pattern of the circuit and the foil, interlayer connections 3 are made in the form of metallized holes. The double-sided printed circuit boards made by this method are glued (pressed) with the foil 6 outward using glass cloth 7.

The process of further processing of the outer layers of the foil is similar to the production of double-sided printed circuit boards. This method produces multilayer PCBs with a maximum of four layers.

Inspection of Multi-layer PCB

 Multilayer Circuit Board

Conclusion:

Although, the multilayer PCB manufacturing process requires specialized equipment as well as a significant commitment to design them perfectly. But they generally have more power, operating capacity, and a rapid speed in comparison to other boards.

Further, they not only can ideally reduce the overall weight and size of electronic devices but provide great functionality. Hence, all these good features make them ideal to use in your complicated electronic projects.

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