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Decoding the Complexity: Exploring Multilayer PCB Technology

Exploring Multilayer PCB Technology

Multilayer Printed Circuit Boards are widely used in the electrical and electronics sector since they can be used in different applications. Now, let’s uncover the complexity, design, construction, technologies, production, and inspection process behind a multilayer PCB.

Definition and Importance of Multilayer PCBs

A multilayer PCB or a multilayer printed circuit board is a form of electronic material mounted in a device or appliance used to connect components. From the word itself, multilayer, it is composed of more than two layers of boards. These layers allow more space for wiring; thus, it is ideal for more complex devices that require a lot of circuits. Some multilayer PCB examples can be seen in smartphones, accelerators, x-ray equipment, aerospace machines, and data storage.

Since the modern world demands more advanced technologies, having a multilayer PCB is crucial for a specific device or piece of equipment to function. This allows for more complex circuits and wiring, which is why it has a higher speed and capacity, unlike single-sided and double-sided PCBs. There are many different multilayer PCB designs, and they are very handy when it comes to compact devices. Just like smartphones, since they are a very complex form of gadget, it requires a small but higher capacity circuit board for it to function well despite its small size. Thus, with multilayer PCB, a wide range of machinery in the manufacturing and industrial sectors can be utilized.

Understanding Multilayer PCB Construction

There are two things to focus on when discussing multilayer PCB construction: its layers and stack up and the core and prepreg materials.

Layers and Stack Up

There are different multilayer types of PCB, from 2-layer up to 10-layer stack-ups. Multilayer PCBs have not less than 3 layers of boards on both faces or sides, and it varies depending on the device where it can be applied. This kind of circuit board comprises different layers: foil, prepreg, power/signal/ground plane, and core. The most commonly used foil for multilayer PCB construction is copper foil. When doing a 2-layer PCB stack up, the first layer is the foil, the core, and the outer layer foil. On the other hand, a 4 layer flex pcb stack-up comprises a top foil layer, prepreg, inner layer foil, core, another inner layer foil, prepreg, and a bottom layer foil. A 6-layer stack up, however, has top layer foil, prepreg, ground plane, core, layer foil, prepreg, layer foil, another core, power plane, prepreg, and an outer or a bottom layer foil. An 8-layer and a 10-layer stack-ups have more layers than the 6-,4-, and 2-.

Core and Prepreg Materials

Multilayer printed circuit board’s core and prepreg are both critical components in constructing this type of PCB. The core serves as the base of the multilayer PCB. Between the core and the prepreg, the core is more rigid than the prepreg material since the core is fully laminated fiberglass resin with copper on each side. The Prepreg material is also a fiberglass resin with bonding chemicals. It serves as a conductor for the foil and coil. It is considered the binding material of the PCB construction since it binds two cores or cores and a layer. There are three significant types of prepreg; standard, medium, and high resin. They are made primarily based on what type of material they are to be used.

Design Considerations for Multilayer PCBs

In making a multilayer PCB, there are design considerations to focus on. These are the signal, power integrity, EMI, and ESD.

Design Considerations for Multilayer PCBs

Signal and Power Integrity

The signal integrity of a multilayer PCB is basically the ability of the signal to work well and pass through the transmission line without any distortion. It is one of the things to consider when making a multilayer PCB in order to achieve a successful and efficient multilayer PCB board. The signal layer of the multilayer must be aligned with the plane because it will allow for better flow and transmission of the signal between layers to the receiver and vice versa. Determining its path and return will tell you how fast the time signal transmits.

On the other hand, power integrity deals with the energy current transmitted and distributed on planes. When a multilayer PCB has power integrity, it can flow and move energy from one place to another without any hindrance, blockage, or barrier. The positioning, mounting, and type of capacitors you use will all impact how well the power integrity works.

EMI and ESD Considerations

EMI and ESD are two considerations regarding the electric movement in the multilayer PCB. An EMI or electromagnetic interference is a destructive effect from EMC– poor design and reception. This kind of interference may also come from outside sources like the surrounding environment. To prevent EMI from happening, designers of multilayer PCB must always adhere to the standard rules in designing and building up compatibility. On the other hand, ESD is also known as electrostatic discharge. This happens when the electric current flows and releases every time the 2 things meet, creating friction. This may result in the building up of the static charge. When this happens, the object with a static charge may transfer this to another conductive material. Preventive measures include strictly following the rules when constructing, especially in handling and manufacturing.

Multilayer PCB Fabrication Process

The flex pcb manufacturing process includes the following:

Multilayer PCB Fabrication Process

Multilayer PCB Fabrication Preparation

Result data are transmitted to a PCB manufacturer shortly after finishing the printed circuit board layout and production standards controls. They produce visuals for PCB fabrication and confirm that the layout is in accordance with their procedures. Various manufacturers employ photoplotters or proficient direct photographic processes like lasers and UV contact. An electronic board imprints track, padding, and various steel elements onto the photoresist.

Developing the Multilayer PCB’s Inner Layers

Multilayer PCB’s innermost layers comprise mixtures of epoxy resin and glass filaments center components. The inner layer of laminated material is created using pre-bonded copper. The copper is coated with a luminescent material substance, which causes visible areas to solidify and shield the metallic component. Left uncovered parts have been carved out, but metallic copper remains. The inside layer’s steel electrical wiring is exposed after the solidified luminescent material has been eliminated. Before moving on to the sealing, machines evaluate each successive layer.


To preserve the proper position of the metal wiring, the innermost layers are arranged in rows after being laminated with fiberglass coated with resin. The outside prepregs are coated with a light covering of metallic copper, and the layers are combined by warming and squeezing the PCB sandwich. The copper material has been covered, and holes are made in the layered PCB. The opposite picture reveals light-resistant material and removes malleable luminescent material before adding the top and bottom circuit design. Only the secured circuitry is left after the remaining luminescent material has been eliminated, and any extra metallic copper is cleaned away.

Final Details

A printed circuit board’s last-minute details include marks, exterior finishing touches, lamination, connect mask application, and etching. For precise manufacture, last assessments and evaluations are essential.

Advanced Technologies in Multilayer PCBs

High Speed Design

One of the advanced technologies in multilayer PCB is high-speed design. From the word itself, high speed allows for fast and quick transactions using signals even before the signal reaches its destination. A multilayer PCB design demands an accurate and standardized layout and lining to prevent any blockage and distortion in transmissions and connections.

HDI (High-Density Interconnect) PCBs

This is another advanced technology for multilayer PCB, in which the PCB should contain lightweight structured wiring that can accommodate all its related functions to attain high performance. This is considered an advanced multilayer aspect as it is a smaller and more compact design that can still perform its function tightly.

Multilayer PCB Testing and Inspection

Multilayer PCB Testing and Inspection

Part of the multilayer PCB manufacturing process is the cross-section that checks the constructed inner parts of the PCB to test and check for analyzing malfunctions. This involves cutting, polishing, and evaluating using the microscope to check quality and the proper assembly. After these, the inspection process begins with visual checking using various lighting and camera setup at different angles. Images captured are then compared to the standard multilayer PCB. Other tests include restriction scans, operational tests, and ICT or the in-circuit assessment.


We cannot deny the fact that there are lots of advantages of multilayer PCB, may it be in the industrial sector or electronic sectors. In making and using this type of circuit board, the designer, manufacturer, or fabricator himself must be well familiar with the rules and standard procedures of a multilayer PCB. Using multilayer technology, any device, gadget, or equipment regardless of its size will surely attain its highest performance because multilayer PCBs are made to provide greater capacity and speed for all technology utilized by a vast majority of people.


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