How do multi-layer PCB work?

What is multi-layer PCB？

Basically, it refers to a circuit board that is printed and has a lot of conductive layers. It is expected that it should have a minimum of three conductive layers. Unlike a double-sided PCB, multilayer PCB is more complex. It has its upper and lower layers more the same as a double-sided PCB but has more layers on either (both) sides of the core. The layers here are connected with copper plates with fitted holes. You can have as many layers as up to 40.

PCB manufacturing process

The manufacturing process requires a lot of precautions. This is because there could be many chances of overlaps, cross connections, and in copper are tracing. The environment in which the whole procedure takes place or rather where it is carried out should be a clean room and an ESD safe environment. And of course, you’ll need to have some special equipment for a multi layered manufacturing process.

To start off, you need to design the PCB layout using any of the designing software, could be eagle, Proteus etc.
The next process is making of the core of the inner lamination to the desired thickness which is done with dry film, copper foil and ultra Violet light.
After lamination, inner layer core, copper foil and prepreg sheets are stuck together under high temperature and pressure to form the inner layer.
Conductors are encapsulated with resins to ensure that no air is trapped within the layers. Adhesives that are used to keep the layers intact are properly cured and melted.
The pressure and heat used here come from a hydraulic press. Depending on the number of layers needed, you’ll at least need to hours for the process above.
The next step is to again use resins to join the foil, sheets and core together thereby coming up with a multi-layer PCB.

Why we need multi-layer PCB？

They can be used with several professional devices for instance computers, heart monitors, mobile phones and so forth. Multi-layer PCB fabrication entails laminating a lot of conductive layers depending on what requirements the application needs. The more the layers the more the wiring and circuitry. The versatility of these PCBs makes them be used widely with many devices.

Benefits of using multi layered PCB

Increased functionality and capabilities- more layers allow for more wiring and circuitry within a board. This can automatically increase the efficiency, capabilities and functionality of circuit board that’s been printed.
Can be designed in small sizes- the stacking of layers together can really save space as it permits high capacities for smaller footprints. This is mostly important with very small devices.
Can be made flexible or rigid- depending on what are client needs, it can be molded to be either flexible or rigid. However more layers make it less flexible and more rigid.
Lightweight- The multi-layer combination makes it easy to get rid of the need to use a connector from a separate PCB. This generally simplifies the whole process as it does not only make it less heavy but also saves on space.
High quality-the extra amount of energy and time invested in designing this type of PCB results in a better quality compared to single and double layered PCBs.
More durable- Due to its many layers, they are designed in a way that they can not only withstand their weight but also the pressure and heat beneath the layers. This feature alone makes them durable.

Disadvantages of a multi-layer PCB

Increased functionality and capabilities- more layers allow for more wiring and circuitry within a board. This can automatically increase the efficiency, capabilities and functionality of circuit board that’s been printed.
Can be designed in small sizes- the stacking of layers together can really save space as it permits high capacities for smaller footprints. This is mostly important with very small devices.
Can be made flexible or rigid- depending on what are client needs, it can be molded to be either flexible or rigid. However more layers make it less flexible and more rigid.
Lightweight- The multi-layer combination makes it easy to get rid of the need to use a connector from a separate PCB. This generally simplifies the whole process as it does not only make it less heavy but also saves on space.
High quality-the extra amount of energy and time invested in designing this type of PCB results in a better quality compared to single and double layered PCBs.
More durable- Due to its many layers, they are designed in a way that they can not only withstand their weight but also the pressure and heat beneath the layers. This feature alone makes them durable.

Uses of a multi-layer PCB

Computer electronics- mother boards and servers rely on multi layered PCBs for their impressive functionality and small size.
Telecommunications- satellite application and signal transmission are some of the application whose device need a multi layered PCB.
Medical devices- medical devices such as heart monitors greatly rely on multi layered PCBs due to their efficient functionality, light weight and small size.
Consumer electronics- most consumer electronics include smartphones, smart watches, microwaves and so on. These devices mostly rely on multi-layer PCB die to their efficient functionality.

Military and defense- The circuits of multi layered PCBs have a high speed and are of a light weight. Their perfect functionality and durability increase their priority with military applications.
Aerospace- Jets and rockets use multi-layer PCB because they are of a light weight and also flexible. On top of that multi-layer PCB are designed in a way that they can resist heat.
Automotive- Electric cars use multi layered PCBs due to their high functioning and heat resistant nature
Industrial- most industrial activities require rough handling and this due to its durability, multi layered PCBs are preferred for such. Their small size is also an added advantage for them to be used to run in industrial manufacturing process.

Improved technology innovation calls for increase in the number of multi layered PCBs in almost all companies. A multi-layer flex PCB is a type of multi-layer PCB that combines single or double layered PCBs.