Multi-layer PCB – benefits, applications, and differences from other PCB types

Multi-layer PCB is smartly packed, thin and small printed circuit board, having multiple layers of copper traces and planes on each side of the board. This type of PCB is used for power distribution as it allows for more efficient routing of power voltages between different parts of the board.
If you want to know more about multi-layer PCBs, their benefits/drawbacks, applications, and differences, this article is for you!

What is multi-layer PCB?

Multi-layer PCB is a way of stacking up multiple layers of copper to create a more dense and stable circuit board.

By looking into it we found, it consists of multiple layers of copper foil laminated onto the substrate. This is done so that it provides a more reliable connection between the chips and components on the board.

Based on the intact structure that makes it durable and powerful to use in electronic circuits, it can also be used in other fields like medical devices, transportation systems, and industrial equipment.

Constitution of multi-layer PCB

The structure of multi-layer PCB seems a bit more complex than the rest of PCB types. But in actuality, it is pretty understandable.

To enhance electrical conductivity, the layers in a multi-layer PCB are usually made of copper in a repeated way. Fibreglass, paper, or plastic insulating layers separate these copper layers, however, other insulating types can also be used

It is possible to have any number of layers (above 3) in a multi-layer PCB, but the most common type has four or six layers. Typically, four layers are used on a PCB: two for power and two for signal. In a six-layer PCB, four layers are used for power and signal, and two layers are used for ground.

These different models of multi-layer PCB make it suitable for different, heavy-duty tasks in electric circuits, described in the applications section below in this article.

Comparisons among single-layer PCB, double-layer PCB, and multi-layer PCB

Difference in Features	Single-layer PCB	Double-layer PCB	Multi-layer PCB
Composition:	A copper-based conductive material usually made up of a single layer	Two layers of conductive material should be present	There are three or more layers on a multi-layer PCB
Thickness:	Generally thicker than double- and multi-layer PCBs	Thinner than single-layer PCBs but thicker than multi-layer PCBs	Thinnest of the three types because they have the most layers packed into a small area
Effectivity:	Least effective at handling high-density and high-speed circuits	Offer more routing space and are more effective	Gives most routing space and is the most effective at handling high-density and high-speed circuits
Usage:	Used in simple circuits or circuits with low density and low-speed requirements	Used in more complex circuits with higher density and speed requirements	Used in the most complex and demanding circuits
Cost:	Generally the least expensive to manufacture because they have the fewest layers	More expensive to manufacture than single-layer PCBs	Most expensive to manufacture because they have the most layers and require the most material and labor

Upsides and downsides of multi-layer PCB

• List of upsides of multi-layer PCB

1. Can be used to reduce the heat generated by signal traces.
2. Highly resistant to corrosion than other types of PCB.
3. Can be printed using more complex designs than other types of boards, allowing for more complex circuitry designs.
4.  Less prone to failure caused by moisture or temperature extremes.
5. High-frequency attenuation, high-speed signal transmission, and low inductance.

• List of downsides of multi-layer PCB:

1. The cost of manufacturing is higher.
2. Speed of assembly is slower.
3. Weight of the boards is more than single-layer PCBs.
4. Number of layers can decrease signal quality and performance, increasing production costs.

Applications of multi-layer PCB

• Polarization

It is used to create circuits with specific electrical characteristics, such as a specific polarity or voltage level, by separating the layers and using them as electrical planes.

• Electrical isolation

It electrically isolates different circuit elements from each other by using insulating layers between the conductive layers. This is useful to prevent electrical interference and improve the overall performance of the circuit.

• Safety and security applications

It’s being used in alarm systems and surveillance cameras, to protect against tampering and improve the reliability of the system.

• Protection against mechanical damage

Protect circuit elements from mechanical damage by enclosing them within the PCB layers. This can help improve the overall durability and reliability of the device.

Manufacturing process multi-layer PCB

Step 1: Layout and design of a PCB sheet

Using computer-aided design (CAD) software, the layout and design of the PCB are created and verified for accuracy and manufacturability.

Step 2: PCB sheet manufacturing

Then comes the photolithographic process, where a photomask with the desired circuit pattern is transferred onto a photosensitive material on the PCB substrate.

Step 3: Burn-in process of the substrate

Next, it is heated to a high temperature in order to harden and strengthen the material.

Step 4: Fabrication of the circuit layer

The circuit layer is then fabricated by applying a layer of conductive material, such as copper, to the surface of the substrate and etching away the excess to create the desired circuit pattern.

Step 5: Burn-in process of the circuit layer

It is done as it helps to ensure the integrity and reliability of the connections between the various components on the PCB.

Step 6: Assembly

Finally, the various components, such as capacitors, resistors, and integrated circuits, are placed onto the PCB and soldered into place to complete the assembly.

Possible problems in multi-layer PCB manufacturing and solutions

1. Solder mask delaminates from the copper layer underneath it,

Solution: Use more flux when applying the solder mask to ensure good adhesion, apply heat slowly, and use a non-hardening flux.

2. Flux can be applied too heavily and cause solder balls to form on the surface of the board

Solution: Reduce flux strength or switch to a low-melting point flux (such as lead-free solder) to prevent solder balls from forming on your boards.

Keep these factors in mind in manufacturing multi-layer PCBs

• The PCB layer count: The lower the number, the better will be the board design.
• The copper thickness: Thinner copper results in less resistance and heat buildup, but it also means you’ll have to use more expensive equipment to make your board.
• Your design criteria: Depending on your application, you may need different specifications for a multi-layer PCB than a traditional single-layer PCB.