Guide

What Are PCB Layers and How Are They Produced?

What Are PCB Layers

One of the basic and necessary elements, without which no electronic project can be created, is certainly a printed circuit board (PCB). Therefore, it is necessary to get to know them somewhat more broadly, as PCBs are known to consist of several layers compressed to end up with a single board that performs a specific task. Below we will learn about these layers in general.

PCB contain some circuits and electronic components that are connected through tracks printed on this board. These paths are created through the layers that make up the PCB. So, what we want to clarify here is what are these PCB layers and what are their functions.

PCB Layers Stackup

What Are PCB Layers?

In general, there are five types of PCB layers, which are as follows:

1. Copper Layer

It is the base layer of the PCB, which contains copper foil. Through it, the components that make up the panel communicate through paths printed on this layer. In other words, it transmits electrical signals between components. So copper layers are critical in all PCB layers.
One of the factors that affect the durability and reliability of the board is the weight of the copper layer, and this certainly varies depending on the type of electronic product. The more power and functionality required, the heavier the copper layer and vice versa.

2. Substrate Layer (Base Material)

It is the layer that gives PCBs a strong and durable appearance so that the board becomes firm and stable to place electronic items on. It is also used to separate copper layers from each other. They are usually made of fiberglass, for example, RF-4, and there are also plastics to produce a flexible board, as well as epoxies, but this results in a weak and not durable board. Therefore, we find that most of what is used for this layer in PCBs is fiberglass, to obtain a stronger and more durable board, to support all the PCB layers.

3. Solder Mask Layer

It is the layer that works to isolate the copper layer and protect it from corrosion or any damage to the copper layer, thus preventing the board from stopping working. We find that the solder mask layer consists of a layer of epoxy ink, which is usually green in colour, and this is what usually gives the board its green colour.

4. Silkscreen (Screen Printing) Layer

This layer, specifically, is placed after the solder mask layer. It contains everything that helps to understand the board, explains component parameters and functions, also shows the dimensions of the elements and other things that can help in correctly placing the elements on the PCBs. The name of the painting designer is also printed on it, or any logo, for example, belonging to the designing company is placed on it, using epoxy ink to print This information, which is usually white.

5. Surface Finish Layer

The surface finish layer is a very thin metal or organic layer on the pads of printed circuit boards. It is used to protect the pads from oxidation, and also it is helpful in the PCB assembly process. So it is very important in all the PCB Layers. The commonly used PCB surface finish types are HAL (Hot Air Leveling), ENIG, immersion tin, immersion silver, OSP, ENEPIG, and hard gold plating. We can choose different kinds of surface finish according to the design, usage, shelf life and other requirements.

PCB Solder Mask and Silkscreen Layers

How Are PCB Layers Produced?

Hence, these PCB layers represent the basic structure of the circuit board. Depending on the increase or decrease in the number of these layers that make up the PCB, we can divide the PCB into single-layer, double-layer layers and multi-layer. Below we will explain what single-layer, double-layer and multi-layer are and how they are produced.

1. How are Single Layer PCBs Produced?

Of course, in the initial design of PCB, it is known as a single layer and is also called single-sided. From this name we can appreciate how it is produced, as the production process is carried out by placing a layer of the substrate, which is the base material, on top of it is a layer of copper, and then the solder mask. All of these PCB layers are from one side of the board.

Single Layer PCB

Single layers PCBs are produced by the following process:

  • Base Material Cutting
  • NPTH Holes Drilling
  • Copper Trace Imaging and Etching
  • Solder Mask Printing
  • Silkscreen Printing
  • Surface Treatment
  • Outline Cutting or Punching
  • E-testing
  • Quality Inspection

Despite its simplicity, we find that it is used in the manufacture of many household electronic devices, and it was relied upon primarily in all initial designs of simple and uncomplicated products.it is low cost so that a large number of them can be produced at a low price, its circuit design is simple and uncomplicated, and modifications or redesigns can be made to it easily.

2. How are Double Layers PCBs Produced?

However, we find that single-layer PCBs are very limited in designs and products, and to expand further in the field of design, what is known as double-layer PCBs were produced. It is originally single-layer, but consists of a layer of substrate, two layers of copper covering the substrate layer, and finally a solder mask layer on the top and bottom of the PCB layers. Thus, it became possible to expand the design field to some extent and produce electronic devices with more uses, certainly while maintaining the advantage of ease of design and speed of production.

Double Layers PCB

Double layers PCBs are produced by the following process:

  • Base Material Cutting
  • Holes Drilling
  • Copper Plating
  • Copper Trace Imaging and Etching
  • Solder Mask Printing
  • Silkscreen Printing
  • Surface Treatment
  • Outline Cutting
  • E-testing
  • Quality Inspection

But with the remarkable development in the field of electronic device manufacturing, the need has become for more sophisticated, flexible, fast, small-sized, and high-capacity systems. However, the use of single or even double PCBs did not help in creating such modern designs, so it was necessary to increase the layers of PCBs in general. Hence the need for multiple layers in PCB.

3. How are Multiple Layers PCBs Produced?

When we say multilayer, it means more than two copper layers, so it can be said that multilayer PCBs have four layers or more. Multilayer PCBs have changed many concepts in industries in the field of electronics in general. They made it possible to make smaller, faster devices while maintaining device efficiency and reliability. Therefore, we find that it is used in all advanced and smart industries. Naturally, these devices need many components and the digital circuits that make them up, which is what multiple layers, a small footprint and more components allow for.

Multilayer PCBs are produced by having a number of double layers stacked together, i.e. they have many layers of substrate and many layers of copper, which are bonded together and pressed using heat and adhesives and then coated with a layer of solder mask on the top and bottom. The number of layers varies according to the functional requirements of the device or product to be designed. It is obvious that multilayer PCBs have more PCB layers. The number of layers typically ranges from 4 to 32 or more for more complex devices.

Multilayer PCB

Multilayer PCBs are produced by the following process:

  • Inner Layer Copper Trace Imaging and Etching
  • Lamination and Pressing
  • Production Panell Cutting
  • Holes Drilling
  • Copper Plating
  • Copper Trace Imaging and Etching
  • Solder Mask Printing
  • Silkscreen Printing
  • Surface Treatment
  • Outline Cutting
  • E-testing
  • Quality Inspection

Although multilayering allows for scalability in electronics, it is more complex, cost-intensive, and time-consuming in the production process. But it is certain that multilayers, which represent the basic technology in modern electronic manufacturing, cannot be dispensed with.

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