PCB Layers

A PCB board can have a single layer, or it may vary from 1 to 30 layers depending upon the application for which it is designed. GWT is a leading manufacturer of PCBs, which provides PCB boards in 1-30 layers (FR- 4, FR- 406, 370 HR), and in 1- 2 Layers (Rogers, Aluminum/Copper Base, Teflon). There are two main layers on any PCB. They are as follows:

Inner Layers

Also referred to as internal layers in multilayer PCBs, the inner layers can be fabricated with a positive or negative polarity. Sometimes, inner layers employ copper pour technique, which helps a lot in layer-to-layer bonding process. The copper pour helps reduce the etchant during the PCB manufacturing process. The copper weight and thickness is customizable and depends on the application requirements. The weight of copper in the layer determines the minimum trace width and spacing that can be manufactured.

Outer Layers

Outer layers are also known as external copper layers of a printed circuit board. These layers are used to attach electronic components either by surface mounting technique or soldering into the through holes. The outer layer consists of a copper foil, which is electroplated with copper. This is basically done to increase the thickness and add copper to the through-hole barrels. The thickness of the finished copper is customizable depending upon the application requirements.

When it comes to electronic PCB boards, there are a variety you can choose from to cater for the needs of your product, from single-sided PCB boards to multi-layer or even flexible boards. Each of these circuit boards has a different number of layers that contribute to their functionality, making them the right choice for different tasks.

With a multitude of options at your fingertips, it can seem like an overwhelming and confusing choice, but we’re here to make the process simple for you by helping you to understand the basics.

Regardless of which board you decide to go for, each board must have an essential foundation on which it’s built, consisting of different materials which are laminated together. 

Substrate Layer

The substrate layer of any PCB is usually made from fibreglass, which gives the board its rigid form. Generally speaking, the majority of boards will have this material for their substrate, with the exception of flexible PCBs, which are built on flexible plastic such as Kapton. Substrate PCB layers can also be made with other materials such as epoxies, however they lack the durability that FR4 (found in fibreglass) provides for a high quality board. 

Copper Layer

Next is a thin layer of copper foil which is laminated to the board using heat. When we are speaking of different layered PCBs, we are referring to how many copper layers they consist of. If you are creating a single-sided PCB the circuit board has one layer of conducting material on one side of the board and the other side is used for incorporating different electronic components. Whereas double-sided PCBs can mount the conductive copper and components on both sides of the board, as opposed to just the one. These double-sided boards allow for closer routing traces as they can alternate between the top and bottom layers using vias. This can be very useful in many electronic products as the circuits on one side of the board can be connected to the other with the help of holes drilled into it. 

The thickness of the copper layer on your PCB will depend on the power the PCB needs to withstand. PCBs that need to handle very high power throughout may have a thicker copper layer than those that do not.

Soldermask layer

Once the copper layer has been applied the soldermask layer is placed on top. This gives the PCB its green colour and is used to insulate the copper layer to avoid any contact with any other metal or elements of the board that could disrupt the copper traces. This layer is also important for the manufacturing process where the components are soldered onto the board, as it helps the user to solder to the correct places.

Silkscreen layer

The silkscreen is mainly for the purpose of us humans to help us better understand the board and the functionality of different pins or LEDs, by adding letters, numbers and symbols to the board.