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An introduction about PCB copper foil types

How many electronic devices you have used today? I can bet there are many because we are surrounded by these devices and we are relying on them. Have you ever wondered how wiring and other stuff is connected between these devices? These devices are made of non-conductive materials and have pathways, tracks within then etched by copper that allows the signal flow within a device. So that’s the reason you need to understand what PCB is because this is a way of understanding the working of electrical devices. Usually, PCBs are used in media devices but as the matter of fact, no electric device can work without PCBs. All the electric gadgets, either they are for domestic use or industrial use they are made up of PCBs. All the electric devices get mechanical support from PCB’s design.

Printed Circuit Board Technology

Printed circuit boards (PCBs) are the ones in which conductive pathways like tracks and traces laminated with copper are used to support and connect electronic components mechanically. So basically printed circuits boards are designed to support pathways in electronic devices. For this purpose, material like plastic and fiberglass is used that can hold copper circuitry easily. In PCBs, the copper sheet is laminated in the non-conductive substrate.  We can say that PCB supports the communication between various parts of electrical components because it helps signals to follow the pathways. PCBs are designed in such a way that they can connect several points in electronic devices. For the signal flowing purpose, solders are used for making the connection between electronic devices and PCB surfaces. Solders are also strong mechanical adhesive because of the metal used in them. You can imagine PCB as a cake having many layers. There are different materials like metals, silkscreen, etc that are placed on the substrate in order to make a PCB.

Basic designing of PCB

Do you know that printed circuit boards are very common in the group of electronics? I am pretty much sure one is present in the electronic device you are using right now. However, using these electronic devices without understanding their technology and the designing method is also a common practice. People are using electronic devices every single hour but they don’t know how they work. So here are some main parts of PCB that are mentioned to have a quick understanding of how printed circuit boards work.

  • The printed circuit board is simple plastic boards with the addition of glass. The copper foil is used for tracing the pathways and it allows the flow of charges and signals within the device. Copper traces are the way to provide power to different components of the electrical device. Instead of wires, copper traces guide the flow of charges in PCBs.
  • PCBs can be one layer and two layers also. One layered PCB are the simple ones. They have copper foiling on one side and the other side is the room for the other components.  While on the double-layered PCB, both sides are reserved for copper foiling. Double layered are the complex PCBs having complicated traces for the flow of charges. No copper foils can cross each other. These PCBs are required for heavy electronic devices.
  • There are also two layers of solders and silkscreen on copper PCB. A solder mask is used to distinguish the color of the PCB. There are many colors of PCBs available such as green, purple, red, etc. Solder mask also specifies copper from other metals to understand the connection complexity. While silkscreen is the text part of the PCB, different letters and numbers are written on silkscreen for the user and the engineer.
  • Then comes the components used in PCB. Components play a vital role in the working of PCB because they are the ones responsible for functionality. Different components will be used in different PCBs depending upon the purpose for which PCB is being used. Some common components include resistors, transistors, LEDs, capacitors, batteries, diodes, switches, and inductors.

What is the Role of copper foiling in PCB?

pcb foil

Printed board circuits are made up of many layers and components that include traces, silkscreen, metal layers, and other materials. Traces are the joining components of the PCBs because no charge flow can happen without traces, so we can say that traces act as blood vessels in the PCB’s Skelton, and without traces, no PCB would able to function. And without PCBs, there is no concept of electronic devices.  In the present age, every single device is making use of PCB. And the PCBs rely most on copper as compare to other components because copper helps in making traces. The reason for using copper is its conductivity. The conductivity of copper metal makes sure the slow of signals in the electronic device without interruption. The reason for copper’s high conductivity is the presence of only one electron in its valence shell. This one-electron can easily move from one atom to another without any resistance. That’s why copper can carry electric charges without losing signals.

For making continuous metal foil, copper which is a negative electrolyte is used on the first layer of PCBs. Due to the low level of surface oxygen; copper can be easily used with various types of substrates, metals, and insulating layers. Copper is used with the protective layer to form different circuit patterns after etching because it can easily make bonds with insulating layers of PCB. Copper foil can provide better continuity of electromagnetic shielding that’s why is being placed on the substrate sheet surface.

The base material used in the copper foil of PCB

As mentioned before, you need to see the step-by-step approach for understanding the manufacturing pattern of the printed circuit board. Fabrications of these boards contain different layers. Let’s understand this with the sequence:

Substrate material:

The base foundation over the plastic board enforced with glass is the substrate. A substrate is a dielectric structure of a sheet usually made up of epoxy resins and glass paper. A substrate is designed in such a way that it can meet the requirement for example transition temperature (TG).


As clear from the name, lamination is also a way to get required properties like thermal expansion, shear strength, and transition heat (TG). Lamination is done under high pressure. Lamination and substrate together play a vital role in the flow of electrical charges in the PCB.


Silkscreen the text part of the printed board circuit and applied it to the part of the board. It consists of logos, numbers, letters that are written for hobbyists and engineers to understand the functionality of printed board circuits.

Solder Mask:

Solder masks identify the color of the printed board circuit. Usually, it is designed to be in green but now there are many other colors readily available in the market or you can also order a specific color from your manufacturer. The color of the printed board circuit would not affect its functionality.

Metal foiling:

For the flow of electrical charges, traces and pathways are made in printed board circuits. These traces join the components of the board and help electric charges and signals flow. So metal plays a significant role in the functionality of the board. For this purpose, copper metal is used in traces because of its high conductivity also copper is inexpensive and easily available.

The thickness of copper foil

The greater the thickness of the copper foil in the printed circuit board, the better is the flow of charges. However, etching of the board can be difficult by thick layers of copper foil. Generally, the copper foil thickness is expressed in an ounce. We will distinguish the thickness per unit area of the printed boards. That means one ounce of copper foil will cover one square foot area of the board. Usually, the copper foil thickness in single-sided and double-sided printed boards is 1.4 mil which is 35 µm. 18 µm, 35 µm, 55 µm, and 70µm are the most commonly used thickness of copper foil in printed circuit boards. 

How many layers are fabricated on PCB?

Usually, there are six layers fabricated on printed circuit boards. It is 4 layers PCB in which two additional layers are added for the internal panel. So in six-layered printed boards, 2 layers are for external use, 2 layers are for internal use and the additional 2 layers improve the internal panel of the printed circuit board.

What exactly is PTH PCB?

Plated through holes (PTH) are drilled from top to bottom of the printed circuit board. Holes are used to connecting components in the printed circuit boards. The electrical connection of the soldered is then made through these holes. Plating through holes means you are using both sides of your printed circuit board. The plating done on the copper holes specifies the flow of electric charges in the circuit board. These wholes can be plated or non-plated. In plated through holes, platted copper is present inside the insulating material of the printed circuit board. The copper foil enhances the electric charges flow and mechanical stability of the printed circuit board.