How are Printed Circuit Boards made?
Printed Circuit Boards or PCB for short, is a plastic board that is created for connecting electronic components and parts together. They are commonly used in all types of electronics, from computers to digital clocks. The board itself is not a conductive material and often plastic or fibre glass is used as the base material. The primary use of PCBs is to control where the electricity is directed to.
There are three main types of circuit boards; single-sided, double-sided and multi-layered.
- A single-sided board has the components and parts on one side of the substrate.
- A double-sided board contains more components than the single-sided board and therefore uses both sides of the substrate. Electrical connections between the two sides are made by drilling holes in the appropriate places.
- A multi-layered board consists of a substrate which is made up of multiple layers of printed circuits. These printed circuits are separated by layers of insulation.
Circuit boards can have a variety of parts that are connected and work together. Each board is unique as they have different uses and functions.
Here are the main stages which circuit boards undergo when being created:
The very first step in creating a printed circuit board is the designing of the board. Similar to all manufactured products, circuit boards require a plan. Depending on your requirements for the functions of the board, the PCB designer can create and design a suitable layout using industry Computer Aided Design software. Some of the most popular CAD software includes; Eagle, Altium, and OrCad.
After designing a layout for the PCB, checks will be carried out to ensure that the data meets your manufacturing requirements. Once the data has been verified, the designer outputs the design for fabrication. The PCB fabricator then checks the design to see if it meets the minimum tolerances during the manufacturing process.
This process prepares for the creation of the printed circuit board. Using laser printers, the manufacturer creates negative photo films of the circuit board and components. The final photo is in black ink and each layer of the printed circuit board has their own film sheet. The black areas show where the conductive materials are and the clear areas show where the non-conductive materials are. These are used to show the PCB alignments.
The base material for a circuit board is usually laminate as it is ideal for use with copper. The plastic or fibre glass material of the laminate provides a strong and resistant body for the PCB and the copper is normally pre-bonded on both sides. In the construction stage, cleanliness and hygiene is very important in order to prevent dust from causing short-circuiting. The laminate board is passed through decontamination and gets prepared with a layer of photo resist film. The film is placed over the laminate board with pins that hold the sheet into place. The board is then exposed to UV light which passes through the clear parts of the film to harden the material that is not conductive. The black part of the film protects the UV light from hardening the conductive parts.
After exposure to UV light, the board is washed with an alkaline solution to remove the unhardened film. The board is then dried and a final check is carried out to ensure that no errors have occurred during this process.
The etching process removes unwanted copper from the board. There are several ways to remove copper, but the most commonly used method is by using a strong chemical. The strong chemical then removes the excess copper and you are left with the copper that is protected under the photo resist film.
After the removal of unwanted copper, the board is exposed to another chemical to remove the black areas and leave a shiny finish on the PCB.
This drilling process prepares the components for attachment to the circuit board through drilling precise holes on the board. As the drill bits are very small, a computer is used to control the movement of the drill to ensure accuracy. In high-volume production, automated drilling machines are used to save time. This process can take a while as the average circuit board has more than one hundred points to drill.
In the plating process, the outer layer of the circuit board houses copper connections which cannot be soldered. To make the copper connections suitable for soldering, the surface is plated with gold, nickel or tin. To protect the other areas that should not be soldered, a masking material is used. This masking material is a type of polymer coating which can prevent short-circuiting from traces of solder.
As part of the quality check and assurance, a technician carries out several checks and electrical tests on the printed circuit board. There are several methods of testing the functionality of a PCB and most tests include the use of computer programs to apply small amounts of voltage to each conductive point. This is to check if the circuit board is functioning as expected and if it conforms to the original designs.
In the final stage, the PCB assembling includes the assembly of all electronic parts onto the appropriate holes on the circuit board. There are a few techniques to achieve this such as through-hole assembly and surface-mount assembly. Both techniques share a common aspect and that is the use of soldering to ensure that the component leads are fixed to the board.
Contact Clarydon for PCB Manufacturing & Assembly Services
Clarydon Electronic Services has a wealth of expertise in the design manufacture and supply of circuit boards. If you require printed circuit board manufacturing or assembly, please get in touch with one of our PCB specialists.
Call us on 01902 606 000 or you can email us at [email protected].