Many electronic devices use printed circuit boards. Your smartphone, tablet, laptop, and coffeemaker all have printed circuit boards (PCB). When you go to the hospital, the heart-rate monitor and CAT scan both use PCBs. In addition, several other electronics, including residential lighting, manufacturing equipment, and other telecommunication devices, all have PCBs. They are sometimes referred to as the āmotherboardā and are the central hub of the components that allow the device to function.
Schematics Design
Every printed circuit board is unique and serves its purpose. Therefore, they are each individually designed using computer software. An engineer draws the schematics for the PCB using a computer-aided design system. It allows the designer to create a unique layout for this specific PCB. Next, the design is printed with a plotted printer, which creates a film that lays out all the specific layers and details; the exact size of the PCB.
What Materials Are Used?
Printed circuit boards use a combination of materials. The first is the fiberglass base, on which all the other components are attached. Engineers use an epoxy resin to help achieve the correct thickness for that specific PCB. The resin will also help keep the rest of the components in place once they are applied to the fiberglass board.
- Copper – All of the essential layers of the PCB are made with copper foil. It is the element that carries a charge, allowing electricity to flow through the board.
- Coating – Layers of tin-lead, nickel, and gold are used to protect the copper from acid. The process is called plating. These materials are sometimes used separately or all together.
- Epoxy – Used at various stages of the manufacturing process. In the beginning, epoxy resin is used as a base on which the circuit components are attached. In subsequent stages, epoxy is used to protect the components from being damaged. It is applied through dipping or spraying.
- Other Materials – The other materials used to manufacture a PCB include resistors, capacitors, transistors, and circuit chips.
How are Circuit Boards Printed?
1. Substrate – The board itself, otherwise known as the substrate, is cut from a fiberglass roll. Depending on how it will be used, it is either rigid or flexible. A designer applies the first layer of epoxy resin, and the board is sent through an oven to cure.
2. Drilling – Once the board is cured, a machine drills several holes into the substrate to create a specific pattern, according to the design. They are plated with copper to help charges flow from one side of the board to the next.
3. Adhesive-backed copper foil is added onto the surface of the board in the pattern laid out in the design. Next, a photo-sensitive film is placed on top, and ultraviolet light hardens and secures the layers together. Tin-lead, nickel, or gold is placed on top of the copper foil to protect it from exposure to acid.
4. Contact fingers are attached to the edges of the substrate, which attach to the printed circuit board. They are also plated with tin-lead, nickel, and gold.
5. The components are sealed with another layer of epoxy resin, which allows the remaining components to be securely mounted onto the board. In addition to the epoxy, solder paste is also applied at specific points.
6. Finally, all the remaining components are soldered onto the board, and the board is cleaned if an excess residue leftover from the manufacturing process. The PCB is then tested and packaged.