How Are Circuit Boards Manufactured?

Circuit Boards

When engineers design circuit boards, they first create a schematic diagram. The schematic is a symbolic representation of the electrical connections between the components of a circuit board. This schematic will eventually become the blueprint for the physical components that must be placed on the PCB to make it work as intended. Once the schematic is finalized, a manufacturing plan can be created. Before sending the circuit board to fabrication, it’s important that it passes a Design for Manufacture (DRC) check. The DRC checks for errors that could cause problems later in the process. This prevents costly back-and-forth between the OEM and CM.

Once the DRC check has been passed, it’s time to get the materials ready for the circuit board. The first step involves creating a copper-clad panel. The copper-clad laminate can be a rigid or flex board, depending on the desired thickness and flexibility of the circuit board. A glass-fiber core supports the copper. Aluminum or other metals can also be used.

The copper-clad panels are then impregnated with epoxy resin. This can be done through dipping or spraying. The boards then pass through an oven where they are semicured. The cured substrate material is then cut into large panels for the next steps.

How Are Circuit Boards Manufactured?

In this step, a special type of printer is used to print the circuit board’s pattern onto the substrate. The printed substrate is called a “photoresist.” This photoresist looks similar to a transparency that you might use in school. The outer layer of the circuit board gets a clear ink while the inner layers and solder mask get black ink. The areas that will not be etched are coated with an acid-resistant coating, like tin.

Next, the photoresist is exposed to UV light. This exposes the copper to be etched. The tin-coated copper protects the desired copper from being etched away. The unwanted copper is then removed through a chemical solution. The copper that is left on the bare circuit board is then plated. The plated copper is then covered with a layer of tin to prevent oxidation. The tin-lead layer is then coated with nickel and then gold for superior conductivity.

After the tin-lead and copper plating, the panel is cleaned with solvents to prepare it for soldering. The panels are then sealed with epoxy and any necessary markings or instructions are stencilled onto them. The panels are then drilled with holes for the individual electronic components. A machine called an optical punch then aligns the inner and outer layers of the circuit board through registration holes.

Once the outer layers have been lined up, a layer of solder paste is applied to each component location. Then the components are placed on the circuit board using either surface mount or insertion technology. The smallest components are placed by hand and the rest are robotically placed. The circuit boards are then inspected for any flaws, like missed holes or misplaced components. If any flaws are detected, the board will be re-drilled or re-imaged.

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