introduction to printed circuit board fabrication processes

The manufacturing process of printed circuit boards is to transform the designed circuit diagrams into actual boards through a series of steps, making it convenient for the installation and connection of electronic components.

Printing Circuit Board Patterns

Print the completed circuit board layout onto transfer paper. Make sure the glossy side of the transfer paper faces up during printing. It is generally recommended to print several copies on a single sheet so that you can choose the one with the best quality for later use.

Cutting the Copper-Clad Board

Copper-clad board refers to a circuit board material with copper foil on both sides. Cut the copper-clad board to the desired size according to the actual needs of the circuit board, avoiding material waste as much as possible.

Pretreating the Copper-Clad Board

Use fine sandpaper to thoroughly remove the oxide layer from the surface of the copper-clad board. The treated board should be shiny and free of obvious stains, which helps the toner adhere firmly to the copper surface during transfer.

Transferring Circuit Board Patterns

Cut the printed circuit pattern to the appropriate size and place the side with the pattern tightly against the prepared copper-clad board. Align them and place the copper-clad board into a heat transfer machine preheated to 160-200°C. Usually, 2-3 transfers are enough to make the pattern adhere firmly. Take care to avoid burns during the operation.

Repairing and Etching the Circuit Board

After transfer, check if the pattern is complete. use a black oil-based pen to touch up any missing parts. Then place the board into an etching solution, typically made by mixing concentrated hydrochloric acid, hydrogen peroxide, and water in a 1:2:3 ratio. Always add water first, then the other chemicals, and take precautions to avoid contact with skin or clothes. Remove the board and wash it thoroughly with water once the exposed copper is fully etched away.

Drilling the Circuit Board

To install electronic components, drill holes in the appropriate locations on the board. Choose the drill bit size according to the thickness of the component leads. Secure the board and maintain a moderate drilling speed to ensure quality.

Surface Treatment of the Circuit Board

After drilling, use fine sandpaper to remove toner (or powder) from the board, then wash it thoroughly with water. Once dry, evenly apply rosin solution to the side with the circuit to improve soldering quality. A hot air gun can be used to help the rosin set in 2-3 minutes.

Layout Design and Selection

• Single-sided Board: Suitable for low-cost and simple circuit designs. Jumper wires can be used if necessary. If too many jumper wires are needed, consider using a double-sided board.
• Double-sided Board: Double-sided boards can be made with or without PTH (plated through holes). PTH is more expensive and is used when circuits are complex or dense. Try to minimize traces on the component side, and use PTH holes mainly for electrical connections, not for mounting components. Reduce the number of holes to save cost and increase reliability.
• Ratio of Component Area to Board Area: When choosing between single- or double-sided boards, consider the ratio of component area (C) to total board area (S) for proper layout and assembly. “US” usually refers to the area of one side of the board. Refer to design manuals for typical S:C ratios.

Safety Precautions

Throughout the entire process, high temperatures, strong corrosive chemicals, and machine operation are involved, so always take protective measures to ensure safety.