PCB Technical - Introduction to PCB production process

1: thin film generation

All copper and solder mask films are made of photo-exposed polyester film. These movies are generated from the design files, creating an accurate (1:1) movie representation of the design. When submitting Gerber files, each individual Gerber file represents one layer of the PCB board.

2: choose materials

Industry standard 1.6mm thick FR-4 laminated copper clad on both sides. The size of the panel will fit multiple circuit boards.

3: drilling

The through holes needed to create the PCB design come from the submitted files, using NC drills and carbide drills.

4: electroless copper

In order for the vias to be electrically connected to different layers of the PCB, a thin copper layer is chemically deposited in the vias. This copper will then be thickened by electrolytic copper plating (step 6).

5: Application of photoresist and image

In order to transfer the PCBdesign from the electronic CAD data to the physical circuit board, a photosensitive photoresist is first applied to the panel to cover the entire circuit board area. Then the copper layer film image (step 1) is placed on the board, and the high-intensity UV light source exposes the uncovered part of the photoresist. Then chemically develop the circuit board (remove the unexposed photoresist from the panel), forming pads and traces.

6: pattern board

This step is an electrochemical process that establishes copper thickness in the holes and on the surface of the PCB. Once the copper thickness is formed in the circuit and the hole, an additional layer of tin is plated on the exposed surface. This tin will protect the copper plating during the etching process (step 7) and will then be removed.

7: etching

This process is carried out in multiple steps. The first is the chemical removal (stripping) of the photoresist from the panel. The newly exposed copper is then chemically removed (etched) from the panel. The tin applied in step 6 protects the required copper circuits from being etched. At this point, the basic circuit of the PCB is defined. Finally, the tin protection layer is chemically removed (stripped) to expose the copper circuit.

8: welding mask

Next, coat the entire panel with a liquid solder mask. The use of thin film and high-intensity UV light (similar to step 5) exposes the solderable area of the PCB. The main function of the solder mask is to protect most copper circuits from oxidation, damage and corrosion, and to keep the circuits isolated during the assembly process.

9: Screen printing

Next, print the reference marks, logos and other information contained in the electronic file onto the panel. This process is very similar to the inkjet printing process, but specifically for PCB design

10: Surface treatment

Finally, the surface finish is then applied to the panel. This surface treatment (tin/lead solder or immersion silver, gold plating) is used to protect the copper (solderable surface) from oxidation and is soldered to the PCB position as a component.

11: Manufacturing

Last, but not least, use NC equipment to route the perimeter of the PCB from the larger panel.