Detailed Process of Printed Circuit Board (PCB) Manufacturing

Detailed Process of Printed Circuit Board (PCB) Manufacturing

1. Design and Layout The PCB manufacturing process begins with the design and layout of the circuit board. Engineers use specialized software, such as Altium Designer or Eagle, to create a detailed schematic and layout for the PCB. This design includes the arrangement of components, routing of electrical connections, and specifications for the board layers.

2. Design Verification Once the design is complete, it undergoes a verification process to ensure that all electrical connections and component placements are correct. This may involve design rule checks (DRC) and electrical rule checks (ERC) to identify any potential issues before proceeding to production.

3. PCB Fabrication

• a. Printing the PCB Design The PCB design is printed onto a film or directly onto the PCB laminate using a photoplotter. This film will be used to create the circuit patterns on the PCB.

• b. Preparing the Substrate The substrate material, usually a fiberglass-epoxy composite known as FR4, is cut into the desired board size. This substrate will be coated with a layer of copper, which will later form the circuit traces.

• c. Applying Photoresist A photosensitive layer known as photoresist is applied to the copper-coated substrate. This layer is sensitive to ultraviolet (UV) light.

• d. Exposing the Photoresist The PCB substrate, with the photoresist layer, is exposed to UV light through the film that contains the PCB design. The UV light hardens the photoresist in areas where it is exposed.

• e. Developing the Photoresist After exposure, the board is developed in a chemical solution that removes the unexposed photoresist, leaving behind a hardened pattern that protects the copper underneath.

• f. Etching The board is then subjected to an etching process where an acidic solution removes the unprotected copper, leaving behind the desired circuit traces.

• g. Stripping the Photoresist The remaining photoresist is stripped away, revealing the clean copper traces that form the circuit pathways.

4. Drilling and Plating

• a. Drilling Holes for through-hole components and vias are drilled into the PCB using a drill press or laser drilling machine.

• b. Plating The drilled holes are then plated with a thin layer of copper to connect the different layers of the PCB. This is done through an electroplating process where copper is deposited onto the inner walls of the holes.

5. Lamination (For Multi-layer PCBs)

• a. Layer Stacking For multi-layer PCBs, various layers of circuit patterns and insulating material are stacked together. The layers are then bonded using heat and pressure in a lamination press to form a single, solid board.

6. Solder Mask Application

• a. Applying Solder Mask A solder mask, which is a protective coating, is applied to the PCB surface to prevent solder from bridging between traces and causing short circuits. The solder mask is typically green but can be other colors as well.

• b. Curing The solder mask is cured using UV light or heat to harden the coating.

7. Silkscreen Printing

• a. Adding Legends A silkscreen layer is applied to the PCB to print text, symbols, and component outlines. This layer helps in identifying components and connections on the board.

8. Surface Finish

• a. Applying Surface Finish To protect exposed copper and improve solderability, a surface finish is applied. Common finishes include HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel Immersion Gold), and OSP (Organic Solderability Preservative).

9. Testing and Inspection

• a. Electrical Testing The PCB undergoes electrical testing, including automated optical inspection (AOI) and flying probe testing, to ensure that there are no short circuits or open connections.

• b. Visual Inspection A final visual inspection is carried out to check for any physical defects or inconsistencies.

10. Cutting and Packaging

• a. Cutting The finished PCBs are cut from the panel into individual boards or specific sizes as required.

• b. Packaging The PCBs are then packaged for shipping, ensuring that they are protected from damage during transit.