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PCB Manufacturing Process: How Are PCBs made?

PCB manufacturing process involves many different steps. These, including what happens in each step of the process, are outlined in this explainer article. This will give you an overview of the entire process and a better understanding of how each stage affects the quality of your final product, especially if you’re considering ordering one.

What is a PCB circuit Board?

A PCB, which is the short form for printed circuit board, is an electronic circuit board which consists of a substrate material, copper circuitry, and other components that are used to connect and control electrical signals or power.

The PCB board holds these components in place and enables them to work together. These include small electrical components such as resistors, capacitors, inductors, and transistors and bigger components such as integrated circuits (ICs) and microprocessors.

PCBs are produced in an intensive manufacturing process that involves many steps. This also remains the most important part of PCB making, as it will determine the functionality and lifespan of the board. Below, we take a look at what happens manufacturing a PCB.

PCB design using PCB design software
PCB design using PCB design software
Resource: https://www.youtube.com/watch?v=2b1UdOmxVrw

PCB Manufacturing Process Step By Step

In this step by step guide, we’ll discuss the typical PCB manufacturing process and how each stage plays a role in producing a high-quality product. We’ll also be discussing some of the different processes available for the PCB production process.

Step 1: PCB Design

PCB design refers to the process of creating representation of the PCB. An engineer or engineers uses CAD software to create a design which includes the wiring and component layout, as well as all other necessary components for the board. The design phase generally involves the following:

  • PCB Schematic diagram
  • PCB Layout drawing
  • PCB components planning
  • PCB routing
  • Designing circuit board
  • Exporting PCB Gerber file

Step 2: PCB Printing

Once the design has been uploaded to the manufacturer’s system, the next stage involves printing. This is the first stage of actual PCB manufacturing. The events that will take place during this step are as follows:

  • A “negative” image of the PCB design is printed on a thin film
  • Black ink is used to represent the copper traces and clear ink the other non-conductive areas
  • The outer layers are the opposite of this: clear ink for the copper traces and black ink for the non-conductive areas
  • The thin film is then used to create a photoresist mask which will be placed over the PCB panel.
  • This mask will become the guide for the etching process that follows
  • Next, the board is exposed to a beam of UV light
  • This causes the polymer on the photoresist mask to harden and become insoluble, but only where the ink is clear. This reproduces the circuitry layout onto the PCB copper layer
  • The PCB is now ready for etching

Step 3: PCB Etching

Etching is one of the most important steps in the process of manufacturing PCBs. It involves exposing the copper layer to a chemical solution, which removes any copper that is not part of the design. Here is what happens in this step of the PCB etching process.

  • The PCB board that has photo resistive mask applied is immersed in a chemical solution.
  • The chemical reaction removes the unwanted copper from the board, leaving only the desired traces and pathways behind.
  • Once this process is complete, the remaining copper will be cleaned to remove any residue or contaminants.
  • Now, the PCB has the desired copper traces and pathways ad can move to the next stage of the process.

Step 4: PCB Layer Alignment and Bonding

PCB layer alignment involves ensuring that all layers of the board are properly aligned and ready to be laminated together. This is done by using a specialized machine called an optical punch.

  • The machine uses a light beam and a pin to align the layers accurately.
  • Using an optical inspection machine (AOI), the board is checked for any defects or discrepancies.
  • This machine checks the board against the original CAD design to identify any issues that need to be corrected.
  • Once the alignment and inspection is complete, the layers can be bonded together

Step 5: PCB drilling

The board will now go through the drilling process. PCB drilling is done to make the necessary holes for mounting components and passing through wires or connecting successive layers. This part of the PCB manufacturing process requires great accuracy and precision, as errors can cause huge loses:

  • X-ray equipment is used to pinpoint the exact locations of the holes.
  • A special CNC drilling machine is then employed to drill these points
  • The registration holes the first to be drilled, since these act as guiding holes to secure the board.
  • Once the PCB holes have been drilled, any excess material is removed to ensure a clean board for the next stage.

Step 6: PCB Plating

The PCB plating process is used to cover the exposed holes on the PCB with a conductive layer of copper. This is done so current can easily travel through the board without any issues. The PCB plating process involves submerging the board in an array of chemical baths.

  • The PCB board is thoroughly cleaned
  • Next, the board is immersed in successive chemical bath
  • These deposit the copper layer on the board.
  • This is usually a computer-controlled process to ensure accuracy and consistency
  • Finally, the board is rinsed in water to remove any residues of the chemicals used.

Step 7: PCB Outer Layer Printing and Etching

In order to create the outer PCB layer, the etching process is employed. Etching involves using a chemical solution to remove unwanted copper on the board, leaving behind the desired traces and pathways.

  • The PCB panel is coated with a photo-resist film that has been printed with the desired design.
  • The board is then exposed to ultraviolet light
  • This causes the photo-resist to harden in the areas that must not dissolve
  • The board is then immersed in a chemical bath
  • This will etch away the unwanted copper traces

Step 8: PCB Solder Mask

Once all of the above PCB manufacturing steps have been completed, it’s time to apply the solder mask. This is a thin layer of protective coating that is applied to the board. The PCB solder mask helps protect the exposed copper traces from any damage and corrosion, as well as providing insulation between components.

  • The PCB is cleaned to remove any residues
  • The board is then coated with a liquid solder mask, usually either green or blue in color.
  • To point out areas that will be soldered, small apertures are opened in the solder mask
  • The PCB is then cured in an oven to ensure it is firmly adhered to the board.

Step 9: PCB Silk Screen Printing

PCB silk screen printing involves applying a thin layer of ink onto the board to label components and pathways, making it easier to read during the inspection process. The layer also prints the company’s logo, warnings, and so on.

  • A special ink jet printer is used
  • The design to be printed is then loaded onto the printer
  • The silk screen can be applied with a single color, or multiple colors depending on the design of the PCB.

Step 10: PCB Finishing

Depending on the customer preference, the PCB manufacturer will apply a surface finish. Mostly, the PCB finishing type will depend on the design and end-use application. Cost and reliability also come into play when selecting the surface finish. Options for PCB finishing include:

  • Immersion silver
  • HASL (Hot Air Solder Leveling
  • ENIG (Electroless Nickel Immersion Gold),
  • OSP (Organic Solderability Preservative)
  • ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold)
  • Immersion tin
  • Gold

The board also undergoes various profiling or shaping steps before the completion of the production process. This includes routing and V-scoring or both.

Step 11: PCB Quality Check

During the PCB quality check, the manufacturer conducts a series of inspections and tests. PCB inspection is aimed at ensuring that the board meets all design requirements, including specifications and tolerances.

PCB testing, on the other hand, is used to measure the performance of the board. Essentially, the board is checked using both manual and automated techniques and equipment.

Overall, the manufacturer uses the quality check step to ensure various PCB standards are met, both in-house and external quality standards.

Step 12: PCB Packaging

Finally, the finished and tested PCBs are packaged. PCB packaging involves the use of appropriate materials such as antistatic bags, bubble wraps and boxes to ensure that boards are securely protected during shipment.

That’s it! This is what goes on behind the scenes to make sure your design for manufacturing PCB boards becomes a reality.

Note that, in addition to the PCB manufacturing service, some companies also assemble the PCBs with components, depending on the customer requirements. This process follows all the previous steps but includes additional steps such as component placement and soldering.

Conclusion

PCBs are the lifeblood of modern electronics. The intricate process of the PCB manufacturing process ensures that your device works as expected, offering years of reliable performance. Having an in-depth understanding of the process helps you to ensure that your PCB design is optimized for manufacturing, increasing the chances of success.

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