November 2, 2023

What is PCB fabrication? Everything you need to know

PCB fabrication means to develop the boards that contain all the PCB parts and where the PCB assembly takes place. The PCB fabricators are important, and they play a huge role in developing transformational PCBs with their skills. 

It is crucial to note that if the fabrication is not up to the mark, it can damage the structure and efficiency of the printed circuit boards. We are discussing PCB fabrication in detail, which includes beginner-level insights for you. 

So even if you are new to this concept, understanding PCB fabrication will not be hard for you. Let’s get started!

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Comparison Between Assembly Process and PCB Fabrication 

PCB fabrication and PCB assembly both are important during the developmental stages of these boards. However, sometimes, things get confusing and we need to draw a line between these two aspects to have a better idea of them. 

  • Fabrication: This means that we are developing a tangible board to place all the PCB components and traces along with contact points through design. 
  • Assembly: The purpose of this stage is to arrange and bring together all the PCB parts including components, traces, paths, and all the critical add-ons which will breathe life into the PCBs and will make them do their job. 

For more details on the assembly process, check out Basic Things You Should Know About PCB Assembly Process.

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PCB Fabrication Procedure

  1. Design & Layout

Designing is the first step of PCB fabrication. The purpose of designing is to sketch out the details so that fabrication can take place successfully. PCB designers use different software and simulators to develop blueprints for the designs. 

During this stage, the routes, widths, components, and traces need to be carefully considered. Since the fabrication will follow this blueprint, there is no margin of negligence. These blueprints also give rise to the PCB prototypes and there are complex software available for doing this. 

For insights into effective PCB layout design, see How to Design a PCB Layout.

NOTE: PCB designers must discuss software options with their contractors. Since there are multiple options available from Altium to Ki-CAD, it is important to discuss the preferred software along with these features. It will help with analyzing whether the software meets the requirements of PCB blueprints or not. 

  • Pre-Production 

At this point, the clients will submit a document so that engineers can take a look at it and check the quotation. Also, they will check if the documentation is complete and everything is in place or not before proceeding. After all the important checks, they will proceed with the PCB development. 

2. Production Preparation

  • Cut Lamination

The first step is to aim for precise laminating of circuit boards. After that, laminating as per the board size and the panel size as mentioned in the requirements. 

  • Drying

We need to include drying because it is crucial for PCBs to be moisture-free, which can later cause rusting and warping. Drying normally takes place at 150 degree centigrade, and it lasts for four hours. 

  • Imaging

Film will cover the copper board, and it will serve the purpose of housing photo-imaging reactions during this process. 

  • Exposure

It's time to develop the core plate. Besides, the copper skin will come out of the dry film, and the worker will try to keep the dry film intact. Use open & short printed circuit boards for photo imaging. To derive positive results, it is important to work in the optimum environment. Air shower doors are used for this purpose. 

3. Etching

The skin of copper encapsulated via the film is easier to obtain by the line of etching, and the non-encapsulated copper skin will undergo the etching process. It is important to keep the pattern of line intact during the etching to tap into the next stage. 

It's time to restore the film on the copper surface of the board, which will also lead to the quick formation of the pattern of line we want to achieve. 

4. AOI of Inner Layer

We should rely on the AOI method to thoroughly check the plate when the etching has been done with the help of open and short circuits at the time when the etching took place. 

5. Lamination Step

We use an insulating medium called PP that helps with compressing the copper-made foil and makes it penetrate through this medium. This takes place in the middle of the circuit layers. 

6. Drilling Step

Now, the drilling will happen for the laminated circuit plates. The holes do not contain any metal at this point, and due to this reason, we cannot link this layer to the other layers. 

7. Deposition of Copper

A small amount of copper is used to cover the thin layer to allow the reaction of chemicals to take place. A particular length is important to consider about 3 micrometers for this step. 

8. Electrolytic Plating in Horizontal Way

As you know, there is an inclusion of the metal in holes, which means that both the copper amounts that are in the void and the plate will be increased in their widths. This happens due to a reaction called electron transfer. 

9. Imaging

A film is used to cover the copper board so that photo-imaging reactions can take place on the surface of the film. This does not happen like the development of the inner layer that we have discussed. We need to stick to the etching process to keep this copper intact and also we can see the copper deposition that we are going to further work with at this stage. 

10. Plating of Graphics

  • Plating of thick copper

The copper that we need to save for later will be suitable with the copper thickness through the process of plating. The thickness that is recommendable for plating is 25 micrometers. We then plate both the copper amounts together so that it can easily meet the thickness requirements as per the PCB projects. 

  • Tin plating

In this process, we use tin for the shielding of copper foil from environmental damage and the same tin we use will also be merged with the copper’s surface. 

  • Leaving the Film

The next step is to separate and exclude the film from the board’s surface. When we do this, the copper beneath this film will come out. This copper is then removed through the etching process, while the copper we want to save from etching will remain intact due to the tin plating. 

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11. Soldering Mask

Now, we have to use a solder mask for the complete coating of the panels. We use UV rays for this purpose. The solder is beneficial for the deep protection of the PCB circuit system and does not let oxidation take place which can ruin the entire setup. We understand the importance of this step and do not charge you extra for it. 

For more on soldering techniques, see PCB Soldering.

12. Silkscreen Step

It is important when we are fabricating PCBs. It will gather crucial information from the PCB designs and will print it on the boards. After silkscreening, the next step will be to tap into surface finishing and final touches of PCBs. 

13. Finishing of Surface

The benefit of using a surface finish on the PCBs is to make them more durable and extra stable to endure possible damage. These also influence solderability and make the PCBs more sophisticated in their performance. Other than this, there are different options for the surface finish available. 

Common ones are HASL, OSP, and ENIG. The results of all these common surface finishes are different from each other. Only a skilled PCB maker knows the art of handling these surface finishes successfully during their application process. 

14. Finishing Procedure

There are other types of surface finishing methods that are commonly practiced in the industry. These include V-CUT, beveling, and gold finger. 

  • V-CUT Process

Here, we need to cut the panels and shape them for particular sizes and to make this happen, we need to rely on Geber files and the information residing in them for the custom designs. We need to use a groove or a router for this purpose. 

The benefit of using a router is that it will develop small voids along the surface of the PCBs. The role of the groove is to make diagonal cuts on the PCBs sides. We can use either of these methods to take out the boards from their panels smoothly. 

  • Gold Finger

The connection points in PCBs normally involve plugging or unplugging because of the presence of other PCBs. If the contact edge is strong, then there is a chance of breaking, which can lead to complete damage to the electronic device. 

However, if proper plaiting takes place with the combination of gold and other metals, then the connectors will be more durable and strong enough to undergo such damage. 

15. Electrical Testing

By far, you will have your printed circuit board fabrication process almost completed. At this point, inspecting the PCBs through electrical testing is crucial. The role of this testing is to assess the functionality of the fabricated PCBs. Two major tests that take place during this process are isolation and continuity of circuits.

We are using the Probe electrical testing methods to execute a collateral inspection of the PCBs. It also enables us to enhance the efficiency of PCBs and make them more durable in the long run. 

For more on testing methods, refer to Guide to PCB Testing.

16.Final Inspection of Circuit Boards Step

We cannot dispatch and forward the PCBs to our customers without visually inspecting them. There are dedicated teams at the PCB manufacturing companies that carefully visualize these PCBs for defects and errors. From warpage measurement to size inspection and number of holes, visual inspection is crucial and ensures the quality of the PCBs as well. 

For more comprehensive information on PCB manufacturing, visit A Complete Guide to the PCB Manufacturing Process.

17. Package and Delivery

After the inspection stage, the PCBs will be sealed properly to ensure there is no debris, moisture or dirt in the package. Also, careful boxing takes place for dispatching them. Shipping arrangements are crucial to deliver these PCBs to the customers in time. We use shipping services like FedEx and DHL that take around 4 days for delivery. 

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Importance of Understanding the PCB Fabrication 

When it comes to learning about PCB basics, we cannot ignore the PCB fabrication process. Therefore, depth learning is important, and below are some considerations while doing this. 

  • Manufacturability: It depends on the magnitude of the PCB design you are aiming for. The PCB should have sufficient clearing exits so that it will create a positive influence on the coefficient of thermal expansion. This becomes crucial when we use no-lead soldering as well.
  • Yield rate: You need to keep in mind the factors that influence your yield rate. The reason is that, without considering this, you won't be able to receive bulk PCBs without any interruptions to meet your urgent requirements. 
  • Reliability: Your PCBs also need to meet industrial standards so that they can have certified reliability that will give a sense of trust and dependence to your buyers and the same applies to your business partners as well. 

Conclusion

Hopefully, now you are well aware of the PCB fabrication process and know exactly whom to reach out to solve your PCB fabrication problems. We are just a text away to be your one-stop solution for this purpose. Book your sit-in with us today!

Article written by Alice Lee