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Complete Explanation for PCB Fabrication Process

Simon / 2021-03-07

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PCB is the cornerstone of all the main electronic components. It is an inexplicable technology that has been embraced in all computational or electronic devices ranging from simple devices such as calculators and digital clocks to more complex devices like home theaters, computers, TVs, cars, among others. Usually, the quality of PCB used on any electronic device will determine workability and performance. For instance, if you purchase a device with a board that is poorly manufactured, you will have a hard time repairing mechanical damages and/or faults. This means you will not fully enjoy the device you bought. Alternatively, investing in a PCB board that has passed through the right manufacturing process should be the ultimate goal.


If you fail to pay close attention to the construction quality of the board, then the PCB manufacturing process will be influenced. These can be premature problems in the field or manufacturing of low-yield boards. Luckily, some methods can be employed to help ease these costly and time-consuming contingencies, which is by design actions. Before getting into design action, let's first start by understanding what the overall PCB fabrication process entails.


pcb fabrication process


What is the PCB Fabrication Process?


It can be unethical to just jump into defining the fabrication process without comprehending the terms employed in the whole process and their interrelationships.


PCB development


This entails the process of introducing the design of the board from the circuit design directly to the production. It usually encompasses 3 processes namely manufacturing, design, and testing. It is also the simplest design that helps you achieve quality results.


PCB manufacturing


This entails making the board design. Typically, it is a two-approach process that starts with the fabrication of the board and finally the assembly of the PCB, better known as PCBA.


PCB testing


This is better perceived to be bringing up. It is the third process in the development of the PCB. It is carried out after the manufacturing process. Testing the board while in the development stage helps to determine the ability of the board to handle the operational functionality that it was accustomed to. At this stage, sections and errors in the board are identified to help resolve and enhance the performance.


PCB assembly


Better referred to as PCBA, the assembly of the PCB is the second stage or step in the manufacturing process. Here the components of the board are mounted on the board via the soldering process.

That said; let's understand what the fabrication process entails.


PCB fabrication process is any procedure or technique that is done on the board to change the design of the circuit board into a physical structure depending on the details given in the package. In other words, the board's layers are aligned in line with particular patterns to enable it to be employed in electronic manufacturing. For this to be successful, the following techniques or actions must be adhered.


  • Removing or etching excess copper

  • Developing the layer of PCB by laminating the materials of the board at extreme temperatures.

  • Drilling holes to enable mounting of the components

  • Plating via and pinholes

  • Including a solder masking or safe surface coating

  • Including polarity indicators

  • Silkscreen printing


Why We Need to Understand PCB Fabrication Process


Many individuals don't find it worth comprehending the whole process of PCB fabrication. Their argument is that the fabrication process isn't a design task but is an outsourced task conducted by the manufacturer. Despite being a complicated task, the PCB fabrication process is one of the best activities to consider knowing. Remember, if you understand the process, you will be able to make the right choice of layout, trace parameters, types, materials, via locations, and other essential board aspects. Here are the reasons to consider understanding the whole process.


Manufacturability


This aspect relies on the design options. These encompass maintaining enough space between the board's edge and surface elements. The material chosen must have pretty enough CTE (coefficient of thermal expansion to help hold PCBA, particularly when employing no-lead soldering.


Rate of yield


In most cases, you can have a well-fabricated board but find issues on the overall outcomes. For instance, pinpointing components that extend the workable boundary of the CM's components can lead to the production of many unusable boards.


Reliability


IPC-6011 is used to categorize the boards depending on their usage. For solid PCB, these boards are grouped into three levels. These levels must offer particular components to help the board construction to meet the reliability level of performance. Ensuring that the board is constructed to achieve a lower categorization than your plea needs will probably lead to premature failures and/or inconsistent operations.


These are just a few reasons for understanding the PCB fabrication process. They actually exhibit the kind of issues that you may have if the right fabrication decisions are not considered when designing. This means that having an idea of this process will help avoid any kind of issue that may arise.


PCB Fabrication Process Guide Step by Step


Despite being minute, the overall process of manufacturing is somewhat expensive. If you are considering making these boards for the first time, the ultimate thing is to first visit the board shop or manufacturers and learn the basics. This will help avoid making errors in the designing phase. Regrettably, most firms outsource these boards, making the process of learning to be unpractical. For that reason, we have developed a comprehensive step-by-step guide to help you best understand the whole PCB fabrication process. Here are the steps that must be considered.


1. Designing


Prior to starting to manufacture the boards, you must have the right design in mind. This will act as the ground of the overall process. Normally, the design process is finalized via computer software. Employing a trace width calculator can be essential with many of the information required for external and internal layers.

After the design is accepted for production, the manufacturer takes the design into support. Extensive examination of the design is done to make sure that it is in line with the minimum requirements.


2. Printing


A unique printer referred to as the plotted printer is employed to help print the board's design. The printing comes up with a film that exhibits the layers and information of the board. After printing is done, two ink colors will be employed inside the board's layer. One-color will be clear to portray a non-conductive section whereas the black color will exhibit the conductive circuits and copper traces. Similarly, this will happen on the outer layers; however, the concept will be reversed.


3. Developing the substrate


At this stage, the PCB board will begin forming. The insulating components, which in this case are the substrate (glass fiber and epoxy) that accommodates the structural elements, start to be created via taking the components to an oven for semi-curing. Pre-bonding of copper is done on both of its sides. Etching follows to exhibits the PCB design from the films that are printed.


4. Printing of the inner layers


Inner layers must be printed to help laminate the design and the overall structure of the body. There will be the utilization of the photo-sensitive film that is made from high-quality photo-reactive components to help make the layer harder when UV light is used. This is essential, especially when aligning the real print and blueprints of the PCB board. What follows is drilling the holes onto the board to assist in aligning the overall fabrication process.


5. UV light


When aligning is complete, the laminate and the resist are taken under the UV light to make it harder. The UV light shows the areas covered by copper. The black color or ink employed on the initial stage assist in avoiding the hardening of sections that will later be removed. Washing of the board is done using an alkaline solution to help get rid of extra photoresist.


6. Getting rid of unwanted copper


At this stage, any unnecessary copper must be removed from the PCB board. You can employ an alkaline solution. It is a powerful chemical solution that consumes excess copper on the board. There is a copper solvent solution that can still be used to eat all the excess and exposed copper on the board. After removing the excess copper, the ideal copper is left fully hardened and protected on the photoresist layer.


Basically, boards are not the same; thus, they require a different amount of solvent when removing the unnecessary copper. This means that heavier copper boards will need extra attention and solution for space tracking compared to the lighter counterparts.


7. Inspection


After ensuring that the layer is perfectly clean, there must be an inspection, especially for alignment. The previously drilled holes are used to align the outer and the inner layers. There is a tool called an optical punch machine that is used to drill a pin via the holes to ensure the layers are in line. Additionally, there is another machine employed in inspecting the PCB board, which helps to monitor defects or issues. After inspecting, it will be easier to note and rectify any fault or missed error.


8. Layer lamination


When the layers start connecting, it will be easier to notice the shape of the board. The layers will be connected by the metal clamps when the process of lamination starts. Epoxy resin, also known as the prepreg layer will go in line with the alignment basin. The next thing is the substrate layer connecting to the Epoxy resin. Other layers follow, including the prepreg resin and copper foil. Finally, no other copper layer is used and this is where the press plate comes into play.


9. Pressing


The layers undergo a mechanical press. Pressing is done to help keep the pins tightly secured and aligned together. You can remove these pins but this will rely on the technology utilized. If properly done, the board will be taken to the press lamination machine, where there are pressure and heat. This makes the epoxy resin melt.


10. Drilling


At this stage, the drilling of the holes is done by the use of a computerized drill to help uncover the inner panels and the substrate. This is also where the extra copper is removed.


11. Plating


Plating the board is easily done at this stage. You can use a chemical solvent to combine with every layer of the board. A thorough cleaning of the board is done using powerful chemical compounds. The powerful chemical solvents also safeguard the panel.


12. Imaging of the outer layer


A similar photoresist layer used in stage 3 is used to the outer surface layer prior to taking it for imaging. UV light is employed to further make the photoresist harder. If there is an unwanted or unnecessary photoresist, it is cleaned or removed.


13. Plating


Further plating on the panel is done by the use of a thin layer of copper. Alternatively, a thin tin protector is used to layer the board. Using tin is essential to safeguarding the outer layer of copper from experiencing etching.


14. Etching


Here, a powerful chemical solvent used on other stages is used to get rid of unnecessary copper on the layer of resin. The tin protector layer safeguards the required copper. This is where PCB connections are fully established.


15. Applying solder mask


Cleaning of the panel must be done prior to considering solder masking. Usually, a solder mask film is employed to layer the epoxy. This is actually the green color found on the PCB board. UV light is used to get rid of any unnecessary solder mask.


16. Silkscreening process


This is an essential step because it counts on what is to be printed on the board. When silkscreening is done, the board is taken to the final process.


17. Finishing


Plating of the PCB board is done using a solderable finish. This typically relies on the need of the board. This is critical, especially when boosting the solder bond/quality.


18. Testing


Prior to assuming your PCB board is fully complete, the manufacturer and/or technician must consider testing it. This is vital, especially when confirming the functionality and performance of the board.


Conclusion


As evidenced from the above information, the PCB manufacturing process entails a lot of steps. These steps can be challenging, especially to the novice that is why it is recommended to first visit the manufacturer or dealers to give insights into the right information. The good news is that following this guide can be a ground for comprehending the process and knowing why you need to keep this process at your fingerprint.