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How PCBs are made inside a factory – From Design to Production – Everything you wanted to know

How PCBs are made inside a factory – From Design to Production – Everything you wanted to know

By Electronics Infoline, Sponsored by PCBWay.
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[ Feature Image Courtesy Iniamart, https://www.indiamart.com ]

 

Today’s world is a world of information technology and electronics serves as the backbone for this crucial technology. Without electronic circuits, the existence of computers, mobile phones and other gadgets cannot be imagined.

Thanks to the fast-paced advancements in electronics technology, thousands of different types of electronic devices are available in the market. From household and commercial to industrial and military, these electronic devices can be found in every arena of modern-day life. The circuit designs and functionalities that these devices exhibit are as varied as one can imagine. However, there is one crucial component that can be found in virtually any type of electronic device. That component is the printed circuit board or PCB.

What is a PCB?

As the name suggests, a PCB is a mechanical structure whose primary function is to keep the electronic components fixed in their places and to interconnect them electrically in order to create a functional electronic circuit.

A PCB consists of single or multiple copper layers which are laminated on top of or in between layers of non-conductive material. Different etching and engraving techniques are employed in order to remove the extraneous copper and to create the circuit design pattern. After the creation of design pattern, the components are soldered onto the PCB. The components can either be placed using the through-hole technique or SMT (surface mount technology).

Figure 1: PCB of a Computer Hard Disk

 

PCB manufacturing process

Since PCBs are an essential part of any type of electronic circuit, therefore, they are used by a whole range of circuit designers. From hobbyists and amateurs to commercial and industrial users, PCBs are used by all types of electronics assemblers. Due to this reason, there exist a number of PCB manufacturing processes. From manual and rudimentary processes to sophisticated and highly automated processes, there are a number of methods to manufacture and assemble PCBs.

However, in this article, we are only going to discuss the PCB manufacturing processes followed inside the factories of professional PCB manufacturers such as PCBWay. The processes and methods observed by such professional manufacturers are highly sophisticated and highly automated.

PCB manufacturing is a complex process that involves multiple phases and steps. In the following sections, we will describe each of these steps in comprehensive detail.

PCB designing

The first step in the PCB manufacturing process is that of PCB designing. The PCB design is created by a professional designer using PCB designing software such as Altium. This PCB design serves as the blueprint for the actual finished product.

The PCB designing is usually carried out by the client and the design files are then sent off to the PCB manufacturer for production. The most widely used PCB design file format is the Gerber format. The Gerber file format is an open vector image file format which is the de facto industry standard.

Figure 2: A typical PCB Design Layout. Courtesy: https://www.pcbway.com/project/shareproject/SOLID_SLAVE_RELAY_module_for_using_arduino__ESP__IOT_projects_.html

 

Inspection and DFM review

Once the PCB design files are received by the manufacturer, the second process step of inspection is conducted by engineers. The inspection process consists of DFM (design for manufacturability) review. During this process trace widths, trace spacing, hole sizes, and other design parameters are validated. This is done in order to make sure that the design is error-free and falls within the manufacturing capabilities of the company.

Once the design is validated, multiple instances of the same design are combined in order to be manufactured on a single large panel. In this way, the cost and complexity are reduced and faster production rates are achieved.

Figure 3: PCB panel. Image source:
https://www.pcbway.com/project/shareproject/W69656ASZ2_PANEL_HAND_ON_SOLDER_BOARD.html

 

Cleaning and cutting

Once the design validation and inspection are done the large-sized PCB sheet is thoroughly dry cleaned in order to remove contaminants that can disturb the manufacturing process or PCB quality. The board sheet is then cut into smaller PCB panels which are suitable for manufacturing. The cutting and cleaning of the PCB sheet are done using specialized machines.

Figure 4: PCB sheet cutting machine. Image source: https://longterm01.en.made-in-china.com/product/ZsqnbeDcykhM/China-Automatic-360mm-PCB-Sheet-Cutting-Machine.html

 

 Drilling

Once the bigger PCB sheet is cut into smaller panels, the next process step is drilling holes into these sheets. There are two purposes which drilling serves. The first purpose of drilling is the placement of through-hole components on the board.  The second purpose of drilling is to make connections between various copper layers of the PCB.

For the drilling process, the human operator takes an MDF (medium density fiber) board and fastens the PCB panel to the MDF board. An aluminum sheet is also attached to the board as entry foil so that burr-free drilling is achieved.

Once the sheet is prepared, it is fed into the computer-controlled machine which automatically drills holes into the PCB sheet based on the program. When the drilling process is completed, the sharp edges of the boards are smoothened with a grinder.

Figure 5: PCB with drilled holes. Image source: https://www.pcbway.com/project/shareproject/Dimmer_Arduino_Blu.html



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Electroplating

The different copper layers on a PCB sheet are separated from each other by means of layers of a non-conductive material such as fiberglass. Therefore to establish connections between isolated copper layers, the process of electroplating is carried out.

During the process of electroplating, the panels are immersed in the electrolyte liquid. The copper on the panels acts as the cathode. A number of chemicals are used during this process. The entire process is computer controlled and deposits a thin layer of copper into the drilled holes.

Figure 6: Copper deposition in the hole. Image source: https://www.pcbway.com/blog/PCB_Manufacturing_Information/Detailed_Procedures_of_Plating_Copper_for_PCB_Processing.html

 

Printing

In this process step, the films with printed circuit diagram are aligned on top of the PCB panels. The panels are then sent into the printer with UV lamps. The printer prints the circuit design on the films onto the PCB panels.

After printing the design onto the panels, the panels are treated with a chemical image developer which removes unhardened residues.

Figure 7: PCB printing. Image source: https://www.indiamart.com/proddetail/printed-circuit-board-pcb-printer-20785863691.html

 

Etching

The next process step in PCB manufacturing is etching. The purpose of this process is to remove the unwanted copper from the board using an alkaline agent. After the copper is removed, the panel is washed to be clean of all chemicals.

Automatic optical inspection

After etching, the panels are inspected and scrutinized using automatic optical inspection machines. The purpose of this inspection is to ensure the quality standards to catch any errors which might have occurred during the previous processes. The machine uses computer vision technology to scan the PCB panels and to detect the faults.

Figure 8: Automatic optical inspection unit. Image source: https://www.pcbdirectory.com/community/what-is-automated-optical-inspection

 

Solder masking

The next process step is known as solder masking. During this process, both sides of the PCB panel are coated with epoxy solder masking. The solder mask protects the copper surface and prevents the solder short-circuiting between components. After the application of the solder mask, the PCB panel is dried and baked so that the mask firmly sets in.

Surface treatment

In order to protect the copper of the solder pads from oxidation, surface finishing is performed using a hot air solder leveling method. Other surface treatment methods include HASL, immersion gold, hard gold, and OSP.

Electrical testing

This is one of the final process steps during which all the connections on the board are tested electrically against the original board design. This automated testing method ensures that all the connections are according to the original design and that there exist no open or short circuits on the PCB.

Figure 9: Flying probe e-testing. Image source: https://www.electronicdesign.com/technologies/test-measurement/article/21808377/flying-probe-testing-the-fixtureless-incircuit-test-that-must-be-fixed

 

Milling

This is the final process step which includes the separation of all individual PCBs from the large panel. This process step is carried out by the CNC milling machine. After cutting, the boards are once again washed, cleaned and dried. Now the PCBs are vacuum sealed and bubble wrapped to resist dirt and moisture. These PCBs are now ready to be shipped to the customers after appropriate packaging.

Conclusion

In this article, we have presented a detailed description of the process steps involved in the manufacturing of a professional-grade PCB. PCB manufacturing is a complex process and requires many processes. From design to packaging, all process steps are described in this article.

This article is sponsored by PCBWay.

A leading and cost-effective Printed Circuit Board manufacturing company located in China.

As a professional PCB manufacturer, they can not only produce FR-4 and Aluminum boards, but also advanced PCB like Rogers, HDI, Flexible and Rigid-Flex boards, with a very reasonable price. Online instant quotes are available at – https://www.pcbway.com/orderonline.aspx. Also, PCBWay has its own community for students and electrical enthusiasts; where they share their own projects.

 

 

 

References

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[1] Altium. (2020, January) www.altium.com. [Online]. https://www.altium.com/solution/what-is-a-pcb/
[2] Sunny Patel. (2018, July) www.candorind.co. [Online]. https://www.candorind.com/pcb-manufacturing-process/
[3] SeeedStudio. (2020, January) seeedstudio. [Online]. http://support.seeedstudio.com/knowledgebase/articles/493833-what-is-gerber-file
[4] Maker.io. (2020, January) digikey. [Online]. https://www.digikey.com/en/maker/blogs/2018/how-is-a-pcb-manufactured

[5]  Detailed Procedures of Plating Copper for PCB Processing
https://www.pcbway.com/blog/PCB_Manufacturing_Information/Detailed_Procedures_of_Plating_Copper_for_PCB_Processing.html

 


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