How to carry out the PCB manufacturing process step by step?

Table of Contents

Step 1: Schematic and Circuit Layout Design

Circuit design before PCB manufacturing

Before embarking on the manufacturing of a printed circuit board, meticulous planning and circuit design are essential to incorporate the desired functionality into the project. The PCB design process typically starts with creating a schematic diagram that outlines the electrical connections and optimal component placement required for the board. This schematic is then translated into a PCB layout, completing the design process. To ensure a seamless and efficient workflow, choosing the right PCB design software is crucial. Popular options like Altium, KiCad, and Eagle are commonly utilized by designers.

Beyond hardware considerations, adherence to industry rules and guidelines is of utmost importance. Strictly following industry standards guarantees the quality, performance, and reliability of the manufactured PCB. These guidelines encompass aspects such as design rules, manufacturing tolerances, and material specifications.

Step 2: Design Review

Design Review in PCB Production

Once the design is completed, it undergoes a thorough review process. In this step, professional engineers and designers conduct a detailed study of the design to identify any defects or errors. The purpose of this review is to ensure that the design meets all the necessary requirements and specifications.

If any faults or discrepancies are found during the review, the engineers refine the design according to the specific needs of the project. This iterative process continues until the design is deemed to be accurate and compliant with the project requirements.

Step 3: Printing Process

Printing process in PCB board production

Once the design is finalized and reviewed, the next step involves generating the PCB artwork. This process involves transferring the digital board design onto a physical medium, which serves as a template for the subsequent manufacturing phases. To achieve this, high-resolution printing technology is employed.

The PCB artwork is printed using a printer with precise output capabilities. It is crucial to ensure that the printer accurately reproduces the intricate details and precise traces of the board design. The choice of printing technique depends on various factors, including the complexity of the design, the level of accuracy required, and the manufacturing capabilities.

The most commonly used techniques for the PCB printing process are inkjet printing, laser printing, and photolithography. Each method offers distinct advantages and is chosen based on the specific requirements of the circuit design and manufacturing process. By using advanced printing techniques, the PCB artwork is accurately rendered, laying the foundation for the subsequent stages of PCB fabrication.

Step 4: Inner Layer Copper Printing

Inner layer copper printing in PCB production process

After printing the board design on film or paper, the next crucial step is to create conductive paths called traces on the inner layers of the board. This is achieved by applying a thin layer of copper using a specialized technique known as copper deposition. The copper layers facilitate the transmission of signals on the board, enabling its functionality.

The copper printing process involves two main steps. Firstly, the surface is prepared for copper deposition by cleaning and treating the internal layers to ensure proper adhesion and conductivity. Once the board surface is prepared, the copper is applied using various techniques.

One commonly used method is screen printing, where a stencil is utilized for selective copper deposition on specific areas of the board. Alternatively, an inkjet printer can accurately deposit copper on the internal layers, providing precise control over the copper distribution. After the copper is applied, the board is dried to ensure a strong bond between the copper layer and the board surface.

Step 5: Inner Layer Etching

 

Inner Layer Etching in Production PCBs

During this step, PCB is immersed in the etchant, and the chemical reaction between the etchant and the copper causes the unwanted copper to be etched away. The areas that are protected by the printed circuit design, including the copper traces, resist the etching process and remain intact.

Etching is a crucial step in the circuit board manufacturing process as it defines the final copper traces on the board, ensuring that the correct conductive paths are formed. Careful control and precision are essential during this stage to achieve the desired circuit pattern and maintain the integrity of the board’s design. Once the etching process is complete, the board is thoroughly rinsed and inspected to ensure that all excess copper has been removed, leaving behind clean and accurate copper traces.

Step 6: Align Layers

Align Layers in circuit board manufacturing

After the etch process is complete, each inner layer is placed in its designated location within the PCB stackup, and this stage focuses on aligning the copper traces and vias on each layer, making sure they correspond correctly to create the desired electrical connections and signal paths.

Step 7: AOI Inspection

AOI Inspection in Printed Circuit Board Manufacturing

For ensuring manufacturing process quality and accuracy, Automated Optical Inspection (AOI) is conducted. This step utilizes advanced instruments and computer algorithms to scan the board for various errors and defects. AOI employs high-resolution cameras and imaging algorithms to capture detailed images of the PCB. These images are then analyzed to detect any defects or deviations from the required design and feature specifications.

Step 8: Lamination

Lamination in circuit boards manufacturing

During the lamination process, multiple layers of the PCB are bonded together to create a single, uniform structure. Specialized lamination presses are utilized for this process. Heat and pressure are applied to the stack of board layers, fusing them into a solid and cohesive structure. A resin material called prepreg, which acts as an insulator, is present between the copper layers.

As the heat is applied, the prepreg softens and flows, ensuring accurate adhesion among the layers. The pressure applied during lamination eliminates any air pockets or voids that may have formed during the layer stacking process. As a result, a robust and durable board structure is created, characterized by firmly bonded layers. Lamination plays a vital role in providing the PCB with structural integrity, stability, and rigidity.

Step 9: Drilling Process

Drilling process when manufacturing circuit boards

After lamination, the next step is to drill holes into the PCB. These holes serve various functions, such as accommodating components and providing interconnections between different layers of the board. Specialized drilling machines equipped with high-speed rotary drill bits are used for this purpose. The drill bits used in the printed circuit board production process are made from materials like tungsten carbide, ensuring precise and accurate drilling.

The drilling process follows the predefined details provided by the board design. The drill bits penetrate the board and create holes at specific points determined by the footprints of components and the interconnection requirements. The size of the holes may vary based on the components being connected and certain design considerations. Proper drilling is crucial to ensure the proper assembly and functionality of the PCB.

Step 10: Plated Through Hole

Plated Through Hole PCB Board Manufacturing

After drilling, the drilled holes and exposed surfaces undergo a plating process to enhance conductivity and durability. This plating technique involves the deposition of thin layers of copper onto the drilled holes and exposed copper surfaces. The plating serves multiple purposes, including improving the board’s performance and preventing corrosion.

Through the PTH process, the drilled holes are coated with copper, creating conductive paths called vias that allow for electrical connections between different layers of the PCB.

Step 11: External Layer Imaging

Imaging of outer layers to manufacture printed circuit boards

During this step, the external layer of the PCB undergoes imaging. A photosensitive material called photoresist is applied to the board, and the board’s design acts as a mask. 

The imaging process starts by placing the board and the mask, which contains the desired design, in contact with each other. The board is then exposed to UV light, causing the photoresist to react and become hardened in areas that correspond to the design on the mask.

After the exposure, the board is developed, which involves removing the unexposed photoresist, leaving only the hardened photoresist on the desired areas. The remaining photoresist acts as a protective layer during subsequent processes such as etching.

Step 12: External Layer Etching

Outer Layer Etching in Printed Circuit Board Manufacturing Process

In this step, the external layer of the PCB undergoes etching to remove the unwanted copper. The hardened photoresist acts as a protective layer, ensuring that only the required copper traces are left behind.

Step 13: External Layer AOI

There is AOI inspection is done like earlier performed for an external layer of the board. It checks the accuracy of the etching process and makes sure that the boards are according to the required features.

Step 14: Solder Mask Application

Solder Mask in Bare PCB Manufacturing

To protect the copper traces and prevent unintended electrical connections, a solder mask is applied to the board. The solder mask is a thin protective coating applied to the entire surface of the PCB, except for the areas where components will be soldered. The solder mask serves several essential purposes: Electrical Insulation, Corrosion Prevention, Solder Bridging Prevention, Component Alignment and Aesthetic Appeal.

The solder mask material is typically a liquid epoxy-based polymer, which is screen printed onto the board and then cured to form a durable protective layer. The color of the solder mask can vary, with green being the most common, but other colors are also used for identification or customization.

Step 15: Silkscreen Application

Screen printing application in bare PCB manufacturing process

During the application of the solder mask, a PCB silkscreen is also added to the board. The silkscreen is a layer that includes labels, symbols, markings, component details, and other pertinent information for troubleshooting and assembly purposes. It is printed on both the upper and lower surfaces of the board.

The silkscreen serves as a valuable guide for engineers during board assembly, aiding them in identifying specific components, connections, testing points, and other relevant data. It enhances the board’s readability and provides a clear view of the circuitry.

To create the silkscreen, specialized ink or paint is used, which is applied to the board through a stencil or mask with open areas corresponding to the required silkscreen markings. This technique ensures precise and accurate placement of the silk screen information on the board.

Step 16: Surface Finishing

Surface Finishing in PCB fabrication process

After the silk screen is applied, the board undergoes the finishing process, which involves the application of surface finishes tailored to specific board requirements. There are several surface finish options available, each serving different purposes:

  • Electroless Nickel Immersion Gold: This popular surface finish provides excellent solderability and corrosion resistance. It consists of an electroless nickel layer followed by a thin layer of immersion gold.
  • Hot Air Solder Leveling: HASL involves immersing the board in molten solder and then using hot air to level the solder, creating a smooth and flat solder coating. While it is a cost-effective option, it may not be suitable for fine-pitch components due to its relatively coarse surface.
  • Immersion Tin: This surface finish involves immersing the board in a tin bath, depositing a thin layer of tin on the copper surface. Immersion tin provides a flat surface and good solderability, making it suitable for SMT assembly and fine-pitch components.

Step 17: Electrical Reliability Testing

Electrical Reliability Testing in Printed Circuit Board fabrication

The electrical reliability test is a crucial step in assessing the board’s electrical characteristics and ensuring its compliance with specifications. These tests are instrumental in identifying various faults, such as open circuits, short circuits, and signal transmission quality issues.

There are several techniques used for electrical reliability testing:

  • Continuity Testing: This technique checks the integrity of electrical connections to ensure there are no breaks or discontinuities in the conductive paths.
  • Resistance Testing: In this test, the resistance value of components and trace paths is measured. Deviations from the required resistance values can indicate damaged components or connection faults.
  • Impedance Testing: Evaluate the impedance characteristics of specific signal paths or transmission lines on the board, ensuring optimal signal transmission.
  • Signal Integrity Testing: High-frequency signals are applied to the board to check for signal distortion or reflections that may affect circuit function.
  • Power Testing: Testing validates the voltage levels, current, and stability of power provided to the board, ensuring that all components receive the required power without issues.
  • Functional Testing: Examines the overall functionality of the board by applying input stimuli and analyzing the corresponding output responses. These tests verify that the board operates as intended according to the design requirements and project specifications.

Step 17: Profiling and Route Out

During this step, the excess material on the board is removed, and the board is shaped to its final dimensions. The profiling process involves cutting the board into the required shape. An accurate milling or routing machine is used to remove the unwanted parts of the board and create the defined outline. Profiling ensures that the board fits accurately in the required assembly.

Rout out is a process used to separate individual circuit boards from a larger panel. The panel contains multiple PCBs that are divided into separate boards. This is achieved by cutting predefined routes or V-grooves to separate each board from the panel. Precision and accuracy are crucial during rout out and profiling to ensure that the resulting board has clean edges and meets the proper dimensions.

Step 18: Quality Check and Visual Inspection

Quality inspection in pcb board fabrication

Now is the time to perform quality checks and visual inspections to ensure that the boards are manufactured according to the required standards and specifications.

  • Visual Inspection: Highly skilled engineers and technicians carefully examine the boards under proper lighting conditions to detect any visible defects such as cracks, soldering issues, scratches, or improper component connections.
  • Dimensional and Mechanical Checks: To verify the board’s dimensions, hole sizes, and component placements in accordance with the designs, various measurements are taken.
  • Environmental Testing: In certain cases, environmental tests are conducted on the board to evaluate its performance under different temperature conditions, vibrations, and humidity levels.

Step 19: Packaging and Delivery

Packaging manufactured PCB

Finally, the finished PCB boards are carefully packed to ensure protection from any damage during storage and transportation. This packaging process safeguards the boards and prepares them for safe delivery to the customers, who can then use them for their respective projects and applications.

Related Articles:

How to DIY design PCB layout by yourself?

How Are Inner Layers of PCB Manufactured

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