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PCB/PCBA knowledge
What Is PCB Plating And What Are The Plating Methods Commonly Used in Manufacturing

PCBs or Printed Circuit Boards are an essential component of almost every electronic device, from smartphones and laptops to home appliances and industrial equipment. The plating of PCBs is an essential process that involves coating the circuit board with a conductive layer of metal to ensure proper electrical conductivity. PCB plating is a critical step in the manufacturing process of these boards, and without it, the boards would not function properly.

In this article, we will delve into the world of PCB plating. We will explore what it is, why it’s important, and what materials are used. We will also discuss the plating process and the different types of PCB plating methods used in manufacturing. We will look at the surface finishes used for PCB plating, and we’ll finish off by exploring the factors that should be considered when plating the PCB.

Table of Contents

What is PCB plating?

PCB plating is a process of coating the copper traces and pads on a PCB with a thin layer of metal to protect it from corrosion and improve its electrical conductivity. The metal is typically deposited onto the copper surfaces of the PCB using an electroplating process.

The most commonly used metal for plating PCBs is gold, but other metals such as silver, nickel, and copper can also be used. The thickness of the plating layer can vary depending on the application and the requirements of the manufacturer.

Why PCB plating should be used?

What are the benefits of PCB plating
What are the benefits of PCB plating

The plating of PCBs is essential to ensure the functionality and reliability of the board. Without plating, the copper traces and pads on the PCB would corrode over time, resulting in a poor connection and eventually causing the board to fail. Plating the PCB also helps to improve the electrical conductivity of the board, which is crucial for its proper functioning.

Moreover, PCB plating also makes the board more durable, protecting it from scratches and other damage that can occur during the manufacturing process or while in use. This increased durability means that the board can be used in harsher environments without fear of damage or failure.

What materials are PCB plating adopted?

There are several different metals that can be used for plating PCBs, each with its unique properties and advantages.

●Gold is the most commonly used metal for PCB plating due to its excellent electrical conductivity, corrosion resistance, and durability. It is also a relatively soft metal, making it easy to work with during the manufacturing process.
●Silver is another popular metal for PCB plating due to its high electrical conductivity, making it ideal for high-frequency applications. However, it is more prone to oxidation than gold, making it less durable over time.
●Nickel is often used as an underplating material due to its excellent adhesion properties. It provides a good base for other metals to be deposited onto, such as gold or silver.
●Copper is also commonly used as an underplating material, as it provides a good surface for subsequent plating layers to adhere to. It is also an excellent conductor of electricity.

What is the PCB plating process?

What is the PCB plating process
What is the PCB plating process

The PCB plating process typically involves several steps, including the following:

Step 1: Cleaning – The first step is to clean the PCB thoroughly to remove any dirt, oil, or other contaminants that may be present on the surface. This is typically done using a chemical cleaning solution.
Step 2: Etching – The next step is to etch the surface of the PCB to remove any unwanted copper. This is done using a chemical solution that removes the copper from the surface of the board, leaving only the copper traces and pads.
Step 3: Pre-dip – Once the PCB has been etched, it is dipped into a pre-dip solution that helps to prepare the surface for plating.
Step 4: Plating – The plating process itself involves electroplating a thin layer of metal onto the copper surfaces of the PCB. The PCB is submerged into an electrolytic solution, and an electrical current is passed through the solution. This causes metal ions in the solution to be attracted to the copper surfaces of the PCB, forming a thin layer of metal.
Step 5: Post-dip – After the plating is complete, the PCB is dipped into a post-dip solution that helps to ensure that the plating layer is fully formed and adheres to the surface of the board.
Step 6: Stripping – In some cases, it may be necessary to remove the plating layer from the PCB, for example, if there is an issue with the plating. This is done using a chemical stripping solution that removes the metal layer from the surface of the board.

What are the types of PCB plating methods for PCB manufacturing?

Methods commonly used in PCB surface plating finishes
Methods commonly used in PCB surface plating finishes

There are several different types of PCB plating methods used in manufacturing, including:

Selective plating – This method involves plating only specific areas of the PCB, rather than the entire surface. This is useful for creating circuits with different layers of metal or for adding additional conductive paths to the board.

Through-hole plating – In this method, metal is plated through the holes in the PCB, connecting the layers of the board together. This method is commonly used in multilayer PCB.

Surface mount technology (SMT) plating – This method involves plating the pads on the surface of the board that is used for attaching components. The plating layer provides a more durable surface for the component to be attached to and also improves the electrical conductivity of the connection.

What are the methods commonly used in PCB surface plating finishes?

There are several different surface finishes used for PCB plating, each with its own properties and advantages:

●Gold plating – Gold is the most commonly used surface finish due to its excellent conductivity and durability. It is also resistant to oxidation, making it ideal for use in harsh environments.

●Electroless nickel immersion gold (ENIG) – This surface finish involves depositing a layer of nickel onto the surface of the board, followed by a layer of gold. The nickel layer provides a good surface for the gold layer to adhere to, and the gold layer provides excellent conductivity and corrosion resistance.

●Tin plating – Tin is a cheaper alternative to gold plating and provides good conductivity and durability. However, it is more prone to oxidation than gold.

●Silver plating – Silver is an excellent conductor of electricity and is commonly used in high-frequency applications. However, it is more prone to oxidation than gold and is less durable over time.

Factors that should be considered when plating the PCB

Several factors should be considered when plating PCBs, including:

1.Thickness – The thickness of the plating layer can affect the performance of the board, with thicker layers providing better conductivity but also increasing the cost and potentially causing issues with component clearance.
2.Adhesion – The plating layer must adhere to the surface of the board properly to ensure proper conductivity and durability.
3.Uniformity – The plating layer should be uniform across the entire surface of the board to ensure proper performance and reliability.

Conclusion

In conclusion, PCB plating is a critical step in the manufacturing process of printed circuit boards. The plating process involves coating the copper surfaces of the board with a thin layer of metal to protect it from corrosion and improve its electrical conductivity. There are several different metals and surface finishes used for PCB plating, each with its own properties and advantages.

When plating PCBs, several factors should be considered, including thickness, adhesion, and uniformity. By understanding the importance of PCB plating and the various methods and surface finishes available, manufacturers can ensure that their PCBs meet the necessary performance and reliability standards.

Overall, PCB plating plays a critical role in the manufacturing of electronic devices and PCBs. Without proper plating, the copper surfaces of the board would be susceptible to corrosion and degradation, leading to performance issues and potentially rendering the device unusable. By using the appropriate plating methods and PCB surface finish, manufacturers can ensure that their PCBs meet the necessary performance and reliability standards and provide optimal performance in a wide range of applications.

FAQ
  • Protect circuit board from oxidation, moisture, and contamination.
  • Reduce the overall cost of printed circuit boards and minimizes downtime.

●Gold plating
●Electroless nickel immersion gold (ENIG)
●Tin plating
●Silver plating

  • Selective plating
  • Through-hole plating
  • Surface mount technology (SMT) plating

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