The usage of PC BOARD is vast in electronic devices, like computers to cell phones, so their construction and design are crucial for proper operation. One of the most important aspects of PCB design is the finish of the board. There are several plating finishes available for PCBs, each of which has its advantages and disadvantages. Here, we will discuss the different types of PCB plating finishes and their various applications.
Electroplating for PCB
When it comes to PCB finish, you will find electroplating at the top. It involves the use of an electric current to deposit a thin layer of metal onto the surface of the board. The metal in this case can be usually gold, silver, or copper.
The thin layer of metal acts as a protective barrier against corrosion and oxidation, and also provides electrical insulation. You can adjust the thickness of the layer to meet specific requirements. Moreover, the metal is easy to deposit in a variety of shapes and sizes.
Immersion Tin Plating
Another PCB plating finish is tin plating which involves the deposition of a thin layer of the tin onto the board. Manufacturers often prefer tin for its low cost, besides, it has excellent corrosion resistance and electrical insulation capabilities. It is also known as white tin and copper is finished with a thin layer of tin. It is an electroless process that involves a chemical bath.
Tin plating is ideal for circuit boards being used in high-temperature environments, such as those found in automotive electronics. Generally, manufacturers use it as a soldering medium, as it is relatively soft and easy to work with.
Another plating finish for PCBs is immersion gold. This technique involves a special electroplating bath that contains gold particles. A PCB Manufacturer will put the board in this bath to attract the gold particles to the surface of the board. This process provides excellent corrosion resistance and electrical insulation. Tin plating makes a circuit board highly reliable. Gold plating is the most expensive but also the most durable. It is used mainly in high-end electronics due to superior corrosion resistance.
There are two ways to use gold, either it is soft gold or hard gold. The soft gold is wire bonded to provide better conductivity and the gold does not vanish during soldering. Soft gold plating involves current so, it is electrolytic.
On the other hand, hard gold plating involves hardeners, and it is also known as deep gold plating because the entire nickel surface is immersed in the plating tank. The process is also electrolytic as soft gold plating.
ENIG- Electroless Nickle Immersion Gold
The name is so because a thin layer of gold is there on the nickel. Before gold, manufacturers apply nickel to copper to prevent gold and copper from mixing into each other. It involves an electroless technique to apply the metallic layer on the board surface without any current. The process depends on the chemical reaction. The application of this process occurs either before soldering or after it. If you plate the entire copper with gold, it will increase the plating cost. The gold gets absorbed while soldering.
ENIG provides a smooth surface for SMD, surface mount devices, and BGA, ball grid arrays. Gold provides excellent electrical conduction.
Hot Air Solder Level-HASL-Plating Finish
This is a simple plating technique that involves molten solder. You have to dip the PCB into the molten tin and lead alloy. It is cheaper than other methods. It covers the copper surface and then you have to level the board with a hot air knife. The HASL provides you with excellent soldering surface and SMT and large parts. Don’t use it for smaller SMT, moreover, it does not suit the FTP (fine pitch technology).
It has a high processing temperature of up to 260-270˚C which can damage the board due to stress. Since it involves lead, it is not a compliant material according to RoHS standards in the U.S. it is not a good option for those who want a lead-free PCB.
Those who want HASL in their PCBs but avoid it due to lead can have lead-free material. The entire soldering process is as HASL excluding lead. Hence, it is compatible with RoHS so it is safer than HASL.
Anodizing for PCB
Anodizing involves the use of an electrolytic solution to deposit a thin layer of metal onto the board. Anodizing provides excellent corrosion resistance and electrical insulation, and it is ideal for boards that require a high level of performance.
Electroless Nickel Plating-ENP
It is the most common plating finish for PCBs and has good corrosion resistance and conductivity properties. It is an economical choice and provides a good bonding surface for components. The plating process involves immersing the board into a bath of salts and acids, which deposits a thin layer of nickel coating onto the board. Then you have to polish the layer to get a mirror-like finish to provide a smooth surface and enhance the electrical properties of the board.
ISP/Immersion Silver Plating
The main purpose of immersion silver is to corrosion in copper and enhance its soldering ability. However, it is not long-lasting like other finishes and should be stored in sheets to avoid tarnishing.
Silver plating provides a smooth surface for SMD, moreover, it is highly conductive. Moreover, it is free from lead and environment-friendly and can bear strong signals. You have to apply immersion silver before soldering but after etching.
OSP or Organic Surface Plating
This technique uses an organic chemical to finish the copper surface. It has a short life, so you should immediately assemble the board after its application. It provides a flat surface for pcb assembly. Moreover, it is free from lead, so it is not toxic to the environment. The process involves a chemical bath that should be applied after other processes.
Each of these different types of plating finishes for PCBs has its advantages and disadvantages, and it is important to choose the one that suits your application.
Things to Consider While PCB Plating
When selecting a plating finish for a PCB, there are several factors to consider. The thickness of the plating layer, the type of metal used, and the environment in which the board will function, all should be considered while selecting the best plating finish for a PCB. For example, if you are going to use the board in a corrosive environment, gold plating may be the best choice.
Whereas, if cost is a major concern, tin plating may be the most suitable option. There are also other considerations when selecting a PCB plating finish. For example, the plating thickness should be considered, as this will affect the performance of the board. The thickness should be sufficient to provide the necessary electrical connection between the components and the board.
Moreover, you should apply the plating evenly to ensure a good electrical connection. Another important consideration is the type of surface finish as it should be compatible with the plating this is because some plating finishes require a certain type of surface finish. For example, gold plating requires a different surface finish than tin plating.
The plating should be compatible with the board components. This is important because some components may not be compatible with certain plating finishes. In these cases, it may be necessary to use a different type of plating.
Frequently Asked Question
What is PCB plating?
To have high-quality PCBs, a variety of plating finishes are there to provide protection from corrosion and wear, and to enhance the electrical conductivity of the board
What Are The Types Of Gold Plating?
There are two ways to use gold plating, either it is soft gold or hard gold. The soft gold is wire bonded to provide better conductivity. The hard gold plating process involves hardeners. Both types involve current.
What To Consider While PCB Plating?
You have to consider the thickness of the plating layer, the type of metal finish, and the environment in which the board will function.
In conclusion, there are several types of PCB plating finishes available, each of which has its advantages and disadvantages. Electroplating, tin plating, immersion gold plating, and anodizing are the four most common types of plating finishes used for PCBs. It is important to choose the type of plating finish that best suits your application, as the wrong choice could lead to poor performance or even failure of the board. Copper plating is also popular, as it provides good electrical conductivity and is relatively low-cost.
Silver plating is also used on PCBs, but it is more expensive than other options and is not as widely used. In addition to these primary finishes, there are a variety of other finishes that can be used to enhance the performance of a PCB. For example, solder masking can be used to protect against accidental soldering. This can be applied as a layer over the primary finish and helps to prevent shorts and other electrical issues.
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