A Printed circuit board is incomplete without a surface finish. There are various types of PCB surface finishes. PCBs need to withstand the rigors of various operational environments. Therefore, a printed circuit needs to be coated with surface finishes. The ENIG plating is one of the commonly used surface finishes. This article provides more details on this type of surface finish.
What is ENIG Plating PCB?
The electroless nickel immersion gold (ENIG) is a type of surface finish that features gold over a layer of nickel. ENIG plating helps to protect against corrosion and oxidation. Also, this surface finish is widely used in the industry. This is because it is RoHS compliant. ENIG plating PCB comprises a two-layer coating. Nickel and gold are the two materials used in this type of plating.
The nickel functions as a barrier to the copper pad. Also, it is material on which the manufacturer solders the components. Meanwhile, gold helps to shield the nickel and offers low contact resistance. ENIG plating is also known as immersion gold. One of the benefits of immersion gold is that it can attach both gold and nickel to the copper without electroplating.
Electroless Nickel Immersion Gold plating uses a layer of gold to cover electroless nickel plating. Furthermore, the immersion gold layer serves as a protective barrier that prevents oxidation. One of the several benefits of ENIG plating is prevention of chemical reaction. Therefore, this surface finish is widely preferred among PCB designers.
ENIG plating involves the combination of traditional electroless nickel with a gold layer. Also, this plating can adhere to metal base material like aluminum. The nickel layer in this surface finish makes it ideal. Also, nickel is suitable for lead-free soldering process.
ENIG plating PCB applies gold through quick immersion. Also, electroless nickel immersion gold enig applies the principle of displacement. Also, this plating uses displacement of the surface atoms to apply a thin layer of gold. ENIG plating helps to increase the shelf life of parts in need of pcb soldering operations. Also, it offers excellent electrical performance.
ENIG Plating PCB Process
Surface preparation
The PCB surface must be very clean before plating occurs. Also, this surface must be free of any dirt. The first process of immersion gold plating is surface preparation. This includes stripping or polishing of the PCB surface. This process involves the use of water or any abrasive material.
Micro etching
This process involves removing the roughness of the copper plate. This step helps to improve the building force of the electroplated layers and the copper surfaces. Also, it improves the quality of the PCB.
Immersion gold activation
This step involves the use of parameters for copper plating. It is possible to regulate the nickel layer’s thickness. The manufacturer dips the nickel-plated pad in gold water. You can then displace the gold from the solution. The last step is to remove the dirt on the pad surface.
Advantages of ENIG Plating PCB
There are several advantages of using ENIG plating which include:
Good oxidation resistance
Experienced PCB manufacturers prefer surface finishes that can resist oxidation. Immersion gold plating PCB provides great oxidation resistance. Also, this type of PCB surface finish comprises an electroless nickel plating covered with immersion gold. The gold layer prevents the nickel from oxidizing. Therefore, ENIG plating ensures a printed circuit is corrosion resistant.
High temperature resistance
This is a significant advantage of immersion gold plating. Most printed circuit boards used in medical and military applications function under high-temperature. Therefore, ENIG plating is an ideal PCB surface finish option in such applications. Also, ENIG is advisable since it withstands high temperatures. An ENIG plating features great thermal diffusion properties. Also, this plating is resistant to extremely high temperatures.
Lead free
Lead is toxic to both humans and their environment. Exposure to high levels of lead can cause health issues. ENIG plating features no lead. Also, this means that PCB manufacturers are not exposed to toxic substances. Therefore, ENIG plating PCB is commonly used in the electronics industry.
Ideal for untreated surfaces
Protecting the untreated surfaces that oxidize immediately is very important. This exercise might be complex depending on the type of surface finish used. ENIG plating is suitable across untreated areas like membrane switches and contact points. Also, immersion gold offers excellent surface planarity.Therefore, this makes it suitable compared to other surface finishes.
RoHS compliance
The RoHS is a directive that bans the use of about 10 most toxic substances when producing electronic devices. ENIG plating meets all RoHS requirements. This is one of the reasons PCB designers prefer to use this surface finish.
Disadvantages of ENIG Plating PCB
Despite its advantages, ENIG plating has some limitations. Some of these limitations include:
Black pad
This is an unwanted formation that occurs in ENIG plating PCB. Also, it is a result of leakage of sulfur-based substance in the solder mask. The formation of black pad can lead to electrical isolation. This is because black pad can’t transmit electrical charge. Furthermore, black pads can cause cracks on the PCB surface. Therefore, this can disrupt evenness and good solderability.
Weak soldering joints
Inadequate wetting can weaken solder joints. Furthermore, this can result in a weak connection within the printed circuit board. Inadequate wetting can result in electrical continuity failure.
Very expensive
Electroless nickel immersion gold plating is highly priced. This PCB surface finish is more expensive than other PCB surface finishes. Also, it is pricier than HASL and OSP. ENIG plating makes use of expensive materials like gold. Also, this surface finish type is not reworkable. Therefore, the cost of plating with ENIG is very high.
Signal loss
Electroless nickel immersion gold can experience signal loss when utilized for a long time. Therefore, this can affect the overall performance of your PCB.
Conclusion
Circuit boards play a vital role in the functioning of electronic devices. There are different types of surface finishes available for PCB plating. ENIG plating is an ideal choice for your PCB assembly. Also, this type of surface finish is ideal for use across applications that require corrosion resistance.
We have discussed the immersion gold plating in this article. Therefore, we have reviewed the advantages and limitations of using this surface finish.
