What is ENIG PCB?

Electroless Nickel Immersion Gold, or ENIG for short, is a surface finish frequently used in producing printed circuit boards. There are several phases involved in this detailed and thorough operation. The ENIG PCB surface finishing technique has several advantages and is essential to top-quality PCB manufacturing. It guarantees the best possible component performance and durability, which qualifies the components for various electronic applications. The fundamental concept behind this procedure is to improve the effectiveness of the PCB by adding protective layers to it. This post will teach us more about ENIG surface finish, its significance, and much more.  

Importance of the Process

Enig printed circuit board coating or surface finishing is vital for various reasons. It enhances the circuit board’s durability and levels out the surface, which aids in more controlled part placement, for instance. Some of the main reasons include the following: 

Suitability for Multi-process Integration Assembly: The ENIG surface finish suits various assembling methods for diverse applications and manufacturing processes. Advanced construction procedures utilized in electronics manufacturing can benefit from the product’s compatibility with different soldering methods.

Dependability and Soldering Capability: Improving the printed circuit board’s capability for soldering is the fundamental goal of ENIG pcb finish. The gold coating can sell Electrical parts on a stable layer. A durable substrate that maintains its solderability throughout time is guaranteed by gold’s neutral and non-oxidizing nature. Providing dependable and uniform solder junctions during manufacturing procedures depends on this feature for parts with tiny contact surfaces or precise spacing.

The ability to resist corrosion: The outstanding durability against corrosion associated with ENIG surface finishing serves another important function. Even under extremely demanding circumstances, gold has greatly resisted oxidation and corroding. By acting as an obstacle, the submerging gold coating keeps the copper lines and the underpinning nickel coating from oxidation. The PCB’s dependability over time and performance under various working circumstances are guaranteed by its ability to withstand corrosion.

Phases of Enig surface finish process 

The comprehensive procedure of creating a PCB finish enig consists of several precise steps. The main steps include the following: 

1. Organizing and Setting Up: Preparing the PCB panel, usually composed of copper, is the first step in enig plating. The copper surface is meticulously cleaned to remove any impurities, oxidation, or remnants that could interfere with the next plating step. By performing this operation, the ENIG procedure is guaranteed a spotless, responsive substrate.
2. Micro-piercing: Following the enig pcb surface finish previous procedure, a micro-etching procedure is used to treat the cleaned copper substrate. To gently roughen the coat of copper, this process necessitates employing alkaline and acidic solutions. By producing a little abrasion on the surface of copper, micro-etching helps improve the adherence of the following coatings.
3. Getting Started: Following micro-etching, a palladium-based activating reagent is applied to the printed circuit board. This mixture starts the catalytic reaction required to perform the following electroless nickel depositing. The catalyst makes it easier for the nickel enig plating to adhere to the copper layer.
4. Electroless Nickel Depositing: After the enig pcb has undergone catalysis, it is submerged into an electroless nickel solution. Compounds within this reagent aid the process of thin-layer nickel depositing upon the activated copper substrate. In contrast to the electroplating process, the electroless nickel deposit uses a chemical procedure for spreading the nickel evenly throughout the substrate rather than an electrical impulse.
5. Nickel Surfaces Treatment: The PCB enig undergoes treatment to improve its solderability after applying the nickel coating. Afterward, it is wiped down to get rid of any remaining solvents. This procedure may entail using an alkaline cleanser or a somewhat acidic bath to increase the adherence of the immersing gold layering.
6. Immersion Gold Deposit: A gold coating mixture is applied for the PCB enig after the nickel coating has been prepared. A slight covering of gold is deposited upon the nickel substrate through a displacement response caused by the chemical compounds in this mixture. Immersion gold offers a smooth surface for element positioning, superior solderability, and corrosion immunity. 
7. Last Rinse and Drying: The printed circuit board is thoroughly rinsed to remove any leftover solvents or impurities after the submersion gold plating enig surface finishing procedure. Lastly, before the assembling procedures, the board undergoes drying to ensure its surface is dry. 

Advantages and Disadvantages

Enig PCB surface finish poses several advantages and disadvantages, which can extend onto the electronic devices within which the PCBs are eventually placed. In this section, we will assess these pros and cons.

Advantages:

• Superior Solderability: Concerning soldering parts, particularly ones with tiny surfaces for contact or tight pitch, ENIG PCB Surface Finish offers a stable substrate. Throughout the assemblage procedure, the gold coating is not affected by corrosion and stays inactive, guaranteeing constant and trustworthy solder junctions.
• Resilience to Corrosion: Promising superior endurance against rusting and corroding, the submersion gold coating serves as an additional layer of defense. Because of this feature, printed circuit boards are guaranteed to perform correctly over a long period, even under challenging conditions for operation. 
• Uniformity and Level Surface: The level and consistent top produced by ENIG surface finish is essential for precisely installing and attaching surface-mount elements. To maximize the dependability of solder junctions, its smoothness encourages consistent soldering paste dispersion while assembling.
• Interoperability with Different Assembling Methodologies: ENIG may use many assembling methods, such as the ball grid array, BGA configurations, surface mount technology, or SMT assembling. Contemporary assemblage procedures can use it because of its capacity to retain solderability during several reflow sessions.
• Enhanced Electrical Operation: Certain applications that use high frequencies wherein reliability of signals is critical could profit from the existence of a nickel coating below the layer of gold, which in certain situations can provide greater electrical conductivity than conventional surface treatments.

Disadvantages 

• Expense: The expense of gold and the intricate nature of the procedure means that enig finish pcb surface treatments are often priced higher than specific other finishes for the surface 
• Frailty: Due to the metal’s comparative brittleness, gold may not be as durable as other metals and can be marred easily throughout handling or construction. 
• Black Pads Imperfections: The reliable enig pcb finish might be jeopardized by the creation of a black pad, also known as nickel rusting, a phenomenon caused by insufficient treatment settings or impurities that occur during the ENIG procedure.
• Issues regarding the Environment: Concerns regarding the environment are brought up by using gold during the ENIG procedure because of the methods involved in its extraction and mining. 

As established through this article, enig surface finishing for PCBs is an essential procedure. It is also equally intricate and can be challenging to perform. Being equipped with the right equipment and machinery helps streamline and simplify the process to achieve optimal results. Difficulty applying solder raises the possibility of reworking or restoration, reflow problems, and soldered joint faults.