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All the Information You Need on the ENIG Black Pad

The capability of vias to carry signals properly is equivalent to the successfully designed Circuit board in consumer electronics along with all other businesses that depend on the well-manufactured circuit boards. The conduits known as vias are what allow electrical signals to move across a PCB’s layers.

Manufacturers frequently add a conductive metal layer, usually copper into the substrate of a PCB to link the layers when the appropriate holes and layout are drilled. Copper plating works well for several purposes. Nevertheless, plated thru holes may additionally be filled with much more conductive material including copper for any application that generate a lot of heat or a lot of current. This configuration produces what are known as the copper filled via.

Electroless nickel immersion gold is proven to be among the most common surface finishes present on the marketplace today for businesses whose applications have become more demanding or/and those desire the newest in Circuit board. Due to the fact that ENIG finishes are lead-free, they are also a wise choice for businesses who wish to adhere to the RoHS directive 2002/95/EC. The use of some hazardous compounds in electronic products and gadgets is restricted by this EU rule.

Every PCB finish has disadvantages. Ball grid array components and other objects linked to the Circuit board run the actual danger of experiencing ENIG black pad issues with ENIG finishes.

However, ENIG finishes cannot be reworked, making the issue of black pad one that must be carefully handled. Otherwise, a whole product might become unworkable, costing money to recall and causing lost sales and disgruntled consumers.

What Does the Term “Black Pads” Mean?


Black pad can be described as a coating of the dark nickel surfaces that has been deposited on your PCB’s exposed portions. Because of the excessive usage of phosphorous during the process of gold deposition, this layer develops throughout the manufacturing process.

This electroless nickel has oxidized and corroded, as shown by the black pad of the metal. The assembly process takes place when different metal components are joined, but as this corrosion gets worse, it slowly spreads.

Because of increased nickel oxidation and increased gold thickness during manufacturing, there is inadequate solderability and improperly constructed soldering connections. The term “black pad” refers to the solder connections that quickly shatter under pressure to reveal rusty nickel underneath.

What Does ENIG Black Pad Mean?

This ENIG black pad controversy in the Circuit board sector may be unmatched by any other issue. Black pads are poorer connections that happen at the nickel and solder interface, to put it simply. Although some estimates place the prevalence of such a phenomenon at far less compared to 1 or 2% of the ENIG PCBs, many industry experts believe it to become very rare.

Nevertheless, because the black pad issue is typically not identified until the assembly process has started, it can be expensive to rectify as well as correct its post-manufacturing stage.

Why Does ENI Black Pads Occur?

A high content of phosphorus

The significant pass phosphorous level in gold deposition method typically results in ENIG black pads because of soldering and reflows.

Phosphorus diffuses through into nickel that causes its oxidization when there is an excess of it. This procedure separates the gold from the nickel, preventing the development of an adhesive bond.

Thus, this may result in dependable solder junctions delaminating and breaking, which might result in electrical shorts on circuit boards.

Corrosion from Gold Deposition

The popular ENIG surface finishes used in PCB manufacturing need the gold deposition technique, which is a vital step in the overall process. Yet if you don’t handle it right, this procedure might also result in the development of ENIG black pads.

Use of vigorous gold baths is among the reasons that enig black pads develop during the deposition of gold. The nickel bath method has the potential to quickly corrode nickel, resulting in the development of black pads.

This creation of ENIG black pads may also be influenced by the excessive gold thickness. When the common nickel substrate treatments contain excessive gold on them, severe galvanic hyper-corrosion as well as the eventual creation of ENIG black pads might result.

Employ gold having a thickness of about 2 to 4 μin, as required by the specification of the IPC-4552 ENIG, to avoid the creation of black pads.

Brittle fracture

Materials that are under tremendous stress might fail in a way known as brittle fracture because they lack the flexibility that can withstand the tension and break down rapidly without any warning or notice.

Typically, the surface of the PCB will have an ENIG black pad due to this failure.

This transformation of tin to nickel is the most frequent reason for brittle fracture. These metallurgical bonds are compromised by the small coating of phosphorus which remains after this transition.

In addition, brittle fractures could be brought on by temperature stress, shocks, and vibrations. Whenever this occurs, the nickel becomes broken, which can result in the electrical shorts.

The Development and Possible Harm of ENIG Black Pad


The composition of the plating solution and temperature when the process of chemical displacement process is on are the two main factors that affect the quality of the nickel coating. The most important thing is how you handle this acid gold water.

This plating layer gets formed during the process of electroless plating by an autocatalytic interaction between nickel salt and hypophosphite on the surface of the pad.

The amount of phosphorus in the finished product is calculated with the use of this processing assist. This industry standard for the phosphorus ratio in the deposition of chemical nickel was found to be between 7 and 10% in several investigations.

However, this proportion will deviate from the ideal range when the temperature changes or composition of the solution’s isn’t maintained under strict control. The coating is going to be more vulnerable to hyper-corrosion through the erosion of the acidic gold waters when the phosphorus content ratio is low. The lack of phosphorous in metallic ion concentration plating prevents the reaction of chemical substitution from occurring effectively during the process of gold immersion, which results in the hyper-corrosion.

When the gold coating develops a substantial number of fissures, it will be challenging to remove acidic residue. Its electroless nickel surface will corrode and also turn black if exposed to acidic water.

On the contrary hand, when the phosphorus levels are excessive, the produced coating’s hardness would rise noticeably, limiting its capacity to be welded and impairing the dependability of the batch solder junctions.

Prevention of Black Pad

About black pad, industry experts unanimously concur that it couldn’t occur at a worse location in the research and manufacturing paths of electronic goods and components.

As a result, it becomes vital for PCB suppliers and manufacturers to prevent ENIG black pads. Of course, understanding that excessive phosphorous levels are the source of ENIG black pad is not the same as properly regulating those levels throughout the production process. In order to prevent black pad concerns with the ENIG finishes, selecting us as your provider is probably the wisest move you can make. We are entirely devoted to giving you PCBs that are made to completely match your requirements, whether you are ordering a small batch or a large quantity.

How Can the Problem With the ENIG Black Pads Be Fixed?

Unfortunately, there isn’t a method to identify any ENIG black pad formation until the process is complete and the results are evaluated.

You can check for particular faults to see if there’s an enig black pad, and then arrange your following actions accordingly.

Some ways to manage black nickel as well as its effects include:

  • Check prospective ENIG suppliers.
  • In order to prepare PCBs for etching, it is important to remove residues and oils;
  • Utilize chelating agent;
  • Prevents the plating out of nickel into tanks;
  • Continually clean areas where black pads appeared;
  • Ensure that this process of immersion gold is carefully controlled to ensure the right nickel to gold ratio;
  • Monitor the level of pH to ensure you plate that right phosphorus content.

Is ENIG Having an Issue with Black Pads?

PCB Manufacturing with Immersion Gold-ENIG Surface Finish
PCB Manufacturing with Immersion Gold-ENIG Surface Finish

Black pads serve as a significant problem even if the process of ENIG finishing includes gold and nickel. Verifying the potential ENIG suppliers is crucial to avoiding potential black pads. Ensure they utilize cutting-edge technology and are aware of proper process management.

Conclusion ENIG Black pads might cause serious problems during the process of ENIG finishing. But, by dealing with a reliable supplier and monitoring the procedure, you may take measures to prevent them. We trust this post made things clearer for you. Contact us at any time if you happen to have any queries.


This ENIG black pad controversy in the Circuit board sector may be unmatched by any other issue. Black pads are poorer connections that happen at the nickel and solder interface, to put it simply.




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