When creating PCBs, every little detail is crucial. A PCB that satisfies specifications is built using a combination of the wire locations, design, and surface finishing touches. However, discussing surface finishing invariably results in an ENIG vs. ENEPIG contrast.
Because they stop the oxidation of copper, which can reduce PCB quality, surface treatments are essential. It might be challenging to decide between the surface finishes of ENIG and ENEPIG. So, how can you make a choice if you are unaware of the potential advantages?
The contrast between ENIG and ENEPIG will be covered in this article. Also, which PCB surface finish possesses the most advantages?
What Is ENIG?
Because of its smooth, planar surface, ENIG has always been a well-liked surface finish of PCB for many years. As a result of the proliferation of fine-pitch Ball Grid Array electronics and other compact surface-mount dimensions, this is necessary for assembly. The method additionally supports several solder reflow phases with the additional advantage of extended shelf-life duration.
However, nickel corrosion has created the “Black Pad” appearance due to past production issues with particular ENIG suppliers. This, however, has been a major flaw in the ENIG finish, but it can be fixed if the right steps are followed.
The nickel deposited underneath the gold finishing corrodes and appears as a “Black Pad,” which is a dark surface. This corrosion may result in the solder pad losing connection to the electrical component pad and a component with poor solderability.
Some PCB producers may find it difficult to generate the ENIG finish. When inspecting the finished item, the gold coating process might cover the finished surface area and hide problems that result in a “Black Pad.” According to the main investigation into the cause of this issue, the nickel contamination that shifts into gold and gives the metal a black tint is most likely the reason.
Through careful observation, your Contract Manufacturer can solve such problems; if no dark bands or spikes appear near nickel borders, a black pad isn’t going to form. A well-managed nickel bath may reduce or even get rid of the flaw. Finally, having a one-year craftsmanship warranty from contract manufacturers like MacroFab gives you additional peace of mind.
Process Implicated In ENIG Surface Finish
The ENIG Circuit board surface coating or finish is a multi-step, drawn-out procedure. To obtain the desired finish, all of these procedures need to be closely watched.
· Copper Activation
Keeping the layer of copper active for the electroless nickel deposition depends on copper activation. This step involves cleaning the PCB. This allows for getting rid of dust and oxidation residues. Additionally, moistening the surface aids in removing any trapped gas or air within the perforations.
The producer must take the micro-etching foundation under great consideration. Sulfuric/peroxide is the finest choice. You should also keep an eye on the bath’s life expectancy and operation temperature. The remnants will disappear with a thorough rinsing. Before micro-etching, appropriate rinsing must be performed. The deposits of palladium in the catalysts may react with oxidation.
Additionally, employing a pre-dip catalyst to get rid of any oxidation residues is a good idea. The pre-dip catalyst also aids in the Circuit surface’s acidification.
· Electroless Nickel
The ENIG procedure’s next stage is this. Here, the producer creates nickel and sodium hypo-phosphite using nickel sulfate. This mixture acts as a reducer. Moreover, the hypophosphite disperses the required electrons to reduce nickel ions. Additionally, this reaction ought to be enhanced at a precise temperature of 175–185°F.
Furthermore, this facilitates the nickel layer’s deposition on the surface of copper. The nickel acts as an inhibitor or barrier to stop the copper surface from reacting with any other elements.
· Immersion Gold
The ENIG procedure comes to a close with this stage. Here, the production of electrons from the oxidation of nickel to the ions of nickel helps to reduce gold in a mixture. Additionally, these electrons reduce ions of gold to a coating of gold metal that protects the nickel. The gold’s thickness needs to match the specified criteria.
Benefits Of ENIG
- An ENIG coating offers various benefits, which include the flatness of the surface for many fine-pitch Ball Grid Array electronics and different small shape factor components.
- Excellent for connections with press-fit inserting posts and electrical testing locations in the circuit.
- Support for edge card connectors and wire bonding.
- Less expensive contrasting to ENEPIG coating or finishes.
Disadvantages OF ENIG
- If the gold and nickel processes are not carefully regulated, there is a possibility for “Black Pads.”
- The electroless gold and nickel plating’s thickness might have an impact on the PCB coating.
- A wet factor that is relatively low
What Is ENEPIG?
The use of a comparable alternate surface finish, such as ENEPIG, is one straightforward fix for the possible black pad problem. The ENEPIG coating resolves this problem by placing electroless palladium over the layer of nickel. Nickel impurities cannot go from the nickel to the layer of gold because of the palladium. ENEPIG is appropriate for PCBs soldered over a system board that uses various packaging methods. It also offers a broad spectrum of applications, including those in the aerospace, military, and some other high-performance medical devices with great density and dependability.
Additionally, ENEPIG is more expensive than ENIG, but it persists as a cost-effective choice that adds tiny palladium and gold layers for increased toughness and superior solderability. The minimal contact resistance of ENEPIG shields against overheating, energy losses, and inadequate grounding.
Applying ENEPIG Surface Finish
ENEPIG comprises four layers of metal which include nickel, copper, palladium, and gold. The activation of the layer of copper with a layer of displacement initiates the process. The copper serves as an initiator or catalyst in this process.
The two components will then combine after nickel is added to the active copper. This combo will safeguard the copper sheet and stop unwelcome metal-to-metal contact.
A palladium coating is added as part of the third procedure to provide further protection. It’s interesting to note that palladium prevents nickel from deteriorating and dissolving the gold coating. Consequently, a chemical reduction of oxidation will take place during an electroless process, resulting in the formation of a thin nickel and palladium layer.
Finally, submerging the PCB in gold finishes the ENEPIG coating process. And the reason is that gold provides the highest level of security while keeping the palladium safe.
Recall that the layer of Gold will completely cover the board.
Benefits Of ENEPIG
- Palladium lessens the quality problems of “Black Pad” that some CMs exhibit during the process of ENIG.
- Preferred for its high solder reflow phases and excellent solderability
- incredibly dependable in terms of wire bonding ability
- Has dense vias and satisfies the wide standards of miniaturization and PCB thinness.
Disadvantages Of ENEPIG
- Being more expensive than ENIG might not be feasible for many applications.
- Decreased SMT Solder efficiency as a result of a palladium layer that is thicker.
- more time to wet
Difference Between ENIG Vs. ENEPIG
There are variances between the two surface coatings, ENIG and ENEPIG. Whereas ENIG only employs immersion gold and nickel, ENEPIG uses palladium. In the ENEPIG, the layer of palladium provides high oxidation resistance and electrical performance. ENIG is most suited for usage in low-end electronics, nevertheless. ENIG solely employs the layer of immersion gold over the layer of the electroless nickel. ENEPIG includes a palladium layer between the layers of nickel and gold.
Additionally, the surface finish of ENIG does not produce consistent fold-wire bonding results. This could be brought on by a drop in solder joint dependability. Furthermore, ENIG needs an appropriate procedure to stop nickel corrosion. However, ENIG surface finishes frequently have issues like these.
Similarities Between ENIG Vs. ENEPIG
Despite the fact that both of these surfaces’ finishes differ. They do, however, have certain things in common. Both ENIG and ENEPIG employ immersion gold and electroless nickel. Both of these surface coatings offer a flat and straight surface. This makes it easier for manufacturers to install components on the surface of the PCB. Additionally, both ENIG and ENEPIG are lead-free. They are, therefore, a green alternative for PCB producers.
Excellent thermal diffusion and electric performance are features of ENIG and ENEPIG. The procedures for both surface coatings are not too difficult. For example, the process of both finishes includes copper activation. The first stage of their procedure is this. The surface goes through a bath of catalyst that contains sulfuric acid and palladium sulfate. This bath creates a foundation for the gold and nickel to deposit on.
The last layer of both surface coatings is immersion gold.
Aspects To Consider While Selecting ENIG Vs. ENEPIG
You have to take a few things into account when picking a surface coating for the PCB. Not every surface finish will work for the PCB needs.
· Application Requirement
The surface finishes you choose will depend on the requirements of your usage and application. ENIG is a great option if the application has to operate in hot conditions. This happens because the surface finish offers excellent heat resistance. It can endure very high temperatures.
· Cost
This consideration plays an important role. You can pick ENIG if money is a concern. The more costly alternative is ENEPIG. This happens because it includes the usage of palladium.
· Pad Flatness
Some Circuit Board surface finishes don’t provide smooth surfaces. This, however, does not happen in ENIG and ENEPIG. Both these surface coatings provide a level surface. ENEPIG or ENIG are excellent options if you need to install extra components on the PCB. Both of these finishes provide thin and uniform layers.
· Wire Bonding Capacity
ENEPIG is a great choice in this regard. When constructing a PCB, the capacity of wire bonding is crucial. Additionally, ENEPIG possesses a strong wire bonding capability.
· ROHS Compliance
Not all Circuit Board surface treatments adhere to the RoHS requirements. This is due to the presence of some hazardous materials in certain surface finishes. Both ENIG and ENEPIG adhere to RoHS regulations. These surface coatings are lead-free. They are, therefore, perfect for usage.
· Shell Life
The Printed Circuit Board surface finish’s shelf life is crucial. Both ENIG and ENEPIG have a greater shelf life. For up to a year, these surface treatments can be stored.
Conclusion
Surface coatings made with ENIG and ENEPIG are particularly dependable. These finishes meet the requirements for PCB quality. These completed products are the best since they were produced without lead. Additionally, both of these surface treatments provide producers with a level surface. Their workings, benefits, and drawbacks have been described above. Additionally, we contrasted both of these surface coatings.
Coatings made of ENEPIG will prove more advantageous for PCBs with numerous layers. Additionally, ENEPIG is capable of meeting any extra specifications for PCB layouts using various packaging techniques.
Furthermore, ENEPIG can handle touch interfaces without creating issues and is less costly than solid gold. It’s interesting to note that ENEPIG frequently produces PCBs for the military, aerospace, and medical industries. Therefore, ENEPIG is the company to contact if you need wire bonding or push contacts.
