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ENEPIG vs. ENIG: Which is the Better Surface Finish?

Every detail is essential when making PCBs. All the wire placements, design, and finishing touches combine to construct a board that meets standards. However, dealing with surface finishing always leads to a comparison of ENEPIG vs. ENIG.

Surface finishes are crucial because they prevent copper oxidation, which can degrade board quality. However, choosing between ENIG or ENEPIG surface finishes can be tricky. So, how do you decide if you don’t understand the possible benefits?

This comparison article will discuss the differences between ENEPIG and ENIG. We’ll also explain which surface finish offers the most benefits.

What is ENEPIG?

PCB with a copper surface

PCB with a copper surface

In truth, the Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG) is not a new surface finish. The method surfaced previously but fell out of favor. In addition, Palladium was expensive, making ENEPIG a costly finish beyond most people’s budgets.

However, palladium is now more affordable, allowing ENEPIG to regain some popularity. Now, many manufacturers consider it the best option for wire bending. 

But what is ENEPIG? It refers to a PCB metal plating process that attaches the board to a conductive surface. 

Interestingly,  ENEPIG has a reputation for being a universal finish. Why? Because it works with almost any PCB, and palladium can replace gold plating.

How do you Apply ENEPIG Surface Finish?

PCB with a gold surface

PCB with a gold surface

ENEPIG consists of four metal layers: nickel, palladium, copper, and gold. The process starts by activating the copper layer with a displacement layer. This reaction causes the copper to act as a catalyst.

Then, adding nickel to the catalytic copper will merge the two materials. This combination will protect the copper and prevent unwanted interaction with other metals.

The third process involves introducing a palladium layer for extra protection. Interestingly, palladium stops nickel from eroding and degrading the gold layer. So, when using an electroless reaction, a chemical oxidation-reduction will occur, forming a thin layer of palladium and nickel.

Finally, immersing the board in gold completes the ENEPIG application process. And it’s because gold adds the ultimate protection while preserving the palladium.

Note: the Gold layer will cover the entire board.

ENIG vs. ENEPIG: What’s the Difference?

The palladium layer is the significant addition that differentiates ENEPIG from ENIG. In other words, Electroless Nickel Immersion Gold doesn’t include palladium between the nickel and gold layers. However, ENIG still provides a solid amount of electric performance, including oxidation and temperature resistance.

Moreover, ENEPIG is more reliable for gold wire bonding, as ENIG often reduces solder joint reliability. ENIG is also unsuitable for touch contact points.

Advantages of ENEPIG

Generally, ENEPIG is more cost-efficient than other hard or soft gold plating alternatives. Gold is currently more expensive than palladium, making the ENEPIG more affordable. Interestingly, it contrasts the surface finish’s initial release as more individuals and businesses can use ENEPIG plating.

In addition, ENEPIG offers an attractive thin finish. And the layer from the electroless reaction between the palladium and nickel is usually not higher than 0.1 microns. Thankfully, this layer thickness is ideal for many boards.

ENEPIG protects the PCB and makes it easier to work with other elements. Also, the surface finish makes soldering more reliable and easy. And it reduces the amount of soldering required on a board.

In addition, ENEPIG plating doesn’t degrade. Hence, you’ll enjoy an increased PCB shelf life.

Disadvantages of ENEPIG

ENEPIG is not without its setbacks. Although this technique is now more affordable, ENEPIG is still one of the most expensive surface finishes. Also, Palladium and gold are precious metals, making them costly to use.

In addition, you may experience reliability issues with an ENEPIG finish, particularly when manufacturers don’t maintain chemistry. For example, copper and palladium can reduce a PCB’s lead and tin bonding integrity.

More importantly, incorrect use of an ENEPIG coating can cause fractures. It’s because the layers above the nickel plating are often brittle. 

Additionally, an excessively thick palladium later will dampen solder reliability and performance.

Closing Words

PCBs using multiple layers will benefit more from ENEPIG coatings. Also, ENEPIG can satisfy all additional requirements for PCB designs with differing packing technologies.

In addition, ENEPIG is less expensive than hard gold and can accommodate touch contacts without causing problems. Interestingly, ENEPIG’s superior quality often creates medical, military, and aerospace PCBs. So, ENEPIG is your go-to if you require push contacts or wire bonding.

Do you have any questions? Feel free to contact us, and we’ll be happy to help.

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