What is Gold Plating PCB?

What is Gold Plating PCB?

gold plating pcb

Gold plating is the process of coating a PCB with gold. It is also called immersion gold. This process is very important, since it provides the best coating for a conductive circuit. There are two types of gold coatings, one is Electro-nickel gold, and the other is hard gold.

Immersion gold vs hard gold

When it comes to choosing a surface finish for PCBs, many factors need to be considered. The cost, performance, and material costs are all important factors. One of the most popular choices for a PCB’s surface finish is Immersion Gold.

Immersion gold is a kind of chemical nickel-gold layer deposition method. This process consists of a dual-layer metallic coating, which activates the nickel layer before allowing the gold layer to be deposited.

Compared to gold plating, immersion gold has a number of benefits. It is easier to weld, offers a smooth surface, and has a long shelf life. These qualities make it the perfect choice for complex surface components.

While gold plating is a good choice for cosmetically pleasing gold contacts, Immersion Gold is the best solution for most surface finish challenges. Besides the fad of hard gold surfaces, Immersion Gold is the right choice for almost all other PCB surface finishes.

In addition, Immersion Gold’s wettability is impressive. Aside from its obvious advantages, Immersion Gold is also environmentally friendly and has great mechanical properties. Moreover, this surface finish is able to resist high temperatures.

Another benefit of Immersion Gold is its ability to be bonded with other metals. This makes it an ideal option for ultrasonic wire bonding and thermosonic bonding processes.

Unlike Gold Plating, Immersion Gold is much harder to oxidize. This feature is helpful in reducing copper’s oxidation on the PCB’s surface. As a result, the quality of soldering will improve.

However, immersion gold does not have a black pad after the assembly is complete. Hence, it is not recommended for a bare PCB.

Immersion gold’s thickness is slightly thicker than that of gold plating. However, this may lead to complications. If the maximum thickness is not adhered to, the gold layer may end up being black. Therefore, the optimum thickness is 0.05 to 0.23 um.

Electroless Nickel Immersion Gold (ENIG) is another popular surface finish option for PCBs. Enabled by its brilliant re-flow cycles and its ability to protect the copper skin, this type of surface finish is particularly advantageous for fine pitch SMD parts.

Electro-nickel gold vs gold plating

Gold plating and electro-nickel gold are popular surface finishes for PCBs. They are known for their hardness and oxidation resistance. Despite their superior performance, there are some drawbacks of both of these methods.

Electro-nickel gold is a relatively expensive process. The nickel layer does not provide a smooth surface, so it is not suitable for contact elements such as contacts or connectors. In addition, the corrosive effect of copper can cause the nickel layer to deteriorate. It is also difficult to use the technique for soldering.

Hard gold is an alloy that contains cobalt and nickel. It is typically used for edge connectors, battery contacts, and test boards. Although it has a good hardness and wear resistance, its abrasion resistance and contact resistance are weaker. This makes it more suited for applications that require force or friction.

Soft gold is not as glossy as chrome. It is also less resistant to oxidation and wear, which can affect the solderability of the circuit. For sensitive joining applications, soft gold is a better choice.

Hard gold is usually alloyed with iron and other elements. Nickel is the most common element. However, gold plating pcb other metals may also be added. Alloys offer better resistance to friction and corrosion, and are more useful in combination with other elements.

ENIG (electroless nickel/immersion gold) is another surface finish for PCBs. It is a two-layer coating that protects the nickel underplate. This finish is based on an intermediate palladium layer that prevents nickel oxidation-related defects. Compared to electro-nickel gold, it is less corrosive.

Electro-nickel gold has excellent oxidation resistance and good anti-friction properties. Nevertheless, it does not have the lubricity needed for sliding. Moreover, its price increases with the thickness of the gold layer. If the thickness is too thick, it can reduce the reliability of the solder joint.

ENIG is considered to be the best choice for circuits that have finely spaced components, and for printed circuits with SMD insertion. But it can have high production costs, and it has some weaknesses with dense PAD. These are discussed in IPC-4552A and IPC-7095D.

Porosity and coating thickness

A gold plating PCB’s porosity and coating thickness are affected by many factors. It depends on the type of PCB you want to apply, as well as your needs for its environment. You can check for gold plating on a PCB using a tape test. This test can show whether there is any sign of the plating process.

One of the most important factors affecting the gold plating PCB’s porosity is its coating thickness. Having the right thickness will allow the PCB to last longer. However, if the coating is too thin, the porosity will be formed.

Another factor affecting the porosity of the gold plating PCB is the thickness of the nickel underplate. The underplate serves as a barrier that prevents corrosion products gold plating pcb from reaching the PCB’s contact surface. In addition, the underplate can also help to reduce the friction coefficient.

The most common types of underplate are sulfamate, electroless nickel and bright electrolytic nickel. While these underplates have great optical properties, they are not ideal for high-density PADs and QFPs.

When choosing an underplate, make sure that it is not porous. It should also be free of defects.

There are some processes for reducing porosity, such as applying metallic brighteners or chelates. They can be either simple or complex. Some of the complex types of brighteners include depolarizing agents.

Other factors that can cause the porosity of the gold plating to increase are surface flaws, improper surface preparation, improper plating solutions, and the thickness of the gold plating itself. Gold can also be prone to oxidation. If you choose to add a hard gold deposit, you may need to choose a thin coating.

The amount of gold required to ensure that the electrical contacts will remain corrosion-free for 24 years can range from a few microns to several millimeters. In order to minimize the porosity of the gold plating, the thickness of the coating should be at least 30 microns.

Although the porosity of the hard gold plating PCB is dependent on its coating thickness, the nickel underplate plays a huge role in its wear resistance. Since the underplate provides a protective barrier, it minimizes the chances of cracking in the hard gold plated contacts.

Shelf life

If you want a longer shelf life for your PCB, gold plating is a great option. The benefits of this finish include corrosion resistance, high density and lead-free components. Moreover, it also has the ability to hold tight tolerances.

In addition to extending the lifespan of your PCB, this coating is ideal for applications that require fine pitch technology. It is also a cost-effective alternative to HASL or ENIG.

Regardless of which type of surface finish you choose, you need to be sure that the surface you choose is resistant to moisture and shock. Additionally, you should be careful about how your board is stored. Moisture can cause oxidation and tarnishing, resulting in damaged boards or a need to rework the finish.

If you decide to use a hard gold surface finish, you need to make sure that your material thickness meets the requirements of your application. Typically, a hard gold surface finish must be at least 50 micro inches thick.

However, this may vary depending on the application. For example, in hard gold wire bonding, the thickness of the gold layer can be reduced by adding palladium.

A thin layer of gold protects the nickel in your PCB and prevents oxidation. This prevents the tarnishing of the highly active nickel. Hard electrolytic gold is also known as deep gold.

Electroless nickel and immersion gold (ENIG) is a PCB finish that uses nickel and a protective layer of gold. This process is RoHS compliant. You can get a PCB with an ENIG finish that has a shelf life of up to 12 months.

Immersion silver is another option for a PCB surface finish. It is commonly used in EMI shielding. Although it has a shelf life of six to twelve months, it can be sensitive to contaminants.

Other options for PCB finishes include tin and LF HASL. These finishes offer a high level of solderability. However, they are both relatively expensive. To determine the best choice, you must evaluate the cost, durability, and storage requirements of your application.

As a rule of thumb, the best finish is one that is durable, environmentally friendly, and low-cost.

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