hard gold pcb

PCB Gold Plating: Hard Gold PCB, PCB Gold Plating Thickness and More

PCBs are the framework of a gold plated circuit board is a type of PCB with gold plating. PCB gold plating is a common practice in today’s electronic Industry. Some applications demand the use of this PCB due to the type of environment it will be used. The use of gold in plating PCBs is common in the PCB industry. Over time, there has been an increasing demand for Gold plated PCBs. We will be discussing everything you need to know about gold plated circuit boards.

What is PCB Gold Plating?

PCB gold plating is simply the process of depositing gold onto the surface of a circuit board through plating. There has been difficulty in SMT placement since IC and IC pins became denser. Plating is an important stage in PCB production. Different types of materials such as copper, nickel, tin, and gold. However, a gold plated circuit board stands out. Gold is useful for plating circuit boards due to its conductive properties.

Aside from its conductive nature, Gold has other properties. These make it ideal for PCB plating. Experts use gold contact surfaces on PCBs with membrane switches. Since the gold plating has strong adhesion, you can attach gold particles to the PCBs. Gold plating is a surface finishing method that uses electrochemical plating to deposit gold onto another metal.

 

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PCB Gold Plating Process

PCB Gold Plating

The plating process in the PCB industry is in two categories; electroless plating and electrolytic plating.

Electroless plating

This is a process whereby a metal atom is deposited on a substrate’s surface to create a metal plating layer. Electroless plating doesn’t depend on the external source of power in the aqueous solution. This plating process doesn’t need an external current. There is a uniform thickness in the electroless plating layer.

Electroplating

This process involves depositing a dense alloy or metal on the PCB’s surface. This process uses an external current to coat the metal. During this process, the anode goes through an oxidation reaction, discharges the electrons, and the metal atoms then become cations.

Types of PCB Gold Surface Finishes

Electroplated Nickel Gold (ENG)

Electroplated Nickel/ Gold has been existing since the invention of PCB. This type of surface finish coats the surface conductor of the circuit board with a layer of nickel. It then uses a layer of gold to coat the surface. After the nickel liquid has been disposed of separately, gold is placed in the chemical syrup. The manufacturer then immerses the pre-processed PCB in the electroplating cylinder.

This PCB gold plating is popular in the electronic industry. This is because gold as a material is oxidation and wear-resistant.

Electroless Nickel/Immersion Gold (ENIG)

This surface finishing attaches gold and nickel to the copper surface. It doesn’t use complex power supply devices for this process. ENIG process often undergoes activation, pickling, cleaning, microetching, electroless, and nickel plating. The major step here is the plating of auto-catalytic nickel on the copper pad. This is done by parameters like additive concentration, temperature, and pH.

The nickel serves as a hindrance to the copper. It also serves as the surface on which PCB manufacturers solder the components. The gold shields the nickel and as well as offers low contact resistance. ENIG is the most commonly used finish in the PCB industry.

Gold Fingers

Gold fingers are useful in various applications. Some gold contacts are ideal for the connection of the edge card. A gold finger is a gold-plated connector of a PCB. Gold fingers feature a gold plated terminal. This surface finish allows the smooth transfer of data and power in a PCB. Gold fingers are specially for edge contacts. They have the ability to resist wear and tear.

Factors to Consider When Plating Gold

Wear

Two major characteristics of the surface treatment determine the lifespan of the plated surface. Hardness and friction coefficient are these two characteristics. The life of the surface treatment increases as the friction coefficient reduces. Electroplated gold enhances the wear resistance of gold.

Nickel underlayer

This is an important factor to consider. Nickel plating has a blocking impact on the diffusion between copper and gold. Nickel underlayer plays a significant role in precious metal plating.  Also, nickel serves as a hindrance that blocks the pores and substrates. This minimizes the possibility of pinhole corrosion. Nickel also offers a hard layer under this metal plating.

Porosity

The gold plating process is porous. This has a significant relationship with the coating’s thickness. The porosity is low when above 0.76 μm. Porosity rises rapidly when it is below 0.38 μm. Porosity is an important factor to consider.

What is a Hard Gold PCB?

Hard gold PCB comprises a layer of gold with additional hardeners to help improve durability. Hard gold is a durable material ideal for plating a circuit board. During the fabrication of a circuit board, gold is used for high-wear areas like edge connectors. Most circuit boards feature metal contacts made from gold.

Hard gold is an example of a surface finish for PCBs. Due to the high cost and poor solderability of hard gold, it isn’t ideal for solderable areas. Hard gold PCBs are ideal for use in applications where friction is required.

 

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Properties of Gold Plated Circuit Board

gold plated circuit board

The gold plated circuit board is commonly used in the electronics industry. The aesthetic appearance of gold makes it a valuable resource to people. However, its properties make it a highly-prized material in the electronics industry. Gold features great thermal, electrical, and mechanical properties. These make them a perfect choice for use in electronic components. A gold plated circuit board features a lot of properties which include;

Wear Resistance

Gold plated circuit boards are very durable. This PCB can resist wear and tear. The coating on this circuit board serves as a shield to the electronic components. Gold plated boards aren’t vulnerable to fretting degradation. Since gold doesn’t corrode, it won’t damage as a result of fretting. The gold plating on this board will last long.

Protection from heat

A gold plated circuit board is ideal for applications involving high temperatures. This circuit board protects other materials from overheating. Gold features a melting point of 1062 ℃. This means that gold has the ability to conduct heat. Gold plated circuit boards will perform well under intense temperatures. This makes it ideal for applications that may be exposed to high temperatures.

Corrosion resistance

This is one of the great properties of gold plated circuit boards. Gold is corrosion-resistant. This means that it can withstand any corrosion. It won’t react to any chemical or rust. Although gold can tarnish, it won’t damage. Gold’s resistance to corrosion is crucial for electronic components. This is because oxidation may result in less functional electrical connection.

Reflectivity

The reflective nature of gold makes it a perfect choice in components. Gold plated circuit boards feature greater amounts of UV radiation. They reflect infrared radiation which keeps electronics in cool conditions. Due to this, gold plated circuit boards are core materials for satellite and spacecraft design.

Expanded connection area

A gold plated circuit board is very malleable and ductile. Gold as a material can stretch out into thin wire under pressure. This makes it cover more surface area. The flexibility of gold plated circuit board enables electronic devices to keep functioning well.

The Difference Between Gold Plating and Immersion Gold

Gold plating and immersion gold processes on a PCB are two different methods. The immersion gold process on a PCB is referred to as chemical deposition. The immersion gold process involves applying a thin layer of gold. Immersion gold is found in aluminum and gold wire bonding. However, its limited adhesion and thickness make it inappropriate to take electrolytic gold plating.

Gold plating involves depositing gold on the surface of a metal. This plating adopts the principles of electroplating. In the immersion gold process, a nickel-gold coating is deposited on the surface of the PCB. Gold plated boards are hard gold while immersion gold is soft gold. This means gold plated boards are wear-resistant. The immersion gold boards are not wear-resistant.

The gold in immersion gold is thicker than that in a gold plating board. It is easy to solder immersion gold. It also has fewer solder problems. For immersion gold, it is much easier to regulate stress. This is because it is softer than gold plating. Another difference between hard gold plating and immersion gold is the color. Immersion gold is more yellow than hard gold plating.

Immersion gold board features gold and nickel on its pad. Therefore, the signal transmission in the skin impact won’t affect the signal on the copper layer. The gold plating process is less expensive than the immersion gold process. Immersion gold is essentially made of pure gold. Gold plating combines other elements to change the gold’s grain structure.

Gold plating features a hardness of 130-200 HK25 while immersion gold features a hardness of 20-90 HK25. This makes gold plating more vulnerable to wear from contact switching.

Application of Hard Gold PCB

Hard gold PCBs are ideal for use in some applications. This type of circuit board is commonly used in industrial intelligent machines. You find them in entertainment, AI, and educational robots. All kinds of electronics devices feature this type of PCB. For instance, mobile phones, computers, and other devices feature this type of PCB. Hard gold PCB can sustain electrical connectivity. This makes it a suitable choice for several types of applications.

Computer system

Gold plated circuit boards are commonly used in the computer system. These boards are available in laptops and desktop computers. Signal integrity and data transfer are key aspects in computer systems.

Telecommunication system

Hard gold PCBs are ideal for use in the telecommunication system. These circuit boards are available in mobile phones, GPS, and satellite systems.

Industrial systems

You will find hard gold plated circuit boards in mechanized equipment. Computerized industrial machines feature this type of PCB because of its properties. Since this board is corrosion and wear resistant, it is ideal in this application.

Consumer Electronics

Hard gold PCBs don’t corrode or rust. Gold has great conductive properties which makes them withstand high temperatures. Consumer electronics like smartphones, TVs, and smartwatches feature hard gold PCBs.

The Effect of Underlayers For Hard Gold Plating PCB

Gold is more useful when used with other metals. A gold plated board features a layer of nickel on the substrate. The nickel is often placed under the gold plating layer. There are several benefits of using an underlayer for gold plating. An Underlayer serves as an additional layer of protection against any form of corrosion. Sometimes, corrosion may pass through the pores in some areas of the gold plating.

The underlayer also prevents metals like copper and zinc from oxidizing. When such metals diffuse into the gold, they may oxidize. Also, underlayers add more thickness to the plating. This additional thickness improves the durability of the plating. You can add nickel or cobalt to the gold to improve the durability of the plating.

PCB Gold Plating Thickness

The gold used for gold plating should be thin. Gold plating can be effective without being thick. However, PCB gold plating thickness varies. This depends on the requirement of your project. This will determine if you should use soft gold or hard gold. In applications where durability is an important factor, hard gold is an ideal choice. If malleability is important, then you can use soft gold.

PCB gold plating thickness ranges from 0.25 microns to 5 microns. That means from 0.00001” to 0.0002.” Hard gold can survive many insertions. The thickness of hard gold can be regulated by changing the plating cycle time. Determining PCB gold plating thickness is a quality control measure in the production of hard gold PCB.

Conclusion

As we can see, most electronic devices contain gold. Gold is a precious metal with great properties. Gold plated circuit boards are one of the most common boards in the electronic industry. These boards are ideal for use in most applications. There are different gold plating processes which include immersion plating and electroplating.  Soft gold plating and hard gold plating are the two major categories of gold plating. This article has explained vital facts about hard gold plating PCB.

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