The conducting paths on a PCB are made of copper and are responsible for transmitting electrical signals. Copper is an excellent conductor, but it cannot stay intact in the atmosphere; it will undergo corrosion. Consequently, the electrical properties of the PCB will degrade with time, and the circuit will not perform as expected. Thus, it is necessary to treat the surface of a PCB and make it corrosion-resistant and long-lasting.
Gold has a commendable resistance to corrosion and oxidation. It has a long life compared to copper exposed in the air. If a PCB has a surface finish of gold, it will last for a long time, and the copper underneath the surface finish will remain intact and sound. Therefore, gold is used in the surface finish to improve and maintain the performance of a PCB and offer it a long life.
When it comes to the gold surface finishing of PCB, two names come to our minds: Gold Plating and Immersion Gold. Beginners usually get confused about these two terms, and they often consider them the same. It is essential to understand the difference between these two types of surface finishes because it will help design a perfect PCB for the project. The PCB buyer needs to know which type of surface finish is suitable for the PCB, the advantages/disadvantages, and its uses.
What is Gold Plating?
Gold Plating is when a thin layer of gold is applied over the PCB through electroplating. The important thing is the method behind it, and that is electroplating. In this method, gold is mixed with a non-precious material, usually nickel, to make it harder. This is the reason Gold Plating is also called Hard Plating.
Pure gold is quite soft; therefore, nickel or other non-precious metals are used in gold plating. It creates an alloy of gold, and it is clear that the gold used in gold plating is not pure.
What is Immersion Gold or ENIG?
ENIG stands for Electroless Nickel Immersion Gold, and it is commonly known as Immersion Gold. Unlike gold plating, ENIG is done through a chemical reaction; there is no electroplating involved. At first, the copper is covered by a thin layer of nickel, and after that, a thin layer of gold is applied over it.
Keep in mind that the gold layer applied to the surface is pure; it is not an alloy. Thus, ENIG is a mixture of nickel and gold layers. The nickel layer protects the copper layer from oxidation and corrosion, and the gold layer protects nickel. Ultimately, there is a commendable resistance from corrosion.
Since the top layer of the ENIG treated PCB is of pure gold, it is much softer than gold plating. Therefore, it is often called soft plating.