Today, PCBs are an integral part of electronic circuits. These circuit boards need to survive the rigors of different operational environments. Hence, these circuit boards are coated with surface finishes of various types. There is a copper layer on a PCB which oxidizes, when it comes in contact with air. This reduces the soldering quality. Surface finishes help reduce oxidizing, as well as contribute to solderability, and electrical performance. There are various types of surface finishes available in the market. In this post, we will concentrate on one such important variant – immersion gold surface finish. Read the post to know more.
A Brief Introduction to Immersion Gold PCB
This surface finish is popularly referred as Electroless Nickel Immersion Gold (ENIG). It comprises of electroless nickel plating, which is covered with a thin layer immersion gold. In immersion gold, the gold layer is generated on the nickel layer through displacement. It continues until generated gold layer is covered with nickel. This is why gold layer is very thin. This layer protects nickel from oxidation. The typical thickness ranges from 0.05 – 0 23 µm (2 – 9 µ in) gold over 2.5 – 5.0 µm (100 – 200 µ in) electroless nickel. This thickness remains consistent throughout the PCB.
Advantages of Immersion Gold Finish
Although ENIG is an expensive surface finish technology, still it is popular due to the following reasons:
- Immersion gold has strong chemical properties. These properties include impressive wettability, surface planarity, coplanarity, and long shelf life. The properties are contributed by nickel and gold layer.
- In ENIG, a nickel layer performs two functions. It acts as a barrier, and can stop the interfusion between gold and copper. However, on the other hand it will react with tin, and produce intermetallic compound (IMC) Ni3Sn4. This compound offers excellent solderability.
- A gold layer provides various advantages including low contact resistance, high strength, few chances of oxidation, and antifriction. These properties help meet circuit conductivity requirements, as well as protect nickel, and copper layers from oxidation. This also contributes to excellent solderability.
- ENIG doesn’t require dummy plating, and has brilliant re-flow cycles too. It provides good adhesion and is well-known for its electrical testability as well.
- Immersion gold provides good plating around the holes in the circuit board.
- The gold plating is gold wire bondable, and can be soldered easily.
- ENIG surface finish is best for fine pitch products because the tracks or pads are square-edged and flat.
- ENIG complies with all RoHS requirements.
- ENIG PCBs are used in computers, mobile phones, consumer electronics, and automotive electronics.
All the above-mentioned advantages will give you reasons why you should go for this coating. Besides this, it is very important that you get your PCB coated with ENIG from a leading manufacturer. The company provides rigid, flex, and rigid-flex circuit boards in various surface finishes. For more information about immersion gold finish pcb coating, please visit http://www.rigiflex.com/ or contact the company at (714) 688-1500.