Immersion Gold Plating
As a barrier layer, it could possibly stop the mutual inter-diffusion of copper and gold. On the opposite hand, it's going to react with tin, with the generation of wonderful IMC Ni3Sn4so that good meeting solderability can be ensured. Under the motion of catalytic surface, ENP leads to the deposition of nickel layer via redox response with NaH2PO2as decreasing agent. As quickly as the nickel layer is totally coated with palladium catalytic floor, the elementary substance nickel makes nickel deposition carry on because the catalyst of ENP.
For the manufacture of printed circuit boards, a brilliant hard gold with a mixture of nickel and/or cobalt is commonly used for card edge connector fingers plated over a nickel underlayment. There are plenty of reasons as to why you could need to make use of ENIG technology over other types of surface end expertise that you might have at your disposal.
For occasion, if you want to use ENIG technology if you will have printed circuit boards that have an extended shelf life. Additionally, if you'll have hassle-free solderability, you could find it necessary to make use of ENIG technology as opposed to other forms of technology out there for you. The remedy is available in as the perfect solution to current industry tendencies similar to lead-free manufacturing and the appearance of advanced floor parts similar to flip chips and BGAs, which need to have flat surfaces. Also often known as immersion gold, trying around, you’ll notice the recognition of ENIG on many PCB floor finishes.
That is to say that when all exposed nickel is covered, the immersion process stops. So to meet the three micro-inch gold minimal, manufactures will speed up the method through chemistry modifications in order that the gold will deposit at the next fee leading to a thicker deposit. This leads to hyper-corrosion of the nickel floor, which might then provoke black pad occurances.
Another possible trigger leading to nickel corrosion is excessive immersion gold deposition. IPC recommends 2-4 micro-inches gold deposition as the immersion gold course of relies on nickel corrosion to complete. During the immersion course of, nickel oxidizes and releases the electrons needed by the gold to form a layer of metallic coating on the nickel. Sometimes there is a requirement of a minimal of three micro-inches gold, which can be troublesome to satisfy persistently because the immersion course of is self-limiting.