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Tribology of Electronic Connectors: Contact Sliding Wear, Fretting, and Lubrication
Published in Paul G. Slade, Electrical Contacts, 2017
Since the mid-1990s, Electroless Nickel and Immersion Gold (ENIG) plating has been used in many electronic components as a metal finish alternative to gold electroplate. An ENIG layer is formed by the deposition of electroless nickel–phosphorus on a catalyzed copper surface followed by a thin layer of immersion gold. The specification covering ENIG requires 3–6 μm of nickel–phosphorus and 0.05–0.1 μm of immersion gold. ENIG is a versatile surface finish and was introduced initially as a viable surface finish on printed circuit boards (PCBs) for surface-mounting microchip packages. The gold layer thickness is about 0.1 μm since the main original objective of the gold was to protect the underlying nickel from oxidizing and becoming difficult to solder. The use of ENIG is being extended to provide a gold coating on contact surfaces of an increasing number of electrical connectors because the deposition process is relatively rapid and inexpensive. This application of ENIG has often proven unsatisfactory because the maximum gold layer thickness achievable is 0.1–0.2 μm, and gold layers of this thickness are not necessarily impervious to air and environmental contaminants and generally do not pass the requirements of a “classic” porosity test. ENIG layers on connectors are thus prone to pore corrosion. In addition, the ENIG deposition process often leads to the formation of black deposits stemming from corrosion of the underlying nickel during deposition and leading to poor adhesion of the ENIG layer to the substrate [42–44]. Properties of ENIG coatings will be addressed in greater detail in Chapter 8.
Electrical Equipment in a Corrosive Environment
Published in Bella H. Chudnovsky, Transmission, Distribution, and Renewable Energy Generation Power Equipment, 2017
Typical PCB consists of copper connecting path integrated in a fiber glass reinforced epoxy polymer. PCB wiring use ENIG-process (EN-Gold). The ENIG consists of a few micron thick Ni–P (EN) coating on the base copper on PCB, followed by a thin gold layer on EN [63]. Thickness of the gold layer varies from 50 to 100 nm.
Localised aqueous corrosion of electroless nickel immersion gold-coated copper
Published in Corrosion Engineering, Science and Technology, 2022
M. Mousavi, A. Kosari, J. M. C. Mol, Y. Gonzalez-Garcia
Preserving the electronic performance of SD memory cards from corrosion attacks is of great importance. The corrosion rate of metallic pins in the SD memory cards is determined by their final finishing and service environment characteristics. Electroless nickel immersion gold (ENIG) is the leading surface finish used in electronic industries, among other types of final finishing such as hot air solder levelling, organic solderability preservatives, immersion tin, immersion silver, etc. ENIG consists of a bi-layered metallic coating of Ni and Au to protect the Cu traces [10,11]. ENIG is characterised by high resistance to corrosion and whisker growth, excellent electrical conductivity and solderability, and represents a lead-free, environmentally friendly fabrication process [1,12–14].
Capillary Performance of Micropillar Arrays in Different Arrangements
Published in Nanoscale and Microscale Thermophysical Engineering, 2018
Sangbeom Cho, Rao Tummala, Yogendra Joshi
First, copper clad PCB is laminated twice with 25 µm-thick dry film negative photoresist. The photoresist layer is then exposed to UV illumination with circular pillar shape patterned mask. The photoresist layer is developed to expose the copper surface, where the copper pillars pattern will be plated. O2/CF4 plasma is used to remove any photoresist residues left in the pillar pattern holes. After the photoresist residue removal, the sample is put in dilute sulfuric acid bath to remove the oxide layer and enhance the wettability of the exposed copper surface. The sample is then placed in a copper plating bath equipped with plating solution and copper source. The current density for the plating is fixed throughout the process, and the plating thickness is checked with a three-dimensional (3D) optical profiler every 2 h. After the pattern holes are filled with pillars, the photoresist is stripped in a sonicator. To enhance wettability and protect copper from oxidation, the sample is plated with 50 nm-thick gold using electroless nickel immersion gold (ENIG) process. Figure 2 (a) shows the scanning electron microscope (SEM) image of fabricated micropillar arrays after ENIG process is finished, and Figure 2 (b), (c), and (d) show the images of micropillar arrays in different arrangements taken from optical profiler.