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Electroless nickel immersion gold (ENIG or ENi/IAu), also known as immersion gold (Au), chemical Ni/Au or soft gold, is a metal plating process used in the manufacture of printed circuit boards (PCBs), to avoid oxidation and improve the solderability of copper contacts and plated through-holes.
The microns of thickness determines how long the gold plating lasts with usage. The jewellery industry denotes different qualities of gold plating in the following terminology Gold flashed / Gold washed - gold layer thickness less than 0.5 micron; Gold plated - gold layer thickness greater than or equal to 0.5 micron
Coatings of moderate thickness 1.8 μm to 25 μm (0.00007" to 0.001") [16] are known as Type II in North America, as named by MIL-A-8625, while coatings thicker than 25 μm (0.001") are known as Type III, hard-coat, hard anodizing, or engineered anodizing. Very thin coatings similar to those produced by chromic anodizing are known as Type IIB.
Electroless nickel plating, covered by a thin layer of gold, is used in the manufacture of printed circuit boards (PCBs), to avoid oxidation and improving the solderability of copper contacts and plated through holes and vias. The gold is typically applied by quick immersion in a solution containing gold salts.
Electroplating of acid gold on underlying copper- or nickel-plated circuits reduces contact resistance as well as surface hardness. Copper-plated areas of mild steel act as a mask if case-hardening of such areas are not desired. Tin-plated steel is chromium-plated to prevent dulling of the surface due to oxidation of tin.
PCBs may be plated with solder, tin, or gold over nickel. [50] [51] After PCBs are etched and then rinsed with water, the solder mask is applied, and then any exposed copper is coated with solder, nickel/gold, or some other anti-corrosion coating. [52] It is important to use solder compatible with both the PCB and the parts used.
Wire bonding can also be used to connect an IC to other electronics or to connect from one printed circuit board (PCB) to another, although these are less common. Wire bonding is generally considered the most cost-effective and flexible interconnect technology and is used to assemble the vast majority of semiconductor packages.
An IBM circuit board from a NASA Space Shuttle computer with a conformal coating applied. Conformal coating is a protective, breathable coating of thin polymeric film applied to printed circuit boards (PCBs). Conformal coatings are typically applied with 25–250 μm [1] thickness on electronic circuitry to protect against moisture and other ...