1. Function and Characteristics: Nickel plating is used as a substrate coating for precious and base metals on printed circuit boards (PCBs), and is also commonly used as a surface layer for some single-sided PCBs. The manufacturer tells you that for some surfaces with heavy load wear, such as switch contacts, contact pads, or plug gold, using nickel as the substrate coating for gold can greatly improve wear resistance. When used as a barrier layer, nickel can effectively prevent diffusion between copper and other metals. Matte nickel/gold composite coatings are often used as corrosion-resistant metal coatings and can meet the requirements of hot press welding and brazing. Only nickel can be used as a corrosion-resistant coating containing ammonia based etchants, and PCBs that do not require hot press welding and require bright coatings are usually coated with glossy nickel/gold coatings. The thickness of nickel coating is generally not less than 2.5 microns, usually 4-5 microns. The deposition layer of low stress nickel on PCB is usually made using modified Watt nickel plating solution and some amino sulfonic acid nickel plating solution with stress reducing additives. The PCB nickel plating commonly referred to as bright nickel and matte nickel (also known as low stress nickel or semi bright nickel) usually requires uniform and fine coating, low porosity, low stress, and good ductility.

2. Nickel aminosulfonate is widely used as a substrate coating on metalized hole electroplating and printed plug contacts. The obtained deposited layer has low internal stress, high hardness, and superior ductility. Adding a stress relieving agent to the plating solution will result in a slightly stressed coating. There are various formulations of ammonium sulfonate plating solutions, and the typical formula for ammonium sulfonate nickel plating solution is shown in the table below. Due to the low stress of the coating, it has been widely used, but nickel aminosulfonate has poor stability and relatively high cost.

3. Modified Watt nickel (sulfur nickel) modified Watt nickel formula, using nickel sulfate, along with the addition of nickel bromide or nickel chloride. Due to internal stress, nickel bromide is mostly used. It can produce a semi bright, slightly internally stressed, and ductile coating; And this coating is easily activated for subsequent electroplating, with relatively low cost.