![]() ![]() Typical stop-offs include tape, foil, lacquers, and waxes. When plating is not desired on certain areas of the substrate, stop-offs are applied to prevent the bath from coming in contact with the substrate. Additionally, non-metal chemicals such as carbonates and phosphates may be added to increase conductivity. These free cyanides facilitate anode corrosion, help to maintain a constant metal ion level and contribute to conductivity. Many plating baths include cyanides of other metals (such as potassium cyanide) in addition to cyanides of the metal to be deposited. The true alloy is more corrosion-resistant than the as-plated mixture. In the case of plated solder, it is sometimes deemed necessary to have a true alloy, and the plated solder is melted to allow the tin and lead to combine into a true alloy. Plated "alloys" are not "true alloys" (solid solutions), but rather they are tiny crystals of the elemental metals being plated. However, some alloys can be electrodeposited, notably brass and solder. The plating is most commonly a single metallic element, not an alloy. In this case, ions of the metal to be plated must be replenished (continuously or periodically) in the bath as they are drawn out of the solution. Oxygen, hydrogen peroxide, and some other byproducts are then produced at the anode instead. The anode may instead be made of a material that resists electrochemical oxidation, such as lead or carbon. The net result is the effective transfer of metal from the anode to the cathode. In this case, the rate at which the anode is dissolved will be equal to the rate at which the cathode is plated and thus the ions in the electrolyte bath are continuously replenished by the anode. For example, copper would be oxidized at the anode to Cu 2+ by losing two electrons. When the anode is made of the metal that is intended for coating onto the cathode, the opposite reaction may occur at the anode, turning it into dissolved cations. At the cathode, the Cu 2+ is reduced to metallic copper by gaining two electrons. For example, the electrolyte for copper plating can be a solution of copper(II) sulfate, which dissociates into Cu 2+ cations and SO 2−Ĥ anions. These cations are reduced at the cathode to the metal in the zero valence state. The electrolyte in the electrolytic plating cell should contain positive ions (cations) of the metal to be deposited. See also: Electrotyping and Electroforming ![]() A copper anode is used to replenish the electrolyte with copper cations Cu 2+ The electrolyte is a solution of copper sulfate, CuSOĤ. Process Simplified diagram for electroplating copper (orange) on a conductive object (the cathode, "Me", gray). It depends mostly on the composition and temperature of the electroplating solution. Throwing power is an important parameter that provides a measure of the uniformity of electroplating current, and consequently the uniformity of the electroplated metal thickness, on regions of the part that are near to the anode compared to regions that are far from it. The term "electroplating" may also be used occasionally for processes that use an electric current to achieve oxidation of anions on to a solid substrate, as in the formation of silver chloride on silver wire to make silver/silver-chloride (AgCl) electrodes.Įlectropolishing, a process that uses an electric current to remove metal cations from the surface of a metal object, is the reverse of the process of electroplating. It is also used to purify metals such as copper. It is used to deposit copper and other conductors in forming printed circuit boards, and copper interconnects in integrated circuits. It is used to build up thickness on undersized or worn-out parts, or to manufacture metal plates with complex shape, a process called electroforming. The current is provided by an external power supply.Įlectroplating is widely used in industry and decorative arts to improve the surface qualities of objects-such as resistance to abrasion and corrosion, lubricity, reflectivity, electrical conductivity, or appearance. ![]() The part to be coated acts as the cathode (negative electrode) of an electrolytic cell the electrolyte is a solution of a salt of the metal to be coated and the anode (positive electrode) is usually either a block of that metal, or of some inert conductive material. Creation of protective or decorative metallic coating on other metal with electric current Copper electroplating machine for layering PCBsĮlectroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the reduction of cations of that metal by means of a direct electric current. ![]()
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