Technical possibilities at Metoba
Metoba offers the following techniques for processing Silver plating :Reel-to-reel-finishingRack-finishingBulk-finishingVibrobot refinement
1. Characteristics and properties
Silver is a shiny, white metal and has the highest specific conductivity of all metals. Metallurgically produced silver is very soft with a hardness of 27 HV 0.1, but electrodeposited silver has a hardness of 80-130 HV 0.1. Silver layers also have good thermal conductivity and are very solderable. Silver is resistant to diluted inorganic and organic acids as well as to alkalis. On the other hand, it dissolves rapidly in nitric acid and in hot, concentrated sulphuric acid.
Hydrogen sulphide leads to the formation of a black-brown layer of silver sulphide in the presence of oxygen. For this reason, electrodeposited layers of silver are provided with a passivation, which maintains the decorative appearance and prevents an increase in contact resistance in electronic components. However, this property of the passivation is strongly dependent on the external environmental influences acting on the coating and is therefore only effective for a limited time.
2. Benefits and areas of application
Nowadays silver is mainly used in the electrical industry as a contact metal, since silver layers have the properties described above, which are only achieved by a few other metals.
3. Basic material
The basic materials that can be silver plated directly are copper, brass, nickel or nickel silver. Other metallic base materials can also be provided with a silver coating by means of intermediate layers. With base materials such as stainless steels, for example, an intermediate layer must first be applied, which usually consists of 0.5-1µm nickel strike.
For technical purposes, layer thicknesses of 1-50µm are applied depending on the stress, for decorative purposes only silver layers of 3-5µm are applied.
4. Required delivery condition
The goods provided must be largely metallically bright. Residual oils or residual impurities must be removable with conventional aqueous alkaline degreasers. Oils containing silicone, alkali/alkaline earth and high-pressure additives must be avoided at all costs.
Since the base materials are less noble than the silver layer applied, it must be prevented that silver is deposited on the surface by charge exchange. For this reason, a thin silver layer is first applied in a pre-silver bath.