The actual metal deposition occurs in the electrolytic solution which containsthe plating material as metal ions. Besides this basic ingredient, the electrolytescontain additional components depending on the processes used, such as forexample conduction salts, brighteners, and organic additives which are codepositedinto the coatings, influencing the final properties of the electroplatingdeposit.

All precious metals can be electroplated with silver and gold by far the mostwidely used ones <xr id="tab:Overview of Important Properties of Electroplated Coatings and their Applications"/> (Tab. 7.1) and (Tab. 7.2).

*Gold electrolytes <br/>For functional and decorative purposes pure gold, hard gold, low-karatgold, or colored gold coatings are deposited. Depending on therequirements, acidic, neutral, or cyanide electrolytes based onpotassium gold cyanide or cyanide free and neutral electrolytes basedon gold sulfite complexes are used.

*Palladium and Platinum electrolytes <br/> Palladium is mostly deposited as a pure metal, for applications inelectrical contacts however also as palladium nickel. For higher valuejewelry allergy protective palladium intermediate layers are used as adiffusion barrier over copper alloy substrate materials. Platinum is mostlyused as a surface layer on jewelry items.

*Ruthenium electrolytes <br/>Ruthenium coatings are mostly used for decorative purposes creating afashionable “grey” ruthenium color on the surface. An additional colorvariation is created by using “ruthenium-black” deposits which aremainly used in bi-color decorative articles.

*Rhodium electrolytes <br/>Rhodium deposits are extremely hard (HV 700 – 1000) and wearresistant. They also excel in light reflection. Both properties are of valuefor technical as well as decorative applications. While technicalapplications mainly require hard, stress and crack free coatings, thejewelry industry takes advantage of the light whitish deposits with highcorrosion resistance.

*Silver electrolytes < br/>Silver electrolytes without additives generate dull soft deposits (HV ~ 80)which are mainly used as contact layers on connectors with limitedinsertion and withdrawal cycles. Properties required for decorativepurposes such as shiny bright surfaces and higher wear resistance areachieved through various additives to the basic Ag electrolyte.

The most important non-precious metals that are deposited by electroplatingare: Copper, nickel, tin, and zinc and their alloys. The deposition is performed inthe form of pure metals with different electrolytes used ''(Table 7.4)''.

*Copper electrolytes < br/>Copper electrolytes are used for either depositing an intermediate layer onstrips or parts, for building up a printed circuit board structure, or for thefinal strengthening during the production of printed circuit boards.

*Tin electrolytes < br/>Pure tin and tin alloy deposits are used as dull or also bright surfacelayers on surfaces required for soldering. In the printed circuit boardmanufacturing they are also utilized as an etch resist for the conductivepattern design after initial copper electroplating.

*Nickel electrolytes < br/>Nickel layers are mostly used as diffusion barriers during thegold plating of copper and copper alloys or as an intermediate

*Bronze electrolytes < br/>Bronze coatings – in white or yellow color tones – are used either as anallergy free nickel replacement or as a surface layer for decorativepurposes. For technical applications the bronze layers are utilized for theirgood corrosion resistance and good brazing and soldering properties.

The complete or all-around electroplating of small mass produced parts likecontact springs, rivets, or pins is usually done as mass plating in electroplatingbarrels of different shape. During the electroplating process the parts arecontinuously moved and mixed to reach a uniform coating.

Larger parts are frequently electroplated on racks either totally or by differentmasking techniques also partially. Penetrating the coating into the interior ofdrilled holes or tubes can be achieved with the use of special fixtures.

These quality tests are performed according to industry standards, internalstandards, and customer specifications resp.

The process for overall electroplating of strips, profiles, and wires is mostlyperformed on continuously operating reel-to-reel equipment. The processingsteps for the individual operations such as pre-cleaning, electroplating, rinsingare following the same principles as those employed in parts electroplating.

The overall coating is usually applied for silver plating and tin coating of stripsand wires. Compared to hard gold or palladium these deposits are ratherductile, ensuring that during following stamping and forming operations nocracks are generated in the electroplated layers.

Since precious metals are rather expensive it is necessary to perform theelectroplating most economically and coat only those areas that need the layersfor functional purposes. This leads from overall plating to selectiveelectroplating of strip material in continuous reel-to-reel processes. Dependingon the final parts design and the end application the processes can be appliedto solid strip material as well as pre-stamped and formed continuous strips orutilizing wire-formed or machined pins which have been arranged as bandoliersattached to conductive metal strips.

The core part of selective precious metal electroplating is the actualelectroplating cell. In it the anode is arranged closely to the cathodic polarizedmaterial strip. Cathode screens or masks may be applied between the two tofocus the electrical field onto closely defined spots on the cathode strip.

Special high performance electrolytes are used in selective electroplating toreach short plating times and allow a high flow rate of the electrolyte for a fastelectrolyte exchange in the actual coating area.

For a closely targeted electroplating of limited precious metal coating of contactsprings so-called brush-electroplating cells are employed ''(Fig. 7.1)''. The “brush”or “tampon” consists of a roof shaped titanium metal part covered with a specialfelt-like material. The metal body has holes in defined spots through which theelectrolyte reaches the felt. In the same spots is also the anode consisting of afine platinum net. The pre-stamped and in the contact area pre-formed contactspring part is guided under a defined pressure over the electrolyte soaked feltmaterial and gets wetted with the electrolyte. This allows the metalelectroplating in highly selective spots.

For special applications, such as for example electronic component substrates,a dot shaped precious metal coating is required. This is achieved with two beltmasks running synchronous to the carrier material. One of these two masks haswindows which are open to the spot areas targeted for precious metal platingcoverage.

Overall or selective electroplating of both sides of solid strips or pre-stampedparts in strip form

Stripe electroplating on solid strips through wheel cells or using maskingtechniques

One-sided selective coating of solid, pre-stamped, or metallically belt-linkedstrips by brush plating

Electroplating in spots of solid strips with guide holes or pre-stamped parts instrip form

Mechanical properties and dimensional tolerances of the carrier materials followthe typical standards, i.e. DIN EN 1652 and 1654 for copper and copper alloys.Depending on the application the following parameters are tested andrecorded (see also: Electroplating of parts):

These quality tests are performed according to industry standards, internalstandards, and customer specifications resp.