Changes

Besides manufacturing contact materials from the solid phase, i.e. by melt orpowder metallurgy, the production starting in the liquid or gaseous phase isgenerally preferred when thin layers in within the μm range are required , which cannotbe obtained economically by conventional cladding methods(<xr id="tab:Overview_of_Important_Properties_of_Electroplated_Coatings_and_their_Applications"/><!--(Tab. 7.1)-->). Such coatingsfulfill different requirements depending on their composition and thickness.They can serve as corrosion or wear protection or can fulfill the need for thincontact layers for certain technical applications. In addition they serve fordecorative purposes as a pleasing and wear resistant surface coating.

<figtable id="tab:Overview_of_Important_Properties_of_Electroplated_Coatings_and_their_Applications"><caption>'''<!--Table 7.1: -->Overview of Important Properties of Electroplated Coatingsand their Applications'''</caption>

To reduce the {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Properties!Applications!Examples|-|Color|Pleasing appearance|Brass plated lamps and furniture hardware|-|Luster|Decorative appearance, Light reflection|Chrome plated fixtures, silver coated mirrors|-|Hardness / Wear Resistance|Prolonging of mechanical wear life|Hard chrome plated tools|-|Sliding properties|Improvement of thin dry sliding wear|Lead-tin-copper alloys for slide bearings|-|Chemical stability|Protection against chemical effects|Lead-Tin coatings as etch resist on PC boards|-|Corrosion resistance|Protection against environmental corrosion|Zinc coatings on steel parts|-|Electrical conductivity|Surface conduction of electrical current|Conductive path on PC boards|-|Thermal conductivity|Improved heat conduction on the surface |Copper plated bottoms for cookware|-|Machining capability|Shaping through machining|Copper coatings on low pressure cylinders|-|Magnetic properties|Increase of coercive force [[#text-reference|^*)]] |Cobalt-nickel layers on sliding magnetic storage media|-|Brazing and connectorsoldering|Brazing without aggressive fluxes|Tin-Lead coatings on PC board pathscontacts additional lubricants |-|Adhesion strength|Improvement of adhesion|Brass coating on reinforcement steel wires in liquid form are often used. On silver contactstires|-|Lubricating properties|Improvement of formability|Copper plating for wire drawing|}</figtable>passivation coatings are applied as protection against silver sulfide formation.<div id="text-reference">*) Coercive force= force to retaim the adopted magnetisation</div>

===7.1 Coatings from To reduce the Liquid Phase===For mechanical wear of thin coatings starting from the surface layers on sliding and connector contacts, additional lubricants in liquid phase two processes form are often useddifferentiated by the metallic deposition being performed either with or withoutthe use of an external electrical current source. The first one is electroplatingwhile the second one is a chemical deposition processOn silver contacts, passivation coatings are applied as protection against silver sulfide formation.

===7.1.1 Electroplating (or Galvanic Deposition)=Coatings from the Liquid Phase==For electroplating of metalsthin coatings starting from the liquid phase, especially precious metals, water based solutions(electrolytes) two processes are used which contain differentiated by the metals to be deposited as ions (i.e.dissolved metal salts). An electric field between metallic deposition being performed either with or without the anode and the work piecesas the cathode forces the positively charged metal ions to move to the cathodewhere they give up their charge and deposit themselves as metal on the surfaceuse of the work piece.Depending on the application, for electric and electronic or decorative end use,different electrolytic bath solutions (electrolytes) are usedan external electrical current source. The first one is electroplatingequipment used for precious metal plating and its complexity varies widelydepending on , while the second one is a chemical deposition process technologies employed.Electroplating processes are encompassing besides the pure metal depositionalso preparative and post treatments of the goods to be coated. An importantparameter for creating strongly adhering deposits is the surface of the goods tobe metallic clean without oily or oxide film residues. This is achieved throughvarious pre-treatment processes specifically developed for the types of materialand surface conditions of the goods to be plated.In the following segments electrolytes – both precious and non-precious – aswell as the most widely used electroplating processes are described.

===7.1.1.1 Electroplating Solutions – Electrolytes(or Galvanic Deposition)===The actual For electroplating of metals, especially precious metals, water based solutions (electrolytes) are used, which contain the metals to be deposited as ions (i.e. dissolved metal deposition occurs in salts). An electric field between the electrolytic solution which containsanode and the plating material work pieces as the cathode, forces the positively charged metal ionsto move to the cathode where they give up their charge and deposit themselves as metal on the surface of the work piece. Besides this basic ingredientDepending on the application, the for electric and electronic or decorative end use, different electrolytic bath solutions (electrolytescontain additional components ) are used. The electroplating equipment used for precious metal plating and its complexity varies widely, depending on the process technologies employed.Electroplating processes usedare encompassing, besides the pure metal deposition, such as also preparative and post treatments of the goods to be coated. An important parameter forexample conduction salts, brightenerscreating strongly adhering deposits is that the surface of the goods has to be metallic clean without oily or oxide film residues. This is achieved through various pre-treatment processes, specifically developed for the types of material and organic additives which are codepositedsurface conditions of the goods to be plated.into In the coatingsfollowing segments, influencing the final properties of electrolytes – both precious and non-precious – as well as the most widely used electroplatingdepositprocesses are described.

===7.1.1.1.1 Precious Metal Electrolytes===All precious metals can be electroplated with silver and gold by far the mostwidely used ones ''Main Articel: [[Electroplating (or Galvanic Deposition)| Electroplating (Tables 7.1 and 7.2or Galvanic Deposition)''.The following precious metal electrolytes are the most important ones:]]

*'''Gold electrolytes''' For functional and decorative purposes pure gold, hard gold, low===<!-karat gold, or colored gold coatings are deposited-7. Depending on the requirements, acidic, neutral, or cyanide electrolytes based on potassium gold cyanide or cyanide free and neutral electrolytes based on gold sulfite complexes are used1.2-->Electroless Plating===

*'''Palladium and Platinum electrolytes''' Palladium Electroless plating is mostly deposited defined as a pure coating process which is performed without the use of an external current source. It allows a uniform metalcoating, independent of the geometrical shape of the parts, to be coated. Because of the very good dispersion capability of the used electrolytes, also cavities and the inside of drilled holes in parts can be coated for applications in electrical contacts however also as palladium nickelexample. For higher value jewelry allergy protective palladium intermediate layers In principal, two different mechanisms are used employed for electroless plating: processes in which the carrier material serves as a diffusion barrier over copper alloy substrate materials. Platinum reduction agent (Immersion processes) and those in which a reduction agent is mostly used as a surface layer on jewelry itemsadded to the electrolyte (Electroless processes).

*'''Rhodium electrolytes''' Rhodium deposits are extremely hard ==<!--7.2-->Coatings from the Gaseous Phase (Vacuum Deposition)==The term PVD (HV 700 – 1000physical vapor deposition) defines processes of metal, metal alloys and wear resistant. They also excel chemical compounds deposition in light reflectiona vacuum by adding thermal and kinetic energy by particle bombardment. Both properties The main processes are of value for technical as well as decorative applications. While technical applications mainly require hard, stress and crack free coatings, the jewelry industry takes advantage following four coating variations (<xr id="tab:Characteristics of the light whitish deposits with high corrosion resistanceMost Important PVD Processes"/><!--(Table 7.6-->):

*'''Silver electrolytes''' Silver electrolytes without additives generate dull soft deposits Vapor deposition *Sputtering (HV ~ 80Cathode atomization) which are mainly used as contact layers on connectors with limited insertion and withdrawal cycles. Properties required for decorative purposes such as shiny bright surfaces and higher wear resistance are achieved through various additives to the basic Ag electrolyte.*Arc vaporizing *Ion implantation

Table 7In all four processes, the coating material is transported in its atomic form to the substrate and deposited on it as a thin layer (a few nm to approx.2: Precious Metal Electrolytes for Technical Applications10 μm)

*<figtable id="tab:Characteristics of the Most Important PVD Processes"><caption>'''Copper electrolytes<!--Table 7.6:-->Characteristics of the Most Important PVD Processes''' Copper electrolytes are used for either depositing an intermediate layer on strips or parts, for building up a printed circuit board structure, or for the final strengthening during the production of printed circuit boards.</caption>

*'''Tin electrolytes''' Pure tin and tin {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Process!Principle!Process Gas Pressure!Particle Energy!Remarks|-|Vapor deposition|Vaporizing in a crucible <br />(electron beam or resistance heating)|10^-3 Pa|< 2eV|Separation of alloy deposits are used as dull or also bright surface layers on surfaces required for soldering. In components may occur|-|Arc vaporizing|Vaporizing of the printed circuit board manufacturing they are also utilized as target <br />plate in an etch resist for electrical arc|10^-1 Pa-1Pa|80eV-300eV|Very good adhesion due to ion bombardement|-|Sputtering|Atomizing of the target plate<br />(cathode) in a gas discharge|10^-1 Pa-1Pa|10eV-100eV|Sputtering of non-conductive pattern design after initial copper electroplating.materials possible through RF operation|-|Ion implantation|Combination of vapor <br />deposition and sputtering|10^-1 Pa-1Pa|80eV-300eV|Very good adhesion from ion bombardment but also heating of the substrate material|}</figtable>

*'''Nickel electrolytes''' Nickel layers are mostly used as diffusion barriers during The sputtering process has gained the gold plating economically most significant usage. Its process principle is illustrated in (<xr id="fig:Principle of copper and copper alloys or as an intermediate layer for tinningsputtering"/><!--(Fig. 7.5)-->).

*'''Bronze electrolytes''' Bronze coatings – <figure id="fig:Principle of sputtering">[[File:Principle of sputtering.jpg|right|thumb|Figure 1: Principle of sputtering Ar = Argon atoms; e = Electrons; M = Metal atoms]]</figure>Initially, a gas discharge is ignited in white or yellow color tones – a low pressure (10^-1 -1 Pa) argon atmosphere. The argon ions generated, are used either as accelerated in an allergy free nickel replacement or as electric field and impact the target of material to be deposited with high energy. Caused by this energy, atoms are released from the target material which condensate on the oppositely arranged anode (the substrate) and form a surface layer for decorative purposeswith high adhesion strength. For technical applications Through an overlapping magnetic field at the bronze layers are utilized for their good corrosion resistance and good brazing and soldering propertiestarget location, the deposition rate can be increased, making the process more economical.

Table 7.2The advantages of the PVD processes and especially sputtering for electrical contact applications are: Typical Electrolytes for the Deposition of Non-Precious Metals

===7.1.1.2 Electroplating *High purity of Parts===the deposit layers The complete or all-around electroplating of small mass produced parts like*Low thermal impact on the substrate contact springs, rivets, or pins is usually done as mass plating in electroplating*Almost unlimited coating materials barrels of different shape. During the electroplating process the parts are*Low coating thickness tolerance continuously moved and mixed to reach a uniform coating.*Excellent adhesion (also by using additional intermediate layers)

Larger parts Coatings produced by PVD processes are frequently electroplated used for contact applications, for example 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 miniature-profiles, in electrical engineering and for electronic components, for solderability in joining processes, for metalizing of special fixturesnonconductive materials, as well as in semiconductors, opto-electronics, optics and medical technology applications.

There are few limitations regarding the geometrical shape of substrate parts. Only the interior coating of drilled holes and small diameter tubing can be more problematic (ratio of depth to diameter should be < 2:1). Profile wires, strips and foils can be coated from one side or both; formed parts can be coated selectively by using masking fixtures that at the same time serve as holding fixtures (<xr id===Electroplated Parts===bild"fig:Examples of vacuum coated semi finished materials and parts"/>).

*'''<table class="twocolortable"><tr><th rowspan="2"><p class="s8">Substrate Materials</p></th><th colspan="12"><p class="s8">Coating thickness'''Materials</p></th></tr><tr><th><p><span>Ag</span></p></th><th><p><span>Au</span></p></th><th><p><span>Pt</span></p></th><th><p><span>Pd</span></p></th><th><p><span>Cu</span></p></th><th><p><span>Ni</span></p></th><th><p><span>Ti</span></p></th><th><p><span>Cr</span></p></th><th><p><span>Mo</span></p></th><th><p><span>W</span></p></th><th><p><span>Ai</span></p></th><th><p><span>Si</span></p></th></tr><tr><td><p class="s8">Precious metal / alloys</p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">NF metals / alloys</p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Fe alloys / stainless steel</p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Special metals (Ti, Mo, W)</p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Carbide steels (WC-Co)</p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Ceramics (Al<span class="s16">2</span>O<span class="s16">3</span>, AlN)</p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Glasses (SiO<span class="s16">2</span>, CaF)</p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Plastics (PA, PPS)</p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr></table>

Precious metals[[File: 0.2 – 5 μm (typical layer thicknesses; for Ag also up to 25 μm)NonK7-precious metals: Up to approxgef. 20 μmpng]] can be producedTolerances[[File: Strongly varying depending on the geometrical shape ofparts (up to 50% at a defined measuring spot)K7-leer.It is recommended to specify a minimum value for thecoating thickness at a defined measuring spotpng]] can be produced with intermediate layer

*{| class="twocolortable" style="text-align: left; font-size: 12px;width:40%"|-!colspan="2" style="text-align:center"|'''Quality criteriaDimensions''' Besides others the following layer parameters are typically monitored in|-|Coating thickness:|10 nm - 15 μm|-process and documented|Coating thicknesses for contact applications:|0.1 - 10 μm|}

===7.1.1.3 Electroplating of SemiCoating thickness &#177;10 -finished Materials===30 %, depending on the thickness The process for overall electroplating of strips, profiles, and wires is mostly*'''Quality criteria'''performed Depending on continuously operating reel-to-reel equipment. The processingsteps for the individual operations such as pre-cleaningapplication, electroplating, rinsingthe following parameters are following the same principles as those employed in tested and recorded (see also: Electroplating of parts electroplating.):

===7.1.1.4 Selective Electroplating===Since precious metals These quality tests are rather expensive it is necessary performed according to perform theelectroplating most economically industry standards, internal standards 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 stripscustomer specifications resp.

==<!--7.3-->Comparison of Deposition Processes==The core individual deposition processes have in part of selective precious metal electroplating is the actualelectroplating celldifferent performance characteristics. In it For each end application, the anode is arranged closely optimal process has to the cathodic polarizedmaterial stripbe chosen, considering all technical and economical factors. Cathode screens or masks may The main selection criteria should be applied between based on the two tofocus electrical and mechanical requirements for the electrical field onto closely defined spots contact layer and on the cathode stripdesign characteristics of the contact component. <xr id="tab:Comparison of different coating processes"/><!--Table 7.7--> gives some indications for a comparative evaluation of the different coating processes.

Special high performance electrolytes are used in selective electroplating toreach short plating times and allow a high flow rate The electroless metal coating is not covered here because of the electrolyte low thickness of deposits, which makes them in most cases not suitable for a fastcontactelectrolyte exchange in the actual coating areaapplications.

Fig<figtable id="tab:Comparison of different coating processes"><caption>'''<!--Table 7. 7.1:Brush (or “Tampon”) plating cell;1 Strip; 2 Anode; 3 Electrolyte feed;4 Felt covered cell-->Comparison of different coating processes'''</caption>

For special applications, such as for example electronic component substrates{| class="twocolortable" style="text-align: left; font-size: 12px"|-!Process / Coating Properties!Mechanical Processes (Cladding)!Electroplating!Vaccum Deposition (Sputtering)|-|Coating material|formabe metal and alloys|metals,alloys only limited|metals and alloys|-|Coating thickness|> 1μma dot shaped precious metal coating is required|0.1 - approx. This is achieved with two belt10 μm <br />(in special cases up to 100 μm)masks running synchronous to the carrier material|0.1 approx. One 10 μm|-|Coating configuration|selectively, stamping edges not coated|all around and selectively<br />stamping edges coated|mostly selectivity|-|Adhesion|good|good|very good|-|Ductility|good|limited|good|-|Purity|good|inclusions of these two masks hasforeign materialswindows which are open to the spot areas targeted |very good|-|Porosity|good|good for precious metal plating> approx. 1μm|good|-|Temperature stability|goodvery good|good|very good|-|Mechanical wear|little|very little|little|-|Environmental impact|little|significant|none|}coverage.</figtable>

===Summary The main differences between the coating processes are found in the coating materials and thickness. While mechanical cladding and sputtering allow the use of the almost any alloy material, electroplating processes are limited to metals and selected alloys, such as for selective example high-carat gold alloys with up to .3 wt% Co or Ni. Electroplated and sputtered surface layers have a technological and economical upper thickness limit of about 10μm. While mechanical cladding has a minimum thickness of approx. 1 μm, electroplating===and sputtering can also be easily applied in very thin layers down to the range of 0.1 μm.

*'''Immersion electroplating'''Overall or selective The properties of the coatings are closely related to the coating process. Starting materials for cladding and sputtering targets precious metals and their alloys, which in the case of gold and palladium based materials, are vacuum melted and therefore exhibit a very high purity. During electroplating , depending on the type of both sides of solid strips or pre-stampedparts in strip formelectrolytes and the deposition parameters, some electrolyte components such as carbon and organic compounds are incorporated into the precious metal coating. Layers deposited from the gaseous phase however are very pure.

*'''Stripe electroplating'''==<!--7.4-->Hot (-Dipped) Tin Coated Strip Materials==Stripe electroplating on solid During hot-dip tinning, pre-treated strip materials are coated with pure tin or tin alloys from a liquid solder metal. During overall (or all-around) tinning the strips through wheel cells a liquid metal melt. For strip tinning, rotating rolls are partially immersed into a liquid tin melt and transport the liquid onto the strip, which is guided above them. Through special wiping and gas blowing procedures, the deposited tin layer can be held within tight tolerances. Hot tinning is performed directly onto the base substrate material without any pre-coating with either copper or nickel. Special cast-on processes or using maskingtechniquesthe melting of solder foils onto the carrier strip, also allows the production of thicker solder layers ( > 15 μm).

*'''Selective The main advantage of hot tinning of copper and copper alloys, compared to tin electroplating'''One, is the formation of an inter-metallic copper-sided selective coating of solidtin phase (Cu₃Sn, Cu₆Sn₅) at the boundary between the carrier material and the tin layer. This thin (0.3 – 0.5 μm) intermediate layer, pre-stampedwhich is formed during the thermal tinning process, or metallically belt-linkedstrips is rather hard and reduces the frictional force and mechanical wear in connectors. Tin coatings produced by brush platinghot tinning have a good adhesion to the substrate material and do not tend to tin whisker formation.

*'''Spot A special process of hot tinning is the “Reflow” process. After depositing a tin coating by electroplating'''Electroplating in spots of solid strips with guide holes or pre, the layer is short-stamped parts time melted ina continuous process.strip formThe properties of these reflow tin coatings are comparable to those created by conventional hot tinning.

Besides overall tin coating of strip material, the hot tinning can also be applied in the form of single or multiple stripes on both sides of a continuous substrate strip (<xr id==="fig:Typical examples of electroplated semi-finished hot tinned strip materials=== (overall or selectively"/>)bild.

 <table border="1" cellspacing="0" style="border-collapseCoating materials:collapse"><tr><td><p class="s8">Type of Coatings</p></td><td><p class="s8">Coating Thickness</p></td><td><p class="s8">Remarks</p></td></tr><tr><td><p class="s8">Precious Metals</p></td><td/><td/></tr><tr><td><p class="s8">Pure gold</p><p class="s8">Hard gold (AuCo 0.3)</p></td><td><p class="s8">0.1 - 3 µm</p></td><td><p class="s8">In special cases up to 10 µm</p></td></tr><tr><td><p class="s8">Palladium-nickel (PdNi20)</p></td><td><p class="s8">0.1 - 5 µm</p></td><td><p class="s8">Frequently with additional 0.2 µm AuCo 0.3</p></td></tr><tr><td><p class="s8">Silver</p></td><td><p class="s8">0.5 - 10 µm</p></td><td><p class="s8">In special cases up to 40 µm</p></td></tr><tr><td><p class="s8">Non-precious Metals</p></td><td/><td/></tr><tr><td><p class="s8">Nickel</p></td><td><p class="s8">0.5 - 4 µm</p></td><td><p class="s8">Diffusion barrier especially for gold layers</p></td></tr><tr><td><p class="s8">Copper</p></td><td><p class="s8">1 - 5 µm</p></td><td><p class="s8">Intermediate layer used in tinning of CuZn</p></td></tr><tr><td><p class="s8">Tintin, tin alloys</p></td><td><p class="s8">0.8 - 25 µm</p></td><td><p class="s8"br>Substrate materials</p></td></tr></table> *'''Carrier Materials'''Copper: Cu, copper alloysCuZn, nickelCuNiZn, nickel alloysCuSn, stainless steelCuBe and others<br />

{| class="twocolortable" style="text-align: left; font-size: 12px;width:40%"Bild |-|Width of tinning: DimensionsCarrier thickness d= 0.1 - |&#8805; 3 &#177; 1 mmCarrier width B= 6 |- 130 mmDistance b > 2 mm|Thickness of tinning: Coating width a= 2 |1 - 30mm15 μmCoating thickness s = 0.2 |- 5 μm|Tolerances (typical rangethickness): Distance from edge b > 0.5 mm|&#177; 1 - &#177; 3 μm depending on the carrier tin thicknessand the plating process *'''Tolerances'''Coating thickness approx. 10 %Coating thickness and position + 0,5 mm|}

Mechanical properties strength and dimensional tolerances of hot tinned strips are closely related to the carrier materials followthe typical standards, i.e. standard for Cu and Cu alloy strips according to DIN EN 1652 and DIN EN 1654 for copper and copper alloys.Depending on the application the following parameters are tested andrecorded (see also: Electroplating of parts): *Coating thickness *Solderability*Adhesion strength *Bonding property *Porosity *Contact resistance These quality tests are performed according to industry standards, internalstandards, and customer specifications resp. ===7.1.2 Electroless Plating=== ===7.1.2.1 Introduction===Electroless plating is defined as a coating process which is performed withoutthe use of an external current source. It allows a uniform metal coatingindependent of the geometrical shape of the parts to be coated. Because of thevery good dispersion capability of the used electrolytes also cavities and theinside of drilled holes in parts can be coated for example.In principal two different mechanisms are employed Quality criteria for electroless plating:processes in which the carrier material serves as a reduction agent (Immersionprocesses) and those in which a reduction agent is added to the electrolyte(Electroless processes). ===7.1.2.2 Immersion Processes===The immersion processes actual tin coatings are usually applied in the plating of the metals gold,silver, and tin. If the material to be coated is less precious, i.e. exhibits anegative standard potential against the metal ions in the surrounding solution, itgoes into solution releasing electrons while the more precious metal ions arereduced by absorbing electrons and being deposited on the electrode. Thisprocess can continue until the complete surface of the substrate is coveredwith a thin layer of the more precious metal. This limits the maximum achievablelayer thickness to approx. 0.1 μm ''(Table 7.5)''. Table 7.5: Immersion Gold Electrolytes<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s8">Type of Electrolyte</p></td><td><p class="s8">pH-Range</p></td><td><p class="s8">Coating Properties</p></td><td><p class="s8">Application Ranges</p></td></tr><tr><td><p class="s8">Type of Electrolyte</p></td><td><p class="s8">pH-Range</p></td><td><p class="s8">Hardness</p><p class="s8">HV 0.025</p></td><td><p class="s8">Punity</p></td><td><p class="s8">Application Ranges</p></td></tr><tr><td><p class="s8">Immersion Gold electrolytes</p></td><td/><td/><td/><td/></tr><tr><td><p class="s8">AUROL 4</p><p class="s8">AUROL 16</p><p class="s8">AUROL 20</p></td><td><p class="s8">3.8 - 4.2</p><p class="s8">5.8 - 6.2</p><p class="s8">5.8 - 6.2</p><p class="s8">5.8 - 6.2</p></td><td><p class="s8">60 - 80</p><p class="s8">60 - 80</p><p class="s8">60 - 80</p><p class="s8">60 - 80</p></td><td><p class="s8">99.99% Au</p><p class="s8">99.99% Au</p><p class="s8">99.99% Au</p><p class="s8">99.99% Au</p></td><td><p class="s8">Thin gold layers on Ni, Ni alloys,</p><p class="s8">Fe and Fe alloys for PCB technology and technical applications</p></td></tr></table> ===7.1.2.3 Electroless Processes===The electroless metal plating with adding reduction agents to the electrolyte isbased on the oxidation of the reducing agent with release of electrons whichthen in turn reduce the metal ions. To achieve a controlled deposition from suchsolutions the metal deposition has to happen through the catalytic influence ofthe substrate surfaceagreed upon separately.

Otherwise a “wild” uncontrollable deposition would occur==<!--7. In most cases5-->Contact Lubricants==palladium containing solutions are used for By using suitable lubricants, the activation which seed mechanical wear and frictional oxidation of sliding and connector contacts can be substantially reduced. In thesurfaces with palladium and act electrical contact technology, solid as well as catalysts in the copper high and nickelelectrolyteslow viscosity liquid lubricants are used.

The electrolytes contain besides the complex ion compounds of the metals Contact lubricants have tobe deposited also stabilizers, buffer and accelerator chemicals, and fulfill a suitablereduction agent.multitude of technical requirements:

These electrolytes are usually operating at elevated temperatures (50° – 90°C)*They must wet the contact surface well; after the sliding operation the lubrication film must close itself again, i.e. mechanical interruptions to heal*They should not transform into resins, not evaporate, and not act as dust collectors*The deposits contain besides the lubricants should not dissolve plastics, they should not be corrosive to non-precious metals also process related foreign inclusionsor initiate cracking through stress corrosion of plastic componentssuch as for example decomposition products *The specific electrical resistance of the reduction agents.lubricants cannot be so low that wetted plastic surfaces lose their isolating properties*The electroless processes are used mainly for copper, nickel, lubricant layer should not increase the contact resistance; the wear reducing properties of the lubricant film should keep the contact resistance low and golddeposits.consistent over the longest possible operation time

===7Solid lubricants include for example 0.105 – 0.2μm thin hard gold layers, which are added as surface layers on top of the actual contact material.4 Electroless Deposition of Nickel/Gold===

Electroless deposited nickel coatings with an additional immersion layer of goldare seeing increased importance in Among the various contact lubricants offered on the coating of printed circuit boards (PCBs)market, contact lubrication oils have shown performance advantages.The process sequence is shown They are mostly synthetic, chemically inert and silicone-free oils which differ in ''(Fig. 7.2)'' using the example of theDODUCHEM processtheir chemical composition and viscosity.

It is possible to enhance this ==<!--7.6-->Passivation of Silver Surfaces==The formation of silver sulfide during the shelf life of components with silver surface in sulfur containing environments, can be significantly eliminated by coating them with an additional protective film layer (Passivation layer combination further ). For electrical contact use, such thin layers should be chemically inert and sufficiently conductive, otherwise they are easily broken by adding a immersionthe applied contact force.<figure id="fig:Typical process flow for the SILVERBRITE W ATPS process">palladium layer between [[File:Typical process flow for the electroless nickel and SILVERBRITE W ATPS process.jpg|right|thumb|Figure 4: Typical process flow for the gold coatingSILVERBRITE W ATPS process]]</figure>The passivation process SILVERBRITE W ATPS is a water-based tarnish preventer for silver (DODUBOND <xr id="fig:Typical process flow for the SILVERBRITE W ATPS process"/>). This Pd It is free of chromium(VI) compounds and solvents. The passivating layer acts as is applied by immersion, which creates a diffusion barrier transparent organic protective film which barely changes the appearance and allows only slightlyincreases thegood electrical properties such as for example the contact resistance. The good solderability and bond properties of silver are notusage negatively affected. Because of its chemical composition, this surface combination also for gold wire bondingprotective layer has some lubricating properties which reduce the insertion and withdrawal forces of connectors noticeably.

FigVinaricky, E. 7(Hrsg.3):Elektrische Kontakte, Werkstoffe und Anwendungen.Coating compositionof a printed circuit board withreductively enhanced goldSpringer-Verlag, Heidelberg 2002

===7Ganz, J.; Heber, J.1; Macht, W.2; Marka, E.5 Immersion Deposition of Tin===: Galvanisch erzeugteA tin coating by ion exchange is usually not possible since copper is the moreprecious metalEdelmetallschichten für elektrische Kontakte. By adding thio-urea the electro-chemical potential of copper isreduced to a level Metall 61 (approx. 450 mV, significantly lower than tin2007) that allows theexchange reaction. Using a suitable electrolyte composition and enhancersolutions like with the DODUSTAN process ''(FigH. 7.4)'' tin coatings can beproduced that6, even under usually unfavorable conditions of copperconcentrations of 7 g/l in the electrolyte, are well solderable.394-398

FigSong, J. 7: Edelmetalle in Steckverbindungen - Funktionen und Einsparpotential.4: Process flow for electroless tin deposition using the DODUSTAN processVDE - Fachbericht 67 (2011) 13-22

The immersion tin deposition is suitable for the production of a well solderableHeber, J.: Galvanisch abgeschiedene Rhodiumschichten für den dekorativensurface on printed circuit boards and electronic componentsBereich. It is also used asan etch resist against ammonia based solutions or as corrosion and oxidationprotection of copper surfacesGalvanotechnik, 98 (2007) H.12, 2931-2935

===7Johler, W.2 Coatings from the Gaseous Phase (Vacuum Deposition)===The term PVD (physical vapor deposition) defines processes of metal; Pöffel, K.; Weik, metalalloysG.; Westphal, and chemical compounds deposition in a vacuum by adding thermal andW.: High Temperature Resistancekinetic energy through particle bombardmentth Galvanically Deposited Gold Layers for Switching Contacts. Proc. The main processes are the15 Holmfollowing four coating variations ''Conf. on Electrical Contacts, Chicago (Table 7.62005)'':48-54

*Vapor deposition *Sputtering Grossmann, H. Schaudt, G.: Untersuchung über die Verwendbarkeit vonÜberzügen der Platinmetallgruppe auf elektrotechnischen Verbindungselementen.Galvanotechnik 67 (Cathode atomization1976)*Arc vaporizing *Ion implantation292-297

Grossmann, H.; Vinaricky, E.: Edelmetalleinsparung in der Elektrotechnik durchselektives Galvanisieren. In all four processes the coating material is transported in its atomic form to the: Handbuch der Galvanotechnik. München, Hanser-substrate and deposited on it as a thin layer Verlag, 37 (a few nm to approx. 10 μm1981)132-141

Table 7Grossmann, H.; Schaudt, G.6: Characteristics of the Most Important PVD ProcessesHochgeschwindigkeitsabscheidung von Edelmetallenauf Kontaktwerkstoffen. Galvanotechnik 84 (1993) H.5, 1541-1547

The sputtering process has gained the economically most significant usageEndres, B. Its: Selektive Beschichtungen von Kontaktmaterial improcess principle is illustrated in ''Durchzugsverfahren. Metalloberfläche 39 (Fig. 7.51985)''H.11, 400-404

FigKaspar, F. 7; Marka, E.; Normann, N.5: Principle of sputtering Ar = Argon atoms; e = Electrons; M = Metal atomsEigenschaften von chemisch NickelGoldschichten für Baugruppen der Elektrotechnik.VDE Fachbericht 47 (1995) 19-27

Initially a gas discharge is ignited in a low pressure (10 – 1 Pa) argonatmosphereSchmitt; W.; Kißling, S.; Behrens, V. The argon ions generated are accelerated in an electric field and: Elektrochemisch hergestellteimpact the target of material to be deposited with high energySchichtsysteme auf Aluminium für Kontaktanwendungen. Caused by thisenergy atoms are released from the target material which condensate on theoppositely arranged anode VDE - Fachbericht 67 (the substrate2011) and form a layer with high adhesionstrength. Through an overlapping magnetic field at the target location thedeposition rate can be increased, making the process more economical.136-141

The advantages of the Freller, H.: Moderne PVD processes and especially sputtering for electrical-Technologien zum Aufbringen dünnercontact applications are:Kontaktschichten. VDE-Fachbericht 40 (1989) 33-39

*High purity of the deposit layers *Low thermal impact on the *Almost unlimited coating materials substrate*Low coating thickness tolerance *Excellent adhesion Ganz, J.: PVD-Verfahren als Ergänzung der Galvanik. Metalloberfläche 45 (also by using additional intermediate layers1991)

Coatings produced by PVD processes are used for contact applicationsSchmitt, forW.; Franz, S.; Heber, J.; Lutz, O.; Behrens, V.: Formation of Silverexample Sulfide Layers and their Influence on miniature-profiles, the Electrical Characteristics of Contacts in electrical engineering and for electroniccomponents, for solderability in joining processesth the Field of Information Technology. Proc. 24 Int. Conf.on Electr. Contacts, for metalizing of nonconductivematerials, as well as in semiconductorsSaint Malo, optoFrance (2008) 489-electronics, optics,and medical technology applications.494

There are few limitations regarding the geometrical shape of substrate parts.Only the interior coating of drilled holes and small diameter tubing can be moreproblematic (ratio of depth to diameter should be < 2:1). Profile wiresBuresch, stripsI; Ganz,and foils can be coated from one side or bothJ.; formed parts can be coatedselectively by using masking fixtures that at the same time serve as holdingKaspar, F.: PVD-Beschichtungen und ihre Anwendungenfixturesfür Steckverbinder.VDE-Fachbericht 59 (2003) 73-80

*'''Examples of vacuum coated semiGehlert, B.: Edelmetalllegierungen für elektrische Kontakte.Metall 61 (2007) H.6, 374-finished materials and parts'''bild379

<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s8">Substrate Materials</p></td><td><p class="s8">Coating Materials</p></td></tr><tr><td><p class="s8">Substrate Materials</p></td><td><p><span>Ag</span></p></td><td><p><span>Au</span></p></td><td><p><span>Pt</span></p></td><td><p><span>Pd</span></p></td><td><p><span>Cu</span></p></td><td><p><span>Ni</span></p></td><td><p><span>Ti</span></p></td><td><p><span>Cr</span></p></td><td><p><span>Mo</span></p></td><td><p><span>W</span></p></td><td><p><span>Ai</span></p></td><td><p><span>Si</span></p></td></tr><tr><td><p class="s8">Precious metal / alloys</p></td><td><p><span>[[File:K7-gefBuresch, I.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">NF metals / alloys</p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef; Bögel, A.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Fe alloys / stainless steel</p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Special metals (Ti, Mo; Dürrschnabel, W)</p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Carbide steels (WC-Co)</p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gefTin Coating for Electrical Components.png]]</span></p></td></tr><tr><td><p class="s8">Ceramics Metall 48 (Al<span class="s16">2</span>O<span class="s16">3</span>, AlN1994)</p></td><td><p><span>[[File:K7-leerH.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Glasses (SiO<span class="s16">2</span>1, CaF)</p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K711-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-leer.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr><tr><td><p class="s8">Plastics (PA, PPS)</p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td><td><p><span>[[File:K7-gef.png]]</span></p></td></tr></table>14

DimensionsCoating thicknessAdler, U.; Buresch, I.; Riepe, U.; Tietz, V.: 10 nm - 15 μmCharakteristische Eigenschaften derCoating thicknesses for contact applications: 0schmelzflüssigen Verzinnung von Kupferwerkstoffen.1 VDE-Fachbericht 63 (2007) 175- 10 μm180

For the geometry of semiHuck, M.: Einsatz von Schmiermitteln auf Gleit-finished products to be coated there are fewrestrictionsund Steckkontakten. Only the coating of the inside of machined holes and tubing haslimitations.Metalloberfläche (1982) 429-435

Coating thickness +10 - 30 %Noel, depending S.; Alarmaguy, D.; Correia, S.; Gendre, P.: Study of Thin Underlayers toHinder Contact resistance Increase Due to Intermetallic Compound Formation.th Proc. 55 IEEE Holm Conf. on the thicknessElectrical Contacts, Vancouver, BC,Canada (2009) 153 – 159

*'''Quality criteria'''Weik, G.; Johler, W.; Schrank, C.: Zuverlässigkeit und Eigenschaften von Gold –Depending on the application the following parameters are tested and recordedSchichten bei hohen Einsatztemperaturen.VDE – Fachbericht 65, (see also: Electroplating of parts2009):13 – 21

These quality tests are performed according to industry standardsBuresch, internalI.: Effekte intermetallischer Phasen auf die Eigenschaften vonstandards, and customer specifications respZinnoberflächen auf Kupferlegierungen.VDE – Fachbericht 67 (2011) 38-46

===7Schmitt, W.3 Comparison of Deposition Processes===The individual deposition processes have in part different performancecharacteristics. For each end application the optimal process has to be chosenconsidering all technical and economical factors; Heber, J. The main selection criteriashould be based on the electrical and mechanical requirements for the contactlayer and on the design characteristics of the contact component; Lutz, O. Table 7; Behrens, V.7: Einfluss des Herstellverfahrens aufgives some indications for a comparative evaluation of the different coatingdas Korrosions- und Kontaktverhalten von Ag – Beschichtungen inprocessesschwefelhaltiger Umgebung.VDE – Fachbericht 65 (2009) 51 – 58