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>

{| 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 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 magnetic storage media|-|Brazing and soldering|Brazing without aggressive fluxes|Tin-Lead coatings on PC board paths|-|Adhesion strength|Improvement of adhesion|Brass coating on reinforcement steel wires in tires|-|Lubricating properties|Improvement of formability|Copper plating for wire drawing|}</figtable><div id="text-reference">*) Coercive force= force to retaim the adopted magnetisation</div>  To reduce the mechanical wear of thin surface layers on sliding and connectorcontacts , additional lubricants in liquid form are often used. On silver contacts, passivation coatings are applied as protection against silver sulfide formation.

For thin coatings starting from the liquid phase , two processes are useddifferentiated by the metallic deposition being performed either with or withoutthe use of an external electrical current source. The first one is electroplating, while the second one is a chemical deposition process.

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 salts). An electric field between 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 surfaceof the work piece.Depending on the application, for electric and electronic or decorative end use,different electrolytic bath solutions (electrolytes) are used. The electroplatingequipment used for precious metal plating and its complexity varies widely, depending on the process technologies employed.Electroplating processes are encompassing , besides the pure metal deposition, also preparative and post treatments of the goods to be coated. An importantparameter for creating strongly adhering deposits is that the surface of the goods has 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. 

===<!--7.1.2 -->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 coating, independent 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 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==-->Coatings from the Gaseous Phase (Vacuum Deposition)==The immersion term PVD (physical vapor deposition) defines processes are usually applied in the plating of the metals gold,silvermetal, metal alloys and tin. If the material to be coated is less precious, i.e. exhibits chemical compounds deposition in anegative standard potential against the metal ions in the surrounding solution, itgoes into solution releasing electrons while the more precious metal ions arereduced vacuum by absorbing electrons adding thermal and being deposited on the electrodekinetic energy by particle bombardment. Thisprocess can continue until The main processes are 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 ''following four coating variations (Table 7.5)''. Table 7.5: Immersion Gold Electrolytes<table borderxr id="1" cellspacing="0" style="border-collapsetab:collapse"><tr><td><p class="s8">Type Characteristics 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="s8the Most Important PVD Processes">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(Table 7.2</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 surface. Otherwise a “wild” uncontrollable deposition would occur. In most casespalladium containing solutions are used for the activation which seed thesurfaces with palladium and act as catalysts in the copper and nickelelectrolytes. The electrolytes contain besides the complex ion compounds of the metals tobe deposited also stabilizers, buffer and accelerator chemicals, and a suitablereduction agent. These electrolytes are usually operating at elevated temperatures (50° – 90°C).The deposits contain besides the metals also process related foreign inclusionssuch as for example decomposition products of the reduction agents.The electroless processes are used mainly for copper, nickel, and golddeposits.:

Electroless deposited nickel coatings with an additional immersion layer of goldare seeing increased importance in In all four processes, the coating of printed circuit boards (PCBs).The process sequence material is shown transported in ''its atomic form to the substrate and deposited on it as a thin layer (Fig. 7a few nm to approx.210 μm)'' using the example of theDODUCHEM process.

After <figtable id="tab:Characteristics of the preMost Important PVD Processes"><caption>'''<!--cleaning (degreasing and etching) a palladium sulfate activator isused which activates the exposed copper surfaces on the printed circuit boardand thus facilitates the nickel depositionTable 7. The electroless working chemicalnickel electrolyte contains – besides other ingredients – Sodium6:-hypophosphite,which is reduced to phosphorus in a parallel occurring process andincorporated into the nickel deposit. At the temperature of 87 – 89°C a veryhomogeneous nickel-phosphorus alloy layer with approx. 9 wt% P is depositedwith layer thicknesses > 5 μm possible. During a consecutive processing stepa very thin and uniform layer (< 0.1 μm) Characteristics of gold is added in an immersionelectrolyte. This protects the electroless nickel layer against corrosion achievinga solderable and well bondable surface for thick or fine aluminum bond wires.Most Important PVD Processes'''</caption>

It is possible to enhance this layer combination further by adding {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Process!Principle!Process Gas Pressure!Particle Energy!Remarks|-|Vapor deposition|Vaporizing in a immersioncrucible <br />(electron beam or resistance heating)|10^-3 Pa|< 2eV|Separation of alloy components may occur|-|Arc vaporizingpalladium layer between |Vaporizing of the electroless nickel and target <br />plate in an electrical arc|10^-1 Pa-1Pa|80eV-300eV|Very good adhesion due to ion bombardement|-|Sputtering|Atomizing of the gold coatingtarget plate<br />(DODUBOND processcathode). This Pd layer acts as in a diffusion barrier gas discharge|10^-1 Pa-1Pa|10eV-100eV|Sputtering of non-conductive materials possible through RF operation|-|Ion implantation|Combination of vapor <br />deposition and allows sputtering|10^-1 Pa-1Pa|80eV-300eV|Very good adhesion from ion bombardment but also heating of thesubstrate materialusage of this surface combination also for gold wire bonding.|}</figtable>

The sputtering process has gained the economically most significant usage. Its process principle is illustrated in (<xr id="fig:Principle of sputtering"/><!--(Fig. 7.3:Coating compositionof a printed circuit board withreductively enhanced gold5)-->).

<figure id====7"fig:Principle of sputtering">[[File:Principle of sputtering.jpg|right|thumb|Figure 1.2.5 Immersion Deposition : Principle of Tin=sputtering Ar =Argon atoms; e =Electrons; M =Metal atoms]]</figure>A tin coating by ion exchange Initially, a gas discharge is usually not possible since copper is the moreprecious metalignited in a low pressure (10^-1 -1 Pa) argon atmosphere. By adding thio-urea The argon ions generated, are accelerated in an electric field and impact the electro-chemical potential target of copper isreduced material to a level (approxbe deposited with high energy. 450 mVCaused by this energy, significantly lower than tinatoms are released from the target material which condensate on the oppositely arranged anode (the substrate) that allows theexchange reaction. Using and form a suitable electrolyte composition and enhancersolutions like layer with high adhesion strength. Through an overlapping magnetic field at the target location, the DODUSTAN process ''(Fig. 7.4)'' tin coatings deposition rate can beproduced thatincreased, even under usually unfavorable conditions of copperconcentrations of 7 g/l in making the electrolyte, are well solderableprocess more economical.

Fig. 7.4The advantages of the PVD processes and especially sputtering for electrical contact applications are: Process flow for electroless tin deposition using the DODUSTAN process

The immersion tin deposition is suitable for *High purity of the production of a well solderabledeposit layers surface *Low thermal impact on printed circuit boards and electronic components. It is also used asthe substrate *Almost unlimited coating materials an etch resist against ammonia based solutions or as corrosion and oxidation*Low coating thickness tolerance protection of copper surfaces.*Excellent adhesion (also by using additional intermediate layers)

==7.2 Coatings from the Gaseous Phase (Vacuum Deposition)==The term produced by PVD (physical vapor deposition) defines processes of metalare used for contact applications, metalalloysfor example on miniature-profiles, in electrical engineering and chemical compounds deposition for electronic components, for solderability in a vacuum by adding thermal joining processes, for metalizing of nonconductive materials, as well as in semiconductors, opto-electronics, optics andkinetic energy through particle bombardment. The main processes are thefollowing four coating variations ''(Table 7medical technology applications.6)'':

*Vapor deposition *Sputtering 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 (Cathode atomizationratio of depth to diameter should be < 2:1)*Arc vaporizing *Ion implantation. 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="fig:Examples of vacuum coated semi finished materials and parts"/>).

In all four processes the coating material is transported in its atomic form to thesubstrate and deposited on it as a thin layer (a few nm to approx. 10 μm) Table 7.6: Characteristics of the Most Important PVD Processes tabelle fehlt! The sputtering process has gained the economically most significant usage. Itsprocess principle is illustrated in ''(Fig. 7.5)''. Fig. 7.5: Principle of sputtering Ar = Argon atoms; e = Electrons; M <figure id= Metal atoms Initially a gas discharge is ignited in a low pressure (10 – 1 Pa) argonatmosphere. The argon ions generated are accelerated in an electric field andimpact the target of material to be deposited with high energy. Caused by thisenergy atoms are released from the target material which condensate on theoppositely arranged anode (the substrate) 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. The advantages of the PVD processes and especially sputtering for electricalcontact applications are"fig: *High purity Examples of the deposit layers *Low thermal impact on the *Almost unlimited coating vacuum coated semi finished materials substrate*Low coating thickness tolerance *Excellent adhesion (also by using additional intermediate layers) Coatings produced by PVD processes are used for contact applications, forexample on miniature-profiles, in electrical engineering and for electronicparts">components, for solderability in joining processes, for metalizing [[File:Examples of nonconductivevacuum coated semi finished 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 moreproblematic (ratio of depth to diameter should be < jpg|left|Figure 2:1). Profile wires, strips,and foils can be coated from one side or both; formed parts can be coatedselectively by using masking fixtures that at the same time serve as holdingfixtures. *'''Examples of vacuum coated semi-finished materials and parts''']]bild</figure>

<table border="1" cellspacing="0" styleclass="border-collapse:collapsetwocolortable"><tr><tdth rowspan="2"><p class="s8">Substrate Materials</p></tdth><tdth colspan="12"><p class="s8">Coating Materials</p></tdth></tr><tr><tdth><p class="s8">Substrate Materials<span>Ag</span></p></tdth><tdth><p><span>AgAu</span></p></tdth><td><p><span>Au</span></p></td><tdth><p><span>Pt</span></p></tdth><tdth><p><span>Pd</span></p></tdth><tdth><p><span>Cu</span></p></tdth><tdth><p><span>Ni</span></p></tdth><tdth><p><span>Ti</span></p></tdth><tdth><p><span>Cr</span></p></tdth><tdth><p><span>Mo</span></p></tdth><tdth><p><span>W</span></p></tdth><tdth><p><span>Ai</span></p></tdth><tdth><p><span>Si</span></p></tdth></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> [[File:K7-gef.png]] can be produced[[File:K7-leer.png]] can be produced with intermediate layer

{| class="twocolortable" style="text-align: left; font-size: 12px;width:40%"|-!colspan="2" style="text-align:center"|'''Dimensions'''|-|Coating thickness: |10 nm - 15 μm|-|Coating thicknesses for contact applications: |0.1 - 10 μm|}

For the geometry of semi-finished products to be coated , there are fewrestrictions. Only the coating of the inside of machined holes and tubing has

Coating thickness +&#177;10 - 30 %, depending on the thickness

Depending on the application , the following parameters are tested and recorded(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.

==<!--7.3 -->Comparison of Deposition Processes==The individual deposition processes have in part different performancecharacteristics. For each end application , the optimal process has to be chosen, considering all technical and economical factors. The main selection criteriashould be based on the electrical and mechanical requirements for the contactlayer and on the design 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 coatingprocesses.

The electroless metal coating is not covered here because of the low thicknessof deposits , which makes them in most cases not suitable for contact

The main differences between the <figtable id="tab:Comparison of different coating processes are found in the coating">materials and thickness<caption>'''<!--Table 7. While mechanical cladding and sputtering allow theuse 7:-->Comparison of almost any alloy material, electroplating different coating processes are limited to metalsand selected alloys such as for example high-carat gold alloys with up to .3wt% Co or Ni. Electroplated and sputtered surface layers have a technologicaland economical upper thickness limit of about 10μm. While mechanical claddinghas a minimum thickness of approx. 1 μm, electroplating and sputteringcan also be easily applied in very thin layers down to the range of 0.1 μm.'''</caption>

The properties of the coatings are closely related to the coating process.{| class="twocolortable" style="text-align: left; font-size: 12px"|-!Process / Coating Properties!Mechanical Processes (Cladding)!Electroplating!Vaccum Deposition (Sputtering)|-|Coating materialStarting materials for cladding |formabe metal and sputtering targets precious alloys|metals, alloys only limited|metals and theiralloysalloys which |-|Coating thickness|> 1μm|0.1 - approx. 10 μm <br />(in the case special cases up to 100 μm)|0.1 approx. 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 gold and palladium based foreign materials are vacuummelted and therefore exhibit a |very high puritygood|-|Porosity|good|good for > approx. During electroplating, depending1μm|good|-|Temperature stability|goodvery good|good|very goodon the type of electrolytes and the deposition parameters, some electrolyte|-components such as carbon and organic compounds are incorporated into|Mechanical wearthe precious metal coating. Layers deposited from the gaseous phase however|littleare |very pure.little|little|-|Environmental impact|little|significant|none|}</figtable>

==7.4 Hot (-Dipped) Tin Coated Strip Materials==During hot-dip tinning pre-treated strip materials The main differences between the coating processes are coated with pure tin or tinalloys from a liquid solder metal. During overall (or all-around) tinning found in thestripsthrough a liquid metal melt. For strip tinning rotating rolls are partiallyimmersed into a liquid tin melt coating materials and transport the liquid onto the strip which isguided above themthickness. Through special wiping While mechanical cladding and gas blowing procedures sputtering allow thedeposited tin layer can be held within tight tolerances. Hot tinning is performeddirectly onto the base substrate use of almost any alloy material without any pre, electroplating processes are limited to metals and selected alloys, such as for example high-coating carat gold alloys with eithercopper up to .3 wt% Co or nickelNi. Special cast-on processes or the melting Electroplated and sputtered surface layers have a technological and economical upper thickness limit of about 10μm. While mechanical cladding has a minimum thickness of solder foils ontothe carrier strip allow approx. 1 μm, electroplating and sputtering can also be easily applied in very thin layers down to the production range of thicker solder layers(> 15 0.1 μm).

The main advantage properties of hot tinning of copper the coatings are closely related to the coating process. Starting materials for cladding and sputtering targets precious metals and copper their alloys as compared totin electroplating is , which in the formation case of an inter-metallic copper-tin phase (Cu₃Sngold and palladium based materials,Cu₆ Sn₅) at the boundary between the carrier material are vacuum melted and the tin layertherefore exhibit a very high purity. This thin(0.3 – 0.5 μm) intermediate layerDuring electroplating, which is formed during depending on the type of electrolytes and the thermal tinningprocessdeposition parameters, is rather hard some electrolyte components such as carbon and reduces in connectors organic compounds are incorporated into the frictional force andmechanical wearprecious metal coating. Tin coatings produced by hot tinning have a good adhesion toLayers deposited from the substrate material and do not tend to tin whisker formationgaseous phase however are very pure.

A special process of ==<!--7.4-->Hot (-Dipped) Tin Coated Strip Materials==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 is the “Reflow” processstrips through a liquid metal melt. After depositing For strip tinning, rotating rolls are partially immersed into a liquid tincoating by electroplating 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 shortperformed directly onto the base substrate material without any pre-time melted in a continuous processcoating with either copper or nickel.The properties Special cast-on processes or the melting of solder foils onto the carrier strip, also allows the production of these reflow tin coatings are comparable to those created byconventional hot tinningthicker solder layers ( > 15 μm).

Besides overall The main advantage of hot tinning of copper and copper alloys, compared to tin coating electroplating, is the formation of strip an inter-metallic copper-tin phase (Cu₃Sn, Cu₆Sn₅) at the boundary between the carrier material and the tin layer. This thin (0.3 – 0.5 μm) intermediate layer, which is formed during the thermal tinning process, is rather hard and reduces the frictional force and mechanical wear in connectors. Tin coatings produced by hot tinning can also be applied inhave a good adhesion to the form of single or multiple stripes on both sides of a continuous substratestripmaterial and do not tend to tin whisker formation.

*'''Typical examples A special process of hot tinned strip materials'''tinning is the “Reflow” process. After depositing a tin coating by electroplating, the layer is short-time melted in a continuous process.bildThe properties of these reflow tin coatings are comparable to those created by conventional hot tinning.

Coating materials: Pure tin, tin alloys<br>Substrate materials: Cu, CuZn, CuNiZn, CuSn, CuBe and others<br />

{| class="twocolortable" style="text-align: left; font-size: 12px;width:40%"|-|Width of tinning: > |&#8805; 3 + &#177; 1 mm|-|Thickness of tinning: |1 - 15 μm|-|Tolerances (thickness): + |&#177; 1 - +&#177; 3 μm depending on tin thickness|}

Mechanical strength and dimensional tolerances of hot tinned strips are closelyrelated to the standard for Cu and Cu alloy strips according to DIN EN 1652 andDIN EN 1654.

==<!--7.5 -->Contact Lubricants==By using suitable lubricants , the mechanical wear and frictional oxidation ofsliding and connector contacts can be substantially reduced. In the electricalcontact technology , solid, as well as high and low viscosity liquid lubricants areused.

Solid lubricants include for example 0.05 – 0.2 μm thin hard gold layers , whichare added as surface layers on top of the actual contact material. Among the various contact lubricants offered on the market contact lubricationoils have shown performance advantages. They are mostly synthetic, chemically inert, and silicone-free oils such as for example the DODUCONTAcontact lubricants which differ in their chemical composition and viscosity. For sliding contact systems with contact forces < 50 cN and higher slidingspeeds oils with a lower viscosity (<50 mPa·s) are preferential. For applicationswith higher contact forces and operating at higher temperatures contact oilswith a higher viscosity are advantageous. Contact oils are mainly suited forapplications at low current loads. At higher loads and in situations wherecontact separation occurs during the sliding operation thermal decompositionmay be initiated which causes the lubricating properties to be lost. Most compatible with plastics are the contact oil varieties B5, B12K, and B25,which also over longer operating times do not lead to tension stress corrosion. For the optimum lubrication only a very thin layer of contact oil is required.Therefore it is for example recommended to dilute the oil in iso-propylenealcoholduring the application to contact parts. After evaporation of the alcohola thin and uniform layer of lubricant is retained on the contact surfaces.  *'''Properties of the Synthetic DODUCONTA Contact Lubricants'''

<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s8">Lubricant</p></td><td><p class="s8">DODUCONTA</p></td></tr><tr><td><p class="s8">Lubricant</p></td><td><p class="s8">B5</p></td><td><p class="s8">B9</p></td><td><p class="s8">B10</p></td><td><p class="s8">B12K</p></td><td><p class="s8">B25</p></td></tr><tr><td><p class="s8">Contact force</p></td><td><p class="s8">&gt;1N</p></td><td><p class="s8">0.1 - 2N</p></td><td><p class="s8">&lt; 0.2N</p></td><td><p class="s8">0Among the various contact lubricants offered on the market, contact lubrication oils have shown performance advantages.2 They are mostly synthetic, chemically inert and silicone- 5N</p></td><td><p class="s8">&lt;1N</p></td></tr><tr><td><p class="s8">Density (20°C)</p><p class="s8">[g/cm³]</p></td><td><p class="s8">1.9</p></td><td><p class="s8">1.0</p></td><td><p class="s8">0.92</p></td><td><p class="s8">1free oils which differ in their chemical composition and viscosity.0</p></td><td><p class="s8">1.0</p></td></tr><tr><td><p class="s8">Specificel. Resis-</p><p class="s8">tance [<span class="s9">S · </span>cm]</p></td><td/><td><p class="s8">2 x 10<span class="s18">10</span></p></td><td><p class="s8">10<span class="s18">10</span></p></td><td><p class="s8">6 x 10<span class="s18">9</span></p></td><td><p class="s8">5 x 10<span class="s18">8</span></p></td></tr><tr><td><p class="s8">Viscosity (20°C)</p><p class="s8">[mPa·s]</p></td><td><p class="s8">325</p></td><td><p class="s8">47</p></td><td><p class="s8">21</p></td><td><p class="s8">235</p></td><td><p class="s8">405</p></td></tr><tr><td><p class="s8">Congeal temp.[°C]</p></td><td/><td><p class="s8">-55</p></td><td><p class="s8">-60</p></td><td><p class="s8">-40</p></td><td><p class="s8">-35</p></td></tr><tr><td><p class="s8">Flash point[°C]</p></td><td/><td><p class="s8">247</p></td><td><p class="s8">220</p></td><td><p class="s8">238</p></td><td><p class="s8">230</p></td></tr><tr><td/><td><p class="s8">220</p></td><td/><td/></tr></table>

<table border="1" cellspacing="0" style="border<!--collapse:collapse"><tr><td><p class="s8">Lubricant</p></td><td><p class="s8">Applications</p></td></tr><tr><td><p class="s8">DODUCONTA B5</p></td><td><p class="s8">Current collectors, connectors, slider switches</p></td></tr><tr><td><p class="s8">DODUCONTA B9</p></td><td><p class="s8">Wire potentiometers, slip rings, slider switches, measuring range selectors, miniature connectors</p></td></tr><tr><td><p class="s8">DODUCONTA B10</p></td><td><p class="s8">Precision wire potentiometers, miniature slip rings</p></td></tr><tr><td><p class="s8">DODUCONTA B12K</p></td><td><p class="s8">Wire potentiometers, slider switches, miniature slip rings, connectors</p></td></tr><tr><td><p class="s8">DODUCONTA B25</p></td><td><p class="s8">Current collectors, measuring range selectors, connectors</p></td></tr></table> ==7.6 -->Passivation of Silver Surfaces==The formation of silver sulfide during the shelf life of components with silversurface in sulfur containing environments , can be significantly eliminated bycoating them with an additional protective film layer (Passivation layer). Forelectrical contact use , such thin layers should be chemically inert andsufficiently conductive, or be otherwise they are easily broken by the applied contact force.<figure id="fig:Typical process flow for the SILVERBRITE W ATPS process">[[File:Typical process flow for the SILVERBRITE W ATPS process.jpg|right|thumb|Figure 4: Typical process flow for the SILVERBRITE W ATPS process]]</figure>The passivation process SILVERBRITE W ATPS is a water-based tarnishpreventer for silver(<xr id="fig:Typical process flow for the SILVERBRITE W ATPS process"/>). It is free of chromium(VI) compounds and solvents. Thepassivating layer is applied by immersion , which creates a transparent organicprotective film which barely changes the appearance and only slightlyincreases the good electrical properties such as for example the contactresistance. The good solderability and bond properties of silver are notnegatively affected. Because of its chemical composition , this protective layerhas some lubricating properties which reduce the insertion and withdrawalforces of connectors noticeably. Fig. 7.7: Typical process flow for the SILVERBRITE W ATPS process