===<!--6.4.5 -->Physical Effects in Sliding and Connector Contacts=== '''Mechanical wear of sliding contacts''' <table class="twocolortable" style="text-align: left; font-size:12px;width:40%"><tr><td>dV/dx = k x F<sub>K</sub> /3 H<sub>W</sub></td></tr><tr> <td>dV/dx Wear volume in mm<sup>3</sup> per slide path length in mm</td></tr><tr><td>k Coefficient of frictional wear</td></tr><tr><td>H<sub>W</sub> Hardness of the softer material <br />(Brinell or Vickers units)</td></tr><tr><td>F<sub>K</sub> Contact force in cN</td></tr><tr><td>'''Wear coefficient k during material transfer'''</td></tr><tr><td>Silver – Silver 120 x 10<sup>-4</sup></td></tr><tr><td>Platinum – Platinum 400 x 10<sup>-4</sup></td></tr><tr><td>Silver – Platinum 1.3 x 10<sup>-4</sup></td></tr><tr><td>'''Coefficient of fractional wear k during wear loss'''</td></tr><tr><td>Silver – silver 8 x 10<sup>-4</sup></td></tr><tr><td>Gold – gold 9 x 10<sup>-4</sup></td></tr><tr><td>Platinum – platinum 40 x 10<sup>-4</sup></td></tr><tr><td>Silver – gold 9 x 10<sup>-4</sup></td></tr><tr><td>Silver – platinum 5 x 10<sup>-4</sup></td></tr></table>
*'''Mechanical wear of sliding contacts'''
{| class="twocolortable" style="text-align: left; font-size: 12px;width:40%"
|-
|dV/dx = k x F<sub>K</sub> /3 H<sub>W</sub>
|-
|dV/dx Wear volume in mm<sup>3</sup> per slide path length in mm
|-
|k Coefficient of frictional wear
|-
|H<sub>W</sub> Hardness of the softer material <br />(Brinell or Vickers units)
|-
|F<sub>K</sub> Contact force in cN
|-
|'''Wear coefficient k during material transfer'''
|-
|Silver – Silver 120 x 10<sup>-4</sup>
|-
|Platinum – Platinum 400 x 10<sup>-4</sup>
|-
|Silver – Platinum 1.3 x 10<sup>-4</sup>
|-
|'''Coefficient of fractional wear k during wear loss'''
|-
|Silver – silver 8 x 10<sup>-4</sup>
|-
|Gold – gold 9 x 10<sup>-4</sup>
|-
|Platinum – platinum 40 x 10<sup>-4</sup>
|-
|Silver – gold 9 x 10<sup>-4</sup>
|-
|Silver – platinum 5 x 10<sup>-4</sup>
|}
'''Contact behavior of connectors'''
<div class="multiple-images">
[[File:Coefficient of frictional wear for the wear loss of sliding contacts Silver Silver.jpg|left|thumb|Figure 1: Coefficient of frictional wear for the wear loss of sliding contacts Silver/Silver and hard gold/hard gold as a function of the contact force]]
<figure id="fig:Contact resistance Rk as a function of the contact force Fk">[[File:Coefficient Contact resistance Rk as a function of frictional wear for the wear loss of sliding contacts Silver Silvercontact force Fk.jpg|rightleft|thumb|Coefficient of frictional wear for the wear loss of sliding contacts Silver/Silver and hard goldFigure 2: Contact resistance R<sub>k</hard gold sub> as a function of the contact forceF<sub>k</sub> for different surface coating materials. Measured against a spherical gold probe; I = 10 mA, U < 20 mV]]</figure>
Fig. 6.15<figure id="fig: Coefficient Contact resistance Rk as a function of frictional the fretting wear for cycles">[[File:Contact resistance Rk as a function of the fretting wear loss of sliding contacts Silvercycles.jpg|left|thumb|Figure 3: Contact resistance R<sub>k</Silverand hard gold/hard gold sub> as a function of the contact forcefretting wear cycles for different surface coating materials]]</figure></div><div class="clear"></div>
*'''Contact behavior of connectors'''
[[File<figtable id="tab:Contact resistance Rk as a function of the contact force Fk.jpg|right|thumb|Contact resistance R<subSurface Coating Materials for Connectors">k</sub> as a function of the contact force F<sub>k</subcaption> for different surface coating materials. Measured against a spherical gold probe; I = 10 mA, U '''< 20 mV]]Fig!--Tab. 6.164: Contact resistance R as a function kof the contact force F -->Surface Coating Materials for different surface kcoating materials. Measured against aspherical gold probe; I = 10 mA, U Connectors'''< 20 mV/caption>
[[File{| class="twocolortable" style="text-align: left; font-size: 12px"|-!Manufacturing method !Coating materials!Intermediate layer!Hardness HV!Frictional factor|-|Electroplating|Tin<br />Nickel<br />Nickel-phosphorus (NiP 6 - 15)<br />Silver<br />Hard gold (< 0.3 wt% Ni or Co)<br />Palladium with Au- flash (<0,2μm)<br />Palladium-nickel with Au-flash (<0.2μm)|For brass:Contact resistance Rk as a function of the fretting wear cyclesCopper or Nickel<br /> <br /> <br /> <br />Nickel, Nickel-phosphorus<br />Nickel<br />Nickel|50 - 90<br />300 - 600<br />500 - 1100<br />70 - 100<br />100 - 200<br />250 - 300<br />300 - 400|0.5 - 1<br /> <br /> <br />0.5 - 0.8<br />0.2 - 0.5<br />0.2 - 0.5<br />0.jpg2 - 0.5|right-|thumbCladding|Contact resistance RGold-nickel (AuNi 5 -10)<subbr />kSilber-palladium (AgPd 10 - 30)|Nickel<br />Nickel|160 - 200<br /sub> as a function of the fretting wear cycles for different surface coating materials120 - 170|0.2 - 0.5<br />0.2 - 0.5|-|Hot-dipped tinning|Tin|Inter-metallic compound[[#text-reference|<sup>(1)</sup>]]Tin–copper|400 - 500|Fig. 6.17: Contact resistance R as a function k|}of the fretting wear cycles for different surface<div id="text-reference">(1) is formed during hot tinning process</div>coating materials</figtable>
'''Tab.6.4: Surface Coating Materials for Connectors'''<div class="clear"></div>
==References==
[[Application Tables and Guideline Data for Use of Electrical Contact Design#References|References]]
[[de:Physikalische_Effekte_bei_Gleit-_und_Steckkontakten]]
