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Electrical Contacts β

Physical Effects in Sliding and Connector Contacts

Physical Effects in Sliding and Connector Contacts

  • Mechanical wear of sliding contacts
dV/dx = k x FK /3 HW
dV/dx Wear volume in mm3 per slide path length in mm
k Coefficient of frictional wear
HW Hardness of the softer material
(Brinell or Vickers units)
FK Contact force in cN
Wear coefficient k during material transfer
Silver – Silver 120 x 10-4
Platinum – Platinum 400 x 10-4
Silver – Platinum 1.3 x 10-4
Coefficient of fractional wear k during wear loss
Silver – silver 8 x 10-4
Gold – gold 9 x 10-4
Platinum – platinum 40 x 10-4
Silver – gold 9 x 10-4
Silver – platinum 5 x 10-4
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


  • Contact behavior of connectors

Figure 1 Contact resistance Rk as a function of the contact force Fk for different surface coating materials. Measured against a spherical gold probe; I = 10 mA, U < 20 mV

Figure 2 Contact resistance Rk as a function of the fretting wear cycles for different surface coating materials

Contact resistance Rk as a function of the contact force Fk for different surface coating materials. Measured against a spherical gold probe; I = 10 mA, U < 20 mV
Contact resistance Rk as a function of the fretting wear cycles for different surface coating materials


Table 1: Surface Coating Materials for Connectors
Manufacturing method Coating materials Intermediate layer Hardness HV Frictional factor
Electroplating Tin
Nickel
Nickel-phosphorus (NiP 6 - 15)
Silver
Hard gold (< 0.3 wt% Ni or Co)
Palladium with Au- flash (<0,2μm)
Palladium-nickel with Au-flash (<0.2μm)
For brass: Copper or Nickel



Nickel, Nickel-phosphorus
Nickel
Nickel
50 - 90
300 - 600
500 - 1100
70 - 100
100 - 200
250 - 300
300 - 400
0.5 - 1


0.5 - 0.8
0.2 - 0.5
0.2 - 0.5
0.2 - 0.5
Cladding Gold-nickel (AuNi 5 -10)
Silber-palladium (AgPd 10 - 30)
Nickel
Nickel
160 - 200
120 - 170
0.2 - 0.5
0.2 - 0.5
Hot-dipped tinning Tin Inter-metallic compound(1) Tin–copper 400 - 500
(1) is formed during hot tinning process

References

References