Physical Effects in Sliding and Connector Contacts
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6.4.5 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 |
Fig. 6.15: 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 Fig. 6.16: 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 Fig. 6.17: Contact resistance Rk as a function of the fretting wear cycles for different surface coating materials
Tab.6.4: 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