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

Contact behavior of connectors

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 2: Contact resistance R_k as a function of the contact force F_k for different surface coating materials. Measured against a spherical gold probe; I = 10 mA, U < 20 mV

Figure 3: Contact resistance R_k 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