General Rules for Dimensioning of Contacts

6.4.6 General Rules for Dimensioning of Contacts

• Recommended Minimum Contact Forces at Slightly Sliding Contact Make:

Gold	0.03 N
Silver	0.1 N
Tungsten	0.5 N

• Contact Force Recommendations:

Signal relays	≥ 3 cN
AC power relays	≥ 20 cN
Automotive relays	≥ 20 cN
Motor switches (Contactors) (Silver – Metal oxide contacts)	0.05 - 0.08 N/A
Power switches	0.1 - 0.2 N/A
Connectors (Gold coating)	≥ 30 cN/contact element
Connectors (Silver coating)	≥ 50 cN/contact element
Connectors (Tin coating)	≥ 1 N/contact element

• General Rules for Dimensioning of Contact Rivets

General Rules for Dimensioning of Contact Rivets

Dimensioning	Solid Rivets (1)	Composite Rivets (2)
a : d	1.5 : 1 bis 2.5 : 1	2 : 1 bis 2.5 : 1
a : b	2.5 : 1 bis 10 : 1	3 : 1 bis 5 : 1
c : b	≥ 1 : 1	≥ 1 : 1
b : s		≥ 2 : 1
smin		0.3 mm

• Head diameter for electrical loads

For AC currents: approx. 1 – 1.5 A/mm² For 1 A min. 2 mm head diameter 10 A approx. 3 – 3.5 mm head diameter 20 A approx. 5 mm head diameter For DC currents: approx. 0.5 – 0.8 A/mm²

• Head radius R for electrical loads

for I < 1 A R 1,5 mm I = 6 A R 5 mm I = 10 A R 10 mm I = 20 A R 15 mm

• Failure Probability of Single and Double (Bifurcated) Contacts (according to Thielecke)

Fig. 6.18: Failure probability of a contact as a function of the voltage (according to Kirchdorfer); Ag/Ni10; 10 mA

Fig. 6.19: Failure probability of a contact as a function of the current (according to Kirchdorfer); Ag/Ni10; F = 0.45 N; U = 24 V

References

References