Electrical contacts have the characteristic of being small in size yet with multiple functions. A good electrical contact should have the following qualities:

a.	Low metal transfer
b.	Low contact resistance
c.	Resistance to arc-erosion
d.	Resistance to sticking
e.	Good mechanical stability
	(ie. workability and resistance to mechanical wear)

We are aware that it is impossible to have one contact material that covers all the above benefits. In low current conditions, when contact stability is the most important requirement, the alloys of Au, Pt, and Pd are usually considered due to their chemical stability.

Below is a classification of materials for different electrical currents:

a.	30~50mA and lower, Au or Au alloys.
b.	Between 50mA~20A, Ag alloys, Pt alloys, and Ag oxide alloys.
c.	20A and above, Ag oxide alloys.

To lengthen the durability of electrical contacts, the following considerations should be made:

a.	The most suitable materials and specifications.
b.	The requirements of voltage, current, AC/DC, etc.
c.	Required contact pressure, switch speed, and vibration frequency.
d.	The environmental influences: dust, humidity, grease, and gases in the atmosphere.

Under all circumstances, all electrical contacts should be contacted fully.

This is essential in (1) reducing the possibility of mal-function caused by dust and (2) avoiding partial contact, which causes material loss and short durability.