General

Chugai makes a wide variety of silver based contact alloys and pioneers the development of many grades of silver materials composed of various combinations of silver, tin, indium, cadmium, and other additives. Chugai holds many patents for this technology. Almost all of these alloys are used in applications where electrical switching is done under arcing conditions as opposed to dry circuit switching conditions.

Table 1. Three different kinds of contact materials supplied by Chugai.

As shown in Table 1, Chugai USA mainly supplies three different kinds of contact materials. Other material compositions are also available on request. Gold plated contacts are also available for silver alloys and copper alloys.

Standard Silver Base
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The standard silver base contact alloys are listed in Table 2.

Table 2: Standard silver base contact alloys

 

 

Silver Tin Oxide
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A listing of silver tin oxide made by Chugai is shown in Table 3. The table is divided into post oxidized and pre-oxidized alloys. All silver-tin oxide alloys produced by Chugai are made by internal oxidation of silver alloys. The process produces a very fine dispersion of oxide particles within the silver matrix. This results in a strong structure that is stable at much higher temperatures than the older standard silver-cadmium oxide and results in a higher resistance to erosion.

Table 3: Chugai silver tin indium oxide and silver tin oxide contact alloys and properties

Noble Metal Contacts
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The Noble Metals as shown in Table 4 are mainly classified as class B materials with only gold in class A. Gold is less prone to film growth than any other material but is rather soft and has a tendency to weld. The platinum family of alloys will develop thicker films than gold but are relatively stable with regard to contact resistance compared to class C and D materials. The high melting point of these metals gives them good resistance to electrical erosion. There are many alloys in this group, some combinations of noble metals and others noble metals alloyed with silver and/or copper. The alloying increases the hardness of the materials and as the gold or noble metal content becomes lower the corrosion resistance decreases. Table 2 lists the most popular grades of materials made by Chugai. Other material compositions are available on request. Gold plated contacts are also available for silver alloys and copper alloys.

Table 4:Noble Metal Electric Contact Materials

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