Silver Cadmium Oxide (SKO) Materials

A long time industry standard

The  excellent anti-welding, low erosion, and superior conductivity properties of Silver Cadmium Oxide (AgCdO) have made it the benchmark material for arcing contacts in most control and switchgear products. While health and environmental considerations have eliminated Cadmium’s use in some countries, the Reduction of Hazardous Substances initiative (RoHS) has exempted Cadmium for use in electrical contact materials and their applications.  Today, silver cadmium oxide continues to be selected where other materials have been unable to adequately perform under more demanding switch applications, including:

  • Contactors
  • Relays
  • Control Switches
  • Railway Switchgear
  • Circuit Breakers

Checon’s SKO Series of Silver Cadmium Oxide materials are produced using one of three methods of internal oxidation techniques: One-Side Internal Oxidation; Through Oxidation, and Fragmental Oxidation; or with a Powder-Metallurgical approach that begins with the blending of Silver and Cadmium Oxide powders. Each method brings differing attributes to an electrical application enabling our customers to select the best approach for their contact assembly system.

Properties of SKO Silver Cadmium Oxide Materials

Material Designation

 

Oxide Content

Wt-%

Method

Density

g/cm3

Conductivity

% IACS

Hardness Range

HV1

SKO-10M

SKO-15M

10

15

One Side

Oxidation

10.2

10.0

76

62

 

60

80

SKO-10D

SKO-15D

10

15

Through

Oxidation

10.2

10.1  

86

80

60

80

SKO-10B

SKO-15B

10

15

Powder

Metallurgy

10.2  

10.0  

88

79

60

75

SKO-10F 10 Fragmental

Oxidation

10.2 89 75

Internal Oxidation Methods

One-Side Oxidation – SKO-M Materials
Cross Sections SKO-M

Short and Long Transverse

 

 

 

 

Checon’s unique method of oxidizing AgCd  alloy from one side yields longer lengths when compared to conventionally welded and oxidized strips. Oxidation is accomplished under high pressure, high temperature conditions, producing a characteristic gradation of oxide particle size from fine to coarse  through the strip thickness. Oxidation is halted before completion, leaving a layer of unoxidized AgCd material to be clad brazed or welded for further assembly operations.

 

 

 

 

Through Oxidation – SKO-D Materials
Cross Sections SKO-D

Short and Long Transverse

 

 

 

 

With oxygen penetrating both sides of a strip of AgCd material, processing of SKO-D material takes less time in oxidation than oxidation from one side only. A fine silver backing layer is hot bonded to the material after oxidation to produce a strong bond that is ideal for the manufacture of long lengths and subsequent cladding operations.  The resulting material’s characteristic structure shows a developed Cadmium depletion zone in the center of the strip.

 

Fragmental Oxidation – SKO-F Materials
Cross Sections SKO-F

Short and Long Transverse

 

 

 

 

Fragmental oxidation allows the production of internally oxidized AgCdO2 with a very uniform CdO2 particle size. In this procedure, processed AgCd alloy is oxidized and then cut to closely controlled dimensions and reconstituted into a billet for subsequent extrusion into either wire or strip form. This material displays excellent ductility,  anti-welding, and arc erosion properties, making it highly suitable for the manufacture of headed rivets.

 

Powder Metallurgical Method

Direct Strip Production – SKO-B
Cross Sections SKO-B

Short and Long Transverse

 

 

 

 

 

Powders laid in a tray, with a layer of pure silver powder are pressed and then sintered into a long, wide bar. This process was first developed over 40 years ago at Checon and has been refined to become a major product at Checon. The bond between fine silver and AgCdO is especially secure and the material exhibits excellent anti-welding properties for DP Contactor applications.  The resultant metallurgy of SKO-B Material is a uniform distribution of fine CdO particles with very little directional orientation.