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  • Writer's pictureMargaret McNair

The Big Switch: Silver Cadmium Oxide to Silver Tin Oxide

Updated: Aug 1

Contacts and relays are critical components in many electrical systems, from simple household appliances to complex industrial machinery and are responsible for opening and closing circuits, allowing electricity to flow or stopping it in its tracks. These contacts and relays have historically and predominantly used Silver Cadmium Oxide as the contact alloy. In recent years though, the need to replace silver cadmium oxide (AgCdO) with a safer alternative has become increasingly more evident. The environmental and personal health risks associated with cadmium make it imperative to transition to a more environmentally friendly alloy such as silver tin oxide (AgSnO2).

This article explores the reasons behind this necessary shift, the challenges it presents, and the potential benefits for both the environment and personal health in making the switch from a Cadmium containing device.


AgCdO Tips

In the low and medium voltage sector a restricted substance - Cadmium alloyed with silver, has been widely used for decades due to its combination of resistance to welding, good conductivity, brazeability and stable mechanical properties. However, this transition is not a simple matter of swapping materials as the alternate alloy will also have its own unique set of limitations. It requires careful consideration of numerous factors, typically necessitating a switch re-design to accommodate the different properties of the alternate metal.


Below are several factors to think about when considering an alternate alloy.


Bi Metal Rivets

Reasons Behind the Big Switch from Silver Cadmium Oxide to Silver Tin Oxide


Environmental and Health Concerns:


Cadmium, a component of silver cadmium oxide, is a toxic heavy metal that poses significant risks to the environment and to human health. Its potential for bioaccumulation and long-term persistence makes it a serious environmental pollutant. This metal can cause serious health problems such as cancer, birth defects, kidney damage, and reproductive harm if inhaled or ingested in large quantities. It is also toxic for aquatic life when released into water bodies. By replacing AgCdO with AgSnO, it has been shown that we can significantly reduce the environmental impact of electrical equipment and promote sustainability by eliminating this hazardous element.


Save the planet poster on tree

Complexities of the Transition:


Switching from AgCdO to AgSnO involves more than just straightforward material swap by changing the alloy. The unique metallurgical and physical properties of each alloy must be taken into account. Factors such as performance under different loads (inductive or resistive), AC or DC operation, erosion resistance, welding characteristics, conductivity, and resistivity all play a crucial role in determining the suitability of the new material. A comprehensive evaluation with subsequent testing under loads is critical in determining the compatibility and effectiveness of the new material and is essential to ensure a successful and reliable transition.


welding contact materials

Research and Development:


Numerous research papers already exist on the subject, providing in-depth analysis and insights into the challenges and potential solutions related to the switch from AgCdO to AgSnO. However, this means that designing a new contact or relay switch with silver tin oxide requires careful consideration and testing. It may even require an entirely new switch design to take into account the unique properties of the new material. Consulting these resources can provide valuable information and a deeper understanding of the complex factors involved in the transition process..


Research and Development Planning

Substantial Benefits in Terms of Sustainability and Personal Well-being


Replacing silver cadmium oxide with silver tin oxide is a necessary step to mitigate the environmental and health risks associated with cadmium. While the switch presents challenges such as a full switch re-design and evaluating the changes in the performance factors, it offers substantial benefits in terms of sustainability and personal well-being. The transition to AgSnO requires a comprehensive and systematic approach, considering each metal's unique properties and ensuring the development of reliable and efficient switch systems. By embracing this change, we can contribute to a greener and safer future.




About the Author


Margaret McNair of InTandem Digital Consulting is head of research, content writing, & business process development. She has over 20 years of experience in marketing spanning across different industries. 10+ years in website in content writing, research, business development, and website design.

InTandem Digital Team Member Margaret McNair

Electrical Contacts International is a contract manufacturer specializing in electrical contact materials and sub-components for switches and breakers. We are founded by engineers with the vision to supply the highest quality materials with knowledgeable, friendly staff while maintaining competitive pricing.


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