Different Materials Used in Manufacturing Electrical Contact Assemblies

The selection of contact materials for your electrical contact assemblies is an incredibly important part of the planning process. It’s always advised that you discuss the application requirements with an engineer or other professional as early in the design process as possible. Of course, depending upon your specific needs, there could be multiple options available in terms of the materials to be used. Each contact material will obviously come with its own pros and cons, whether that’s a tendency toward welding or “sticking,” or simply affordability. There’s also the concern of whether or not you’ll require UL or IEC approval. To learn a bit more about the different materials used in manufacturing electrical contact assemblies, you can continue reading below.

Silver Tungsten

Also known as AgW, silver tungsten is a popular material for use in both large air and oil circuit breakers. It’s known for having a high resistance to arc erosion. It’s also a common choice for re-closures, line disconnects, and both high current contactors and switches. Thanks to its resistance to welding, it can also serve as a good shorting contact. Composites of silver tungsten that contain more silver are used quite often in circuit breakers and in high current contactors.

Copper Tungsten

Commonly known as CuW, copper tungsten is also a very popular contact material. It’s known for being heat-resistant, ablation-resistant, easy to machine, and it’s both highly thermally conductive and electrically conductive. Copper tungsten can serve as an excellent material for switches and contacts for oil-filled devices. Thus, copper tungsten is a material commonly found used in the fossil fuel industry, as well as related industrial and commercial fields. You may also find it used in some oil, gas, or even air circuit breakers.

Silver Graphite

Sometimes shown as AgC, silver graphite is popular for many electrically conductive applications. It’s also known for having the best anti-welding properties of all contact materials. Because it has the best protection against contact welding, it’s an excellent choice for closed contacts under short circuit conditions. It’s also known for having low contact resistance and low erosion. For industrial purposes, silver graphite is excellent for circuit breakers, but it’s also effective for residential circuit breakers.

This is by no means an exhaustive list. Putting together the best electrical contact assemblies always necessities identifying the appropriate materials, so it’s always recommended that you discuss your application requirements at length before making a final decision.

How Electrical Contact Rivets Are Made

In the history of manufacturing, solid contact rivets are known to be the oldest utilized contact parts. While many modern companies have switched or are considering making a switch to wire welded electrical contacts, the solid contact rivet is still widely used and very popular. To learn about how electrical contact rivets are made and their various uses, continue reading below.

Production

The manufacturing of a solid contact rivet requires a ductile contact material. The ductility of the material is incredibly important, since solid contact rivets are formed by hammering or pressing. As you know, only materials which are malleable can be cold formed by pressing or stamping. In order to produce the rivet, a wire slug is cut off. It’s then formed by pressing and hammering. With this process, several different contact shapes can be made. The most common shapes are either rounded or trapezoidal. The trapezoidal head can be either radiused or flat. Depending upon the final application and relay or switch design, you may also find pointed, flat, spherical, or domed head configurations. Solid contact rivets are produced without scrap. However, composite rivets are also produced via a scrap-less manufacturing process.

Construction

Copper is commonly used as a contact material, but silver is also popular for electrical contact rivets. For composite contact rivets, cold bonding is typically used. For composite rivets, the body is most commonly copper. Composite riveting is often used to save on expense with both bimetal and trimetal variations being used, depending upon the material costs and application needs.

Uses

As mentioned previously, a silver alloy is often favored for electrical contact rivets. Popular applications include all kinds of switches, as well as automobiles and electrical appliances. Additionally, relays, thermostats, and contactors often employ a silver alloy for their electrical contact rivets. As with copper, silver has great ductility, and it can be cold formed via pressing or hammering. These rivets are commonly used in automotive applications, as well as in aerospace and household electronics. Bimetal silver contact rivets are quite popular for microswitches or for relay contacts, and trimetal varieties are also used. However, you can also find pure silver solid electrical contact rivets. Beyond relays and switches, they also find common usage in circuit breakers. While wire welded electrical contacts are increasing in popularity daily, rivets are still widely in use.

Different Metals Used in Making Electrical Contacts

There are several materials and alloys that are used in creating contact materials in electrical contacts, which are both meant to help construct electrically conductive connective materials. Here are some different alloy materials used in constructing electrical contacts.

Refractory Contacts

Refractory contacts are important in helping conduct electrical current through strategic placement in devices. The necessary conductivity and resistance help determine just what materials should be chosen for your product. The following are materials used to create refractory electrical contacts:

  • Silver tungsten
  • Silver Tungsten Carbide
  • Silver Graphite
  • Silver Tungsten Graphite Carbide
  • Copper Tungsten
Buttons

In successful electrical contacts manufacturing, buttons help your finished product be as effective as possible. The following are alloys used in the composition of creating both single buttons and multi-layer buttons:

  • Silver Cadmium Oxide
  • Silver Tin Oxide
  • Silver Nickel
  • Silver Alloy
  • Copper and Copper Alloy
  • Steel and Nickel Monel
  • Braze Alloy
Rivets

Rivets are created with the distinct purpose of extending that conductivity. The materials used and how they are constructed need to target the specific construction needs of the end-result product. The following are types of rivets that are manufactured to serve electrical contacts:

  • Construction
    • Solid
    • Multi-Layer
    • Head and Shank
      • Straight Side
      • Chamfer Side
      • Step Side
      • Indent
      • Chamfer
      • Riveted Assemblies
Surface Features and Shapes

Varied shapes serve distinct purposes for the benefit of your products. The following alloy distinctions can help make a more intuitive design that enables a more efficiency and resiliency. Here are some characteristics that can be expected:

  • Knurl and Score Lines
    • For Backing Designations
    • Projections
      • For Welding
      • Nibs
        • For Locating on the Substrate
        • Serrations
          • For Desired Performance
          • Shapes
              • Square
              • Rectangular
              • Circular
              • Washer
              • Cylindrical
              • Spherical

            There are a wide range of metals that are used in making electrical contacts. In order to create a manufacturing plan best suited to your product, it doesn’t hurt to consult with an electrical contacts manufacturer to learn more.

Understanding the Principles and Applications of Electrical Contact Assemblies

Electrical contact assemblies are important in creating a wide range of products and components used in electrical devices. Let’s take a look at what exactly they are, and how they work.

The Basics of Electrical Contacts

An electrical contact is a component found in an electrical circuit that helps to complete it and allow for electrical current to successfully flow from one point to another. These electrical contact components occur in switches, connectors, circuit breakers, and relays, and they can be formed out of a range of materials depending on how well those materials both successfully conduct electricity and resist corrosion over time. The materials used in electrical contacts are also often chosen related to how affordable they are and how cost effective they are over time.

Electrical Contact Assemblies

Creating these small parts and components is just one phase of the process. Some companies also offer to help assemble these parts into a specific device, taking a set design, interpreting it, and putting into action the needs of a design plan according to what electrical contacts are needed and where. These assembly services can also involve a company partnering with an assembly group in order to have them manufacture electrical contacts that meet certain custom specifications.

Types of Electrical Contacts

These conductive parts can get pretty specialized. Buttons, rivets, various conductive surface features, and an array of refractory contacts are used to make up electrical contacts. They can be made from silver tin oxide, copper tungsten, silver graphite, and a wide range of other alloys that can accommodate different needs.

Electrical contact assemblies are incredibly important in the design and manufacturing of a wide range of electronics. These tiny conductive parts make the most everyday tools we use possible, from a television remote to a light switch to our cell phones. The next time you flip that switch or turn that knob, think about the tiny parts that are all working together to connect that circuit and make it work for you.

Your Forecast Is More Than Hot Air!

Many of Checon’s major customers provide us with forecasts of one sort or another. Most are loosely based on their customers’ expected orders as well as on any additional estimates their customers may provide to them. As you can imagine, this continues on to our customers’ customer, that customer’s customer, and so on. So it comes as no surprise that any changes in demand from the end user of our products will often result in significant fluctuations in the forecasts throughout the supply chain.

For many suppliers this can lead to frustration. If you schedule production based on a forecast and the forecast then changes you may end up with excess inventory of one product and shortages of another. I’ve heard other manufactures express this frustration with statements like “their forecast is worthless”, or “full of hot air”, or “I don’t even bother to look at it”. That’s because they are using it for the wrong purpose. Don’t build based on forecast, plan with it!

Checon understands that we need a flexible manufacturing system that can respond to changes in demand both small and large. How large? Well that depends on our customer’s ability to ramp up its production. For those that can react, we have tailored our system to respond to large fluctuations. Working closely with our suppliers, we have integrated their response capabilities into a manufacturing system built on a foundation of short setup times, small production runs, strategic inventory points, and a fully automated Kanban pull system. How we load that system is based on our customer’s demand profile. The result is fast and flexible delivery that has been over 96% on-time for more than five years!

So what does this have to do with forecasts? Absolutely nothing! Checon’s agility allows us to manufacture based on our customer’s demand, not on their forecast. But their forecast can provide information about their current outlook. Will they take what they forecast? Probably not, but we can still glean valuable information from what they think they will take, and plan accordingly. So please, keep giving us your best guess at what you will need, and we’ll take it from there.

Checon Corporation a Platinum Sponsor of the 2016 HOLM IEEE Conference on Electrical Contacts October 9-12, 2016

NORTH ATTLEBORO, MA, SEPTEMBER 15, 2016: Checon Corporation is pleased to participate as a Platinum Sponsor of the upcoming 2016 HOLM IEEE Conference on Electrical Contacts, October 9-12th, in Clearwater, Florida, USA. This will be the twelfth year that Checon will co-sponsor this important technical forum covering the latest developments in the field of electrical contacts, contact materials and connectors. As a Platinum Level Sponsor and active participant in the HOLM Intensive Course that precedes the conference, Checon is committed to helping this event deliver on its promise of a dynamic program featuring technical research and practical application information critical to our customers.

Engineers, designers and research scientists interested in learning more can contact Steve Carter at carter@checon.com, or go directly to the Conference website at www.ieee-holm.com.

For additional information on Checon and Checon PMC, visit the web site at www.checon.com.

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Customer Success With Silver Tin Oxide

Years ago, in response to growing environmental concerns from Europe over the handling, use, and disposal of Cadmium (Cd) in a wide variety of electrical and industrial applications,  Checon began developing its plan to create a silver cadmium-oxide free contact material that would meet the needs of our rapidly expanding international interests as well as satisfy those of our evolving North American customers.  The initiative was no small undertaking as we knew we would be challenged by multiple cost and performance issues, compounded by the slow to market process of electrical testing and customer adoption programs. While the switching industry had already developed silver tin-oxide solutions, for several low power DC applications, the same opportunity seemed less achievable with mid to high power AC devices that depended so heavily on cadmium’s unique electrical capabilities.

Recognizing the inevitability of ROHS sanctions against continued use of cadmium in electrical contacts, Checon moved its development efforts beyond its own lab to a customer collaborative program focused on tightly monitored material testing in device application environments.  Our revised plan was to develop a new silver tin-oxide material system that performed in specific customer applications while carefully maintaining investment in existing product designs. In order to control costs and maintain the highest reliability and quality characteristics, we drilled down to identifying mechanical ductility as an essential ingredient in preserving the processing efficiencies of toplay construction, while meeting the demanding mechanical and electrical properties across many applications including AC contactor, motor protection, and telecommunications.

And so the process began to unfold with appreciative milestones in silver tin-oxide product development and testing. Backed by customer investment in the expansion of a rigorous electrical and mechanical testing program, our proprietary silver tin-oxide products offered under the Checon GTi Series are now fully approved across multiple customer product lines, actively on par with the performance of previously specified silver cadmium-oxide materials as well as outperforming our cadmium-free competition.

Given the varied interpretation and uncertainty regarding the status of cadmium exemptions both present & future, we welcome the opportunity to work directly with customers just beginning or revisiting a material change to match our tested solutions with your specific application requirements.

Please contact me directly at: thomsen@checon.com.