Understanding silicone rubber keypads: Applications, UL746 compliance, and UL F1 ratings

Before we explore the latest article of our Keypad Series, we invite you to explore the two preceding articles, providing essential insights and context for our ongoing exploration of innovative switches and keypad technology.

A quick guide to the popular user interface – membrane switches

Medical membrane switch considerations

Silicone rubber is unreactive, stable, and capable of withstanding extreme environments and temperatures ranging from -55 to 300 °C

(-70 to 570 °F) while retaining its valuable properties.

These qualities make silicone keypads a top choice for switch and keypad manufacturing. These materials are also subject to rigorous evaluation under standards like UL 746C, ensuring that the safety and reliability of silicone-based products meet industry standards, giving engineers and consumers confidence in their performance.

From this article, we will learn more about UL 746C F1-ratings and why you should consider silicone keypads for your project.

What does the UL 746 F1 rating mean for the manufacturing standards of silicone rubber keypads?

UL 746C is crucial for ensuring the safety and performance of polymeric materials in electrical equipment. It offers quality control, global recognition, and compliance with regulations, instilling customer confidence. 

Materials intended for outdoor use undergo UV exposure and water immersion testing. UV exposure includes 720 hours in a twin-enclosed carbon weatherometer or 1000 hours in a xenon-arc weatherometer. Water immersion testing lasts for 7 days at 70°C. Specimens are tested before and after exposure for flammability, mechanical impact, and strength. 

Materials that don’t significantly degrade in these areas pass and are fit for outdoor use. F1 rating ensures the material has met both UV and water immersion requirements. As silicone rubber fits this contest, it is safe for manufacturers to meet safety standards, environmental resistance, and legal obligations.

Now, let’s discover more about silicone rubber and considerations if the material is chosen for your project.

Why should you consider silicone rubber?

Silicone rubber parts are common in rugged environments such as outdoors or where the design needs to be modified to deal with other severe environmental conditions or to cover components less forgiving to the human hand. This can be as simple as a rubber boot on a mechanical switch or as complex as a rubber keypad covering a membrane switch or PCB.

Another reason to use silicone is to get higher relief than can be achieved on a plastic overlay or to create a flange edge for a specialized bezel.

Design considerations

Once chosen a rubber keypad, there are several decisions to make:

  • Durometer = Shore = hardness
  • Key Height and shape
  • Carbon, Nickel, Gold, or no Pills – to improve actuation and tactile feedback
  • 3D edges, buttons, etc. 
  • Colors – always translucent

Our Design Guide and your Melrose Account Manager can assist you in making these choices.

UL746 dictates requirements for silicone usage for electrical in buildings & other public construction environments.

Melrose can assist you in navigating flammability and other UL requirements.

Making informed choices for your project success

Silicone rubber keypads are the go-to choice for engineers in various industries. Their versatility makes them ideal for outdoor and customized applications, providing durability and compliance for demanding projects. Talk with engineering experts and get advice if you consider silicone rubber for your custom project requirements.