Silicone Rubber Heaters
Epec silicone rubber flexible heaters can be custom designed to various shapes and sizes, ranging from 1” X 1” to 18” X 24”. If larger sizes are needed, then switching from an etched element to a wire element would be required. Based on the element used, the overall average thicknesses are 0.030" (etched element) to 0.056" (wire wound).
The etched or wire circuit is attached to power leads with solder and then vulcanized between two layers of silicone rubber, resulting in a completely homogenous unit. The silicone offers protection from physical damage such as scraping or scuffing and acts as a moisture barrier to allow for operation in wet and outdoor environments. Silicone is also resistant to most chemicals.
We offer multiple heating elements for silicone heaters such as stainless steel 304, CuNi44, and Inconel600, with excellent dielectric properties and operating environments between -70°F (-56.6°C) and 392°F (200°C). It should be noted that silicone heaters have a delay of transfer from the resistive foil or wire to the mounting surface.
Current Specifications for Silicone Heaters
- Maximum Watt Density: 60 W/in²
- Maximum Operating Temperature: 392°F (200°C)
- Minimum Operating Temperature: -70°F (-56.6°C)
- Wattage Tolerance: ±10%
- Dielectric Strength: 1000 VAC
Types of Flexible Silicone Rubber Heaters
Flexible silicone rubber heaters use wire-wound elements (resistance wire) laminated between silicone rubber to ensure a uniform heat profile and excellent physical strength. This technology is typically used in lower volume or larger size applications as it is easier to conform to the size and shape of the application, avoiding holes and cutouts, or to concentrate the heat profile in a specific section or sections of the heater as required. Wire wound design is a solution to the limitations or etched foil technology.
Below are the different types of resistance wire used in wire wound flexible heaters.
- Nickel Chrome (NiCr) alloys are the most common material used in silicone rubber heater applications with maximum operating temperatures up to 1,250°C (2,280°F). Typically called Nichrome wire, it is a non-magnetic alloy that has high resistivity and good oxidation resistance.
- Copper Nickel (CuNi) alloys have medium range electrical resistivity and very low temperature-coefficient of resistance so they are typically used in flexible heater applications with maximum operating temperatures up to 600°C (1,110°F).
- Iron Chrome Aluminum (FeCrAl) alloys are high-resistance materials with very good form stability resulting in long element life typically used in applications with maximum operating temperatures up to 1,400°C (2,550°F). Because silicone rubber heaters made with this material will have higher surface loading capability, higher resistivity, and lower density than traditional Nichrome alloys, the heater can be designed with less material to provide weight savings.
* The above data is a representation of the resistance wire temperature.
Etched Foil Heaters
These heaters utilize chemically etched circuits which are laminated between thin sheets of silicone to give even quicker heat transfer properties for applications that require precise temperature control. While etched foil circuits need wider widths to accomplish equivalent resistance of a wire, the traditional print/etch process that has been used in printed circuit board fabrication for decades provides tight spacing control which enables spacing between elements to be as tight as 0.004”. The ability of our design teams to create the precise circuit geometry allows even thermal distribution and precise repeatability through production.
Silicone rubber heaters using an etched foil circuit can provide twice the output wattage of the older wire wound technology. This technology allows us to provide multiple heating zones on the same heater and is also attractive for designs that require watt densities greater than 5 W/in2. in as the foil thickness for the circuit can range from 0.0005” to 0.004”.
The etched foil can be created out of many different types of alloys such as aluminum, stainless steel, nickel-chrome non-magnetic alloys, copper, constantan, and others. Our experience with all of these various materials ensures that we can design and provide the best solution possible for your application.
Applications and Industry Benefits
There are many applications in a variety of industries, whether it be medical, aeronautical, military, foodservice, etc., that can benefit from the heating capabilities of a custom designed flexible silicone heater.