Thick film on steel

A novel type of heating element opens up a wide range of design possibilities where there is a requirement to heat fluids of any type

A facility capable of producing up to a million heating elements per annum, in a highly automated process has been opened by Welwyn Components.

The process uses a 13% to 17% chromium ferritic stainless steel substrate, with thicknesses ranging from 0.9mm to 1.5mm. An insulating layer of glass or ceramic is deposited onto the substrate, giving electrical isolation of up to 2500V, and this is fired onto the steel at high temperature, forming a chemical as well as a mechanical bond to the steel.

Conductor and resistor elements are screen printed on, either soldered connector pads or spring contacts, and there is a printed and fired overglaze, which gives mechanical and environmental protection.

Heating elements can be printed onto either flat or formed steel substrates, and can also be printed onto cylindrical shapes.

Current technology uses a tubular mineral filled element, such as the familiar coil in the domestic kettle. While this is reliable and low cost, it has restrictions because of its inflexibility in design freedom. the thermal mass means it has an inherent inability to control temperature accurately. It takes a long time for the system to respond.

The latest technology has the ability to achieve high power density in a small area, which gives thermal efficiency, and design freedom. It is also said to have other important benefits.

Heat dissipates very quickly, and is not retained as in the traditional mineral insulated wire and sheath. The planar technology is very thin, with the heating element itself only 13mm thick, and as the speed of heating is extremely fast, so the heat immediately disappears, and the temperature starts to fall straight away. The system is low thermal mass, and, because of the fast response, much simpler control and feedback systems can be used to control temperature to +/-1 degrees C.

Welwyn Components 01670 822181