Ferro Techniek are masters of Thick Film Technology, and we have been at the forefront of its development for most of our history.
With extensive experience and a large portfolio of exclusive innovations, you can be confident that your requirements can be fulfilled with our thick film technology.
Below you will find a technical overview of Thick Film, as well as information on some of our more advanced techniques.
The base of a Thick Film element is typically a stainless steel substrate. This substrate is enamelled with a glass-ceramic for electrical insulation. The heater tracks are screen printed on top of the insulation. Finally a protective layer of enamel is applied, with exposed areas for electrical connections.
The element substrate is the carrier for the enamel and the screen printed layers.
Typically the substrate is stainless steel, however other materials such as ceramic can also be used. The substrate can be virtually any two dimensional shape. Three dimensional forms which can be screen printed, such as tubes, are possible.
Substrate Insulating Enamel
The enamel layer electrically insulates the substrate from the screen printed heating tracks. This is unique to Ferro Techniek and they can adapt the formula for different application requirements. eg 230V 3kW or flexibility or 800V DC.
Thick Film Heating Tracks
Resistive tracks are screen printed and fired onto the dielectric, to provide the heating function.
By varying the chemical composition and the geometry of the tracks, the element power and heat distribution can be finely controlled. Silver is selectively printed to create cooler, lower resistance areas for making electrical connections. For information on more advanced track design, see the link below.
Thick Film Track Layouts are often customised, to give even heat distribution across the thin substrate or to concentrate the heat where it is needed. A good example is in a milk frother to avoid burning. There can be multiple tracks for different purposes, such as fast heat up & keep warm or zonal heating.
The power density across the area of the heating element can be designed, to put more energy into some areas than others. This is useful when trying to optimise energy transfer from the heater into another material (eg food) as fast as possible, without burning it.
To do this we can work with the track material, the width of a track, and the spacing of the tracks. Narrower tracks, close together = hotter
The element substrate acts as the carrier for the enamel and screen printed layers.
Typically the substrate is stainless steel, however other materials such as ceramic can be used. The substrate can be any two dimensional shape. Three dimensional forms, which can be screen printed, such as tubes, are possible.
Applying the tracks is a precision screen printing process. This means the elements can be virtually any two dimensional shape. This includes holes through the substrate.
One limitation is that its not too large to fit inside our furnaces for processing.
Thick Film Elements have extensive assembly options, and can even form an integral part of the structure of your product.
Whether housed in a plastic moulding, welded into a metal vessel or directly brazed to the element substrate, there will be an option for your project.
With a steel substrate, other assemblies can be brazed directly onto the element.
The process is exceptionally durable and long lasting. We braze steel to steel in our Flow Through Heaters creating an assemble that can operate at extreme high pressure (20 bar). We can also braze steel to aluminium as seen in the Fin Pack for transferring the heat from the element into an air or gas stream.
A Thick Film element can be mounted in an application by using a compression seal. This is the technology most seen in kettle-like applications. In-particular Ferro developed a method using side compression (radial rather than axial) which has proven extremely reliable.
EFAST and Integrated sensing
EFAST – Electronic Full Area Sensor Technology, provides a means of near instantaneous overheat detection covering the entire element surface.
When an area of the element exceeds a specified temperature, our specialised EFAST enamel changes resistance. Electrical current is then allowed to leak from the heating tracks, through the EFAST enamel to the detection grid. This leak is detected by corresponding electronics and appropriate actions taken.
Embedded EFAST uses vertically stacked layers. The heating tracks are separated from the detection grid by a layer of EFAST enamel. When a section of track gets to a certain temperature, the EFAST enamel drops in resistance and a leakage current passes through to the detection grid.
This method instantly detects overheating as the EFAST enamel is thin & in direct connection to the tracks & the grid. The element can have very high power density and be pushed to the limit without risk of a long switch off time & high overshoot shortening its life.
Parallel EFAST relies upon the heating track and detection track being on the same layer, with the EFAST enamel over the top and filling the gaps between the tracks. In this method when it gets too hot, the leakage current travels through the EFAST enamel from the heater track to the sensor track, parallel to the element surface.
This method is less layers than embedded EFAST, so more cost effective.
EFAST and Steam
EFAST can be used in more creative ways than a simple overheat detection method. It can detect food burning anywhere on the surface or lime scale build up.
EFAST is the underlying technology which allows our Flow Through Heaters to produce an instant, controlled flow of steam without causing overheating or self damage.
Protection and Connections
In addition to our EFAST technology, more conventional methods of thermal protection are available.
Thermal fuses and Bimetallic cut-outs can be provided and integrated into the element surface.
We often find customers using these methods as a low cost secondary protection method to meet certification and approvals requirements.