A Passion For Problem Solving

A thick film device is built by printing different thick film ink layers onto a base substrate using a screen printing process. The base substrate can be either ceramic, stainless steel and in some applications, aluminum.  A thick film device could come in the form of a thick film heater, custom power resistor, resistor array or thick film circuit board.

The thick film inks used to make thick film products are broadly distributed into 3 categories: Dielectrics, Conductors and Resistors.   The dielectric materials are generally glass and ceramic based and are not conductive.  The conductors contain precious metal particles such as silver, palladium, gold or platinum and their alloys. Resistors are blends of glasses, metals and metal oxides such as silver and ruthenium in various combinations to achieve inks with different resistance values.  All the ceramic based thick film inks are blended with glass particles called frit. During the firing process the metal and metal oxide particles bond together in a solid state process called sintering to form a network of millions of electrical connections between the conductive particles. Also during the firing process the glass particles melt, flow and act as an adhesive and filling voids between particles of metal and metal oxides and bonding the entire structure together and to the base substrate.

ThickFilm Technologies selects different dielectric, conductor and resistor ink combinations depending upon thermal and electrical requirements of the design and the properties of the substrate material. The materials chosen are determined by the application or process compatibility with the operating environment, operating temperature and cycle rates.

If your current solution is insufficient for your application or you are having problems and are looking for a different approach then it would be worthwhile to look at thick film technology. Below are some characteristics of thick film heaters, resistors and circuits that may be useful in determining if thick film is the right solution for you:

The need for even heat, thermal uniformity across a surface or if you need to be able to specify different power densities (heat) in different areas of the heater. By distributing the heater traces as needed, more power can be targeted in particular areas to meet the needs of the application. Low thermal mass means thick film heaters are very fast to respond both heating and cooling

Custom foot print.  We laser cut all our ceramic and stainless steel substrates and therefore heaters and resistors can be in almost any 2-dimensional shape.  If you have an odd form factor and off the shelf heaters don’t fit or don’t perform, then a custom designed thick film heater might be the answer- we are happy to discuss your application and help you determine if thick film is the right choice.

Space saving is another important advantage because thick film heaters  and resistors offer a very low profile this is especially true when compared to bulky wire wound type heaters or resistors. The ability to select a thick film resistor ink of a particular value allows much less “real estate” to be used-this is particularly true when a compared to a wire wound type resistor or heater that requires a high resistance value-with wire wound technology the wires has to either be very long or the gage of the wire to be very small.

Most of our thick film products are custom designed and annual volumes can range from one to several thousand.  Our NRE and development costs are very reasonable.

Ceramics: Aluminum Oxide, Aluminum Nitride, Zirconium oxide

Stainless Steel: Types 304 and 430

Aluminum

Thick film heaters are very low profile.  They can be laser cut into almost any 2-dimensional shape to accommodate features or components in the application.  They have a fast thermal response and low thermal mass. Because the heater traces can be tailored to the application they are able to maintain a uniform thermal distribution and or increase or decrease watt density as needed by the design.  Multiple independent heat zones can be designed into one heater. Operating temperature of 550°C (1025°F)  may be attained depending upon application, substrate material and type of electrical termination. Thick film heaters resist corrosion and have a long life. Custom designs for specific application are our specialty.

Generally the Substrate material is selected based on the application and the environment in which the device will operate.  Compatibility with the process environment, operating temperature, power requirements and price feed into the calculus in determining which substrate type to use. We are happy to discuss with you your requirements and help in selecting the material set.

There are various metals and alloys available for termination pads.  We can offer silver, , platinum and gold (though gold has gone out of favor in recent years due to cost).  We also have alloys such as silver/palladium, silver/platinum, silver/palladium/platinum. This allows options such as spring contacts to be used as well as soldered leads and ultrasonic wire bonding.  We can supply wire to the length and type required by customer design, and can encapsulate the solder joints or tack wires in epoxy or silicon as needed.

Watt densities of the standard products range between about 20 W/in² and 40 W/in². Custom designs can reach around 100 W/in².

We specialize in customized heaters, we can design a thick film heater to fit your needs. Often customer will purchase a few heaters of a current design and evaluate them in their process.  If they decide that thick film is the right technology for their application we can design a custom heater for their specific application at a very reasonable cost.