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.
Fullchance 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.