TABLE OF CONTENTS Thick film circuits as depicted in Fig. 8.12 are fabricated by screen printing conductive, resistive, and insulating materials in the form of a viscous paste onto a ceramic substrate. The printed film is dried to remove volatile components and exposed to an elevated temperature to activate the adhesion mechanism that adheres the film to the substrate. In this manner, by depositing successive layers as shown in Fig. 8.13, multilayer interconnection structures can be formed that may contain integrated resistors, capacitors, or inductors.
All thick film pastes have two general characteristics in common.
They are viscous fluids with a non-Newtonian rheology suitable for screen printing.
They are composed of two different multicomponent phases: a functional phase that imparts the electrical and mechanical properties to the finished film, and a vehicle phase that imparts the proper rheology.
There are numerous ways to categorize thick film pastes. One way is shown in Fig. 8.14, which depicts three basic categories: polymer thick films, refractory thick films, and cermet thick films. Refractory thick films are a special class of cermet thick films and are frequently categorized separately. These materials are designed to be fired at much higher temperatures (1500 to 1600 C) than conventional cermet materials and are also fired in a reducing atmosphere.
Polymer thick films consist of a mixture of polymer materials with conductor, resistor, or...
