TABLE OF CONTENTS Thick film conductors must perform a variety of functions in a hybrid circuit.
The most fundamental function is to provide electrically conductive traces between the nodes of the circuit.
They must provide a means to mechanically mount components by solder, epoxy, or direct eutectic bonding.
They must provide a means for the electrical interconnection of components to the film traces and to the next higher assembly.
They must provide a means of terminating thick film resistors.
They must provide electrical connections between conductor layers in a multilayer circuit.
Thick film conductor materials are of three basic types: air fireable, nitrogen fireable, and those that must be fired in a reducing atmosphere. Air-fireable materials are made up of noble metals that do not readily form oxides. The basic metals are gold and silver, which may be used in the pure form or alloyed with palladium and/or platinum. Nitrogen-fireable materials include copper, nickel, and aluminum, with copper being the most common. The refractory materials, molybdenum, manganese, and tungsten, are intended to be fired in a reducing atmosphere consisting of a mixture of nitrogen and hydrogen.
Gold has many varied requirements in thick film circuits, as shown in Table 8.17. It is most often used in applications in which a high degree of reliability is required, such as military and medical applications, or wherein gold wire bonding is desirable for reasons of speed. The assembly processes (i.e., soldering, epoxy bonding,...
