2-40
composed of parts so closely associated with one another that repair becomes almost impossible. In case
of trouble, the entire circuit is replaced as a single component.
Basically, there are two general classifications of integrated circuits: HYBRID and MONOLITHIC.
In the monolithic integrated circuit, all elements (resistors, transistors, etc.) associated with the circuit are
fabricated inseparably within a continuous piece of material (called the SUBSTRATE), usually silicon.
The monolithic integrated circuit is made very much like a single transistor. While one part of the crystal
is being doped to form a transistor, other parts of the crystal are being acted upon to form the associated
resistors and capacitors. Thus, all the elements of the complete circuit are created in the crystal by the
same processes and in the same time required to make a single transistor. This produces a considerable
cost savings over the same circuit made with discrete components by lowering assembly costs.
Hybrid integrated circuits are constructed somewhat differently from the monolithic devices. The
PASSIVE components (resistors, capacitors) are deposited onto a substrate (foundation) made of glass,
ceramic, or other insulating material. Then the ACTIVE components (diodes, transistors) are attached to
the substrate and connected to the passive circuit components on the substrate using very fine (.001 inch)
wire. The term hybrid refers to the fact that different processes are used to form the passive and active
components of the device.
Hybrid circuits are of two general types: (1) thin film and (2) thick film. "Thin" and "thick" film
refer to the relative thickness of the deposited material used to form the resistors and other passive
components. Thick film devices are capable of dissipating more power, but are somewhat more bulky.
Integrated circuits are being used in an ever increasing variety of applications. Small size and weight
and high reliability make them ideally suited for use in airborne equipment, missile systems, computers,
spacecraft, and portable equipment. They are often easily recognized because of the unusual packages that
contain the integrated circuit. A typical packaging sequence is shown in figure 2-22. These tiny packages
protect and help dissipate heat generated in the device. One of these packages may contain one or several
stages, often having several hundred components. Some of the most common package styles are shown in
figure 2-23.
