Semiconductor Materials
Many of the air conditioning controls are operated by solid-state devices as well as magnetic and mechanical devices. If a service technician is to install and troubleshoot control systems, he or she must have an understanding of electronic devices as well as relays.
Solid-state devices, such as diodes and transistors, are often referred to as semiconductors. The word semiconductor refers to the type of material solid-state devices are made of. To understand how solid-state devices operate, one must study the atomic structure of conductors, insulators, and semi conductors.
CONDUCTORS
Conductors are materials that provide an easy path for electron flow. Conductors are generally made from materials that have large, heavy atoms. This is why
most conductors are metals. The best electrical conductors are silver, copper, and aluminum. Conductors are materials that have only one or two valence electrons in their atom, Figure 49–1. An atom that has only one valence electron makes the best electrical conductor because the electron is loosely held in orbit and is easily given up for current flow.
INSULATORS
Insulators are generally made from light-weight materials that have small atoms. The atoms of an insulating material will have their outer orbits filled or almost filled with valence electrons. This means an insulator will have seven or eight valence elec- trons, Figure 49–2.
Because an insulator has its outer orbit filled or almost filled with valence electrons, they are tightly held in orbit and not easily given up for current flow.