24 Computer Service and Repair
pattern of valleys and ridges on the surface of the
wafer. These valleys are filled with conductive
materials. The process of filling in these valleys
is called doping or implantation. This process is
repeated many more times until twenty or more
layers are developed over the surface of the entire
wafer. A single wafer consists of many integrated
circuits. The wafer is cut into individual integrated
circuits and then packaged.
One of the most difficult parts of packaging
the integrated circuit is connecting the fine wires
between the wafer circuits and the much larger
pins on the outside of the package. The entire
wafer and thin connection wires are encapsulated
in a hard insulating material resembling black
plastic.
Modern computer technology would not be
possible without the techniques used in building
integrated circuits. The ICs used in computers
have many specialized purposes. For example,
the CPU is a very large and complex IC that
controls all PC activities. The computer modem,
used to communicate across telephone lines, has a
specialized chip that changes computer data into
a stream of various voltage levels that represent
the data. It also converts the stream back into
digital data at the receiving end. There are various
other chips on the motherboard that have special
purposes. Some assist the CPU with data flow
across the motherboard. Others control devices
such as the hard drive and optical drive. The RAM
used in computers is nothing more than a group
of ICs mounted on an insulated circuit board.
Electrostatic Discharge (ESD)
Electrostatic discharge (ESD) is best defined
in the world of computer maintenance as the
transfer of static electrical energy from one
object to another. ESD can destroy the miniature
circuits inside a computer chip. Static charges are
usually created by friction. When two dissimilar
materials are rubbed together, an electric charge is
produced. Static buildup is always greatest when
the air is dry and cool.
A common example of static electricity
buildup and discharge is when you walk across a
surface such as a rug and then reach out and touch
A B
International Business Systems Corporation
Figure 1-34. Manufacture of an integrated circuit. A—Circuit drawing uses a template to form circuits on silicon wafers.
B—Fine layers are created in the silicon. The layers are controlled in such a way to create the millions of transistors and
other electronic components used in the integrated circuit.