[Table of Contents]People old and young enjoy waxing nostalgic about
and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged.
wiring of electronics assemblies is rarely seen these days. For that
matter, the use of leaded components is rarely seen these days. The
advent of printed circuit boards was a real breakthrough concept when
they became commercially viable in the 1950s. As the comic at the bottom
of the page suggests, many people did not even know what a printed circuit
The air traffic control radar unit that I worked on
in the USAF had all point-to-point wiring in a trailer-full of chassis.
Terminal strips and bus strips, bifurcated terminals, tube socket terminals,
and studs from relays and switches were the connection points that the
leaded components and wiring stretched between. Compared to a PCB (especially
multi-layered through-hole), servicing those assemblies was a piece
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Printed Circuits Come of Age
By ALLEN LYTEL
circuits have come of age. Today they are an integral part of almost
all electronic equipment. Look at the nearest device: if it has been
made in the past year, the chances are that in it you will find printed
circuits or components.
Some of the newest uses for printed
circuits are in the instrument cluster connections in an auto dashboard
(see photo above). Guided missiles have compact, reliable controls which
use printed circuits, and so do midget tape recorders, jet planes, hearing
aids, electronic organs, and hundreds of other devices.
The most common type is an insulating board* with a pattern of conducting
wires (below right). A photo or printing process transfers the design
to the copper-clad base and an etching process removes the excess copper,
leaving the circuit. In other methods, the conductors are built up on
the insulated base. Next step is the placement of components, handled
mechanically. In one machine all heads are controlled simultaneously,
and as the board is positioned, all the capacitors and resistors are
inserted in one operation. In another machine, they are inserted one
at a time as the board moves down the line. After the components are
inserted, all parts are dipsoldered in place in a single operation.
Printed Circuit Board (PCB)
Figures 3, 4, and 5
The use of printed circuits has led to the development of modules. These
are complete circuits such as audio amplifiers, cathode followers or
Modules are built on a single board
as a unit, acting as a standard circuit which can be used in different
end products. Figure 1 on the next page shows an experimental TV receiver
built of 17 modules which hold 153 of the 195 components (resistors,
capacitors, etc.) exclusive of the tuner. Other modular construction
is of the type in Fig. 2. These are plug-in boards as used in many computers
and industrial controls. Tube and tubeless types with diodes are shown.
These modules can be made up of smaller units. For example,
several resistors and capacitors can make up a package -- a "super component"
-- and can be used on a printed-circuit board (Fig. 3). In another way
of treating the same situation, the components are encapsulated in phenolic
material (Fig. 4).
The newest development is flat Tape
Cable (Fig. 5) which eases the task of interconnecting printed wiring
(see October issue of POPULAR ELECTRONICS, p. 72).