December 1957 Popular Electronics
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 are hereby acknowledged. See all articles from
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 board was.
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 of cake!
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 pulse generators.
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).
Posted July 10, 2011