January 1972 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
When I first read the title
for this article, "A Look at the PC Market," I was thinking personal computers, not printed
circuits. It being from a 1972 issue of Popular Electronics, my assumption was that the
photos of circuit boards were from early kit format computers, but then it finally dawned
on me that there were no personal computers in 1972 - not even in kit form. Actually,
that is not entirely true since there were advertisements for hokey contraptions called
"computers" that combined some switches, logic gates, and LEDs for implementing simple
multiple choice true/false testing boxes or rudimentary (with emphasis on "rud[e]") calculators.
Getting to the real story, though, the 1970s was the decade where printed circuit boards
(PCBs) were replacing point-to-point wiring wherever possible. If you opened a radio
or television of the era, there were still lots of wires running everywhere inside the
chassis, but they were mostly connections to switches, potentiometers, indicators, and
interconnections between PCBs. Nowadays, there are very few wires, with most controls
being PCB-mounted. Hobbyists were doing a lot of PCB etching and drilling using DIY kits
from Radio Shack, Lafyette Electronics, and other hobby-related firms. Looking at the
products presented in this article, I remember using the Circuit-Stik's "Quik-Circuits,"
Vector photoresist kits, and Vero perf boards in my work.
A Look at the PC Market
Kits and Basic Materials Simplify Making Printed
Circuit Boards at Home
By Alexander W. Burawa
Any hobbyist who has ever worked with integrated circuits and other
miniature components knows that the printed circuit board offers the only realistic approach
to assembling a project containing these devices. Traditional point-to-point wiring is
clumsy, inefficient, unsightly, and potentially dangerous to the new breed of delicate
components used by hobbyists.
Yet, until a few years ago, materials for making printed circuit boards in the home
workshop were difficult to come by. Often, materials had to be bought piecemeal; etchant
here, board blank there, and resist another place. Some experimenters were very ingenious
in their searches. Resist, usually the most difficult material to come by, took many
forms, from nail enamel to China markers. Needless to say, results were crude.
In just three years, the situation in PC board materials has changed drastically.
Now, every major mail-order house and most local electronic parts dealers are stocking
a full line of PC materials, including kits. One need only order from a catalog or pick
off a shelf anything he might need to fabricate any type of PC board in his home workshop.
Circuit-Stik's "Quik-Circuits" employ foil conductors on plastic laminates
and perforated boards to take the mess out of designing PC boards.
Typical of Kepro kits are Pyrex glass etching trays. Photosensitized
board blanks are packaged in opaque plastic sleeves. Other materials in kit are etching
and developing solutions, photo-flood and safe lights, design items.
Called an "Industrial Laboratory," Techniques' kit includes everything
needed for turning out first-rate printed circuit boards. Included in the well-rounded
kit are a small drill, exposure jig (top left), and tube and transistor sockets. Both
phenolic and epoxy-fiberglass base board blanks are supplied.
The printed circuit kit offers the hobbyist his best dollar value.
Here, the purchaser receives several items which, if bought separately, would undoubtedly
cost him considerably more than the asking price of the kit. For the avid hobbyist who
makes many projects a year, on the other hand, considerably greater savings can be effected
if materials are bought in quantity - etchant in gallon and five-gallon bottles, large
board blanks instead of several small ones, etc.
In the kit area, there are many offerings. The most basic PC kits contain at least
one or more board blanks, one or more of several types of resist, etchant for removing
from the board unwanted copper, and an etching tray which is usually the plastic tray
in which the kit is packaged. In addition, some basic kits include one or more of the
following items: resist remover, board cleaner, small drill, design paper, stencil cutter,
In classifying a PC kit as "basic," we refer to the finished printed circuit board
which it is capable of producing and not its price (although most manufacturers price
their kits accordingly). Hence, our term "basic" refers to the fact that such a kit is
primarily intended for the beginner and the hobbyist whose interests lean towards simple,
A basic kit will yield varying results, according to the experience of the user. Working
only with the materials provided in the kit, most non-IC projects should present no difficulties.
The projects using IC's - especially the DIP's, or dual in-line packages - will require
some talent in translating the original design into a usable printed circuit board on
which the closely spaced conductors and solder pads nearly touch.
Generally speaking, the basic printed circuit board kit (containing those items mentioned
above) will provide excellent results every time if its limited materials are not taxed.
The suggestion here is that if you plan to work with IC's and other components that demand
more rigid control over the etching and drilling steps, it is better to move up to one
of the so-called "lab" PC kits that are designed to cope with more precise demands.
As far as we have been able to determine, most printed circuit board kits fall into
either the basic or the lab category with only one in the intermediate category. There
is, however, no disadvantage to this step adopted by the industry since even intermediate
hobbyist projects tend to take advantage of a potpourri of solid-state devices, including
Although not all lab-type kits contain the same list of materials, there are certain
items that are common to all of them. Among the standard items are various sizes and
types of board blanks (clad on one or both sides, employing phenolic or epoxy-glass bases,
photo-sensitized and unsensitized, and perforated and blank), etchant resists (usually
a combination of the various types available), and etchant. While the list so far resembles
that of the basic kit, the lab-type kit contains considerably more of each item. Then
there are the other items in the kit which are designed to assure professional results.
Almost without exception, the lab-type PC kit features a dual-resist system. The primary
system is based on a photographic technique in which a foil pattern "negative" is used
to "expose" the photo-sensitized board. The negative itself is made from materials supplied,
or it can be carefully drawn on a white background with India ink and submitted to a
professional photographer to be make into a film negative. The latter approach, of course,
will yield the best results and allow for finer detail.
In most cases, the exposing medium in an intense white light source or a medium-wave
ultra-violet source (for the former, most kits also supply a photo-flood lamp). To prevent
the negative from slipping around during exposure, and to keep it flat against the board
blank, most kits also contain a plate glass sheet or jig that is used to clamp the two
Vero's non-etch kits employ perforated boards with copper foil strips.
Special foil cutter and push-in solder terminal insertion tools included.
Injectorall photo-resist kit contains usual materials plus test negative,
stencil knife, cleaning pad. Clips and glass are exposure jig.
Eico kit is unique; it employs enamel resist (in tube), and includes
design template, materials for removing enamel, and cleaning board.
Example of Vector photoresist kit shows etching crystals (lower left),
rub-on resist patterns, burnisher, design materials, and board blanks.
Once the board has been exposed, it must be immersed in a developing solution (also
supplied) to remove the resist over the areas of the board where you want to etch away
the copper. Then the board, after rinsing in water, goes into the etching solution where
it is converted from a blank to a PC card ready for drilling.
For unsensitized blanks and sensitized blanks which have accidentally been exposed
(and thoroughly cleaned of photo-resist). conventional hand-apply resist can be used
for making the PC board. Most kits supply more than enough of the hand-apply resist materials
to take care of just about any contingency.
The etched and cleaned PC card can be given a professional appearance by immersing
it in a tin-plating bath. The tin covers only the exposed copper, facilitating easy soldering
and sealing the copper against oxidation.
One more PC kit is worthy of mention here, although its appeal is mainly to the hobbyist
who has to make multiple runs of a single type of board. This kit employs a silk-screen
technique that can provide almost as fine a detail as is obtainable with the film-negative
technique. All materials for making the silk screen master are supplied.
In the non-etch category, there are at present only two types of
kits available. In one, a combination of different types of perforated boards are employed,
one of which has a series of parallel strips of copper foil on one side. The foil can
be easily cut to form the PC pattern. A special tool, supplied with the kit, is used
for cutting the foil.
Calectro: Basic kits and materials; photo-resist not used.
Circuit-Stik: Sold under name of "Quick-Circuits." Kits and materials;
non-etch system employs perforated board and solder pads on heat-resistant laminates;
suitable for all levels of work.
Eico: Basic kits; use enamel resist exclusively; include stencil
knife, paint remover, design template, board cleaner.
Injectorall: Basic kits employ tape-and-dot resist; intermediate
kits have photo-resist and include photo-flood lamp.
Kepro: All levels of kits, all types of resist. Nameplate and panel
kits; silk-screen kit; individual PC materials available separately; advanced kits can
be used in critical designs.
Techniques: All levels of kits; silk screen kit.
Vero: Industrial design PC kits employing non-etch system and separate
items available; based on parallel conductors on perforated boards; can be used for all
levels of work.
Dynachem Corp.: Aerosol photo-resist; developer; aerosol dye for
photographic process in making PC boards; available in starter kit or separately.
Vector: All levels of kits; employ photo-resist; dry-transfer resist,
and tape-and-dot resist; etchant comes as crystals to be mixed with water; suitable for
all types of PC work.
Printed circuit boards made with the parallel conductor pattern must be laid out to
take full advantage of the hole matrix and foil strip orientation. And, although this
type of kit was designed primarily for use in breadboarding and setting up original circuit
prototypes to serve as models prior to industrial production runs, the carefully designed
printed circuit board made at home can serve equally well as the finished product in
The second type of kit also employs perforated boards (none with copper conductors
on it). Different configurations of solder pads on heat-resistant laminates and copper
foil, both adhesive-backed, are used in making up the printed circuit pattern. The adhesive
is a special formulation that resists breakdown under normal soldering temperatures,
and the laminate on which the soldering pads are deposited will resist even higher temperatures
There is a considerable variety of paste-down solder pads available, including those
for 6-, 8-, 10-, and 12-lead round IC's 14- and 16-pin dual in-line (DIP) IC's, flat
packs, 3- and 4-lead signal and low-power transistors, tag-strip layouts, multiple-lead
connection points, etc. To further simplify matters, the hole locations on the pads mate
exactly with the hole matrix on the perforated boards. And, since the foil and solder
pads are adhesive-backed, any mistakes made in the layout can be quickly rectified.
Design and Layout Aids. When making up your shopping list, include
a few items (available from most stationary or art supply stores) that will simplify
the design and layout tasks. Include graph paper with ten divisions/inch, tracing paper
(vellum is best), clear sheet acetate, soft-lead pencils, and India ink and pen for the
design end. For actual layout work, add opaque flexible tape in several narrow widths,
amberlith sheets, a dry-transfer lettering kit, and a hobby knife.
If you want really professional photographic-quality negatives for exposing sensitized
board blanks, look into the drafting aids available at art supply stores and from some
of the mail order electronics houses. These items are fairly expensive but well worth
the investment if you are planning to make multiple runs or require precise control of
the PC foil pattern.
Directly from the electronics supply houses, you can get nibbling tools for cutting
boards to size, PC board repair kits, board blanks, etchant, all types of resist, sockets,
etc. And make a trip to your hardware store to pick up several small-diameter drills.
After working with PC boards for a while, you will realize that you no longer have
to depend on commercial sources of boards to complete a project. With a little practice,
you will be turning out boards every bit as good as those made by industrial techniques
- and you will save a lot of money in the bargain.
Posted January 4, 2019