Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to circuit boards with die
stamped contact pads and conductive ink circuit patterns, and to a
process for making such boards.
Circuit boards are made using techniques such as using
porcelainized steel blanks with screened silver inks which are fired;
copper patterns on dielectric boards; polymer thick films on
dielectric boards. Connections can be made by soldering for the
first two examples, while a connector is required for polymer thick
films as these are not solderable. For copper patterns on dielectric
boards, contact areas are generally produced by plating on to the
conductor patterns at desired places.
To reduce the cost it has been proposed to use
conventional printed circuit board copper patterns, screen printed
with conductive inks at positions where contact pads are required. A
further reduction in cost could be obtained by avoiding the
preparation of the copper patterns and printing the pattern directly
on the board. However, this would require a connector to connect the
ink circuitry to components or other boards or devices.
The present invention proposes the die stamping of
contact pads on to the dielectric board, at desired locations,
followed by screen printing of conduc~ive ink patterns. Typically, a
strip of copper is fed over boards; the contact pads are die cut from
the copper strip and pressed onto the boards, with the perforated
strip wound up; the copper pads are bonded to the boards with heat
and pressure; conductive ink patterns are then printed on the boards,
connecting with the contact pads. The copper strip has an adhesive
on its lower side and this adhesive is cured by the heating and
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pressure. While the boards can be singly fed, with suitable locating
means, it will usually be more effective to feed the boards in
strips, with punchiny or shearing of finished boards ~rom the strips,
The invention will be readily understood by the
following description of typical circuit boards and a process, in
conjunction with the accompanyirg drawings, in which:-
Figures 1 and 2 illustrate two typical examples ofcircuit boards for telephone keypads;
Figure 3 illustrates a modification to the board of
Figure 2, with enlarged contact pads; and
Figures 4(a) to 4(d) illustrate the steps in the
production of boards, in accordance with the present invention.
In the circuit boards illustrated in Figures 1 and 2,
the dielectric base or board is indicated at 10, circuit patterns at
11, formed by copper, with contact pads at 12. The contact pads 12
usually have holes 13 therethrough for reception of pins of a
connector, or passage of wires, usually afterwards soldered to the
pads 12. Contact areas for push-button keys are formed at 14, as by
printing conductive inks at areas indicated at 15. It is often very
difficult to obtain accurate register between the conductive ink
areas 15 and the copper pattern at those areas. Clearances between
the various areas 15 at a position 14 are very small, as are the
clearances between the copper areas at these positions and
short-circuits can occur~
Figure 3 illustrates a board which is similar to that
of Figure 2, but with contact pads 12 made slightly elongate. The
pads are applied by die cutting or stamping from copper film or
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strips, and the circuit patterns 11 are formed by printed conductive
ink~ Holes 13 can be provided in die pads 12. The contact areas 14
in Figure 2 are formed by printing ink on to copper. In a board as
in Figure 3, the contact areas are formed at the same time as the
patterns 11 are formed. Thus the need for accurate register between
contact areas and conductor patterns is avoided.
A process, or method, of forming circuit boards is
illustrated in Figures 4(a) to 4(d). In Figure 4(a), a strip of
dielectric material 20 is fed along on a support surface, holes 21 in
khe strip acting as locating means. A strip of copper foil 22 is fed
from a feed roll 23 beneath a press 24 with a die 25. The strip has
an adhesive on its lower surface. The die 25, which may be heated,
stamps out contact pads from the copper foil and presses them on to
the strip 20, the pads seen at 26. The scrap, perforated strip is
wound up on a take-up roll 27.
In Figure 4(b) the strip 20 passes beneath a press 30
having a heated pad 31 which presses on the pads 26 and cures the
adhesive. In Figure 4(c) a printing machine 34 prints the circuit
pattern on the strip 20, the circuit patterns indicated at 3S. In
Figure 4(d) the strip passes beneath a blanking press 37. The press
37, in addition to blanking out the circuit boards, indicated at 38,
can also form any holes required in the circuit board.
The strip of dielectric material is of a length
sufficient to produce a predetermined number of circuit boards. The
strips are fed beneath the various presses and other apparatus by
means of a conventional stepping mechanism which feeds the strip in
steps, a step being equal to the pitch of holes 21 for exampleO The
presses 24, 30, and 37 and printing machine 3~ are shown electrically
operated, the operation being readily controlled by d central
control. T~us the strip 20 is moved one pitch, then the various
presses and printing machine actuated, then the strip advanced one
step, and so on. ~owever, it would be possible to actuate the
presses and printing machine hydraulically or pneumatically. The
heating pad 31 would normally be heated electrically. If desired,
some form of heating of the printed strip, after printing of the
circuit pattern, can be provided.
Various advantages result from the invention. The
die-press application of the contact pads is simple and accurate.
The step of printing the conductive ink circuit patterns is also
simple and inexpensive. No very accurate register between the
printing of the circuit patterns and the contact pads is required and
shorting between adjacent areas of a circuit pattern is avoided. The
overall cost is reduced. The scrap f-ronn the contact pad forming foil
has a high resale value as it is clean and has very little
contamination. It is also possible to apply the invention to
individual precut circuit boards. It would be necessary to provide
the circuit boards with some locating rnenas, such as holes, to ensure
that the individual boards are fed consequtively alony beneath tlle
various machines. In this arrangement, the blanking press may not be
required, or may be required for forming holes only.
