Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to devices for connecting
electrical conductors~ and especially for terminating a
plurality of closely spaced conductors to a conecctor
or other substrate.
5Joining flat cable or ribbon cable to connectors
can be accomplished by a number of different methods,
with soldering being probably the most reliable.
~owever, if all the solder terminations must be done by
hand, the costs involved and the time re~uired to
perfo~m a multiplicity of repetitive soldering op-
erations far outweigh any gains in reliability.
In addition, as connector pin spacing decreases, due to
higher interconnection densities, the reliability of
hand soldering decreases because of the possibility of
solder bridging terminations and shorting out adjacent
connectors. It would therefore be desirable to have a
solder system in which all leads can be soldered to the
connector simultaneously, rapidly and reliably for a
wide range of a number of terminations and spacings.
20In the past, various systems have been developed
for simultaneously applying a plurality of bodies of
solder. One such system is that disclosed in U.S.
Patent number 3,396,894, which discloses the pre-
packaging of metered amounts of flux and solder in a
heat-reco~erable preformed polymer sheet which forces
the solder into place. The patent teaches the use of
discrete pieces of solder which must be precisely
positioned above regions to be soldered. As heat
is applied, the polymer sheet returns to its original
flat configuration prior to solder melting.
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U.S. Patent 3,719,981 discloses an alternative
method of applying solder balls, which are appro-
priately spaced on the tacky surface of a pressure-
sensitive tape, to solder bumps used for connections.
Both of the above methods rely on the positioning
of the small pieces of solder immediately adjacent to
the terminals which are to be soldered, and, because
small pieces of solder are used, each of the solder
systems disclosed is difficult to manufac~ure.
U.S. Patent number 3,750,252 discloses the use of
a single continuous piece of solder to simultaneously
solder a large number of terminals. The solder wire
extends along a terminal strip and, on heating, the
solder melts and coalesces on the individual contacts
to form independent connectionsO
With the increasing use of ribbon or "flexprint"
cable, especially multilayer cable, which is analogous
to flexible printed circuit board, and the decreasing
size of many electronic assemblies, so that bulky
connectors are disadvantageous, a method of terminating
flat cables to flat substrates has also become ex-
tremely desirable.
This invention provides a device for electrically
connecting at least one first conductor to at least one
second conductor, which comprises:
(al a layer of polymeric material having at least
one window therein; and
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(b) a strip of fusible electrically conductive material
disposed with respect to the window or windows to allow
the conductive material to flow through the or each
window when heated and to form a conductive connection
between conductors placed on opposite sides of the
polymeric layer;
the or each window being capable of gripping a first conductor
to maintain it in position with respect to the device.
~he fusible, electrically conductive material may be
formed from any of a number of materials, e.g. fusible plastics
materials that have a high loading of a metal filler in the form
of particles or flake. ~referably, however, the fusible, conduc-
tive material comprises solder. As used herein, solder means any
metal or metallic alloy used to join metallic surfaces by melting
that metal or metallic allo~ and then allowing it to cool. A
solder strip, as used herein, means an elongated, continuous
element of solder of any cross-section including, but not limited
to, round, square, flat, or any other cross-section. Such a
solder strip may contain a flux core and/or may be coated on
~0 all or a part of its outer surface with a flux coating. The
strip may be perforated to enable better flow of a flux core.
In one pre~erred embodiment the device includes a tem-
porary backing layer located on the polymeric layer, which backing
layer is capable of being removed after the or each first con-
ductor has been positioned in the device. Alternatively, the de-
vice may include a
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backing layer of such configuration that a part of the
window or windows extends through the backing layer,
the said part being adapted to receive the ends of
conductors inserted therein.
The polymeric layers should preferably be made
of materials capable of resisting elevated temperatures
for the ti~e needed to melt and flow the solder,
generally about 15 seconds~ Suitable materials in-
clude, for example and not by way of limitation,
polyvinylidene fluoride, poly(parabanic acid)~ and
poly~pyromelittimide) or other high-temperature poly-
amides or -imides. These polymers may be cross-linked
by either chemicals or radiation to improve their
high-temperature properties.
Lower-temperature polymers, such as polyethylene,
etc., may be used depending on ~he particular use to
which the terminator is to be put, and the choice of
suitable materials is considered to bve within the
scope of one skilled in the art in view of this dis-
closure.
While the provision of adhesive and sealant layers
is contemplated by this invention, and will be dis-
cussed in more detail below with respect to certain
preferred areas, it is also contemplated that the
polymeric layers may themselves be intrinsically
adhesive even though they are generally required to be
non-melting in use. Such properties may be par-
ticularly desirable Eor the window layer, and may
be provided, for example, by extensive cross-linking of
an adhesive material. By this means, the device may be
adhered to a substrate in use.
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The layer of polymeric material may be heat-
recoverable or heat stable. He~t recoverable polymers
and methods of rendering polymeric articles heat
recoverable, are well known in the art. These are
generally cross linked, at least partially crys-
talline po-lymers, or mixtures incorporating them.
Preferably, however, it is heat stable.
The polymeric materials can be tailored to suit
the intended use by the addition of fillers, e.g.
10 flame~retardantsr plasticizers, pigments, stahilizers,
co-curing agents to facilitate cross-linking, etc.
The polymeric materials used in the construction
of this invention are important in the transfer of
thermal energy. While the primary heat transfer occurs
lS through the metallic elements, including the con-
ductors, terminals, and solder, a significant amount of
heat is transf2rred through the window in a parallel
manner. Additionally, the flux trapped within the
window spaces is a significant source of circulatory
20 liquid and vapor mass heat transfer. The presence of
these additional heat transfer paths contributes
to the overall speed and quality of the desired solder
connections.
According to another aspect, the invention pro-
2S vides a method of electrically connecting at least one
first conductor to at least one second conductor, which
comprises positioning the or each first conductor and
the or each second conductor on opposite sides of a
B layer of polymeric material having one or more windows
30 therein and having a ~t~y-of fusible electrically
conductive material disposed with respect to the window
or windows to allow the conductive material to flow
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through the or each window when heated, maintaining the
or each first conductor in position within the or one
of the windows, and heating the device to melt the
electrically conductive material ancl cause it to form a
conductive connection between the or each first conduc-
tor and the or each second conductor.
Figures 1 and 2 depicit a method of connection
according to the invention.
Figure 3 depicts another method in which the
device has a backing layer with holes through which the
conductors may protrude, and Figure ~ depicts that
embodiment with a cable ready for soldering.
Figure 5 depicts the use of windows shaped to
retain the conductors of a cable, while Figure 6 is a
side view of Figure 5; and
Figures 7 and 8 show another form of device
Figures 1 and 2 show a method of terminating a multi-
conductor cable 89 by means of a device comprising a
polymeric heat-stable layer 91 having an array of
elongate windows 93 therein a strip of solder 97
extending accross the windows 93 and a temporary
backing layer 95.
As shown in Fi~ure 1 a cable 89 with stripped
conductors 90 is placed on the device. The backing
layer 95 may adhere to the cable, and the system is
placed initially so that the windows 93 are aligned
with the conductors as they emerge from the cable
insulation .
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As shown in Figure 2, a burnisher 92 or similar
tool is stroked along the conductors in the direction
of arrow A, away from the cable i.nsulation, to align
the misaligned conductors. Downward pressure is also
applied to cause the wires to move in the direction of
arrow B and enter the windows 93, thus aligning them.
Pressure may then be applied tc the assembly to cause
good adhesion of the aligned components, and alignment
should thus be re ained until soldering, thus pre-
venting deformation of individual wires within thecable during handling, etc.
Figure 3 depicts an another embodiment of this
invention which also facilitates conductor alignment.
lf the backing layer 95 is placed so as to expose
window 93 to the back via a small aperture 94 (or if
the backing layer has suitable perforations), a hole
for each wire is created. The misaligned wires may be
straightened with a comb-like device 96 and the tips of
the conductors 90 threaded through the apertures 94.
The comb may then be removed and the cable 89 bent in
the direction of arrowlprod~ee afford the arrangement
of Figure 4. If desired, before soldering occurs
the cable may be pulled back (once the assembly is
emplaced against the termination substrate) to leave no
protruding conductor ends.
An additional feature of the window means of the
invention is that they may keep conductors aligned
during actual soldering. In particular, when soldering
a multiplicity of small diameter wires to a printed
wiring board, the wires may tend to fall off during
application of heat and force. The windows may be
further configured to minimize this tendency.
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Maintenance of conductor alignment is shown in
Figures 5 and 6 by one of many possible window shape
variations. The windows 93 in window layer 91 have
localized areas of restricted width ("grips") 98 on the
precise locations desired which provide the positioning
elements. The window layer portions adjacent to each
end of the windows provide structural rigidity and
location accuracy for every conductor~ In the case
shownl the grip width is an interference fit to the
diameter of the conductors 90, and partly overlays the
solder strip 97, shown shaded. In such a case, the
grips are preferably staggered so that the potential
growth incurred when the conductors are forced into
place may be absorbed by simple bending of the window
frames~ The balance of the window remains wide enough
to permit formation of a good solder fillet along the
remaining conductor length, and the solder is placed to
correctly guide the flow into each window. Figure 6
illustrates this in side Vi2W~
Another device is shown in figures 7 and 8 in
which a heat stable polymeric layer 110 has a number of
windows 112 each of which is formed with a narrow
portion or neck 116 for gripping a conductor, the neck
constituting a positioning element. The polymeric
layer is placed over the substrate so that the windows
112 are in register with conductive regions of the
substrate. The underside of the layer 110 is prefer-
ably adhesive in nature so that it will adhere to
the substrate. The layer 110 has a tear-off portion
119 which is then separated from the remainder of the
layer along a line of weakness 120, e.g. a score-line
or a line of perforations, and conductors 118 are then
placed over the layer 110 so that they are gripped by
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the necks 116 of the windows and thereby held in
alignment as shown in figure ~. The device may then
be heated to fuse the solder strip 114 and form a
connection between the conductors 118 and the con-
ductive regions of the underlying substrate. Advan-
tageously, the upper surface of the layer 110 is alsoadhesive in nature to assist in holding the conductors
118 in place.
Whilst the device preferably is formed with a
tear-off strip 119, it is also possible to form the
device initially as shown in figure 8.
