Note: Descriptions are shown in the official language in which they were submitted.
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HIGH C.Z~PAClT.Z~NcE BUS BAR AND
METHOD OF MANUFACTURE TI~EREOF
Background of the Invention:
(1) Field of the Invention
The present invention relates to bus bars and
; particularly to miniaturized bus bars having a low charac-
teristic impedence with low inductance and high distribu-
ted capacitance. More specifically, this invention is di-
rected to methods for the production of miniaturized bus
bars having plural dielectric members, and particularly
relatively fragile ceramic wafers, disposed between a
pair of bus conductors. Accordingly, the general objects
of the present invention are to provide novel and improved
articles and methods of such character.
(2) Description of the Prior Art
Multiconductor bus bars of the type which in-
clude either flat plate capacitors or discrete dielectric
elements positioned between parallel conductors are known
in the art. Such bus bars are characterized by a low
characteristic impedence r low inductance and high distri-
buted capacitance. These characteristics are highly de-
sirable, and in many cases essential, to protect electroniccircuit components from disturbing influences such as high
frequency ir'luences such as high frequency noise. The
aforementioned characteristics of bus bars of this type;
i~e., bus bars with discrete elements positioned between
the parallel conductors; are superior to those of prior
laminated bus bars of the type wherein the conductors were
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separated by a dielectric film or films. However, because of
the increased number of individual elements which must be
handled, and especially because of the fragile nature of the
thin ceramic wafers which are preferred dielectric elements,
bus bars of the type being discussed have been comparatively
expensive to produce.
Summary of the invention:
The present invention overcomes the above briefly
discussed deficiencies and disadvantages of the prior art by
providing novel and improved laminated bus bars of the type
which includes plural discrete dielectric elements. The
present invention also encompasses a unique and economical
method for the manufacture of the said laminated bus bars.
In accordance with an embodiment of the invention
a bus bar comprises at least a pair of elongated, flat,
parallel conductors and a layer of insulating material bonded
to facing surfaces of each of the conductors. A plurality of
flat rectangular dielectric elements are sandwiched between
the layers of insulating material, the dielectric elements
having oppositely disposed metallized faces and being
spacially separated. Means are provided for establishing
electrical connection between an exposed edge portion of each
of the conductors and an adjacent metallized face of the
dielectric elements. The connection establishes means
bridging the layers of insulating material.
The dielectric elements can consist of wafers of
dielectric material, ceramic chips for example, and the
dielectric wafers may initially be electrically isolated
from the conductors by the binder. The dielectric wafers
and the conductors will be electrically connected such that
the bus bar forms a capacitor, or more precisely a plurality
of parallel capacitors, with the bus conductors defining the
capacitor plates. After establishing electrical connection
between each of the bus conductors and the side of the di-
electric wafer adjacent thereto, the entire bus bar may beencapsulated in a suitable insulating material.
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In accordance with a first embodiment of the
invention, the dielectric wafers are of greater width
than the conductors and thus extend outwardly with res-
pect to at least first edges thereof. The electrical
connection between the conductors and the adjacent sides
of the dielectric wafers is accomplished by forming a
bead of solder or other conductive ~aterial on the
shoulders defined by the conductor edges where the dio
electric wafers extend outwardly therefrom. The beads
of conductive material will bridge the in-
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sulating binder in which the dielectric wafers are embedded.
In accordance with a second embodiment of the inven-
tion, the dielectric wafers are of the same width as the
conductors and the conductors and insulating binder are
cut away in regions, preferably elongated regions at an
edge of the conductor, to expose areas on opposite faces
of the dielectric ~afer. A suitable conductive material
is subsequently flowed into these cut-out regions.
In accordance with yet another embodiment of the inven-
tion the conductors and insulating binder are removed inplural spaced regions which are in registration with each
dielectric wafer, for example by drilling, and these plural
regions are filled with conductive material.
A preferred assembly technique in accordance with the
present invention consists of producing a subassembly
wherein a layer of insulating binder having a strip of re-
lease paper on a first side thereof is formed. The dielec-
tric wafers are positioned on the exposed surface of the
binder. Subsequently, a second layer of binder, also
ca-ried by a strip of release paper, is positioned over
the dielectric wafers. It is to be noted that, depending
upon the required capacitance of the bus bar, the dielec-
tric wafers may be comprised of different materials. For
example, a bus bar may include alternating ceramic chips
and spacers of an easier to handle dielectric material.
Whether it is desired to complete assembly of a bus
bar in accordance with the present invention, the release
paper is removed from the outwardly facing surfaces of
the layers of binder, copper foil conductors are positioned
over the binder and the resulting laminate is hot pressed
in order to bond the elements to one another and cure the
binder. Subsequently, the electrical connections between
the conductors and the dielectric wafers will be established,
employing one of the techniques described above, and the bus
bar may then be encapsulated in a suitable insulating
material. In the case where the bus bar includes both cera-
mic chips and insulating spacers comprised of a different
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material, such spacers having the same thickness as the
ceramic chips, electrical connection will typically be
established only between the conductors and the ceramic
chips.
Brief Description of the ~rawing:
.,
The present invention may be better understood and
its numerous objects and advantages will become apparent
to those skilled in the art by reference to the accompany-
ing drawing wherein like reference numerals refer to like
elements in the several FIGURES and in which:
FIGURE 1 is a top plan view, with elements partly
broken away, of a laminated bus bar in accordance with a
first embodiment of the present invention;
FIGUPE 2 is an enlarged view, taken along the line
X-X of FIGURE 1, of the bus bar of FIC.URE l;
FIGUPE 3 is a perspective view, with elements partly
broken away, showing an intermediate employed in the manu- !
facture of the bus bar of FIGU~ES 1 and 2;
FIGURES 4~1) through 4(6) are cross-sectional side
elevation views, on an enlarged scale, of the bus bar of
FIGU~ES 1 and 2 in various stages of manufacture;
FIGUPE 5 is a partial plan view of a bus bar in accor-
dance with a second embodiment of the present invention;
FIGURE 6 is a cross-sectional view, taken along the
line Y-Y of FIGURE 5, of the bus bar of FIGURE 5;
FIGU~E 7 is a partial plan view of yet another embcdi-
ment of a bus bar in accordance with the present invention;
and
FIGURE 8 is a cross-sectional view, taken along line
Z-Z of FIGURE 7, of the bus bar of FIGU~E 7.
Description of the Preferred Embodiment:
With reference jointly to FIGU~ES 1-3 a bus bar in
accordance with a first embodiment of the present invention
employs a pair of oppositely disposed parallel conductors
1 and 2. Conductors 1 and 2 ~?ould typically be formed from
a copper foil or other thin copper sheet and will respec-
tively have, extending outwardly from aligned first edges
thereof, terminals or tabs lA and 2A. Conductors 1 and
2 are separated by wafers or plates 3 and 4 which are em-
bedded in an insulating binder 5. The binder 5 is bondedto the conductors and thus holds the laminate together.
In the embodiment disclosed in FIGURE 1, the wafers 3 will
be comprised of thin plates of a ceramic material having
the opposite faces thereof metallized and having the de-
sired dielectric properties. The wafers 4 will comprisespacers which have the same thickness as the ceramic plates
but which are less fragile and thus easier to handle. It
will be understood that the choice of materials for wafers
3 and 4 and the dimensions thereof will be a function of
the desired electrical characteristics of the bus bar and,
in some instances, all of the wafers 3 and 4 may be com-
prised of the same ceramic material. As shown in FIGURES
1 and 3, the ceramic plates 3 and spacers 4 are arranged
in alternating fashion and are aligned along the lenath
of the bus bar. Spaces are left between adjacent wafers
3 and 4 to accommodate dimensional changes which may occur
during the bonding process wherein heat and pressure is
applied to cure the binder.
The embodiment of the invention represented by FIGURES
1-3 is characterized by the fact that the ceramic plates
3, and possibly also the spacers 4, extend outwardly be-
yond at least a first edge of the conductors 1 and 2.
This arrangement may best be seen from FIGURE 2. After
bonding of the conductors to the binder 5, the metallized
ceramic plates will be insulated from the conductors by
means of the binder. Portions of the planar oppositely dis-
posed faces of the ceramic plates will, where the plates
extend outwardly past the edges of the conductors, be ex-
posed. The conductors are electrially connected to the
metallized coatings on respective oppositely disposed
sides of the ceramic plates by means of forming beads 6
of solder or other flowable electrical conductive mate-
rial on the shoulders defined by the edges of conductors
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1 and 2, where the cexamic plates extend outwardly there-
~rom, as shown in FIGURE 2. These beads 6 of conductive
material will bridge the insulating binder 5.
After the assembly of the bus bar has been com-
pleted, by application of the beads of conductive mate-
rial 6, it is usually desirable to hermetically encapsule
the bus bar assembly by means of forming an insulating
coating 7 thereabout. In one embodiment the coating 7
is formed by uniformly applying a resin in powdered
form and subsequently heating the bus bar to melt and cure
the resin. The resin may, for example, be a polyester,
acrylic or epoxy. As shown in FIGURE 7, it is usually
customary to bend the terminals lA and 2A such that all
of the terminals extend outwardly from the bus bar in the
same plane. This would typically be accomplished by bend-
ing the terminals at their roots such that all of the ter-
minals lie in the plane of the wafers 3 and 4. The bending
of the terminals may be performed at any stage during the
assembly process and will typically occur immediately
prior to application of the protective coating 7.
The ceramic plates 3 are thin and very fragile. The
assembly technique in accordance with the present invention
facilitates the handling of these plates. Referring to
FIGURE 3, and as will be described in greater detail be-
low in the discussion of FIGURE 4, a subassembly comprisingthe binder 5 and wafers 3 and 4 is formed and protected on
opposite sides by means of strips of release paper 8.
When it is desired to complete assembly of the bus bar,
the release paper is removed and replaced by conductors 1 and
2 and the conductors are subsequently bonded to the resin
by means of the application of heat and pressure. As men-
tioned above, during the course of preparation of the
subassembly of FI~.URE 3, depending upon the electrical re-
quirements of the bus bar, the spacer wafers 4 may be re-
placed by ceramic plates 3 or the wafers 3 and 4 may be ofdifferent size.
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Referring now to FIGURE 4, the fabrication of a bus bar
in accordance with a preferred embodiment of the present
invention is depicted. As a first step, as represented at
(1), a "tape" of the non-conductive binder 5 is laminated
with a strip of release paper 8. Next, as depicted at ~2~,
the ceramic plates 3 and spacers 4 are positioned on the ex-
posed surface of binder 5 in alternating fashion. A narrow
gap is left between the adjacent wafers 3 and 4 in order to
compensate for shrinkage of binder 5 during subsequent curing
thereof. As shown at step (3) of FIGURE 4, a second binder-
release paper laminate is prepared and applied over the
wafers 3 and 4; the binder adhering to the surfaces of the
wafers. Referring back to FIGURE 3, in tne assembly pro-
cess being described the width of the layers of binder 5 and
the release paper 8 will be the same while the ceramic plates
3, and usually also the spacers 4, will extend outwardly from
a first side edge of the binder-tape laminates.
When final assembly is desired, as shown in steps (4)
and (5) of FIGURE 4, the release paper 8 will be removed
from the opposite sides of the subassembly depicted in step
(3) and conductors 1 and 2 will be positioned in contact with
binder 5. The conductors 1 will typically have length and
width dimensions which are the same as the binder 5. After
application of the conductors, the bus bar is hot pressed
in order to cure the binder and strongly bond the binder to
the wafers 3 and 4 and the conductors 1 and 2. Next, the
beads of conductive material 6, which may be seen from
EIGURES 1 and 2, are applied to establish electrical contact
between the conductors 1 and 2 and respective adjacent metal-
lized faces on the ceramic plates 3. Finally, the assemblyof the bus bar is completed by forming the encapsulating
layer of insulating resin 7 as indicated in step (6) of
FIGURE 4.
Referring simultaneously tG FIGURES 5 and 6, a second
embodiment of the present invention is assembled in the same
manner as described above with the exception that the ceramic
plates 3A, and also the spacers 4A, are of the same width as
the conductors 1 and 2. In the embodiment of FIGURES 5 and
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6 the conductors and binder are provided with aligned
holes 9 and, after lamin~tion, the holes 9 are filled
-; with a conductive material 10. In the FIGURE 5 embodiment,
there are three of the holes 9, linearly aligned along the
length of the conductor, in registration with each side of
each of the ceramic plates 3A. The bus bar of FIGURES 5
and 6 will typically, subsequent to application of conduc-
-` tive material 10, be encapsulated as discussed above.
The bus bar of FIGURES 7 and 8 is assembled in the
same manner as discussed above with respect to FIGURES 5
and 6; i.e., the wafers 3A and 4A have the same width di-
mension as the conductors. In the embodiment of FIGURES
7 and 8 the conductors and binder 5A are cutaway in elon-
gated regions 11, which are preferably along an edge of the
conductors, so as to provide shoulders similar to those re-
sulting from the extension of the ceramic plates beyond the
edges of the conductors as described above in the embodiment
of FIGURES 1-4. A bead of conductive material 12 is de-
posited on each of the shoulders; i.e., in each of the cut-
outs 11; to establish the electrical connections betweenthe conductors and the metallized ceramic plates.
As will be obvious to those skilled in the art~ the
present invention provides an economical method for the fab-
rication of bus bars of the type wherein discrete elements
having a very high dielectric content are sandwiched be-
tween the bus conductors. The present invention also pro-
vides the advantage of being able to encapsulate a bus bar
having a high distributed capacitance easily and effectively
since such encapsulation may be achieved employing a pow-
dered resin.
While preferred embodiments have been shown and descri-
bed, various modifications and substitutions may be made
thereto without departing from the spirit and scope of the
invention. Accordingly, it is to be understood that the
present invention has been described by way of illustration
and not limitation.
