Note: Descriptions are shown in the official language in which they were submitted.
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S P ~ C I F I C A T I 0 N
This inventlon relatos to capacitors and mors partl-
cularly relates to ceramic capacitors having a higher
capacltance valu2, and a method of making the same.
The present invention is directed to capacitors which
are of the single layer type, that is, include only two
electrodes with a dlelectric spacing therebetween, where
such capacitors are manufactured in multiple. At the present
time, capacltors of the typo to which this invention relate3
are made with a flred ceramic dielectric which, after curing,
- ls coated wlth a conductive substance on each side thereof.
The dlelectrlc ls then cut into indlvidual capacitors,
leads applied, and the ceramic with conductive coating~
thereon encapsulated in an insulating material.
The production of this single layer type capacitor -
by present methods results in a capacltor of limited
capacitan~e value pr~marlly due to the thickness of the
ceramlc dlelectrlc. The dlelectric must be made sufficiently
thlck to have the required physical strength for handling
both in a greenware state and in the fired state, and also
whlch ls sufflclently thick so tha~ it will not unduly
warp when the ceramlc greenware is fired.
The present lnventlon provides a new and improved
method of manufacturlng single layer capacitors which
enables the use of very thin ceramic spacers between the
capacltor electrodes and permits a plurality of capacitors
to be defined on a strlp of ceramlc greenware ln such a
manner a~ to decrease the possibility of leakage between
the capacitor electrodes.
Brlefly stated, the invention in one form thereof
comprises the steps of defining a plurality of conductive
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patterns on opposite sides of a thin sheet of ceramic green-
ware, covering said thin sheet on either side with other sheets
of ceramic greenware having apertures therein in registry with ~-
the conductive pattern, scoring the laminations between con-
ductive patterns, firing the laminate to produce a cured
ceramic containing a multiplicity of capacitors, attaching
leads to the capacitor electrodes through the apertures, and
thereafter breaking individual capacitors from the sheet at
the score lines.
An object of this invention is to provide a new and
improved method of making single layer capacitors in multiple.
Another object of this invention is to provide a ~ ~ -
method of making single layer capacitors in multiple which per-
mits such capacitors to be made in greatly increased capacitance
values for a given size.
A further object of this invention is to provide a
method of making single layer capacitors in multiple which
facilitates the handling of the capacitive elements.
A still further object of this invention is to pro-
vide a new and improved ceramic capacitor of increased capaci-
tance value for a given electrode area.
In one aspect of the present invention there is pro-
vided a method of making capacitors in multiple which com-
prises providing a first thin flat sheet of ceramic greenware, ~`
defining a multiplicity of conductive patterns on either side
thereof in alignment to form a multiplicity of opposed indivi-
dual capacitors, prouiding second and third sheets of ceramic
greenware, laminating said second and third sheets to either
side of said first sheet, thereafter scoring said lamination
to define individual capacitors between but not extending to
said score marks, firing said lamination to produce a cured
ceramic assembly of multiplicity of single layer capacitors,
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and thereafter breaking capacitors from said assembly along ~ ~
the score marks. `~ .
In a further aspect of the present invention there is
provided a method of making capacitors in multiple which
comprises providing a thin flat first sheet of ceramic green-
ware, defining a multiplicity of conductive patterns on either :.
side thereof in alignment to form a multiplicity of opposed
individual capacitors, providing second and third sheets of
ceramic greenware sheets with apertures therein and laminating
L0 said second and third sheets to ei~her side of said firstsheet with the apertures in registry with said patterns, scor-
ing said lamination to define individual capacitors between but
not extending to said score marks, firing said lamination to
produce a cured ceramic assembly of a multiplicity of capacitors, .
and thereafter breaking capacitors from said assembly along
said score marks.
The features of the invention which are believed to
be novel are particularly pointed out and distinctly claimed
in the concluding portion of this specification. The invention,
20 however, both as to its organization and operation, together :
with further objects and advantages thereof, may best be appre- ~;
ciated by reference to the following detailed description
taken in conjunction with the drawings, wherein:
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FIG. 1 is a view in perspective of a multiple
capacitor construction embodying the invention;
FIG. 2 is a top view of a rnultiple capacltor
construction made in accordance with the invention;
FIG. 3 is a longitudinal sectional view seen in
the plane of lines 3-3 of Fig. 2, with leads attached;
FIG. 4 is a vlew of a SinglQ capacitor made ln
accordance wlth the lnvention;
FIG. 5 ls a view similar to Fig. 1 showing another
method of practiclng the invention;
FIG. 6 is a sectlonal vlQw of a capacitor made in
accordance with the structure of Fig. 5;
FIG. 7 ls a view in perspectlve of another multi-
capacitor structure made in accordance wlth the
invention;
FIGS. 8 and 9 are views of opposite sides of one
of the elements of Flg. 7 showing capacitor electrodes
defined thereon; and
FIG. 10 is a longi~ud~nal sectlonal vlew of a ;-
single capacitor made ln accordance with the embodiment
of Figs. 7 - 9.
Flgs. 1 - 3 exempllfy an assembly 10 of single layer
capacitors in multiple and comprises first and second
strips 11 and 12 of ceramlc greenware in strip form. Strlps
11 and 12 have a plurality of pQrforatlons 13 and 14,
respectively, deflned therein in a coordinate arrangement.
A central strlp of ceramlc greenware 15 has a plurallty
of conductive areas 16 on one side and a llke plurallty
Or conductlve areas 17 on the other slde. The opposite
areas or patterns 16 and 17 are parallel and ln vertlcal
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alignment when the strips are horizontally disposed.
The strips 11, 15 and 12 are laminated together under
heat and pressure, then scored as shown in Figs. 2 and 3 along
coordinate lines 18 and 19 to provide breaking or snapping lines.
The laminated and scored assembly is then fired at a high temp-
erature to fuse the ceramic. Thereafter, connector leads 20 and
21 preferably of the nailhead type are positioned in perfora-
tions 13 and 14, respectively, and bonded to patterns 16 and 17.
Then rows of capacitors may be snapped or broken from the assembly
at the score lines 18 and individual capacitors at the score
lines 19, or vice versa.
In the practice of the invention, the strips 11, 12 and
15 are slip cast to the desired thickness from a mixture com-
prising ceramic particles, plasticizer binder and solvent. In
one example, the ceramic may be lead barium niobate (PBN) mixed
with liquid methyl methacrylate and Monsanto Chemical Company
#160 Santicizer* (a plasticizer) and an ethylene dichloride sol-
vent. The resulting mixture is slip cast to the desired thick-
ness, dried, and cut into strips of predetermined size. The mix-
ture may be ceramic 40-70%, binder 20-50%, plasticizer 1-4%, and
solvent 10-20%. The mixture is blended and then cast. After a
period of air drying, the resultant strip or tape may be dried at
elevated temperatures of 200 - 400F to completely drive out sol-
vents, water, etc. The strips 11 and 12 are then perforated in
the illustrated coordinate pattern. The strips 15 are coated with
the conductive patterns 16 and 17 on each side thereof. The
three strips are then laminated to a homogeneous assembly.
The conductive patterns are defined on strips 15 in any
suitable manner. One technique is to utilize a screening pro-
cess wherein conductive material in a liquid vehicle is screened
or squeezed through a screening pattern. A suitable substance
for this process is Quick Film Conductor Ink #MBl-l69
* - Trade mark
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of ~latthey Blshop, ~nc., Melvern, Pennsylvania which contains
a gold, palladium and platinum in a thick liquid binder.
The binder burns off when the ceramic ls flred leaving a
metallized conductor.
Where the strip 15 is extremely thin, and therefore not
easily handled, the patterns 16 may be placed on a release
surface, the strip 15 laid or cast on patterns 16 and on
the release surface; patterns 17 are then screened on the ,~
upper surface. One of strips 11 or 12 is placed on strlp
15 over patterns 17. The strips are then peeled upwardly
taking patterns 16 from the release surface, and then the ¦
other of sbrips 11 or 12 is applied to strip 15 over patterns
16. The assembly is then laminated, scored and fired. The
strips may be laminatsd at a pressure of 2000 psi and a
temperature of 120F.
In this technique the release surface may be substantially
transparent or translucent, and the greenware strip due to
its small thlckness is also translucent. A source of light
may be placed behind the release surface to illuminate the
patterns through the greenware strip.,
Firing of the above-described assembly may be accompllshed
in a through oven with an entrance-exit time of six hours,
where the assembly is exposed to a top temperature of 2300F
for approximately one hour. Ths time and temperature may vary
in accordance,with various types of ceramic which may be used.
Upon flrlng or sintering the organic constituents of the green
ceramic strips or sheets volatize and the csramic becomes a
monolithic structure.
For physlcal strength of the fired ceramic, it ls
preferred that the overall thickness be at least 0.002".
The strlps 11 and 12 are therefore on the order of O.OOl'
or'greater while the strip 15 may be only 0.0005" thick.
Inasmuch as the capacitance value of each unit is
proportional to the spacing betwQen the conductors 16 and 17,
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as well as the ar~a of the patterns, the m~n~mal thickness
of the strip provides individual capacitors of greatly
increased capacitance valu~.
In one product, conductors 0.103" on sides are
defined in eight columns of t~enty-three on a strip 15,
one and one-quar~er inch by four and one-half inches and
0.001" thick. The perfora~ions are made .050" to
accept connectors having 0.045" heads. This product with
a strip 15 which is 0.001" thick yields capacitors of over
3800 picofa~ads.-
The connectors may be formed ~or predoterminQd spaclngof the leads. Fig. 4 illustrates an individual capacitor
22 having connectors 20a and 21a preformed to provlde a
predetermining dimension therebetween. The connectors are
applied in multiple, being held in a fixture, inserted into
the perforations, and heated in an oven to solder the
heads thereof to the conductors. The solder may be initially
deposited in the perforations, or the connector heads dipped
into a solder bath prior to insertion into the perforations.
After the indivldual capacitors are separated they may be
encapsulated and color coded if desired. However, this is
not necessary.
In an alternate technlque, the center strip 15 may be
defined by two strips positioned back-to-back with the
conductive patterns defined on the outer surfaces. This
- permits the center strips to have the patterns defined on
only one side and thus decrease the physical handling of
one thin strip.
The edges of the conductive patterns are spaced from
the score llnes which define the physical edges of
the individual capacitors. This provides an increased
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path for any leakage wlth respect to capacitors where
the conductor extends to the physical edge of the
capacltor.
Where the conductive patterns are initially applied
to a release surface such as release paper, plastic
tape, etc., the patterns may be printed by varlous presses
and techniques. The greenware may be applied over the
release surface by slip casting, or any other suitable technique.
FIGS. 5 and 6 exemplify another embodiment of the
lnvention. In thls embodiment outer strips 25 and 26 are ;
formed wlth coordinate rows and columns of perforations
27 and 28, respectively. Conductive patterns 29 and 30
are then defined in coordinate rows and columns on the
faclng surfaces of the s~rips 25 and 26, respectively.
An intermediate strip 32 has coordinate rows and columns
of small clrcles or dots of conductive material 31 defined
thereon. The dots, which are preferably circular, but
need not be, are of an area larger than the perforations 27
and 28 and are ln registry with such perforations so as
to complete the conductive surface interrupted by the
perforations 27 and 28.
In assembly, the strips 25, 26 and 32 are placed
together ln allgnment laminated under pressure and heat as
previously described, and a cross-section of the resulting
product will appear as shown in Fig. 6. Fig. 6, however,
for purposes of illustration exaggerates the th~ckness of
the conductive patterns and particularly the dots 31, inas-
much as the dots 31 will blend or merge into the patterns
29 and 30. The resulting assem~ly is scored as previously
described and indicated by the score mark 33. Thereafter,
the ceramic is fired, leads are applied to the areas of
the perforations as prevlously described.
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The lnventlon may also be embodied in the makin~ of
sinæle layer capacitors of the so-called chip type in
multiple, as shown in Figs. 7 - 10. Plain strips of
greenware 40 and 41 are arranged to receive therebetween
a strip 42 having opposi~e sides 43 and 44 as more
clearly shown in Figs. 8 and 9. Printed or ctherwise
deflned on the sides 43 and 44 are coordinate rows and
columns of conductive patterns 45 and 46, respectively,
whlch are prlnted in registry on either side and each
pattern 45 and 46 has a tab-like extension 47 and 48,
respectively, extending in opposite directions to provide
leads for terminals.
After assembly of the strips 40, 41 and 42, they
are coordinately scored as indicated by the lines 49 and
50 and fired. Thereafter, a strlp defined by a score
mark 49 may be snapped from the assembly, the ends
metallized to provide external electrical connections to
the tabs 47 and 48 and lndividual capacitors may be
snapped from each row. This provides the so-called chip-
type capacitor wherein the metallized ends 51 and 52 areelectrically connected to tabs 47 and 48, respectively,
and are adapted to be placed on or in an electrlcal
circuit. A cross-sectlon of such a capacitor ls shown
in Fig. 10 with metallized opposed edges 51 and 52.
After the assembly of strips and lamination thereof,
the score marks may be deflned ln any suitable manner.
This may be done by a knife-edge wherein the assembled
greenware is moved beneath a plurality of knives in
coordinate directions. A die may be used, a rectangular
grid~ preferably heated, may be used to lndent the score
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marks or a laser beam may be utili~d for the scoring.
Dependent upon the depth and wldth of the scoring, a
score depth of six to twenty-five percent of the overall
thickness will be sufficient. Then a forcs in the
range of eight to twenty-fivQ thousand ps~ will be all
that is required to snap off a row of capacitors.
While thls pressure in pounds per squa~e inch may seem
to be high, it will be apparent that the area involved is
extremely small.
In some instances, lt may be desirable not to score
the gresnware assembly prlor to c~ng. In this situation,
scoring may be accomplished througn use Or a laser beam.
The inventlon rurther permits the use of a plurality
of single layer capacitors in onQ body, so that a slngle
capacitor structure including a plurality of distinct
capacitors may be connected in a circult. Either a column
or row, or even two or three capacitors, may be left in an
lntegral strip, and the capacitors connected individually
in a circuit. Alt~rnaf-lv~ty,some capacitors may be connected
individually, while others would have their leads connected
in parallel for increased capacltance.
From the foregoing disclosure it may be seen that the
objects of the invention ar~ efficiently attained. While
preferred embodiments of the invention have been set forth
for purposes of disclosure, it is to be understood that
other embodlments to the invention as well as modifications
to the disclosed embodiment which do not depart from the
spirit and scope of the invention may become apparent to
those skilled in the art. Accordingly, the appended claims
are intended to cover all embodiments and modifications of
the invention which do not depart from the spirit and
scope o~ the invention.
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