United States Patent
`
`[72] Inventors
`
`[2i ] Appl. No.
`[22] Filed,
`[45] Patented
`[73] Assignee
`
`Donald J. Veater;
`Sumner B. Hill; Lawrence J. Ruffner, all of
`State College, Pa.
`1 1,929
`Feb. 19, l 970
`May 25, 1971
`Erie Technological Products, Inc.
`Continuation of application Ser. No.
`761,436, Sept. 23, 1968, now abandoned.
`
`[54] REINFORCED CERAMIC CAPACITOR AND
`METHOD OF MAKING THE SAME
`.
`.
`.
`7 Clmms?nrawmg Flgs'
`[52] ‘LS. CI ...................................................... ..
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`[5
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`lilt
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`................................................ .§ ..... ..
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`of Search .......................................... ..
`258;29/25~42
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`29/25-42
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`[56]
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`3,002,137
`
`_
`References cued
`UNITED STATES PATENTS
`8/1961 Kahn .......................... ..
`
`317/261
`
`["1 3,581,167
`
`3,258,665
`3,244,951
`3,310,719
`
`6/1966 Sperry ........................ ..
`4/1966 Wallace...
`3/1967 Seney ......................... ..
`
`317/249(D)
`317/261UX
`3l7/261X
`
`FOREIGN PATENTS
`’
`6/1939 Great Britain.....
`507,143
`1,068,319 4/1967 Great Britain .............. ..
`Primary Examiner—Elliot A. Goldberg
`Attorney-Ralph Hammar
`
`317/261
`317/261
`
`ABSTRACT: A ca acitor havin an extreme] thin central
`layer (as little as 0.2)002 inches)gwith electrodgs sintered on
`both faces and surrounded by ceramic margin& The central
`layer is sandwiched between thick outer ceramic layers in face
`to face engagement
`the electrodcs and margins
`[he
`margins Sintered to the outer ceramic layers to provide a uni
`tary ceramic assembly. The outer layers have perforations
`rovidin access to the electrodes and have terminal coatin s
`:Ihich exgtend into the perforations to make contact with tlge
`electrodes. Leads are soldered to and extend from the ter
`minal coatings.
`
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`000001
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`AVX CORPORATION 1006
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`

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`PATENTEU HAYES 197i
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`3.581.167
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`PIC-3.4‘
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`INVENTOR
`§ Veal?”
`5W 8 ma
`
`BY
`
`/2
`
`ATTORNH?
`
`000002
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`

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`3,581,167
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`20
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`1
`WETNFORCED CERAMIC CAPAClTOR AND METHOD OF
`MAKING THE SAME
`Thisapplication is a continuation of Ser. No. 761,436 ?led
`Sept. 23, I968 now abandoned.
`This invention is intended to increase the capacity of ceram
`ic capacitors by a laminated construction consisting of a thin
`central ceramic layer sandwiched between two outer thick
`ceramic layers. The capacitor electrodes are sintered to op
`posite faces of the central layer and the outer layers which are
`in face to face engagement with the electrodes and margins
`are sintered to the central layer to provide a unitary ceramic
`assembly of adequate mechanical strength. Terminal coatings
`on the outer surfaces of the outer ceramic layers are soldered
`to leads which extend from the coatings. The terminal
`coatings make contact with the electrodes through perfora
`tions which extend to the electrodes.
`in the accompanying drawing, FIG. 1 is a plan view of the
`central layer of the ceramic capacitor, FIG. 2 is an edge view
`of the central layer, FlG. 3 is a plan view of one of the outer
`layers of the capacitor, FIG. 4 is an edge view of FIG. 3, FlG. 5
`is a section through a ?nished capacitor taken on lines 5-5 of
`P16. 6, FIG. 6 is a plan view ofa ?nished capacitor.
`The capacitor consists of a central ceramic layer 1 sand
`wiched between two outer layers 2, 3. On opposite faces of the
`central layer are painted metallic electrodes 4, 5 which are
`sintered to the central layer at the ceramic ?ring temperature.
`For titanate ceramic requiring a high ?ring temperature, the
`electrodes 4,5 might be of one of the platinum-palladium
`paints while for ceramics requiring a lower ?ring temperature,
`other metals might be used. The outer layers 2, 3 are of the
`same ceramic as the central layer 1 or at least of a ceramic
`compatible with the central layer. Each outer layer 2, 3 has
`one or more perforations 6 extending in the thickness
`direction through the layer in the region to which a terminal
`coating 7 is to be applied.
`I
`In the manufacture of the capacitor, the electrodes 4, 5 are
`painted on opposite sides of a green ceramic central layer 1.
`The electrodes are painted so as to leave a margin 8 surround
`ing the electrodes. The central layer 1 is then sandwiched
`between green ceramic outer layers 2, 3. So long as the outer
`layers register with the central layer, no particular orientation
`is required. The perforations 6 on opposite sides of the layer 1
`are shown out of register with each other in H0. 6. The as
`sembly is then pressed together to insure intimate contact
`between the outer layers 2, 3 and the margin 8 surrounding
`the electrodes 4, 5. The assembly is then ?red at ceramic ?ring
`temperatures to sinter the electrodes 4, 5 to the central layer l
`and to sinter or unite the outer layers 2, 3 to the margin 8 of
`the central layer ll. At the end of the ?ring operation, the as
`sembly is a unitary ceramic with the margins 8 sealed to the
`outer layers of ceramic and with the electrodes in intimate
`contact with the central layer. There is no tendency for the
`electrodes 4, 5 to separate or delaminate from the layer 1.
`Since the layers 2, 3 do not contribute to the capacitance of
`the unit, any tendency to delamination of the layers 2, 3 will
`have no effect upon the capacitance.
`The sealed margin 8 provides humidity protection since the
`opposing electrodes of opposite polarity are buried within the
`unit, and moisture cannot penetrate to the edges of the dielec
`tric, where humidity failure normally occurs with an ordinary
`single sheet dielectric. This is an important advantage for
`capacitors which are used under conditions of high heat and
`humidity. The sealed margins also reduce or eliminate corona.
`The capacity of the assembly is determined by the thickness
`of the central layer 1 and the overlapping area of the elec
`trodes 4, 5. Because of the mechanical support provided by
`the outer layers 2, 3 the layer 1 can be of extreme thinness.
`The layer 1 may have a thickness as little as 0.0002 inch and
`usually will not exceed 0.003 inch thickness. The layer 1 is
`much too thin to permit handling if it were separately ?red.
`The mechanical strength of the assembly is derived from the
`outer layers 2, 3 which have a thickness such that the overall
`thickness of the complete ceramic assembly provides
`adequate strength for ?ring and subsequent handling. While
`
`2
`the layers 2, 3 could have a thickness of as little as 3 mils, it
`will ordinarily be more convenient to have these layers in the
`range of from 5 to 10 mils so that the complete assembly will
`be a rugged part. The mechanical strength may be further in
`creased by using ceramics for the outer layers 2, 3 which have
`less shrinkage during sintering than the central layer 1. This
`places the outer layers in compression.
`The dielectric strength of the central layer 1 which is in the
`range of from 300 to 50 volts per mil of thickness permits the
`capacitors to be conservatively rated at a voltage of from 50 to
`100 volts per mil. thickness of the layer 1. On reason this rat
`ing is possible is that the fused ceramic margins 8 surrounding
`the electrodes 4, 5 permit the capacitor to be rated on its volt
`age breakdown through the thickness of the layer 1 rather
`than on the basis of the voltage breakdown over the edge of
`the layer 1.
`At the end of the ?ring operation, portions of the electrodes
`4, 5 are accessible through the holes 6 in the outer layers 2, 3
`so that the capacitance of the ?red unit can be measured. By
`providing several holes, one or more of which occupies a
`known percentage of the electrode area, it is possible to make
`an adjustment of the capacitance of the ?red unit in order to
`bring it within the desired tolerance. For example, if one of the
`holes 6 had an area equal to l0 percent of the area of elec
`trodes 4, 5, it would be possible to effect a l0 percent adjust
`ment in the capacitance of the ?red unit by removing all of the
`portion of the electrode exposed at the bottom of the hole.
`This could be conveniently done by a sandblasting operation.
`The capacitor terminals are applied, for example in the
`form of a silver paint, within the area indicated at 7 in FIG. 3.
`The silver paint as shown at 11 and 12 runs into the holes 6
`and makes contact with the outer surface of the electrode
`coating. After painting the terminals 9, 10, the silver paint is
`baked to mature the paint and to provide a surface to which
`solder connections may be made. Capacitor leads such as the
`hairpin lead 13 having crossover or X ends l4, 15 are soldered
`to the terminals 9, 10 by the usual dip soldering operation in
`which the terminals 9, 10 are gripped between the crossover
`ends while the capacitor is dipped in solder. The ends 14, 15
`of the leads lie ?at on the terminal surfaces and are ?rmly held
`in place by the solder 16. The grip of the solder on the ter
`minals is further increased by the solder which runs into the
`openings or holes 6 as shown at 17. At the completion of the
`soldering operation, the arch 18 of the lead 13 is cut, leaving
`ends 19, 20 which extend edgewise beyond the capacitor for
`making electrical connections into a circuit.
`The adjustment of capacity as described above is made
`either after the ?ring of the silver paint or after soldering. If
`the removal of the electrode at the bottom of the selected hole
`6 is done before the application of the silver paint, the elec
`trode areas removed for adjustment will be ?lled in with the
`silver paint and the capacitance will return to what it was be
`fore adjustment. Adjustment after ?ring of the silver paint is
`not nulli?ed by the subsequent soldering operation. Adjust
`ment may be made wither after the silver ?ring or after solder
`mg.
`There are several advantages of the capacitor unit. It has a
`higher voltage rating because the edges of the capacity deter
`mining layer 1 are sealed in ceramic and the capacitor may be
`rated on its voltage breakdown in the thickness direction
`rather than on the lesser over edge breakdown voltage. The
`sealing also improves the rating of the capacitor under high
`humidity conditions. There is no way for moisture to get into
`the ceramic. Painting the electrodes 4, 5 on opposite sides of
`the capacity determining layer 1 minimizes delamination and
`thereby prevents loss of capacitance clue to the loss of intimate
`contact between the electrodes 4, 5 and the layer 1. Any ten
`dency to delamination takes place between the outer layers 2,
`3 which do not enter into the capacitance. The capacitor is not
`subject to silver migration which could cause breakdown.
`Reaction between the ceramic of layer 1 and the frit in the _
`paint for the terminals 9, 10 is eliminated.
`What We claim is:
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`3,581,167
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`4
`stacking and with the perforations in the outer layers opposite
`the electrodes and subjecting the laminate of stacked layers to
`ceramic ?ring and thereafter applying to the surfaces of the
`outer layers of the tired laminate remote from the central
`layer the terminal layers providing surfaces to which solder
`connections may be made.
`5. The capacitor of claim 4 in which the capacity of the unit
`is adjusted by removal of a portion of the electrode area of one
`of the electrodes accessible through one of said perforations
`and in capacity relation to the other electrode after removal of
`the portion of the metal terminal layer overlying said portion
`of the electrode area.
`6. A ceramic capacitor unit consisting essentially of a sinter
`united laminate having a central ceramic layer sandwiched
`between two outer ceramic layers of a ceramic compatible
`with the central layer, the central layer being imperforate and
`having a thickness too thin to be handled if separately fired, a
`pair of metal paint electrodes sintered respectively to opposite
`faces of the central layer, said electrodes being in capacity
`relation to each other through the thickness of the central
`layer and spaced from the periphery of the central layer to
`provide a margin of ceramic surrounding each of the elec
`trodes, said outer layers each having a thickness of 3 mils. or
`more and respectively having one face overlying and in con
`tact with one and the other of the electrodes and its margin of
`ceramic, the outer layers having perforations opposite and oc
`cupying a minor portion of the area of said electrodes and
`spaced from the periphery of said layers and extending in the
`thickness direction through each outer layer but not through
`the electrode with which it is in contact, the perforations on
`opposite sides of the central ceramic layer being out of re
`gister with each other, the layers and electrodes being a unita
`ry sintered ceramic structure with each of the margins of the
`central layer fused to the outer layer with which it is in contact
`to seal the edges of the central ceramic layer in ceramic to
`prevent voltage breakdown over the edge of the central layer
`and to prevent penetration of moisture, metal paint terminal
`layers on the faces of each outer layer remote from the central
`layer, said terminal layers providing surfaces to which solder
`connections may be made and extending into the perforations
`and into contact with the electrodes.
`7. The capacitor of claim 6 in which there is more than one
`perforation in one of the outer layers and at least one perfora
`tion in the other outer layer.
`
`3
`1. A ceramic capacitor unit consisting essentially of a sinter
`united laminate having a central ceramic layer sandwiched
`between two outer ceramic layers of a ceramic Compatible
`with the central layer, the central layer being imperforate and
`having a thickness too thin to be handled if separately ?red, a
`pair of metal paint electrodes sintered respectively to opposite
`faces of the central layer, each electrode covering at least
`major surfaces of the central layer, at least portions of said
`electrodes being in capacity relation to each other through the
`thickness of the central layer and spaced from the periphery of
`the central layer to provide a margin of ceramic surrounding
`each of the electrodes, said outer layers each having a
`thickness of 3 mils or more and respectively having one face
`overlying and in contact with one and the other of the elec
`trodes and its margin of ceramic, the outer layers having per
`forations opposite and occupying a minor portion of the area
`of said electrodes and spaced from the periphery of said layers
`and extending in the thickness direction through each outer
`layer but not through the electrode with which it is in contact,
`the layers and electrodes being a unitary sintered ceramic
`structure with each of the margins of the central layer fused to
`the outer layer with which it is in contact to seal the edges of
`the central ceramic layer in ceramic to prevent voltage break
`down over the edge of the central layer and to prevent
`penetration of moisture, metal paint terminal layers on the
`faces of each outer layer remote from the central layer, said
`terminal layers providing surfaces to which solder connections
`may be made and extending into the perforations and into
`contact with the electrodes.
`2. The capacitor of claim 1 in which one or more of the per
`forations is opposite and therefore makes accessible through
`said perforations a portion of the electrode area of one of the
`electrodes in capacity relation to the other electrode so said
`accessible portion may be removed to reduce the capacity
`after the metal terminal layers have been applied and after
`removal of the portion of the metal terminal layer overlying
`said portion of the electrode area.
`3. The capacitor of claim 1 in which the outer layers have
`less shrinkage during sintering than the central layer so that
`the outer layers are placed under compression to increase the
`mechanical strength of the capacitor.
`4. The capacitor of claim 1 made by the method which con
`sists of stacking the ceramic layers of the laminate in the green
`state with the central layer painted with the electrodes prior to
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