(12)
`
`United States Patent
`Liebowitz
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,690,572 B2
`Feb. 10, 2004
`
`US006690572B2
`
`(54) SINGLE LAYER ELECTRONIC
`CAPACITORS WITH VERY THIN
`DIELECTRICS AND METHODS T0
`
`5,737,180 A * 4/1998 Yoo ......................... .. 361/313
`6,207,522 B1 * 3/2001 Hunt et al. . . . . .
`. . . .. 438/393
`6,366,443 B1 * 4/2002 Devoe et al.
`361/313
`6,433,993 B1 * 8/2002 Hunt 61 8.1.
`............... .. 361/303
`
`(76) Inventor: Larry A. LiebOWitZ, 129 Adirondack
`Ave., SpotsWood, NJ (US) 08884
`
`JP
`
`FOREIGN PATENT DOCUMENTS
`P-2000-327964 A * 11/2000
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC 154(b) by 0 days.
`
`(21) APPL NO; 10/090,816
`(22) Filed:
`Mar. 6, 2002
`
`(65)
`
`Prior Publication Data
`
`""""""""""""
`""
`
`Us 2003/0169555 A1 Sep' 11’ 2003
`(51) Int. c1.7 ........................... .. H01G 4/06; H01G 4/00
`(52) us CL
`361/311. 361/303
`(58) Field of
`B01 4 ’303_305
`320
`1_321 5’
`’
`'
`
`’
`
`'
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,689,810 A * 9/1972 Walles ...................... .. 361/305
`3,882,059 A * 5/1975 Elderbaum ............... .. 29/2542
`5,254,360 A * 10/1993 CroWnover et a1. ........ .. 427/79
`
`44
`
`* Cited by eXaIIliner
`
`Primary Examiner—Dean A. Reichard
`Assistant Examiner—Eric Thomas
`(74) Attorney, Agent, or Firm—Leonard Cooper
`(57)
`ABSTRACT
`
`A SLC has a thin brittle ceramic dielectric layer less than
`0.0035 inches thick and as loW as 0.0005 inches or less.
`Electrodes are thick and strong enough either singly or
`together to give the Structure required physical Strength for
`manufacture, handling, and usage. Electrodes are (1) a
`ceramic metal composite, (2) a porous ceramic in?ltrated
`With metal or other conductive material, (3) a resin ?lled
`With metal or other conductive material, or (4) combinations
`of the above. The very thin and, in itself, fragile dielectric
`layer provides exceedingly high capacity per unit area With
`temperature stability and loW losses. A 0.00001-inch thick
`dielectric of titanium dioxide is also used.
`
`23 Claims, 2 Drawing Sheets
`
`ELECTRODE
`44
`
`DIELECTRIC f6
`
`ELECTRODE 3g
`
`GLASS CERAMIC 40
`
`000001
`
`AVX CORPORATION 1004
`
`

`
`U.S. Patent
`
`Feb. 10, 2004
`
`Sheet 1 0f 2
`
`US 6,690,572 B2
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`m
`/4 ELECTRODE
`DIELECTRIC
`/2
`
`t
`‘L
`
`/0'
`
`I
`
`D'E E
`L cm“:
`Q
`
`T ELECTRODE
`
`f6
`F lG.1a
`
`ELECTRODE
`FIG.1 b
`
`PASTE Z0
`
`PASTE 20
`
`A; “GREEN” TAPE
`
`FIG.2
`
`ROGUE FILLED CERAMIC
`TAPE Z4
`
`METAL PASTE Z51
`
`DIELECTRIC GREEN
`TAPE
`
`FIG.3
`
`000002
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`

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`U.S. Patent
`
`Feb. 10, 2004
`
`Sheet 2 0f 2
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`US 6,690,572 B2
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`CONDUCTIVE
`RESIN 34
`
`DI ELECTRIC
`32
`
`ELECTRODE
`
`ELECTRODE
`44
`
`ELECTRODE
`50
`
`DIELECTRIC
`46
`
`CONDUCTIVE
`SUBSTRATE
`
`FIG.6
`
`000003
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`US 6,690,572 B2
`
`1
`SINGLE LAYER ELECTRONIC
`CAPACITORS WITH VERY THIN
`DIELECTRICS AND METHODS TO
`PRODUCE SAME
`
`BACKGROUND OF THE INVENTION
`The simplest instance (FIG. 1a) of an electronic capacitor
`10 includes a dielectric material 12 sandwiched betWeen tWo
`metal electrodes 14, 16. More complex examples (not
`shoWn) include multi-layer devices Which incorporate addi
`tional alternating layers of dielectric and electrode, electri
`cally connected in parallel by terminations so as to cause the
`net capacitance value of the assembly to be equal to the sum
`of the values of the individual layers.
`The dielectric 12 may be any electrical insulator, but
`required properties of the device 10 dictate Which materials
`are satisfactory for the application at hand. One of the
`important properties of dielectric materials is dielectric
`constant
`This property, along With the thickness (t) of
`the dielectric layer 12, determines the magnitude of capaci
`tance C achievable per unit of active area Aof the dielectric/
`electrode sandWich. When face area A is ?xed, capacitance
`is directly proportional to the dielectric constant K and
`inversely proportional to dielectric thickness t. Commonly
`used dielectrics include mica, thin ?lms of various oxides
`such as those of aluminum, tantalum and silicon, and various
`electronic ceramics Whose dielectric constants span the
`range of about 6 to 20,000.
`In general, it is desirable to get the highest capacitance per
`unit area from a given chip because of limited circuit board
`space, particularly in today’s miniature equipment such as
`Wireless phones and hand-held computing devices.
`Accordingly, this high capacitance density Will be attained
`by choosing a material With high dielectric constant and
`minimum thickness. Choice of dielectric is limited by losses
`and temperature stability requirements so thickness becomes
`a critical factor.
`Ceramics are one of the most useful classes of dielectric
`materials for present applications. HoWever, due to their
`fragility and the difficulty in ?ring them at thicknesses much
`beloW 0.004 inch, ceramics are usually used in multi-layer
`form, Which yields high capacitance per unit board area but
`also causes high inductance, an undesirable property, rela
`tive to single layer devices. This high inductance draWback
`also applies to devices With a single dielectric layer and one
`or more electrodes buried Within a multi-layer structure in
`Which electrical contact(s) to said buried layer(s) are brought
`to the surface through vias, edge connections, etc. The
`present invention avoids any of these inductance-increasing
`methods and in fact makes practical a classic single layer
`ceramic capacitor With dielectric thickness of 0.001 inch or
`less.
`Once a given dielectric is selected the siZe of the resulting
`device for any given capacitance is conventionally deter
`mined by the number of layers and their thicknesses. True
`single layer capacitors (SLCs) have loWer inductance and
`thus higher resonant frequencies than their multi-layer coun
`terparts and, as stated, are useful at higher frequencies, a
`necessity for many of today’s broadband, Wireless and other
`applications. Since SLCs have a much more limited capaci
`tance range than multi-layer devices, When area is predeter
`mined; e. g., by a circuit con?guration, it is very important to
`get the dielectric thickness as loW as possible. True SLCs
`currently available are limited to about 0.004 inches in
`minimum thickness because of the fragility of the dielectric
`materials at lesser thickness.
`
`2
`This disclosure focuses on examples With thin ceramic
`dielectrics, Which ceramics are by nature brittle and there
`fore very fragile in thicknesses beloW about 0.005 inch. The
`application discloses methods of manufacturing true SLCs
`With such ceramic dielectric having thickness as loW as
`0.0005 inch. The term “true SLC” is used to distinguish
`those physical embodiments and methods disclosed herein
`from single buried layer devices conventionally manufac
`tured With the same design as multi-layer devices and having
`similar negative features.
`What is needed is a physically and electrically reliable
`true single layer capacitor of high capacity per unit area
`using a thin ceramic dielectric that is less than 0.004 inch in
`thickness.
`
`SUMMARY OF THE INVENTION
`
`An SLC 10 (FIG. 1a) in accordance With the invention has
`a thin ceramic dielectric layer 12 (less than 0.004 inch and
`as loW as 0.0004 inch or less), Which has as electrodes
`conductive layers 14, 16 that are thick and strong enough
`either singly or together to give the structure 10 the required
`physical strength for manufacturing, handling and usage,
`and having electrical properties giving the device its
`required performance properties. An electrode(s) 14, 16, for
`example, is composed of (1) a ceramic-metal composite, (2)
`a porous ceramic in?ltrated With metal or other conductive
`material, (3) a resin ?lled With metal or other conductive
`material, or (4) combinations of the above.
`Thus, a very thin and in itself, fragile, dielectric layer 12
`provides exceedingly high capacity per unit area, While
`thick, strong electrodes 14, 16 provide structural strength
`and support that protect the dielectric of the capacitor during
`manufacturing and usage.
`Several exemplary methods are presented herein that are
`suitable for mass production of SLCs in accordance With the
`invention. Embodiments of the invention using an oxide of
`titanium as a very thin dielectric 12 are also disclosed.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1a is a schematic perspective partial vieW of a
`conventional single-layer capacitor SLC having coextensive
`electrodes; FIG. 1b is a similar SLC having one patterned
`electrode;
`FIG. 2 illustrates partially and in perspective embodiment
`I of an SLC in accordance With the invention before ?ring;
`FIG. 3 partially and in perspective illustrates embodiment
`II in accordance With the invention before ?ring;
`FIG. 4 partially and in perspective illustrates embodiment
`III in accordance With the invention before ?ring;
`FIG. 5 illustrates embodiment V in accordance With the
`invention before ?ring; and
`FIG. 6 illustrates embodiment VII in accordance With the
`invention.
`The ?gures are illustrative and not draWn to any scale.
`
`DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`Several basic methods are noW described for producing
`(true SLC) capacitors, and resultant SLC products in accor
`dance With the invention are described.
`Embodiment I; Composite Electrode
`A green ceramic tape 18 serves (FIG. 2) as a precursor for
`the dielectric layer of the ?nished capacitor. This green tape
`of desired ceramic composition Was cast to proper thickness
`
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`000004
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`US 6,690,572 B2
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`3
`for providing the desired ?red thickness, and Was trimmed
`to Whatever green substrate siZe is preferred.
`A conductive paste 20 contains metal and ceramic poW
`ders to provide a suitable conductive electrode after ?ring.
`The metal and ceramic poWders are suspended in a plastic
`vehicle With solvent to attain the desired viscosity. A small
`amount of ?ux (not shoWn) may be added to improve
`Wetting characteristics and/or promote adhesion of the paste
`to the dielectric tape. The paste 20 is applied to the thin
`green ceramic tape 18 (the dielectric) by stencil, screen
`printing or other suitable method at a thickness that Will
`assure the physical integrity of the ?nished product. This
`paste is prepared by standard processes such as passing the
`ingredients several times through a three-roll mill.
`The green tape and paste, as Work-in-progress, are then
`subjected to thermal processing (?ring) that results in a thin
`dielectric layer adhering to a conductive electrode (or tWo
`electrodes). The green tape typically shrinks 10% to 30% in
`a high temperature furnace depending on its composition.
`Depending on the dielectric’s composition and subse
`quent ?ring conditions, the metal in the paste may be either
`noble or non-noble. For air ?ring the metal may be platinum,
`palladium, gold, silver, alloys of these, or others that do not
`react With the air. Metals such as nickel and copper may be
`used for non-oxygen ?ring. Oxidation of the metal must be
`avoided.
`The ceramic poWder in the paste is, for example, a single
`compound or a combination of compounds. The ceramic
`poWder can comprise metal oxides and/or titanates, similar
`to those used for the dielectric in other embodiments. The
`ratio of metal to poWder in the paste can range from about
`0.4 grams to 9 grams of metal per gram of poWder.
`The paste is precursor to one or both of the ?nished
`devices’ electrodes and is initially applied to one or both
`sides of the dielectric green tape as required by the design of
`the particular device being manufactured. When the paste is
`applied only on one side, a thin solid or patterned layer of
`co-?reable metal may be applied to the other side of the tape
`that, When ?red, becomes the counter electrode.
`Alternatively, the counter electrode may be applied after
`?ring by any standard method; e.g., plating, sputtering,
`screen-printing, etc.
`The metal poWder in the paste is chosen so that it does not
`melt nor react With the dielectric at its sintering temperature,
`but forms a strong electrically conductive bond With it. The
`ceramic poWder in the paste is selected so that it imparts
`physical strength to the sintered product While at the same
`time does not signi?cantly diminish the electrical conduc
`tivity of the metal in the ceramic to metal ratio that is
`employed.
`The entire paste composition is such that shrinkage of the
`layers’ planar surfaces during the burnout/sintering process
`matches the shrinkage of the dielectric green tape. After
`application of the paste to the dielectric tape, the tape and
`electrode(s) paste are co-?red at the prescribed temperature
`for the given ceramic composition.
`After the ?ring process With paste on only one side of the
`tape, the counter electrode is applied and any required
`desired pattern etching is done. The composite electrode
`may also have a thin conductive layer applied to its outer
`surface by methods such as plating, sputtering, etc.
`The total after-?ring thickness of the dielectric 12 plus
`tWo electrode layers 14, 16 should be about 0.003 inch or
`more (0.004 is preferred) to alloW advantageous handling
`characteristics. After ?ring, the individual devices are sepa
`rated by dicing and subjected to normal and customary
`processing. The devices 10, 10‘ thus formed Will have, after
`
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`shrinkage in ?ring, a thin (0.0004 to 0.0015 inch) stratum of
`dielectric material 12 sandWiched betWeen adherent conduc
`tive electrodes 16 either extending to the extent of the chip
`surface A (FIG. 1a) or to a lesser extent A‘ leaving a margin
`of unelectroded dielectric.
`Thus, devices are formed With capacitance values up to
`about 10 times (or more) the value of a conventional single
`layer device of their siZe, by virtue of the actual dielectric
`after ?ring being a fraction as thick as the conventional
`device. Capacitance is further enhanced by the fact, observ
`able With an electron microscope, that the electrode(s)
`penetrate into the body of the dielectric, further reducing the
`effective dielectric thickness. Other properties; e.g., tem
`perature stability, losses, of the present invention are similar
`to or better than those of conventional single layer capaci
`tors. It is also possible to dice an assembly in the green or
`intermediate bisqued states if this timing is more suitable to
`a given assembly line.
`Embodiment II; Porous Electrode
`To form an electrode, a “rogue” material is incorporated
`into a suitable ceramic tape 24 (FIG. 3). The rogue material
`burns off during the sintering process (as described beloW),
`leaving the resultant ?red material porous. Typically, this
`rogue material may be graphite, rice starch, ?nely ground
`Walnut shells, or a host of other organic and inorganic
`materials. The ceramic tape 24 is formulated so that it is
`co-?reable With a ceramic dielectric green tape 26 and is
`compatible after ?ring as Well.
`One major concern is matching the shrinkages of the
`electrode and dielectric tapes during sintering and the
`as-?red thermal coef?cients of expansion. Hence, the com
`position of the ceramic in the rogue material ?lled tape 24
`preferably is similar to the ceramic of the dielectric tape 26.
`Thickness of the green dielectric tape 26 is chosen to give
`the desired end result capacitance per unit area and is usually
`betWeen 0.0005 and 0.005 inch. Thickness of the rogue
`material ?lled tape 24 is selected to give the desired struc
`tural integrity and overall ?red thickness of the ?nished
`product.
`A co-?reable conductive metal paste 28 is applied to
`either the dielectric tape 26 or rogue material ?lled tape 24,
`or to both, in most instances by screen-printing. Dielectric
`and rogue material ?lled tapes are then laminated by con
`ventional means, encasing the metal paste betWeen them,
`and then are ?red.
`After the ?ring process, the noW porous electrode layer
`precursor 24 is impregnated from its outer surface 30 With
`conductive metal (not shoWn) by processes such as, for
`example, plating, sputtering and/or osmosis, thus forming an
`electrical link through pores to the previously applied metal
`layer 28 and causing the entire “porous” layer (noW ?lled
`With metal) to act as an electrode.
`The counter electrode (not shoWn) is then applied to the
`opposite outer surface of the dielectric 26 by any of the
`means mentioned above, and the resultant Wafer is diced as
`may be required.
`Embodiment III; Metal Filled Resin Electrode
`Apreviously ?red ceramic dielectric material 32 (FIG. 4)
`of about 0.003 to 0.015 inch in thickness is coated on one
`side With a conductive metal-?lled resin 34. The metal-?lled
`resin 34 is formulated to have the least possible shrinkage
`during subsequent cure and to match the thermal coef?cient
`of expansion of the dielectric material 32 as closely as is
`practical. Many metal and resin combinations are Well
`knoWn for electrode 34, the most Widely used of Which is
`silver-?lled epoxy. Other metals used for this application
`include gold, nickel, copper, etc. as Well as plated metals.
`
`000005
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`

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`US 6,690,572 B2
`
`5
`Other resins include silicones, polyesters, etc. After the
`?lled resin is cured, the exposed side (bottom surface in FIG.
`4) of the dielectric 32 is acted upon, for example, is ground
`doWn, to provide Whatever thickness is required for the
`desired capacitance, typically under 0.001 inch. The
`exposed side is then electroded by one of the previously
`mentioned methods, and the device is diced as may be
`required.
`Embodiment IV; Preformed Composite Electrode
`This embodiment(s) (not shoWn) is similar to Embodi
`ment I With the exception that the composite electrode is
`preformed as a ?exible or rigid form of proper siZe and
`thickness, Which is then laminated to the thin dielectric
`green tape. The electrode can be formed, for example, by
`casting, molding, roller milling or other method of compac
`tion. If desired, this electrode can be formulated so as to
`have very loW planar shrinkage during ?ring and at the same
`time limit the dielectric’s planar shrinkage to a similar loW
`amount, in effect stretching the dielectric and causing addi
`tional shrinkage in thickness, the net results of Which are
`additional capacitance per unit area and a greater yield of
`devices from a given green substrate. Other processing of
`the capacitor is similar to Embodiment I.
`Embodiment V; Surface Mount Series Capacitors
`Apreviously ?red dielectric 36 (0.003 to 0.015 inch thick)
`has a thin conductive electrode 38 applied to (FIG. 5) one
`surface by screen-printing, stenciling, plating, sputtering, or
`other suitable method. This electrode may be continuous or
`patterned as internal “pads”. If necessary, post application
`processing, such as ?ring, annealing, curing, etc. to assure
`good bonding of the electrode material 38 to the dielectric 36
`is performed. The conductive electrode 38 is composed of
`noble metal(s) such as platinum, palladium, gold, etc. Silver,
`or base metals such as nickel or copper, for example, may
`also be used.
`A layer 40 of un?red glass ceramic, formulated so as to
`exhibit minimum shrinkage during sintering, is applied to
`the metalliZed (38) side of the dielectric 36, the minimum
`thickness (typically 0.003—0.004 inch) of said glass ceramic
`layer being such that it supports the dielectric layer 36
`during subsequent processing as Well as handing and instal
`lation by the user. As long as this structural requirement is
`met, the thickness of this glass ceramic layer can be as
`desired.
`After application of the glass ceramic, the combination is
`?red at the proper temperature to fully sinter the added layer
`40 and permanently bond it to the dielectric 36. The ?ring
`temperature, Which can be as loW as 400 degrees C.,
`determines Which material(s) is selected for the inner elec
`trode 38. After ?ring, the bare side 42 of the dielectric is
`acted upon, for example, ground doWn to provide the desired
`thinness.
`The counter electrode 44 (shoWn With hatched lines) is
`then applied by any of the standard methods; e.g., plating,
`sputtering, screen or other printing techniques, etc. to the
`exposed (ground off) surface to give the desired series
`capacitor con?guration. Chemical etching, lasering, ion
`milling, air or Water abrasion, surface grinding or other
`techniques may also be employed to get the desired external
`electrode patterns in the counter electrode 44.
`In an Embodiment VI (not shoWn), a prefabricated con
`ductive electrode of proper ?nished dimensions is laminated
`(as in Embodiment IV) to a thick dielectric ceramic layer
`(0.003 to 0.015 inch). After they are joined, the exposed face
`of the dielectric is Worked; e.g., ground off, to the desired
`layer thickness t and a counter electrode is added to the
`exposed face by any of the above-mentioned techniques.
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`The embodiments I to VI, When complete, result in
`structures as illustrated schematically in FIGS. 1a, b,
`although an external glass ceramic layer not shoWn in FIGS.
`1a, b is included in Embodiment V When complete.
`It Will be apparent to those of only moderate skill in the
`art that, in use, each electrode of a capacitor must be
`electrically connected into a circuit. Frequently, the physi
`cally tiny capacitors, such as in the present invention, are
`?ush-mounted With one electrode bonded directly to a
`conductive substrate. Various locations are used in connect
`ing to the other electrode. Capacitors in accordance With the
`invention may be smaller than a grain of sand.
`In the present invention, the electrodes are each substan
`tially planar, each having an inner surface adjacent to a
`planer surface of the dielectric and each electrode having an
`outer surface A, A‘ (see FIGS. 1a, b) that is substantially
`parallel to it inner surface. To achieve the advantages of the
`present invention; e.g., greatly enhanced capacity per unit
`area, the connection of at least one electrode to an external
`circuit is made by connection to the outer surface A, A‘ of
`that electrode. Thus, the manufacturing process can leave or
`later provide an exposed portion on the outer surface A, A‘
`for such connection. The circuit designer determines
`Whether such portion remains exposed after the connection
`is complete. For practical design considerations in produc
`ing the exposed portion, at least one dimension of the outer
`electrode surface is made equal to or greater than approxi
`mately 0.004 inches in consideration of present manufac
`turing techniques and performance requirements. Of course,
`changes in these parameters Will likely occur in the future.
`Conventional single layer capacitors of the parallel layer
`construction of electrodes and dielectric generally have a
`dielectric thickness in the order of 0.003 inch and greater.
`The great advantage of the present invention, increased
`capacitance per unit area, results from a thinner ceramic
`dielectric layer that can be in the order of 0.0005 inch. The
`invention is noticeably advantageous When dielectric thick
`ness t is in the range of approximately 0.0025 inch and less,
`for example, 0.0005 inch. The capacitors With thin ceramic
`dielectric in accordance With the invention have also dem
`onstrated improved temperature characteristics and loW
`losses as compared With prior art SLCs of similar dimen
`sions.
`An example of the method is noW described to produce a
`capacitor of Embodiment I.
`Preparation of the Electrode Precursor
`Blend 52 parts by Weight (pbW) of ?ne (1 micron)
`platinum poWder and 22 pbW Ferro Corp. (Penn Yan, N.Y.)
`dielectric poWder X5000 into 26 pbW of a saturated solution
`of ethyl cellulose in kerosene.
`Preparation of the “Green” Dielectric Tape
`Mix the folloWing ingredients in a 1000 cc porcelain mill
`jar With 500 cc of 1A-inch diameter by 1A-inch length
`porcelain cylinders:
`96 g Air Products (AllentoWn, Pa.) Airvol 21—205 poly
`vinyl alcohol
`6.6 g Triethylene Glycol
`0.6 g Air Products Dynol 604 surfactant
`1.2 g Glacial Acetic Acid
`150 g Ferro Corp. X5000 dielectric poWder
`46.5 g distilled Water
`Roll mixture for 48 hours at 100 rpm.
`Discharge mixture (“slip”) and cast as folloWs:
`1. Put container With slip into vacuum chamber. Close
`chamber and turn pump on. Adjust for vacuum of 27:1
`inches of Hg. Deair (operate pump) for 30 minutes.
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`US 6,690,572 B2
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`7
`2. Set the Doctor Blade to 0.001 and cast on polypropy
`lene ?lm at a rate of 0.75 inch/second. Allow to dry.
`3. Peel cast tape from ?lm.
`As is Well known in the art, a Doctor Blade is a callibrated
`slit through Which ?oWs the liquid “slip”, the precursor to
`green tape. The height of the slit determines the thickness of
`the green tape.
`Manufacture of Capacitors
`1. Cut green tape into 2 inch by 2 inch sections.
`2. Stencil previously prepared electrode precursor onto
`2><2 section, completely covering one surface With a 0.004
`inch thick layer of electrode precursor.
`3. Dry in oven at 80 degrees C. for 4 hours.
`4. Fire in programmable furnace as folloWs:
`a. Bring temperature from room temperature to 2375
`degrees F. at 2 degrees F. per minute.
`b. Hold for 2 hours at 2375 degrees F.
`c. Turn heat off and alloW to cool to room temperature in
`closed furnace.
`. Sputter each side With metal as folloWs:
`. 10 micro inch titanium-tungsten
`. 30 micro inch nickel
`. 80 micro inch gold
`. Dice to speci?ed chip siZe.
`Embodiment VII; Titanium Dioxide Dielectric
`Titanium dioxide has a dielectric constant of only 90, but
`using the methods of the disclosed invention titanium diox
`ide can be applied in thickness as loW as 0.00001, Which
`yields an effective K of 36,000 relative to the 6—20,000 in a
`conventional device. Even at dielectric thickness of 0.00005,
`the subject device has an effective K of 7200, Which is 80
`percent higher than most conventional devices. In addition,
`the subject dielectric has DF of less than 0.005, Which is
`very important at microWave frequencies, and temperature
`dependence of capacitance of about 17.5% over the tem
`perature range, about half that of the conventional device.
`An SLC in accordance With the invention (FIG. 6) is made
`by applying a thin layer 46 of titanium dioxide dielectric
`onto a conductive substrate 48 of proper thickness for the
`device being constructed, the substrate also being one of the
`device’s electrodes. Then, the counter electrode 50 is
`applied atop the dielectric layer.
`The conductive substrate 48, for example, can be com
`posed of a metal of high conductivity Which Will not melt
`and Will resist oxidation at temperatures as high as 700
`degrees C.; e.g., silver or a noble metal, a porous ceramic
`in?ltrated With metal With the same properties as above, a
`conductive ceramic-metal composite, or combination of the
`above. The counter-electrode can be a pure metal or com
`bination of metals, metal ceramic composite, metal polymer
`(epoxy, polyester, etc.) composite, conductive polymer, etc.,
`the requirement for any of the above being high electrical
`conductivity.
`In the method of the invention, a thin layer 46 of titanium
`is deposited on the conductive substrate 48 by sputtering, by
`evaporation, by electro or electroless plating, or other suit
`able means. The layer 46 has a thickness to yield the
`speci?ed dielectric thickness after the next step, Which is
`conversion of the deposited layer to titanium dioxide by
`subjecting the Ti to oxygen at about 650 degrees C. After the
`conversion to titanium dioxide dielectric is complete, the
`counter electrode 50 is applied by vapor deposition, electro
`or electroless plating, screen-printing, or other suitable
`method. For particular applications, it may be desirable to
`apply intermediate layers (not shoWn) betWeen the dielectric
`and substrate and/or counter electrode as penetration
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`55
`
`60
`
`65
`
`8
`barriers, adhesion promoters, etc. It may also be desirable to
`bake or otherWise process the ?nished substrate to achieve
`optimum properties.
`After any such processing is completed, any desired
`pattern etching of the electrodes is done and the material is
`diced into ?nished chips, per FIGS. 1a, b.
`In summary, the problems related to the fragility of thin
`ceramic dielectric are overcome by supporting the ceramic
`dielectric before it is made thin in the production process.
`This is basically accomplished by connecting precursor
`dielectric material or thick pre?nished dielectric material to
`a thick strong electrode element before or concurrently With
`thickness reduction of the dielectric material. If the initial
`conductive electrode material is thin, it is reinforced during
`manufacture of the SLC With a resin or glass ceramic so that
`the thin dielectric is never Without adequate structural sup
`port.
`What is claimed is:
`1. A single-layer capacitor (SLC), comprising:
`a ?rst conductive electrode having a ?rst planar face area;
`a second conductive electrode having a second planar face
`area, said face areas being parallel one to the other;
`a brittle dielectric layer having a ?rst planar surface and
`a second planar surface parallel to said ?rst planar
`surface;
`said ?rst planar face area of said ?rst electrode being in
`contact With said ?rst planar surface of said dielectric
`layer With loW electrical resistance betWeen them,
`said second planar face area of said second electrode
`being in contact With said second planar surface of said
`dielectric layer With loW electrical resistance betWeen
`them,
`Wherein said brittle dielectric has a thickness t betWeen
`said ?rst and second planar surfaces less than approxi
`mately 0.0025 inches, and said ?rst electrode and said
`second electrode each having a second face area, at
`least a portion of each said second face area being
`externally exposed for making an external electrical
`connection directly Without a via to said exposed
`electrode portion, said second face area of at least said
`?rst electrode being substantially parallel to said ?rst
`face area of said ?rst electrode, the sum of thicknesses
`of said ?rst and second electrodes being greater than
`said dielectric thickness t to structurally support said
`brittle dielectric layer against breakage.
`2. A capacitor as in claim 1, Wherein at least one dimen
`sion of said second face is approximately equal to or greater
`than 0.004 inches.
`3. A capacitor as in claim 1, Where said dielectric layer
`and said ?rst and second electrodes each has a respective
`thickness, and a total thickness of said dielectric and tWo
`electrodes at least equals approximately 0.003 inches.
`4. A capacitor as in claim 3, Wherein said dielectric layer
`is ceramic.
`5. A SLC as in claim 4, Wherein at least one said
`conductive electrode includes a metal and a ceramic
`material, said metal and ceramic material being poWders in
`said paste prior to said ?ring process.
`6. A SLC as in claim 4, Wherein said capacitor is the
`product of a method comprising the steps of:
`a) providing a green tape including ceramic material for
`comprising said dielectric layer;
`b) coating a ?rst planar surface of said green tape With a
`paste including electrically conductive material for
`comprising said ?rst electrode;
`c) ?ring said coated green tape in a prescribed ?ring
`process that converts said tape and said paste into said
`dielectric layer and said ?rst electrode respectively;
`
`000007
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`

`
`US 6,690,572 B2
`
`9
`d) applying one of a thin solid and patterned layer of
`electrically conductive material to said dielectric layer
`opposite to said ?rst electrode to comprise said second
`electrode.
`7. A SLC as in claim 6, Wherein at least one said
`conductive electrode includes a metal and a ceramic
`material, said metal and ceramic material being poWders in
`said paste prior to said ?ring process.
`8. A SLC as in claim 4, Wherein said capacitor is the
`product of a method comprising the steps of:
`a) providing a green tape including ceramic material for
`comprising said dielectric layer;
`b) coating tWo opposed planar surfaces of said green tape
`With a paste including electrically conductive material
`for comprising ?rst and second planar electrodes;
`c) ?ring said coated green tape in a prescribed ?ring
`process that converts said tape and said paste into said
`dielectric layer and said ?rst and second electrodes
`respectively.
`9. A SLC as in claim 8, Wherein at least one said
`conductive electrode includes a metal and a ceramic
`material, said metal and ceramic ma