PT104881A - DIGITAL COMPONENT TUNING AND MANUFACTURING PROCESS - Google Patents

Abstract

The present invention relates to composite dielectric materials of low dielectric strength and high reliability of the dielectric perimetry relative to thick films for application and integration into circuits as passive components of tunable devices for use in the frequency and frequency frequencies And the method of manufacturing such thick films, more specifically with the combination of the electrophoretic deposition process with the sol gel process, for the manufacture of the said composite thick films, constituted by a dielectric phase of low dielectric loss (Q HIGH), BIO-TITANATES OF RARE LANDS, BAO-RE2O3-TIO2 (BEING RE, N, S, LA, NOMINALLY), AND OF NEODYMUS (BAND2TIO14, BNT), IN PARTICULAR, AND BY A PHASE OF DIELECTRIC PERMITIVITY TUNED BY ACTION OF THE ELECTRIC FIELD, AS COMPOUNDS OF THE SOLID SOLUTION BETWEEN TITANAT THE BÁRIO AND THE ESTRÔCIO TITANATO, BATIO3 - SRTIO3, AS (BA0.5 SR0.5) TIO3 (BST), NOMINALLY.

Description

1

Description " DIELECTRIC COMPONENT TUNING & FABRICATION PROCESS "

TECHNICAL FIELD OF THE INVENTION The present invention relates to: (1) dielectric materials, more specifically relates to low dielectric dielectric materials with high tunability of the relative dielectric permittivity by the action of the electric field, in the form of thick films , of a thickness in particular greater than 10 microns and in particular less than 100 microns, over flexible metal substrates and rigid non-metallic substrates for applications and integration into circuits as passive components of tunable devices, such as tunable oscillators, " phase shifters " (phase displacement devices), varactors, among others, namely of use to radio frequencies and microwave frequencies, and (2) the method of manufacturing these same thick films, more specifically with the combination of the electrophoretic deposition process with the The sol gel process for manufacturing said thick composite films, consisting of a dielectric phase of low dielectric loss (high Q), such as rare earth barium titanates, BaO-Re203-TiO2 (Re = Nd, Sm, La , among others), such as neodymium (BaNd2Ti50i4, BNT), among others, and by a dielectric permittivity phase tunable by the action of the electric field, as compounds of the solid solution between barium titanate and strontium titanate, BaTiCR -SrTi03, as (Ba0.s Sr0.5) TiO3 (BST), among others.

SUMMARY OF THE INVENTION The present invention is useful for: making compatible in the same film low dielectric losses with the tonality of the dielectric permittivity, properties not existing in a single material and fundamental for devices operating at high frequencies; the miniaturization of devices for applications to microwave frequencies; and the possibility of application to many other electroceramic systems, anticipating the extension of existing applications and the manufacture of new electronic devices for application at high frequencies. The present invention describes a tunable composite dielectric having the feature of comprising a tunable dielectric material and comprising a non-tunable dielectric material comprised of one or more of the tungsten bronzoid family material, namely BaO-Re203-TiO2, Re = Nd, Sm, La, among others; MgTi03; Ba2Ti902o; Zro.8TiSn0.204; Ba (MgI / 3Ta2 / 3) 03; or the like; or compositions thereof.

A preferred embodiment of the present invention has the feature that said non-tunable dielectric material is BaNd2Ti50i4, BNT.

A preferred embodiment of the present invention has the feature of said tunable dielectric material comprising one or more of: the solid solution of barium titanate and strontium, BaixSrxTi03, BST; BaTi03; Pb (Zr, Ti) 03; or the like; or compositions thereof.

A preferred embodiment of the present invention has the feature that said tunable dielectric material is (Bao.s Sro.s) TiO 3. 3

A preferred embodiment of the present invention has the feature of comprising 80 to 95% by weight of said low loss non-tunable dielectric material, such as Ba0-Re203-TiO2, Re = Nd, Sm, La, among others, and comprises 5 to 20% by weight of at least one additional high-tune phase, such as solid solutions of barium titanate and strontium.

A preferred embodiment of the present invention has the feature of comprising dielectric and tunable layers having thicknesses of from 5 to 100 microns, preferably from 10 to 80 microns, still more preferably from 50 to 80 microns thick. A preferred embodiment of the present invention has the feature of additionally comprising a metal substrate, such as platinum, gold, silver, copper, nickel, among others; or substrate such as alumina, Al 2 O 3, among others, for deposition of said thick layer of low dielectric losses, BNT.

Preferred embodiments of the present invention comprise electronic devices, comprising varactors, tunable filters, co-planar and linear phase shifters, and phase array antennas, multilayer thick film capacitors, planar capacitors having the feature of comprising one or more tunable dielectric composites as previously described. The present invention further describes a method of manufacturing said tunable composite dielectric having the feature of combining the electrophoretic deposition process with sol gel deposition in obtaining an association of a low loss non-tunable dielectric material and a tunable dielectric material, namely the solid solution of barium titanate and strontium, Bai_xSrxTi03, BST, in particular (Bao.s Sro.s) TiO 3, or compositions thereof.

A preferred embodiment of the present invention has the feature of comprising the following steps: • thick layer dielectric deposition of dielectric matrix of low dielectric losses not tunable, such as Ba0-Re2C> 3-Ti02, where Re = Nd, Sm, La, among others, or compositions thereof; • infiltration by phase sol gel methodology of tunable characteristics, of said dielectric material tunable in the matrix layer; • sintering of the composite film for its densification.

A preferred embodiment of the present invention has the feature of comprising for depositing said thick layer of the dielectric low loss phase matrix, BNT: metal substrates, such as platinum, gold, silver, copper, nickel, among others; or non-metallic substrates such as alumina, Al 2 O 3, among others.

A preferred embodiment of the present invention comprises the following steps: • synthesis of the ceramic matrix powders by the preparation of thick composite films which involves the prior preparation of ceramic powders of the matrix composition which, for the particular case of BaNd2Ti50i4, BaCCq precursors, 5

Nd 205 and TiO 2 are mixed in the proportions suitable to obtain the subject compound in ball mills with zirconia bodies for about 24 hours in an aqueous or alcoholic medium, the resulting mixture being dried and calcined for synthesis of said compound; Stable suspension preparation of the matrix powders for electrophoretic deposition by preparing the stabilized suspension in different suspending media, such as acetone, (CH 3) 2 CO,> 99.9%, ethanol, C 2 H 5 OH, > 99.9% and acetic acid CH 3 COOH, > 99.9%, which in the case of acetone I2 99.8%, dissolved in isopropanol, C3 H7 OH, > 99.9%, is used as an additive to adjust the pH value of the suspension, in this case of BNT, where the suspensions used have the concentration of 10 g / liter of BNT powders and are sonicated until the complete dispersion of the powders; • electrophoretic deposition of a thick layer of the matrix composition, the substrates being chosen from a group of flexible metals comprising Pt, Ni, Cu among others, and from a group of rigid oxides comprising AI2O3, among others, being that the thick layer of the matrix material is deposited by electrophoretic deposition which under the action of an electric field the charged particles suspended in the suspending medium move towards the opposite charge electrode and are deposited on the substrate forming a continuous layer , the film thickness being dependent on the concentration of the suspension, applied voltage and time, and films of 10 to 80 microns thickness can be deposited under 40 V at 600 V in 30 s at 10 min, the films deposited being dried at 90 ° C for periods of time up to 24 h. • the stable sol preparation of the composition of the second phase, wherein the phase sol is prepared using as starting precursors Ba (CH 3 COO) 2,> 99.9%, Sr (CH 3 COO) 2 · V 2 H 2 O,> 99.9%, and Ti (OC 4 H 9) 4,> 99.9%, wherein glacial acetic acid CH 3 COOH,> 99.9%, and ethylene glycol, HOCH 2 CH 2 OH, > 99.9%, are used as solvents, and acetylacetone 05-802, > 99.9%, as (CH 3 COO) 2 · 1 / 2H 2 O with a 5: 5 molar ratio dissolved in acetic acid under constant stirring at 80øC, Ti (OC 4 H 9) 4 stabilized with ethylene glycol and acetylacetone and this solution mixed with the solution of Ba (Ac) 2 / Sr (Ac) 2 with a molar ratio of 1: 1 under constant stirring, and after mixing for 2 hours, the concentration of the solution is adjusted to 0.25 mol / l and stirred for another 1 hour; • spin coating of the second stage sol, after drying the films are infiltrated by scattering with the tunable dielectric phase sol, and after infiltration the films are dried and pyrolyzed at 350 ° C for 5 minutes on a hot plate, this cycle being repeated up to 10 times; • sintering of the composite films, in air atmosphere, between 1100 and 1300 ° C for different periods of time, depending on the substrate, to densify the composite.

Background of the Invention

Wireless applications, based in part on RF and integrated circuit devices, are rapidly expanding and constitute an important market for semiconductor manufacturers [1]. These applications include mobile phones, " blue tooth " (personal wireless connections), " office voice " 7 (digital business voice communications), video, data transmission through wireless local area networks (WLAN), global positioning systems (GPS) and automobile safety control, among others [2].

In terms of materials, the need to use microwave frequencies in miniaturized circuits has resulted in a growing and continuous demand for electrically tunable passive components such as tunable oscillators, &quot; phase shiffters &quot; (devices for phase displacement), varactors, among others [3] [4]. For these applications a dielectric permittivity, sr, moderate to high (the dielectric resonator size is proportional to 1 / Er1 / 2), associated with low dielectric losses (0.005 <tan <0.01), (high factor of quality, Q) and high dielectric tunability, &gt; 10% [5, 6]. The quality factor Q (defined as the inverse of the dielectric loss 1 / tan δ) is considered the most important parameter of the dielectric behavior of a material for an operating device at microwave frequencies. The Q parameter has a significant effect on the speed and quality of the electromagnetic wave that crosses the component, contributing to the reduction of noise, a high Q allows distribution or storage of signal with minimum losses. The use of high Q dielectric materials thus results in the consumption of less power in operation, increased battery life and service life, and reduced size and weight of the device. It is recognized that future communications will require a broad frequency band for communication, using &quot; frequency hopping &quot; (frequency change), so that a large amount of data can be transmitted for each bandwidth. Under these circumstances the fast-acting tunable filters &quot; fast-acting tunable filter &quot; (fast-acting tunable filters) are a fundamental component [7].

However, low dielectric losses at the same time with dielectric permittivity and high tunability in the same material have proved to be problematic, so far no material has been known to meet these characteristics, since the combination of these two properties is, from the point of view fundamental, difficult to achieve [6]. In general dielectric materials having high dielectric permittivity values (> 500) and good tunability of the dielectric permittivity, of which ferroelectric materials are a good example, exhibit high dielectric losses concomitantly, which drastically limits their use at microwave frequencies . There is thus in practice a compromise between the tunability of the dielectric permittivity and the dielectric loss of a given material.

Among the ferroelectric materials, it is known that compositions of the solid solution of barium titanate and strontium (Bai_xSrxTi03) (BST) are promising candidates for applications in tunable devices for use at microwave frequencies, such as filters, &quot; phase shifters &quot; (devices for phase displacement), varactors, among others [8]. The maximum dielectric permittivity occurring near room temperature and the ability to modify it by changing the stoichiometry of the Bai-xSrxTi03 solid solution make this family of 9 potential candidate materials for said applications. However, there are numerous problems associated with the use of BST compositions at high frequencies, in particular related to the high dielectric losses that characterize these materials [9, 10]. Numerous investigations have been conducted with the aim of reducing the dielectric losses of BST [11], for example by adding additives such as MgO, Al2O3, among others known as Q promoters [7,12,13]. However, these additives may chemically react with BST, making their properties at microwave frequencies markedly dependent on processing parameters that may impair the performance of the device.

Another approach referred to in the literature, because it is intuitively believed that ferroelectric dielectric losses can be improved by combining linear and low loss dielectrics, is the &quot; combination &quot; of these materials. By combining a dielectric dielectric material with low dielectric loss in series with tunable BST, the reduction of dielectric losses and the tunable structure of the layers was predicted [14],

Nd, Sm, La

In terms of linear dielectric materials that can be used at microwave frequencies, these should also exhibit low losses or high Q, high dielectric permittivity, and low permittivity temperature coefficient ΤΟΣγ (ΤΟΣγ low avoids frequency deviations due to temperature variations) [ 15]. Within the linear dielectrics of low dielectric losses, the family of titanium, barium and rare earth bronzes, Ba0-Re203-TiC> 2 (Re = Nd, Sm, La, among others) 10 represents a commercial family of materials with applications in the microwaves, due to the high values of Σγ (85), tanõ low (0.0005) a ~ 1 MHz and ΤΟΣγ low (-113 ppm / ° C) (BaNd2Ti50i4 data) [16].

General Description of the Invention

In the context of the manufacture of dielectric low dielectric loss materials with high tunability of the relative dielectric permittivity, in the form of thick films, the combination of compositions of Ba0-Re203-Ti02 with Bai_xSrxTi03 compositions, hitherto not mentioned, may result in materials with low dielectric losses and high tonality of the dielectric permittivity.

From a manufacturing point of view, this growing wireless device industry needs low-cost manufacturing technologies that enable the manufacturing of devices with high density, low component integration, small size and low weight [17]. Miniaturization of planar circuits, antennas, filters, couplers, are some examples of the current needs. And because of this current volume reduction requirement, one of the solutions to be considered is the manufacture of the ceramic dielectric in the form of film (thick or thin) to replace the current dielectrics in the form of monolithic ceramics, which is also a force to the demand for mass production processes associated with low production costs [18].

The techniques of preparation of thick films are usually based on the densification of porous films. A layer of powders is obtained upon deposition of a suspension on a substrate, and the distinction between the different methodologies is made on the basis of the methodology used to deposit the powder on the substrate and includes, &quot; tape casting &quot; ("screen printing"), jet printing ("jet printing") and electrophoretic deposition (EPD) [19].

Thus, dielectric thick films made by tape deposition or screen printing have high potential for use as hybrid radio frequency / microwave circuit elements, because of the low associated costs. It has been argued that the principles that guide the design and operation of components / devices of functional materials (dielectrical and ferroelectric) for operation at microwave frequencies can be applied to devices made from thick films with small adjustments [20]. However, to date, high losses and technological limitations in linear dimensions associated with thick film technology continue to limit the use of thick films of functional materials in tunable devices. At the same time, planar devices based on thick films are expected to exhibit a lower tunability than thin films, since only the top of the thick film will effectively contribute to the tuning, while the remaining film may be considered as a region of non-tunable capacity in parallel with the upper part of the film [9, 10].

In terms of methodologies for deposition of thick films, the importance of electrophoretic deposition stems from their unique characteristics, of which it is worth emphasizing the conformability over a wide range 12 of complex and porous three-dimensional shapes and structures. In addition, and no less important for the manufacture of the aforementioned devices, it is a simple, versatile, low cost manufacturing method and easily adaptable to an industrial production scale. And, when compared to other thick film manufacturing methods, electrophoretic deposition allows the production of very uniform layers with easy thickness control [21].

In this embodiment, the present invention has been conceived to overcome the difficulty associated with the inexistence of material that combines low dielectric losses with high dielectric permittivity and contribute to the development of versatile, inexpensive and geometrically limited manufacturing techniques that allow or the manufacture of miniaturized devices at competitive costs. Thus, the present invention combines in a composite material, composed of two materials, each having optimized properties: one characterized by low dielectric (high Q) losses and the other by a high dielectric permittivity tunability. On the other hand, the present invention combines the electrophoretic deposition method with the sol-gel deposition for the manufacture of thick composite films of controlled thicknesses and on variable geometry substrates. The present invention seeks to fabricate thick films of dielectric materials of optimized properties (low dielectric losses, high Q and high tunability) to be used in, for example, varactors, tunable filters, &quot; phase shifters &quot; (phase displacement devices) co-planar and linear and phase array antennas (&quot; phase array antennas &quot;). The present invention may also produce multilayer thick-film capacitors so as to enable the manufacture of tunable vertical condensers of high capacities and at low costs. These capacitors as well as the planar capacitors form the basis of high power tunable filters and resonators.

References cited: [1] H. S. Bennett, R. Brederlow, J. C. Costa, P. E. Cottrell, W. M. Huang, A. A. Immorlica, J. E. Mueller, M. Racanelli, H. Shichijo, C. E. Weitzel, B. Zhao, IEEE Trans.

Electron Devices, 52, 1235, 2005 [2] K. Yao, W. G. Zhu, X. Yao, IEEE Trans. Compon Packaging Technol. 21, 20, 1998 [3] Horwitz JS, Chang W., Carter AC, Pond JM, Kirchoefer SW, Christy DB, Levy J., and Hubert C., Integrated Ferroelectrics, 22, 799, 1998 [4] Levin I. , Leapman RD, and Kaiser DL, J. Mater. Res., 15, 1433, 2000 [5] Park B.H., Peterson E.J., Jia Q. X., Lee J., Zeng X., Si W., and Xi X. X., Appl. Phys. Lett., 78, 533, 2001 [6] Sengupta L. C. and Sengupta S., Mater. Research Innovations, 2, 278, 1999 [7] Sengupta et al., U.S. patent application Ser. No. 09 / 882,605 filed June. 15, 2001, (Assignee: Paratek Microwave, Inc.) [8] Chang W. and Sengupta L.C., J. Appl. Phys., 92, 3941, 2002 [9] Tagantsev A.K., Sherman V.O., Astafiev K.F., Venkatesh J. and Setter N., Journal of Electroceramics, 11, 5, 2003 [10] Gevorgian S. S. and Kollberg E.L., IEEE Trans. on Microwave Theory and Tech., 49, 2117, 2001 [11] Chen C. L., Feng Η. H., Zhang Z., Brazdeikis A., Huang Z.J., Chu W. K. And Chu C.W., Appl. Phys. Lett., 75, 412, 1999 [12] 15. Wu L., Chen Y.C., Huang C. L., Chou Y. P. and Tsai Y. T., J. Am. Ceram. Soc., 83, 1713, 2000 [13] Ngo E., Joshi P.C., Cole M.W., and Hubbard C. W., Appl. Phys. Lett., 79, 248, 2001 [14] Irvin P., Levy J., Guo R., and Bhalla A., Appl. Phys. Lett., 86, 042903, 2005 [15] R.J. Cava, W. F. Peck, J.J. Krajewski, G.L. Roberts, B. P. Barber, Η. M. O'Bryan, P. L. Gammel, Appl. Phys. Lett. 70, 1396, 1997 [16] D. Kolar, Z. Stadler, S. Gaberacek, D. Suvorov,

Berichte der Deutschen Keramischen Gesellschaft, 55, 346, 1978 [17] D. Stephens, P. R. Young, I. D. Robertson, IEEE Trans. Microw. Theory Tech. 53, 1, 2005 [18] K.J. Williams, A. Curley, M. Tunnicliffe, P. Barrett, P.J. Scott, J. Ferguson, EUROCON'2001, Trends in

Communications, 1, 178, 2001 [19] A. L. Kholkin, A. Y. Wu, P. M. Vilarinho, Recent Res. Mat. Sci., 5, 1. 2004 [20] C. Weil, P. Wang, H. Downar, J. Wenger, and R. Jakoby, Frequenz, 54, 250, 2000 [21] I. Corni, Μ. P. Ryan, A. R. Boccaccini, J. Eur. Ceram. Soc. 28, 7, 1353, 2008

Patent documents cited [1] Sengupta et al., U.S. patent application Ser. No. 09 / 882,605 filed June. 15, 2001, (Assignee: Paratek

Microwave, Inc.) 15

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises, in particular: (i) the manufacture of low dielectric low loss (high Q) dielectric films, less than 0.001 to 1 MHz, intermediate dielectric permissibilities having values ranging from 70 to 300 and high (t = 1). The results are shown in Fig. 2 and Fig. 2 shows the results obtained in the case of the tungsten bronzoids BaO-Re2C &gt; 3-T1O2 (Re = Nd, Sm, La). , as BaNd2Ti50i4 (BNT) and the phase responsible for the high tuning is of the BaTiC> 3 - SrTiC> 3 solid solution family, as Bao.s Sr0.5 TiO3 (BST), allowing: 1) to make compatible in the same film low dielectric losses with the tonality of the dielectric permittivity, properties not existing in a single material and fundamental for devices that operate at high frequencies, 2) the miniaturization of devices for applications to microwave frequencies and (3) the possibility of application to many other electroceramic systems, anticipating the extension of existing applications and the manufacture of new electronic devices for application at high frequencies; ii) the development of a method to manufacture these composites by combining the electrophoretic deposition methodology for the deposition of a thick layer of low dielectric loss (BNT) phase matrix on metallic substrates such as platinum, gold, silver, copper , nickel, among others, and non-metallic substrates such as alumina (Al 2 O 3) and others, with the sol gel methodology, for infiltration of the tunable phase (in this case BST), in this thick layer, so that the final properties of the composite can be controlled by the thickness and proportion of each of the phases in the composite.

Brief presentation of the invention

Dielectric composite films are shown which combine the properties of low dielectric loss (high Q) and intermediate dielectric permittivity with that of the dielectric permittivity and the method of manufacture of these same films. Composite thick dielectric films with these characteristics are intended for applications in phased array antennas ("phased array antenna systems"), filters and similar devices for operation at high frequencies. Their principle is the conjugation in the composite film of a low dielectric loss phase, namely the barium and rare earth titanate family (Ba0-Re203-Ti02 (Re = Nd, Sm, La, among others), such as BaNd2Ti50i4 (BNT), with a high throughput phase of the dielectric permittivity, namely the Bai_xSrxTi03 solid solution family, which allows to combine in the same film characteristics of dielectric permittivity with low dielectric losses, characteristics that are impossible to compatibilize in a material thus filling a technological gap in terms of materials for applications to microwave frequencies and opening up the possibility of developing new devices.

There is disclosed a method of manufacturing dielectric films having low dielectric and tunable losses in thicknesses between 5 and 80 microns, preferably in thicknesses between 10 and 50 microns, by the combination of electrophoretic deposition and sol gel, on metallic substrates such as platinum, gold, silver, copper, nickel, among others and non-metallic substrates such as alumina (Al2O3) and others, comprising: 1) thick layer deposition of the dielectric dielectric of low dielectric losses by deposition electrophoretic, 2) infiltration by phase sol gel methodology with tunable characteristics in the matrix layer, 3) sintering of the composite film for its densification.

The composite films are composed of about 80 to 95% by weight of low loss (high Q) dielectric phase material, such as barium and rare earth titanates and about 5 to 20% by weight of at least one phase high tunability, such as solid solutions of barium titanate and strontium. The final properties of the composite thick film can be controlled by the thickness and proportion of each of the phases in the composite. The relevance of the invention relates to: i) the possibility of making dielectric losses compatible with the dielectric permittivity in the same film, properties which are not present in a single material and are fundamental for devices operating at high frequencies, ii) the possibility of miniaturization of devices, and (iii) the possibility of application to many other electroceramic systems, anticipating the expansion of existing applications and the fabrication of new electronic devices for application at high frequencies.

Detailed Description of Preferred Embodiments 18

In order to fill a current gap in high frequency tunable dielectric materials, the present invention discloses thick composite films and methodology for manufacturing such tunable films and low dielectric losses. Thick dielectric composite films have several advantages over materials for tunable applications currently in use. These advantages include: i) possibility of compatibilization in the same film of the high Q phase with the high tonality phase, characteristics not present in a single material, ii) possibility of manipulation of the final dielectric characteristics of the film by manipulation of the process variables manufacture and iii) the possibility of integration of several elements of the circuit in the same substrate and iv) miniaturization of the devices.

The composite thick films object of this invention preferably comprise a matrix of (Ba0-Re203-TiC> 2 (where Re = Nd, Sm, La, among others) as BaNd2Ti50i4 (BNT), and a second phase of high dielectric permittivity , in particular from the solid solution family of Bai-xSrxTiO3, for example Bao.sSro.sTiCg. However, other low dielectric loss dielectrics may be partially or fully used in place of Ba0-Re203-TiO2 (Re = Nd, Sm , And the like, such as MgTiCg, Ba2Ti9C> 2o, ZrSsi.2O4, Ba (MgI / 3Ta2 / 3) and the like, and the tunable dielectric permittivity phase may include (BaixxSrx) TiO3, BaTiCp, Pb The preparation of these thick composite films involves the following steps: 1) synthesis of the ceramic matrix powders: the preparation of the composite thick films involves the preparation of ceramic powders first of the matrix composition. For the particular case of BaNd2Ti50i4 powders, BaCC 3, Nd 20s and TiO 2 precursors are mixed in suitable proportions to obtain the subject compound in ball mills with zirconia-based bodies for about 24 hours in an aqueous or alcoholic medium . The resulting mixture is dried and calcined for synthesis of said compound. The calcination temperature is determined by thermogravimetric analysis and the sintering temperature, determined by dilatometric analyzes, is chosen in order to guarantee the maximum densification of the composite film. 2) preparation of stable suspension of the matrix powders for electrophoretic deposition: the preparation of the stabilized suspension can be carried out in different suspending media, such as acetone ((CH3) 2CO,> 99.9%), ethanol (C2H5OH,> gt; 99.9%) of acetic acid (CH 3 COOH,> 99.9%). In the case of acetone I 2 (99.8%, Aldrich) dissolved in iso-propanol (C 3 H 7 OH, &gt; 99.9%) is used as an additive to adjust the value of suspension pH, in this case BNT. The stability of the suspensions is analyzed by UV light transmittance, mean particle size distribution and zeta potential of the suspension. Based on the variation of the zeta potential, the pH of the suspension is regulated in order to obtain optimum homogenization for the suspension, which will guarantee the quality of the final films. The suspensions used have the concentration of 10 g / liter of BNT powders and are sonicated until complete dispersion of the powders. 3) thick-layer electrophoretic deposition of the matrix composition: the substrates are chosen from a group of flexible metals comprising Pt, Ni, Cu among others and a group of ruled oxides comprising Al 2 O 3, among others. The thick layer of the matrix material is deposited by electrophoretic deposition. Under the action of an electric field the charged particles suspended in the suspending medium move towards the opposite charge electrode and are deposited on the substrate forming a continuous layer. The film thickness depends on the suspension concentration, applied voltage and time. In the present conditions, films of 10 to 80 microns thick can be deposited under 40 V at 600 V in 30 s at 10 min. The deposited films are dried at 90 ° C for periods of time up to 24 h. 4) stable sol preparation of the second phase composition: The sol of the phase is prepared using as starting precursors Ba (CH 3 COO) 2 (> 99.9%), Sr (CH 3 COO) 2 V 2 H 20 (> 99.9%) and Ti (OC 4 H 9) 4 (&gt; 99.9%). Glacial acetic acid (CH3COOH) (> 99.9%) and ethylene glycol (HOCH2CH2OH,) (&gt; 99.9%) are used as solvents, and acetylacetone (C5H8O2) (&gt; 99.9%) as Ti alkoxy stabilizer. (CH 3 COO) 2 and Sr (CH 3 COO) 2 · 1 / 2H 2 O with a 5: 5 molar ratio are dissolved in acetic acid under constant stirring at 80øC. Ti (OC4H9) 4 is stabilized with ethylene glycol and acetylacetone and this solution is mixed with the solution of Ba (Ac) 2 / Sr (Ac) 2 with a molar ratio of 1: 1 under constant stirring. After mixing for 2 hours, the concentration of the solution is adjusted to 0.25 mol / l and stirred for an additional 1 hour. (5) spin coating (&quot; spin coating &quot;) of the second stage sol: After drying the films are infiltrated by scattering with the tunable dielectric phase sol. After infiltration the films are dried and pyrolyzed at 350 ° C for 5 minutes on a hot plate. This cycle is repeated up to 10 times. 6) sintering of the composite films, as described below: thick composite films are sintered in air between 1100 and 1300 ° C for different periods of time, depending on the substrate, to densify the composite.

Although thick composite films have already been fabricated for electronic applications using different materials, compositions of the tungsten bronzoid family such as BaNd2Ti50i4 and other low dielectric (high Q) dielectrics have not yet been combined in the form of thick films with compositions, oxides or additives with the tensile permittivity property of the dielectric permittivity through the electric field, to adjust the electronic properties to the pitch / phase shifter of thick films.

Description of Figures

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the invention, the following are attached figures which represent preferred embodiments of the invention which, however, are not intended to limit the subject matter of the present invention. Figure 1 illustrates the X-ray diffractograms of the BNT-BST composite films on Pt substrates and sintered at 1300 ° C / lh. For comparison purposes 22 the X-ray diffraction patterns of the individual members of the solid solution BNT and BST are also represented. The diffraction stripes of JCPDS 33-0166 are indicated at the bottom of the figure. The thickness of the composite films is variable and depends on the processing parameters, thicknesses of about and above 50 microns being most advisable. Figure 2 shows the microstructure of BNT - BST thick composite films on Pt substrates and sintered at 1300 ° C / lh (a) and (b) and also the elemental chemical analysis (c) of strontium by electron diffraction. Figure 3 illustrates the dependence of dielectric permittivity (a) and dielectric loss (b) as a function of the frequency of thick BNT-BST composite films on Pt and sintered at 1300 ° C / lh. The individual electrical response of each member of the solid solution is indicated for comparison purposes.

Composite thick films of BaNd2Ti50i4 with 5 weight percent Bao.sSo.sTiCb exhibit the dielectric constant at 1 MHz of 280, the dielectric loss at 1 MHz of 0.0014, and the tonality of 14 percent at 2 kV / cm. The tunability of these thick films can reach 30 percent depending on the composition of the composite thick film and the applied electric field. Figure 4 shows the relative dielectric permittivity dependence and dielectric loss of the DC field of thick films of (a) BST, (b) BNT-BST and (c) BNT sintered at 1300 ° C / 1. Figure 5 represents the temperature dependence of thick Pt and sintered films at 1300 ° C / lh.

Lisbon, December 11, 2009

Claims (12)

A tunable composite dielectric characterized in that it comprises a tunable dielectric material and comprises a non-tunable dielectric material composed of one or more of: tungsten bronzoid family material, namely BaO-Re203-TiO2, Re = Nd, Sm, La, among others; MgTi03; Ba2 Ti9 O20; Zro.8TiSn0.204; Ba (MgI / 3Ta2 / 3) 03; or the like; or compositions thereof. A tunable composite dielectric according to the preceding claim, characterized in that said non-tunable dielectric material is BaNd2Ti50i4, BNT. A tunable composite dielectric according to any one of the preceding claims characterized in that said tunable dielectric material comprises one or more of: the solid solution of barium titanate and strontium, BaixSrxTi03, BST; BaTi03; Pb (Zr, Ti) 03; or the like; or compositions thereof. A tunable composite dielectric according to the preceding claim, characterized in that said tunable dielectric material is (Bao.s Sr0.5) TiO 3. A tunable composite dielectric according to any one of the preceding claims, characterized in that it comprises 80 to 95% by weight of said low loss non-tunable dielectric material, such as BaO-Re203-TiO2, Re = Nd, Sm, La, among others , and in that it comprises 5 to 20% by weight of at least one additional phase of high tunability, such as solid solutions of barium titanate and strontium. A tunable composite dielectric according to any one of the preceding claims, characterized in that it comprises dielectric and tunable phases with thicknesses of from 5 to 100 microns, preferably from 10 to 80 microns, still more preferably from 50 to 80 microns thick. A tunable composite dielectric according to any one of the preceding claims, characterized in that it additionally comprises a metallic substrate, such as platinum, gold, silver, copper, nickel, among others; or substrate such as alumina, A1203, among others, for depositing said thick layer of low dielectric losses, BNT. An electronic device comprising varactors, tunable filters, coplanar and linear phase displacement devices, and phase array antennas, multilayer thick film capacitors, planar capacitors according to any one of the preceding claims, characterized in that it comprises one or more more tunable dielectric composites as previously described. A method of manufacturing a tunable composite dielectric characterized by combining the electrophoretic deposition process with the sol gel deposition in obtaining an association of a low loss non-tunable dielectric material and a tunable dielectric material, namely the solid solution of 3 barium and strontium titanate, Bai_xSrxTi03, BST, in particular (Bao.s Sro.5) TiC> 3, or compositions thereof. Method for manufacturing a tunable composite dielectric according to the preceding claim, characterized in that it comprises the following steps: a. thick dielectric deposition of dielectric matrix of low dielectric losses not tunable from the family of tungsten bronzoids, namely Ba0-Re203-Ti02, Re = Nd, Sm, La, among others, or compositions thereof; B. infiltration by phase sol gel methodology of tunable characteristics, of said dielectric material tunable in the matrix layer; W. sintering of the composite film for its densification. Method for manufacturing a tunable composite dielectric according to the preceding claim, characterized in that it comprises for the deposition of said thick layer of the low dielectric loss phase matrix BNT: metal substrates, such as platinum, gold, silver, copper, nickel, among others; or non-metallic substrates such as alumina, Al 2 O 3, among others. Process for manufacturing tunable composite dielectric according to the preceding claim, characterized in that it comprises the following steps: a. synthesis of the ceramic powders of the matrix by the preparation of the composite thick films involving the preparation of ceramic powders of the matrix composition, which for the particular case of BaNd2Ti50i4 powders, BaCC ™ 3, Nd2Os and TiO2 precursors are mixed in the 4 proportions suitable for obtaining the compound in question in ball mills with zirconia bodies for about 24 hours in an aqueous or alcoholic medium, the resulting mixture being dried and calcined for synthesis of said compound; B. stable preparation of the matrix powders for electrophoretic deposition by the preparation of the stabilized suspension carried out in different suspending media, such as acetone, (CH 3) 2 CO, &gt; 99.9%, ethanol, C 2 H 5 OH, &gt; 99.9%, and acetic acid CH 3 COOH, &gt; 99.9%, which in the case of acetone I2 99.8%, dissolved in isopropanol, C3 H7 OH, &gt; 99.9%, is used as an additive to adjust the pH value of the suspension, in this case BNT, where the suspensions used have the concentration of 10 g / liter of BNT powders and are sonicated until complete dispersion of the powders; W. electrophoretic deposition of the matrix composition, the substrates being chosen from a group of flexible metals comprising Pt, Ni, Cu among others, and from a group of ruled oxides comprising A1203, among others, being that the thick layer of the matrix material is deposited by electrophoretic deposition which under the action of an electric field the charged particles suspended in the suspending medium move towards the opposite charge electrode and are deposited on the substrate forming a continuous layer, and the film thickness depends on the concentration of the suspension, applied voltage and time, and films of 10 to 80 microns thickness can be deposited under 40 V at 600 V in 30 s at 10 min, the films deposited being dried at 90ø C for periods of time up to 24 h. 5 d. stable sol-composition of the second phase composition, wherein the phase sol is prepared using as starting precursors Ba (CH 3 COO) 2,> 99.9%, Sr (CH 3 COO) 2 → 2H 2,> 99.9%, and Ti (OC 4 H 9) 4,> 99.9%, wherein glacial acetic acid CH 3 COOH,> 99.9%, and ethylene glycol, HOCH 2 CH 2 OH, &gt; 99.9%, are used as solvents, and acetylacetone 05-802, &gt; 99.9%, as stabilizer of alkoxy of Ti, post-Ba (CH 3 COO) 2 and Sr (CH 3 COO) 2 · 1 / 2H 2 0 with a 5: 5 molar ratio dissolved in acetic acid under constant stirring at 80øC, Ti (OC 4 H 9) 4 being stabilized with ethylene glycol and acetylacetone and this solution is mixed with the solution of Ba (Ac) 2 / Sr (Ac) 2 with a molar ratio of 1: 1 under constant stirring, and after mixing for 2 hours, the concentration of the solution is adjusted to 0.25 mol / l and stirred for an additional 1 hour; and. spin coating, spin coating, and after drying the films are infiltrated by scattering with the tunable dielectric phase sol, and after infiltration the films are dried and pyrolyzed at 350 ° C for 5 minutes in a hot dish, this cycle being repeated up to 10 times; f. sintering of the composite films, in air atmosphere, between 1100 and 1300 ° C for different periods of time, depending on the substrate, to densify the composite. Lisbon, December 11, 2009