METHOD OF FORMING PIEZO DRIVER ELECTRODES

Abstract

A method for forming piezoelectric transducers for inkjet printheads includes: forming at least one piezoelectric layer on a substrate; forming at least one electrode pattern by depositing a conductive material on an exposed surface of the at least one piezoelectric layer; and forming a plurality of individual piezoelectric elements from the at least one piezoelectric layer before or after the forming of the at least one electrode pattern.

Claims

1. A method for forming piezoelectric transducers for inkjet printheads, comprising: forming at least one piezoelectric layer on a substrate; forming at least one electrode pattern by depositing a conductive material on an exposed surface of the at least one piezoelectric layer; and forming a plurality of individual piezoelectric elements from the at least one piezoelectric layer before or after the forming of the at least one electrode pattern.

2. The method of claim 1, wherein the depositing comprises jetting the conductive material from an inkjet printhead and in a predetermined pattern.

3. The method of claim 1, further comprising placing a pattern-mask over the at least one piezoelectric layer and wherein the conductive material passes through openings of the pattern-mask and forms on the exposed surface.

4. The method of claim 1, further comprising dicing the at least one piezoelectric layer to form the plurality of individual piezoelectric elements.

5. The method of claim 4, wherein the dicing of the at least one piezoelectric layer is performed before the depositing of the conductive material.

6. The method of claim 4, wherein the dicing of the at least one piezoelectric layer is performed after the depositing of the conductive material.

7. The method of claim 6, wherein a pattern-mask is used for preventing the depositing of conductive material on at least one hold-back zone of the at least one piezoelectric layer.

8. The method of claim 7, wherein a dicing blade used for performing the dicing does not contact the deposited conductive material when forming the plurality of individual piezoelectric elements.

9. The method of claim 4, wherein the at least one electrode pattern extends from a first edge to a second, opposing edge of a corresponding at least one of the plurality of individual piezoelectric elements.

10. The method of claim 1, wherein the depositing of the conductive material comprises covering less than all of the exposed surface.

11. The method of claim 1, wherein the conductive material is a printhead-jettable conductive material.

12. The method of claim 1, wherein the conductive material comprises a conductive ink.

13. The method of claim 1, wherein the conductive material comprises a solution processable or printable silver-base conductive material.

14. The method of claim 1, wherein the conductive material comprises a silver nanoparticle ink or a silver nanoparticle paste, wherein silver nanoparticles of the silver nanoparticle ink or of the silver nanoparticle paste have a diameter of about 1 nm to about 50 nm.

15. The method of claim 1, further comprising forming at least one of a second electrode pattern by depositing a second conductive material on an exposed surface of the substrate, wherein the at least one of the second electrode pattern is disposed between the at least one piezoelectric layer and the substrate, and wherein the substrate comprises a body plate cavity having a diaphragm and an adhesive that bonds to the at least one second electrode pattern.

16. An inkjet printhead, comprising: at least one inkjet ejector, wherein the inkjet ejector comprises a body coupled to an ink manifold and an ink drop-forming nozzle; a continuous conduit extending between the manifold and the nozzle, the conduit comprising a pressure chamber bounded by a flexible diaphragm; and a piezoelectric transducer secured to the diaphragm and comprising a first electrode, a second electrode and at least one piezoelectric layer disposed between the first and second electrodes, wherein the piezoelectric transducer comprises one of a plurality of individual piezoelectric elements formed by a method comprising: forming at least one piezoelectric layer on a substrate, and forming a plurality of patterned electrode by depositing a conductive material on an exposed surface of the at least one piezoelectric layer, wherein the first electrode comprises one of the plurality of patterned electrodes, and wherein the second electrode comprises the same or a different material as the first electrode.

17. The inkjet printhead of claim 16, wherein the depositing comprises jetting the conductive material from an inkjet printhead and in a predetermined pattern.

18. The inkjet printhead of claim 16, further comprising placing a pattern-mask over the stack and wherein the conductive material passes through openings of the pattern-mask to reach the exposed surface.

19. The inkjet printhead of claim 16, wherein the first electrode, the second electrode or both comprise silver nanoparticles.

20. The inkjet printhead of claim 16, wherein the piezoelectric transducer comprises one of a plurality of individual piezoelectric elements formed by a method comprising dicing the at least one piezoelectric layer to form the plurality of individual piezoelectric elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1A is a schematic side-cross-sectional view of a prior art embodiment of an inkjet.

[0024] FIG. 1B is a schematic view of the prior art embodiment of the inkjet of FIG. 1A.

[0025] FIGS. 2A-2D are flow charts depicting methods of forming piezoelectric transducers according to various embodiments.

[0026] FIGS. 3A-3D illustrate cross-sectional views at stages of production in a method for fabricating a piezoelectric transducer according to an embodiment such as the method described in the flowchart of FIG. 2A.

[0027] FIGS. 4A-4C illustrate cross-sectional views at stages of production in a method for fabricating a piezoelectric transducer according to an embodiment such as the method described in the flowchart of FIG. 2B.

[0028] FIGS. 5A-5D illustrate cross-sectional views at stages of production in a method for fabricating a piezoelectric transducer according to an embodiment such as the method described in the flowchart of FIG. 2C.

[0029] FIGS. 6A-6C illustrate cross-sectional views at stages of production in a method for fabricating a piezoelectric transducer according to an embodiment such as the method described in the flowchart of FIG. 2D.

[0030] FIGS. 7A-7D illustrate cross-sectional views at stages of production in a method for fabricating a piezoelectric transducer according to an embodiment.

[0031] FIGS. 8A-8E illustrate cross-sectional views at stages of production in a method for fabricating a piezoelectric transducer according to an embodiment.

DESCRIPTION OF THE EMBODIMENTS

[0032] Reference will now be made in detail to the present embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0033] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the embodiments are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less that 10” can assume negative values, e.g. −1, −2, −3, −10, −20, −30, etc.

[0034] The following embodiments are described for illustrative purposes only with reference to the figures. Those of skill in the art will appreciate that the following description is exemplary in nature, and that various modifications to the parameters set forth herein could be made without departing from the scope of the present embodiments. It is intended that the specification and examples be considered as examples only. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0035] Embodiments disclosed herein are directed to, but not limited to, forming piezoelectric transducers for use in inkjet printheads and in particular, forming electrodes of the transducers by depositing conductive material in a predetermined pattern. In an example, the methods described here can provide for an inkjet printhead, such having features depicted in FIGS. 1A-1B but having at least one piezoelectric transducer disposed therein formed according to a method described herein.

[0036] Embodiments of the present teachings can include methods for forming a piezoelectric transducer for use with an inkjet ejector of an inkjet printhead. FIGS. 2A-2D are flow charts that illustrate methods 300, 400, 500 and 600 of forming piezoelectric transducers according to various embodiments such as those illustrated as various stages of fabrication in FIGS. 3A-3D, FIGS. 4A-4C, FIGS. 5A-5D and FIGS. 6A-6C, respectively. In each method, a conductive material, such as a conductive ink or other material as described below, is used for forming the piezo electrode. In some embodiments, such as methods 300 and 400 and depicted as various stages of fabrication at FIGS. 3A-3D and FIGS. 4A-4C, respectively, the conductive material is deposited through openings of a pattern-mask. In some embodiments, such as methods 500 and 600 and depicted as various stages of fabrication at FIGS. 5A-5D and FIGS. 6A-6C, the conductive material is deposited using a printhead capable of jetting conductive inks. In any of the embodiments, a print pattern is achieved such that conductive material is deposited at preselected locations and forms patterned electrodes of a piezo actuator/transducer.

[0037] In some embodiments, such as methods 300 and 500 which may be depicted as various stages of fabrication at FIGS. 3A-3D and FIGS. 5A-5D, the conductive material is deposited onto individual piezoelectric elements formed from a piezoelectric slab which may be one or more of a piezoelectric layer. The conductive material may be deposited either before or after forming individual piezoelectric elements (i.e., individual actuators), via, for example, dicing the piezoelectric slab. This allows for forming the top electrode on either diced or thick-film piezoelectric elements. In some embodiments, such as methods 400 and 600, which may be depicted as various stages of fabrication at FIGS. 4A-4C and FIGS. 6A-6C, the conductive material may be deposited either before or after forming the individual piezoelectric elements, that is, prior to or after dicing the piezoelectric slab into individual actuators. A hold back zone may be preselected at designated locations where conductive material is not to be deposited. This avoids the possibility of smearing electrode material into unintended electrical paths (e.g., actuator to actuator, actuator to ground, etc.). While not limited to any particular method or embodiment, by forming piezo electrodes from conductive inks that are deposited according to predetermined patterns, electrode deposition can be performed downstream in the build process.

[0038] In forming a piezoelectric transducer for inkjet printheads according to an embodiment, a method 300 is illustrated as a flowchart in FIG. 2A and as various stages of fabrication in FIGS. 3A-3D. The method 300 includes forming at least one piezoelectric layer on a substrate, which may be a transfer carrier that may include an adhesive layer or may be a printhead diaphragm; dicing the stack (if necessary) to form a plurality of individual piezoelectric elements; and forming at least one electrode pattern, for example, a plurality of patterned electrodes, by depositing a conductive material on an exposed surface of the at least one piezoelectric layer. Further, a pattern-mask may be placed over the substrate such that at least one electrode pattern is formed by depositing the conductive material through openings between portions of the pattern-mask and onto an exposed surface of the at least one piezoelectric layer. The pattern-mask can overlap the underlying piezoelectric layer in order to form a ‘hold-back’ zone that prevents contact of the dicing blade with the deposited electrode material

[0039] FIG. 3A-3D illustrate cross-sectional “in-process” views of various stages of fabrication based on method 300. At FIG. 3A, at least one piezoelectric layer 20 is formed on a substrate 22. The substrate may be a transfer carrier or a printhead diaphragm. The at least one piezoelectric layer may be bonded to the substrate via an adhesive 24. In one embodiment, a plurality of individual piezoelectric elements 20′ are formed from the at least one piezoelectric element layer 20, for example, via dicing the piezoelectric layer 20. Accordingly the structure of FIG. 3B may be attained after forming the FIG. 3A structure. Alternatively, the step in FIG. 3A may be omitted and the plurality of individual piezoelectric elements 20′ shown in FIG. 3B may instead be formed directly by providing at least one piezoelectric layer in a predetermined pattern.

[0040] After forming the individual piezoelectric elements 20′, at least one electrode pattern 34 may be formed on exposed surfaces of the at least one piezoelectric material. For example, as shown in FIG. 3C, a quantity of conductive material 33 is deposited on a top surface of each individual piezoelectric element 20′ to form electrode pattern 34 as shown in FIG. 3D. That is, the conductive material 33 may be deposited in a pre-determined layout, for example, the predetermined pattern defined by openings between portions of a pattern mask 30. It is noted that pattern-mask 30 may block conductive material from being formed in a hold-back zone 35 that may run the periphery of one or more of the plurality of piezoelectric element 20′. The hold back zone 35 extends across a hold-back distance (i.e., the distance defined by the horizontal arrows at 37 in FIG. 3D) which may provide for an additional buffer to prevent shorting between electrodes.

[0041] In forming a piezoelectric transducer for inkjet printheads according to another embodiment, a method 400 is illustrated as a flowchart in FIG. 2B and as various stages of fabrication in FIGS. 4A-4C. The method 400 includes forming a at least one piezoelectric layer on a substrate, which may be a transfer carrier that may include an adhesive layer or may be a printhead diaphragm; forming at least one electrode pattern, for example, a plurality of patterned electrodes; and forming a plurality of individual piezoelectric elements. The plurality of patterned electrodes may be formed by depositing a conductive material on an exposed surface of the at least one piezoelectric layer. Further, a pattern-mask may be placed over the substrate such that at least one electrode pattern is formed by depositing the conductive material through openings between portions of the pattern-mask and onto the exposed surface of the at least one piezoelectric layer. The pattern-mask can overlap the underlying piezoelectric stack in order to form a ‘hold-back’ zone that prevents shorting between electrodes. The forming of the plurality of individual piezoelectric elements may be performed by dicing the at least one piezoelectric layer, or by forming the at least one piezoelectric layer as a pattern of individual elements.

[0042] FIG. 4A-4C illustrate cross-sectional “in-process” views of various stages of fabrication based on method 400 of FIG. 2B. At FIG. 4A, at least one piezoelectric layer 20 is formed on a substrate 22. The substrate may be a transfer carrier or a printhead diaphragm. The at least one piezoelectric layer may be bonded to the substrate via an adhesive 24. After forming the FIG. 4A structure, a pattern mask 30 is placed over the piezoelectric element layer 20 and conductive material 30 is deposited 31 so as to form a pattern of top electrodes 34 on the exposed surfaces of piezoelectric element layer 20. For example, as shown in FIG. 4B-4C, a quantity of conductive material 33 is deposited on a top surface of piezoelectric element layer 20 and forms electrode pattern 34, which may be used as the top electrode of a transducer in a printhead. That is, as shown in FIG. 4B, the conductive material 33 may be deposited in a pre-determined layout, for example, the predetermined pattern defined by openings between portions of a pattern mask 30, to form the electrodes. The piezoelectric element layer 20 may be diced to form a plurality of individual piezoelectric elements 20′ as depicted in FIG. 4C. It is noted that pattern-mask 30 may block conductive material from being formed in a hold-back zone 35 that may run the periphery of one or more of the plurality of piezoelectric element 20′. The hold back zone 35 extends across a hold-back distance (i.e., the distance defined by the horizontal arrows at 37 in FIG. 4C) which provides an additional buffer to prevent shorting between electrodes.

[0043] Accordingly, in some embodiments, such as methods 300 and 400 which are depicted as various stages of fabrication in FIGS. 3A-3D and 4A-4C, respectively, a patterned mask 30 can be used in conjunction with the depositing 31 of the conductive material 33 to provide at least one of an electrode pattern 34.

[0044] In some embodiments, such as methods 500 and 600 which are depicted as various stages of fabrication in FIGS. 5A-5D and 6A-6C, respectively, a patterned mask may not be required for depositing of the conductive material. For example, forming of the electrodes may be performed by depositing conductive material via a printhead which may jet droplets of jettable conductive material according to predetermined pattern defined by, for example, printing software.

[0045] For example, FIGS. 5A-5D illustrate cross-sectional “in-process” views of various stages of fabrication based on method 500 of FIG. 2C. At FIG. 5A, The method 500 includes forming a at least one piezoelectric layer on a substrate, which may be a transfer carrier that may include an adhesive layer or may be a printhead diaphragm; forming a plurality of individual piezoelectric elements; and forming a plurality of electrodes by jetting droplets of conductive material onto a surface of each of the individual piezoelectric elements. The forming of the plurality of individual piezoelectric elements may be performed by dicing the at least one piezoelectric layer, or by forming the at least one piezoelectric layer as a pattern of individual elements. The plurality of electrodes may be formed in a predetermined patterned and areas on which no conductive material may form a ‘hold-back’ zone that prevents shorting between electrodes.

[0046] FIG. 5A-5D illustrate cross-sectional “in-process” views of various stages of fabrication based on method 500. At FIG. 5A, at least one piezoelectric layer 20 is formed on a substrate 22. The substrate may be a transfer carrier or a printhead diaphragm. The at least one piezoelectric layer may be bonded to the substrate via an adhesive 24. In one embodiment, a plurality of individual piezoelectric elements 20′ are formed from the at least one piezoelectric element layer 20, for example, via dicing the piezoelectric layer 20. Accordingly the structure of FIG. 5B may be attained after forming the FIG. 5A structure. Alternatively, the step in FIG. 5A may be omitted and the plurality of individual piezoelectric elements 20′ shown in FIG. 5B may instead be formed directly by providing at least one piezoelectric layer in a predetermined pattern of the individual piezoelectric elements.

[0047] After forming the individual piezoelectric elements 20′, at least one electrode pattern 34 may be formed on exposed surfaces of the at least one piezoelectric material. For example, as shown in FIG. 5C, a quantity of conductive material 33 is deposited on a top surface of each piezoelectric element 20′ and forms at least one electrode pattern 34 as shown in FIG. 5D. That is, the conductive material 33 may be deposited in a pre-determined layout, for example, as droplets jetted from an inkjet printhead (not shown).

[0048] FIGS. 6A-6C illustrate cross-sectional “in-process” views of various stages of fabrication based on method 600 of FIG. 2D. The method 600 includes forming a at least one piezoelectric layer on a substrate, which may be a transfer carrier that may include an adhesive layer or may be a printhead diaphragm portion of an inkjet printhead; forming at least one electrode pattern, for example, a plurality of patterned electrodes; and forming a plurality of individual piezoelectric elements. The plurality of patterned electrodes may be formed by depositing a conductive material on an exposed surface of the at least one piezoelectric layer, for example, by jetting droplets of conductive material onto a surface of the individual piezoelectric elements in a predetermined pattern. Surface portions on which conductive material is not deposited may form a ‘hold-back’ zone that prevents shorting between electrodes. The forming of the plurality of individual piezoelectric elements may be performed by dicing the at least one piezoelectric layer, or by forming the at least one piezoelectric layer as a pattern of individual elements.

[0049] At FIG. 6A, at least one piezoelectric layer 20 is formed on a substrate 22. The substrate may be a transfer carrier or a printhead diaphragm. The at least one piezoelectric layer may be bonded to the substrate via an adhesive 24. After forming the FIG. 6A structure, conductive material 33 is deposited so as to form at least one electrode pattern 34 on the exposed surfaces of piezoelectric element layer 20. For example, as shown in FIG. 6B-6C, a quantity of conductive material 33 is deposited on a top surface of piezoelectric element layer 20 to form the at least one electrode pattern 34 which may be used as the top electrode of a transducer in an inkjet printhead. That is, as shown in FIG. 6B, the conductive material 33 may be deposited in a pre-determined layout, for example, the predetermined pattern defined by jetting droplets of conductive material from a piezoelectric inkjet printhead. After forming the at least one electrode pattern 34, the piezoelectric element layer 20 may be diced to form a plurality of individual piezoelectric elements 20′ as depicted in FIG. 6C. It is noted that the printhead may deposit conductive material in a pattern such that areas where conductive material is not deposit form a hold-back zone 35 that may that prevents shorting of electrodes between the individual piezoelectric element 20′. That is, the conductive material 33 may be deposited to cover less than all of the exposed surface of the individual piezoelectric elements to form a hold-back zone defined by the horizontal arrows at 37 in FIG. 6C.

[0050] In the case wherein the substrate 22 is a transfer substrate, any of the resulting structures of FIGS. 3D, 4C, 5D or 6C may be further processed in order to add a bottom electrode on an opposing side of at least one piezoelectric layer to the electrode pattern 34 as illustrated in FIGS. 7A-7C. For example, a structure comprising the individual piezoelectric elements 20′ with electrode pattern 34 formed thereon may be transported on substrate 22 (e.g., a carrier substrate with the individual piezoelectric elements attached thereto by adhesive layer 24) and flip bonded via a second adhesive layer 74 onto a second substrate 72, such as the plurality of top electrodes 34 contacts the adhesive layer 74. The substrate 22 and adhesive 24 may be removed, thereby exposing a released surface of the piezoelectric elements 20′ to the patterned electrode 34. A plurality of electrodes 36 can be deposited on the released surfaces of the piezoelectric elements 20′ via similar methods as for electrodes 34 as described in methods 300 or 500 above. While the methods 300, 400, 500 and 600 and corresponding illustrations in FIGS. 3A-3D, 4A-4C, 5A-5D and 6A-6C, respectively, depict the at least one piezoelectric layer as being formed into individual piezoelectric elements, the invention is not so limited. For example, electrode patterns 34 may be formed on at least one continuous piezoelectric layer that is not diced into or formed as a pattern of individual piezoelectric elements. Accordingly, the addition of opposing electrodes, such as depicted in steps in FIGS. 7A-7D may be performed by transferring at least one continuous layer piezoelectric layer with at least one electrode pattern 34 formed thereon from a transfer substrate onto another substrate such as a component of an inkjet printhead stack, for example, a diaphragm.

[0051] In an alternative embodiment, at least one transducer may be formed directly on components of a piezoelectric ink jet, such as on a body plate having a diaphragm formed thereon. At least one piezoelectric layer can be formed on a diaphragm as individual piezoelectric elements or as a continuous piezoelectric layer that is then diced to form the individual piezoelectric elements, for example, by dicing directly on a diaphragm of a print head, rather than on a transfer substrate, as described in U.S. Pat. No. 9,139,004, the contents of which are hereby incorporated by reference herein in its entirety.

[0052] Accordingly, in a method illustrated in the cross-sectional views shown in FIG. 8A-8E, a conductive material 33 is deposited 31 on a substrate comprising a diaphragm 72 of a body plate so as to form at least one patterned electrode 34 (with an step illustrated in FIG. 8B to at least partially cure or dry the conductive material). At least one piezoelectric layer 20 may then be formed on the at least one patterned electrode 34 as shown in FIG. 8C. Conductive material 38 may be deposited 32 on the piezoelectric layer 20 as shown in FIG. 8D so as to form at least one electrode pattern 36. The method continues by forming a plurality of individual piezoelectric elements 20′ from the at least one piezoelectric layer 20. The plurality of individual piezoelectric elements 20′ may be formed by dicing. Accordingly, in order to avoid, minimize or eliminate problems associated with shorting due to blank deposition processes, portions of the piezoelectric layer on which the conductive material 33 is not deposited may define a hold back zone 37. It is noted that although FIGS. 8A-8E show a plurality of individual piezoelectric elements 20′ being formed from a slab comprising at least one semiconductor layer after depositing conductive material 38, the embodiments are not so limited. For example, the at least one piezoelectric layer could be diced after being formed on electrodes 34 but before depositing of the conductive material 38 (i.e., the dicing would be performed between FIGS. 8C-8D) instead of at FIG. 8E as shown.

[0053] The dicing of the various embodiments can be performed using mechanical techniques such as with a saw such as a wafer dicing saw, using a dry etching process, using a laser ablation process, etc. To ensure complete separation of each adjacent piezoelectric element 20′, the dicing process can terminate after removing a portion of the adhesive 24.

[0054] The at least one piezoelectric layer 20 of the embodiments can include multiple layers of the same or different piezoelectric materials, including ceramic piezoelectric elements such as soft PZT (lead zirconate titanate) and hard PZT, or other functional ceramic materials, such as antiferroelectric materials, electrostrictive materials, and magnetostrictive materials. The composition of the piezoelectric ceramic elements can also vary, including doped or undoped, e.g., lead zirconate titanate (PZT), lead titanate, lead zirconate, lead magnesium titanate and its solid solutions with lead titanate, lithium niobate, and lithium tantanate, or any lead-free piezoelectric material. The piezo element layer 20 can have a thickness in the range of from about 0.010 mm to about 0.150 mm, for example, from about 0.010 mm to about 0.03 mm to function as an inner dielectric of, for example, a transducer.

[0055] The conductive material of the embodiments shown as the conductive material 33 or the conductive material 38 as used for forming electrodes, such as electrode 34 or electrode 36 as described above, can be a conductive ink, a conductive epoxy, a conductive paste, or any conductive material that can be deposited using an inkjet printhead. The conductive material can be a solution processable or printable silver-base conducting material. In an example, the conductive material 33 and the conductive material 38 may comprise the same material. Alternatively, the conductive material 33 and the conductive material 38 may comprise different materials. In an example, the conductive material 33, the conductive material 36, or both may be a silver nanoparticle ink or a silver nanoparticle paste. The silver nanoparticle ink may comprise a composition that includes silver nanoparticles, a hydrocarbon solvent, and an alcohol co-solvent, with the silver nanoparticles being present in an amount of at least 35 weight percent of the ink composition; and wherein the weight ratio of hydrocarbon solvent to alcohol co-solvent is from about 2:1 to about 1:1. The silver nanoparticle ink composition may have a viscosity of from about 2 to about 15 centipoise, and/or a surface tension of from about 22 to about 35 millinewtons/meter. In embodiments, the silver nanoparticles have a particle size of from about 0.5 nm to about 1000 nm, from about 1 nm to about 500 nm, from about 1 nm to about 100 nm, and particularly from about 1 nm to about 20 nm. The particle size is defined herein as the average diameter of the silver nanoparticles, as determined by TEM (transmission electron microscopy). The silver nanoparticles can have a particle size from about 1 nm to about 50 nm. They can also have a low polarity surface. The hydrocarbon solvent may be an aliphatic hydrocarbon having at least 5 carbon atoms to about 20 carbon atoms, such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, dodecene, tetradecene, hexadecene, heptadecene, octadecene, terpinenes, isoparaffinic solvents, and their isomers. Alternatively, the hydrocarbon solvent can be an aromatic hydrocarbon having from about 7 carbon atoms to about 18 carbon atoms, such as toluene, xylene, ethyltoluene, mesitylene, trimethylbenzene, diethylbenzene, tetrahydronaphthalene, and ethylbenzene. The alcohol co-solvent has at least 6 carbon atoms and can be, for example, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tetradecanol, and hexadecanol; a diol such as hexanediol, heptanediol, octanediol, nonanediol, and decanediol; an alcohol comprising an unsaturated double bond, such as farnesol, dedecadienol, linalool, geraniol, nerol, heptadienol, tetradecenol, hexadeceneol, phytol, oleyl alchohol, dedecenol, decenol, undecylenyl alcohol, nonenol, citronellol, octenol, and heptenol; a cycloaliphatic alcohol with or without an unsaturated double bond, such as methylcyclohexanol, menthol, dimethylcyclohexanol, methylcyclohexenol, terpineol, dihydrocarveol, isopulegol, trimethylcyclohexenol; and the like. In particular, the alcohol co-solvent may be a terpineol solvent comprising a majority of alpha-terpineol by weight.

[0056] The conductive material 33 can be deposited on the piezoelectric element by any suitable method such as by screen printing, drop application, spraying, or ink jetting, rather than via sputtering or vapor depositing. In some embodiments, a patterned mask (not depicted) can be used in conjunction with the depositing method the conductive material 33 to provide patterned top electrode 34.

[0057] While embodiments have been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of an embodiment may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. For example, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

[0058] Further, the term “at least one of” is used to mean one or more of the listed items may be selected. Further, in the discussion and claims herein, the term “on” used with respect to two materials, one “on” the other, means at least some contact between the materials, while “over” means the materials are in proximity, but possibly with one or more additional intervening materials such that contact is possible but not required. Neither “on” nor “over” implies any directionality as used herein.

[0059] Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” As used herein, the phrase “one or more of”, for example, A, B, and C means any of the following: either A, B, or C alone; or combinations of two, such as A and B, B and C, and A and C; or combinations of three A, B and C.

[0060] Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the embodiments being indicated by the following claims.