Magnetoelectric macro fiber composite fabricated using low temperature transient liquid phase bonding

Abstract

A composite material fabricated using a novel process and materials. The piezoelectric and magnetostrictive layers of the composite material are coated, layered, and bonded using a process known as LTTLP bonding. The resulting magnetoelectric composite fibers are bonded to a polyimide film based copper flexible circuit using a room temperature curing epoxy. The sensor that results is an MEMFC that outperforms conventionally fabricated MEMFCs.

Claims

1. A magnetoelectric composite material comprised of: a layer of piezoelectric (PE) material; a layer of magnetostrictive (MS) material; the layer of piezoelectric material bonded to the layer of magnetostrictive material using low temperature transient liquid phase (LTTLP) bonding, forming a composite material; the LTTLP bond comprised of: titanium, gold, and a solder alloy; the titanium used to form an adhesion layer on the PE material and the MS material; the gold used to form a bonding layer on the PE material and the MS material; and the solder alloy used to bond the PE material and MS material together by diffusing into the bonding layers; the composite material divided into multiple fibers: a flexible circuit; the flexible circuit applied to the composite material; an epoxy spin coating applied to the combination of the flexible circuit and composite material; wherein the solder alloy has a melting point at or below a Curie temperature of the PE material and at or below a Curie temperature of the MS material.

2. The composite material of claim 1, further comprising: an interdigitated electrode having a first electrode pattern and a second electrode pattern, the interdigitated electrode bonded to either the PE material or the MS material; whereby deformation of the composite material causes a voltage difference between the first electrode pattern and the second electrode pattern.

3. The composite material of claim 1, wherein the solder alloy the solder alloy is 52% Indium (In) and 48% Tin (Sn), with a eutectic point of 118 C.

4. A method of fabricating a composite material with piezoelectric (PE) and magnetostrictive (MS) layers, the method comprising: creating a PE adhesion layer by coating one side of a piezoelectric material with a layer of a first metal; creating an MS adhesion layer by coating one side of a magnetostrictive material with a layer of the first metal; creating a PE bonding layer by coating the PE adhesion layer with a layer of a second metal; creating a MS bonding layer by coating the MS adhesion layer with a layer of the second metal; creating an PE solder layer by depositing solder alloy on the PE bonding layer; creating a MS solder layer by depositing solder alloy on the MS bonding layer; pressing the PE solder layer and MS solder layer against one-another while heating to a temperature; the temperature no greater than a Curie temperature of the magnetostrictive material; thereby bonding the PE and MS materials to each other, resulting in the composite materials; slicing the composite material into fibers; applying a flexible circuit to the composite material; spin coating the composite material and flexible circuit with epoxy; and vacuum bonding the composite material and flexible circuit.

5. The method of claim 4, further comprising the step of: bonding an interdigitated electrode on the piezoelectric material, the interdigitated electrode having a first electrode pattern and a second electrode pattern.

6. The method of claim 4, wherein: the first metal is titanium; and the second metal is gold.

7. The method of claim 4, wherein: the solder alloy is composed of 52% Indium (In) and 48% Tin (Sn), with eutectic point of 118 C.

8. A composite material fabricated by the process of: coating a piezoelectric (PE) material with one or more layers of metal; coating a magnetostrictive (MS) material with one more layers of metal; creating a first solder layer by depositing solder alloy on the one or more layers of metal of the PE material; creating a second solder layer by depositing solder alloy on the one or more layers of metal of the MS material; pressing the first solder layer and second solder layer together while applying heat, thereby bonding the PE and ME materials to each other, resulting in a magnetoelectric composite materials; slicing the magnetoelectric composite material into fibers; applying a flexible circuit to the magnetoelectric composite material; spin coating the magnetoelectric composite fibers and flexible circuit with epoxy; and vacuum bonding the magnetoelectric composite material and flexible circuit; thereby creating an MEMFC.

9. The composite material fabricated by the process of claim 8, wherein: the one or more layers of metal applied to the PE material is titanium.

10. The composite material fabricated by the process of claim 8, wherein: the one or more layers of metal applied to the PE material is a layer of titanium followed by a layer of gold.

11. The composite material fabricated by the process of claim 8, wherein: the solder alloy has a melting point at or below a Curie temperature of the PE material and at or below a Curie temperature of the MS material.

12. The composite material fabricated by the process of claim 8, further comprising the step of: bonding an interdigitated electrode on the piezoelectric material, the interdigitated electrode having a first electrode pattern and a second electrode pattern.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which:

(2) FIG. 1 illustrates a first embodiment with the PE and MS layers separated by the solder alloy layer.

(3) FIG. 2 illustrates a first embodiment of the electrode layer including the polyimide film.

(4) FIG. 3 illustrates a MEMFC with the electrode layer bonded to the PE and MS layers.

(5) FIG. 4 illustrates an isometric view of the PE and MS layers separated by the solder alloy layer.

(6) FIG. 5 illustrates an isometric view of the PE and MS layers after slicing and filling with epoxy.

(7) FIG. 6 illustrated the PE and MS layers with the electrode layer bonded to the top.

(8) FIG. 7 illustrates a side view of the completed MEMFC.

(9) FIG. 8 is a photograph of an embodiment produced according to the disclosed method.

DETAILED DESCRIPTION

(10) Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures.

(11) Referring to FIG. 1, a first embodiment with the PE and MS layers separated by the solder alloy layer is shown.

(12) Piezoelectric layer 10 is shown atop the magnetostrictive layer 12, separated by the solder alloy 20. Not shown are the adhesion and bonding layers present on the facing surfaces of the piezoelectric layer 10 and magnetostrictive layer 12.

(13) The solder alloy 20 separates the piezoelectric layer 10 and magnetostrictive layer 12. This is a simplification for the purposes of illustration. Once the LTTLP bonding occurs the solder alloy 20 becomes an indistinct layer more properly referred to as a bond line, as is shown in FIG. 8. But for the purposes of discussion the solder alloy 20, or bond line, will be shown as a distinct layer.

(14) Referring to FIG. 2, a first embodiment of the electrode layer including the polyimide film is shown. Electrode film layer 30 is shown, which consists of first interdigitated electrode film pattern 32 and second interdigitated electrode film pattern 34, which are not shown.

(15) Polyimide film 42 is shown reinforcing and separating the electrodes of the electrode film layer 30.

(16) Referring to FIG. 3, a MEMFC with the electrode layer bonded to the PE and MS layers is shown.

(17) The electrode film layer 30 is in electrical contact with the piezoelectric layer 10 and magnetostrictive layer 12 through the solder alloy 20, which after bonding becomes the bond line.

(18) The polyimide film 42 again separates the electrodes 30.

(19) Referring to FIG. 4, an isometric view of the PE and MS layers separated by the solder alloy layer is shown.

(20) Again shown is the piezoelectric layer 10 and magnetostrictive layer 12 separated by the solder alloy 20. But in FIG. 4 the layers 10/12 are shown prior to the step of cutting to create fibers/strands.

(21) Referring to FIG. 5, an isometric view is shown of the PE and ME layers after slicing to create fibers/strands and when filled with epoxy. Epoxy 40 fills the spaces between each fiber/strand of the MEMFC, each fiber composed of a piezoelectric layer 10 and magnetostrictive layer 12 joined by a solder alloy 20, forming a bond line.

(22) While not shown in the figure, during fabrication the MEMFC is stabilized using an underlayer of dicing tape. The dicing tape holds the divided fibers/strands of the composite material in position relative to one-another after slicing, and before the spaces are filled with epoxy 40.

(23) Referring to FIG. 6, the PE and MS layers with the electrode layer bonded to the top is shown.

(24) The fibers formed by the piezoelectric layer 10 and magnetostrictive layer 12 are topped with the electrode film layer 30, shown divided into the two electrodes, the first interdigitated electrode film pattern 32 and the second interdigitated electrode film pattern 34. The patterns 32/34 connect electrically through the piezoelectric layer 10 and magnetostrictive layer 12. Thus, deformation of the piezoelectric layer 10 and magnetostrictive layer 12 creates a voltage across the electrode patterns 32/34, or application of a voltage across the electrode patterns 32/34 results in deformation.

(25) The electrode layer is bonded to the ME composite using epoxy.

(26) Referring to FIG. 7, a side view of the completed MEMFC is shown.

(27) Shown is a slice of the MEMFC illustrating the continuity across a single electrode connecting multiple fibers.

(28) Referring to FIG. 8, a photograph of an embodiment produced according to the disclosed method is shown.

(29) Starting at the top of the figure, polyimide film 42 is shown, with electrode film layer 30 beneath. This is followed by the piezoelectric layer 10 and magnetostrictive layer 12. The solder alloy 20 has dispersed within the adhesion and bonding layers of the piezoelectric layer 10 and magnetostrictive layer 12, thus making the bond indistinct.

(30) The sliced fibers are separated by epoxy 40.

(31) Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result.

(32) It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.