# US 10,312,429 B2 · Magnetoelectric macro fiber composite fabricated using low temperature transient liquid phase bonding

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- Number: US 10,312,429 B2
- Document ID: US10312429B2
- Status: Granted
- Kind: B2
- Application number: 15/222,070
- Filed: 2016-07-28
- Published: 2018-02-01
- Granted: 2019-06-04
- Earliest claimed: 2016-07-28
- Assignees: Eyob LLC
- Applicants: Eyob LLC
- Inventors: Ron Varghese
- Web page: https://patentgrep.com/patent/US10312429B2

## CPC

- H10N 35/85: Magnetostrictive active materials
- B23K 1/0016: {Soldering of electronic components}
- G01R 33/18: Measuring magnetostrictive properties
- H10N 30/073: by fusion of metals or by adhesives
- B23K 2101/36: Electric or electronic devices
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## 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

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 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.

### Claim 5 (depends on 4)

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.

### Claim 6 (depends on 4)

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

### Claim 7 (depends on 4)

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.

### Claim 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.

### Claim 9 (depends on 8)

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.

### Claim 10 (depends on 8)

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.

### Claim 11 (depends on 8)

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.

### Claim 12 (depends on 8)

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.