# US 10,371,581 B2 · Alumina diffusion barrier for sensing elements

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- Number: US 10,371,581 B2
- Document ID: US10371581B2
- Status: Granted
- Kind: B2
- Application number: 15/612,583
- Filed: 2017-06-02
- Published: 2018-12-06
- Granted: 2019-08-06
- Earliest claimed: 2017-06-02
- Assignees: Sensata Technologies, Inc.
- Applicants: Sensata Technologies, Inc.
- Inventors: Petar Mitsev; Radostina H. Tsoneva; Nikolay K. Nikolov; Benny Van Daele; Peter Tilmans; Christiaan Baerts
- Web page: https://patentgrep.com/patent/US10371581B2

## CPC

- G01K 1/10: for preventing chemical attack
- C23C 14/081: {of aluminium, magnesium or beryllium}
- C23C 14/083: {of refractory metals or yttrium}
- C23C 14/221: {Ion beam deposition (C23C14/46, C23C14/48 take precedence)}
- C23C 16/483: {using coherent light, UV to IR, e.g. lasers}
- G01K 1/12: for preventing damage due to heat overloading
- G01K 7/16: using resistive elements
- G01K 7/18: the element being a linear resistance, e.g. platinum resistance thermometer (G01K7/26 takes precedence)
- G01K 2205/04: for measuring exhaust gas temperature
- G01M 15/102: {by monitoring exhaust gases}
- G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR

## Abstract

A sensing element for a temperature sensor including a base with a platinum meander applied thereto. An alumina diffusion barrier (ADB) covers the meander to provide protection against contamination and structural stabilization, wherein the alumina diffusion barrier is a contiguous polycrystalline layer fabricated from alumina and approximately 1% by weight of a rutile additive to be substantially devoid of network porosity. The contiguous polycrystalline layer includes grains with a typical grain size being in a range of 0.5-3 μm. A method for fabricating an alumina diffusion barrier includes the steps of: combining a nano-alumina and nano-rutile powder to create a formulation; applying the formulation to the platinum meander to form a layer; and sintering the layer to create a contiguous polycrystalline layer covering the platinum meander.

## Claims

### Claim 1

A sensing element for a temperature sensor comprising:
a substrate;
a platinum trace or meander applied to the substrate;
lead wires with chip pads electrically connected to the Pt meander;
an alumina diffusion barrier (ADB) covering the Pt meander to provide protection against contamination and structural stabilization, wherein the alumina diffusion barrier is a contiguous polycrystalline layer fabricated from alumina and approximately 1% by weight of a rutile additive to be substantially devoid of network porosity.

### Claim 2 (depends on 1)

A sensing element as recited in claim 1, further comprising:
a glass layer applied onto the ADB;
a second alumina diffusion barrier applied to the glass layer;
a second glass layer applied to the second alumina diffusion barrier;
a cover plate applied to the second glass layer;
fixing glass applied to the cover plate; and
a case enclosing the base, the platinum trace, the lead wires, the glass layers, the alumina diffusion barriers, the cover plate, and the fixing glass.

### Claim 3 (depends on 1)

A sensing element as recited in claim 1, wherein the rutile or anatase additive is a highly reactive form of nano-TiO2.

### Claim 4

A method for fabricating an alumina diffusion barrier for a temperature sensing element having a platinum meander on a substrate, the method comprising the steps of:
combining a nano-alumina and nano-rutile powder to create a formulation;
applying the formulation to the platinum meander to form a layer; and
sintering the layer to create a contiguous polycrystalline layer covering the platinum meander on the substrate.

### Claim 5 (depends on 4)

A method as recited in claim 4, wherein the nano-alumina powder and nano-rutile substantially consist of particles typically less than 150 nm in size.

### Claim 6 (depends on 4)

A method as recited in claim 4, further comprising the step of combining at least one of a sintering promoter, minor fritted glass, and magnesium oxide (MgO) with the formulation.

### Claim 7 (depends on 4)

A method as recited in claim 4, wherein a ratio of rutile to magnesium oxide is 2:1.

### Claim 8 (depends on 4)

A method as recited in claim 4, wherein the formulation is prepared by a high shear rate planetary ball mill process.

### Claim 9 (depends on 4)

A method as recited in claim 4, wherein the formulation is applied using a deposition process.

### Claim 10 (depends on 4)

A method as recited in claim 4, wherein the layer is approximately 2 μm thick.

### Claim 11 (depends on 4)

A method as recited in claim 4, wherein the sintering is between 1250-1350° C.

### Claim 12 (depends on 4)

A method as recited in claim 4, wherein the substrate is selected from the group consisting of alumina (Al2O3) and magnesium titanite (MgTiO3).

### Claim 13

A diffusion barrier for a sensing element having a platinum meander, the diffusion barrier consisting of:
a contiguous polycrystalline layer fabricated from alumina and approximately 1% by weight of a rutile additive to be substantially devoid of network porosity.

### Claim 14 (depends on 13)

A diffusion barrier as recited in claim 13, wherein the contiguous polycrystalline layer includes grains with a typical grain size being in a range of 0.5-3 μm.

### Claim 15 (depends on 13)

A diffusion barrier as recited in claim 13, wherein the contiguous polycrystalline layer is at least 2 μm thick.