Temperature sensor having a cover layer with aluminum oxide, silicon oxide, yttrium oxide and boron oxide

Abstract

A temperature sensor includes a substrate, a platinum resistor arranged on at least one surface of the substrate, a protective layer covering at least a portion of the platinum resistor and a cover layer covering at least a portion of the protective layer, the cover layer including Al2O3, SiO2 and Y2O3. The cover layer may also include B2O3. A conductive wire may be electrically connected to the platinum resistor. A glass ceramic may be covering at least a portion of the conductive wire, platinum resistor, protective layer and cover layer.

Claims

1. A temperature sensor, comprising: a substrate; a platinum resistor arranged on the substrate; a protective layer covering the platinum resistor; and a cover layer covering the protective layer, the cover layer containing Al.sub.2O.sub.3 and Si.sub.2O, wherein the cover layer also contains Y.sub.2O.sub.3 and B.sub.2O.sub.3: wherein the cover layer contains 30 to 70% by weight of Si.sub.2O; and wherein the cover layer contains 1 to 20% by weight of B.sub.2O.sub.3.

2. The temperature sensor according to claim 1, wherein the cover layer contains at least 5% by weight of Y.sub.2O.sub.3.

3. The temperature sensor according to claim 1, wherein the cover layer contains at least 10% by weight of Y.sub.2O.sub.3.

4. The temperature sensor according to claim 1, wherein the cover layer contains more Si.sub.2O by weight than Al.sub.2O.sub.3.

5. The temperature sensor according to claim 1, wherein the cover layer contains more Al.sub.2O.sub.3 by weight than Y.sub.2O.sub.3.

6. The temperature sensor according to claim 1, wherein the cover layer contains less than 30% by weight of Y.sub.2O.sub.3.

7. The temperature sensor according to claim 1, wherein the cover layer contains less than 20% by weight of Y.sub.2O.sub.3.

8. The temperature sensor according to claim 1, wherein the cover layer contains 15 to 30% by weight of Al.sub.2O.sub.3.

9. The temperature sensor according to claim 1, wherein the cover layer contains 20 to 25% by weight of Al.sub.2O.sub.3.

10. The temperature sensor according to claim 1, wherein the cover layer contains 40 to 60% by weight of Si.sub.2O.

11. The temperature sensor according to claim 1, wherein the cover layer contains 1 to 25% by weight of B.sub.2O.sub.3.

12. The temperature sensor according to claim 1, wherein the cover layer contains less than 20% by weight of components that are not Al.sub.2O.sub.3, Si.sub.2O, Y.sub.2O.sub.3, nor B.sub.2O.sub.3.

13. The temperature sensor according to claim 1, wherein the cover layer contains less than 10% by weight of components that are not Al.sub.2O.sub.3, Si.sub.2O, Y.sub.2O.sub.3, nor B.sub.2O.sub.3.

14. The temperature sensor according to claim 1, wherein the cover layer is a glaze layer.

15. A temperature sensor, comprising, a substrate; a platinum resistor arranged on the substrate; a protective layer covering the platinum resistor; and a cover layer covering the protective layer, the cover layer containing Al.sub.2O.sub.3 and Si.sub.2O, wherein the Si.sub.2O is 30 to 70% by weight, wherein the cover layer also contains Y.sub.2O.sub.3 and contains 1 to 20% by weight of B.sub.2O.sub.3; wherein the cover layer protects the temperature sensor above 1000° C., the temperature sensor configured to measure temperatures up to 1200° C.

16. A temperature sensor, comprising: a substrate; a platinum resistor arranged on at least one surface of the substrate; a protective layer covering at least a portion of the platinum resistor; and a cover layer covering at least a portion of the protective layer, the cover layer comprising Al.sub.2O.sub.3, Si.sub.2O, Y.sub.2O.sub.3 and B.sub.2O.sub.3 wherein the cover layer contains 1 to 20% by weight of B.sub.2O.sub.3; wherein the cover layer contains 30 to 70% by weight of Si.sub.2O; and wherein the cover layer protects the temperature sensor above 1000° C., the temperature sensor configured to measure temperatures up to 1200° C.

17. The temperature sensor of claim 16, including a conductive wire electrically connected to the platinum resistor.

18. The temperature sensor of claim 17, including a glass ceramic covering at least a portion of the conductive wire, platinum resistor, protective layer and cover layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings illustrate the invention. In such drawings:

(2) FIG. 1 shows a schematical cross-section of an embodiment of a temperature sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) An embodiment of a temperature sensor shown in FIG. 1 comprises a substrate 1, for example an alumina substrate. A platinum resistor 2, which may be connected to a wire 3, is arranged on the substrate 1. The platinum resistor 2 is a resistive layer and may be made of any platinum metal or platinum metal based alloy. The platinum resistor 2 is covered by a protective layer 4, for example a ceramic layer. The protective layer 4 can be made of alumina or other ceramic material. A cover layer 5 is arranged on top of the protective layer 4. The cover layer 5 can be covered by an additional layer 6, e.g. a glaze layer. A connection area of the wire 3 and the platinum resistor 2 may be covered by a glass ceramic 7 in order to secure and protect the connection between lead wire 3 and platinum resistor 2.

(4) The cover layer 5 may be a glass ceramic or glaze layer. The cover layer 5 contains SiO2, Al2O3, and Y2O3. For example, the cover layer 5 may contain 40 to 60% by weight of SiO2, 20 to 25% by weight of Al2O3, and 10 to 19% by weight of Y2O3. The cover layer 5 may also contain up to 20% by weight of B2O3, e.g. 5% to 20% by weight of B2O3, and up to 20% by weight of other components, especially other oxides. Such a temperature sensor can be used for measuring temperatures up to 1200° C.

(5) The protective layer 4 can be applied by a vapour deposition method or as a green foil that is later fired. The cover layer 5 can be produced by a screen-printing method, for example. In the embodiment of FIG. 1, which is not to scale, the cover layer 5 is thicker than the protective layer 4. If an additional layer 6 is placed on top of the cover layer 5, this additional layer 6 may be even thicker than the cover layer 5. Any additional layer 6 may be applied as a paste, e.g. by printing and later fired. The thickness of the various layers may not be critical for the functioning of the temperature sensor and may be chosen for manufacturing considerations.

REFERENCE NUMERALS

(6) 1 Substrate

(7) 2 Platinum resistor

(8) 3 Wire

(9) 4 Protective layer

(10) 5 Cover layer

(11) 6 Additional layer

(12) 7 Glass ceramic

(13) Although several embodiments have been described in detail for purposes of illustration, various modifications may be made to each without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.