Pressure transducer

• US 20040255683A1
• Filed: 06/19/2003
• Published: 12/23/2004
• Est. Priority Date: 06/19/2003
• Status: Active Grant

• Current Assignee: Dynisco Instruments S.a.r.l. (Roper Technologies, Inc.)
• Original Assignee: Dynisco Instruments S.a.r.l. (Roper Technologies, Inc.)
• Inventors: Barron, Leo
• Granted Patent: US 6,923,068 B2
• Time in Patent Office: Days
• US Class Current: 73/719
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 9/0052 of piezoresistive elements circuits therefor G01L9/06

Abstract

One aspect is a pressure transducer package comprising a housing, a diaphragm, a support disposed in the housing and a sensing element disposed in the housing between the diaphragm and the support so that the pressure from the environment acts on the diaphragm to compress the sensing element. The sensing element comprises at least one substrate having a coefficient of thermal expansion greater than 4 ppm/k. In another aspect, the sensing element comprises at least one substrate formed of a first material and an epitaxial layer of a second material having a lower coefficient of thermal expansion. In a further aspect, the support abuts the housing at a spherically-shaped interface to compensate for misalignment between the support and the sensing element to ensure that the sensing element is evenly loaded.

Claims

1. A pressure transducer package for measuring the pressure in an environment, the pressure transducer package comprising:

a housing;

a diaphragm supported by the housing;

a support disposed in the housing; and

a sensing element disposed in the housing between the diaphragm and the support so that the pressure from the environment acts on the diaphragm to compress the sensing element, the sensing element comprising;

at least one substrate; and

at least one piezoresistor formed on the at least one substrate;

wherein the at least one substrate is formed of a material having a coefficient of thermal expansion greater than 4 ppm/k at 600 degrees kelvin.

2. The pressure transducer package of claim 1, wherein the substrate material has a coefficient of thermal expansion greater than 4.5 ppm/k at 600 degrees kelvin.

3. The pressure transducer package of claim 1, wherein the substrate material has a coefficient of thermal expansion greater than 5 ppm/k at 600 degrees kelvin.

4. The pressure transducer package of claim 1, wherein the substrate material has a coefficient of thermal expansion greater than 5.5 ppm/k at 600 degrees kelvin.

5. The pressure transducer package of claim 1, wherein the substrate material has a coefficient of thermal expansion greater than 6 ppm/k at 600 degrees kelvin.

6. The pressure transducer package of claim 1, wherein the substrate material has a coefficient of thermal expansion greater than 6.5 ppm/k at 600 degrees kelvin.

7. The pressure transducer package of claim 1, wherein the substrate material has a coefficient of thermal expansion greater than 7 ppm/k at 600 degrees kelvin.

8. The pressure transducer package of claim 1, wherein the substrate material is sapphire.

9. The pressure transducer package of claim 1, wherein the at least one substrate comprises first and second substrates, and wherein the first and second substrates each is supported by a filler disposed between the first and second substrates.

10. The pressure transducer package of claim 9, wherein the filler is formed of a material that is less expensive than the substrate material.

11. The pressure transducer package of claim 9, wherein the substrate material is sapphire for each of the first and second substrates, and wherein the filler is alumina.

12. The pressure transducer package of claim 1, wherein the support is separate from and not integral with the housing.

13. The pressure transducer package of claim 1, wherein the support is integral with the housing.

14. The pressure transducer package of claim 1, further comprising a compensator disposed between the diaphragm and the sensing element.

15. The pressure transducer package of claim 14, wherein the compensator is formed of a material having a coefficient of thermal expansion greater than that of the substrate.

16. The pressure transducer package of claim 14, wherein the compensator is formed of a material having a coefficient of thermal expansion greater than that of the housing.

17. A pressure transducer package for measuring the pressure in an environment, the pressure transducer package comprising:

a housing;

a diaphragm supported by the housing;

a support disposed in the housing; and

a sensing element disposed in the housing between the diaphragm and the support so that the pressure from the environment acts on the diaphragm to compress the sensing element, the sensing element comprising;

at least one substrate formed of a first material having a first coefficient of thermal expansion;

an epitaxial layer of a second material formed on the at least one substrate, the second material having a second coefficient of thermal expansion that is less than the first coefficient of thermal expansion; and

a plurality of piezoresistors formed in the epitaxial layer.

18. The pressure transducer package of claim 17, wherein the second material is one of silicon or gallium nitride.

19. The pressure transducer package of claim 17, wherein the first material is sapphire.

20. The pressure transducer package of claim 17, wherein the at least one substrate comprises first and second substrates, and wherein the first and second substrates each is supported by a filler disposed between the first and second substrates.

21. The pressure transducer package of claim 20, wherein the filler is formed of a material that is less expensive than the substrate material.

22. The pressure transducer package of claim 20, wherein the substrate material is sapphire for each of the first and second substrates, and wherein the filler is alumina.

23. The pressure transducer package of claim 17, wherein the support is separate from and not integral with the housing.

24. The pressure transducer package of claim 17, wherein the support is integral with the housing.

25. The pressure transducer package of claim 17, further comprising a compensator disposed between the diaphragm and the sensing element.

26. The pressure transducer package of claim 25, wherein the compensator is formed of a material having a coefficient of thermal expansion greater than that of the substrate.

27. The pressure transducer package of claim 25, wherein the compensator is formed of a material having a coefficient of thermal expansion greater than that of the housing.

28. The pressure transducer package of claim 27, wherein at least a portion of the housing is formed from Incoloy 909.

29. A pressure transducer package, comprising;

a diaphragm capable of deflecting in response to pressure detected in an environment;

a sensing element that is mechanically coupled to the diaphragm to detect deflections in the diaphragm;

a support that supports the sensing element and resists movement of the sensing element in response to deflections in the diaphragm; and

a housing that receives the sensing element and the support and that has an opening that is at least partially covered by the diaphragm, wherein the support abuts the housing at a spherically-shaped interface.

30. The pressure transducer package of claim 29, wherein the spherically-shaped interface comprises a first spherically shaped surface on the housing that has a curvature that faces toward the sensing element and the diaphragm.

31. The pressure transducer package of claim 30, wherein the curvature has a center and a radius, and wherein the center of the curvature is disposed within the sensing element.

32. The pressure transducer package of claim 30, wherein the curvature has a center and a radius that defines a sphere that extends beyond an interior of the housing.

33. The pressure transducer package of claim 29, wherein the support is held against the housing only by compression forces exerted on the support by the sensing element and is not secured to the housing.

34. The pressure transducer package of claim 29, wherein the sensing element mates with the support along an engagement interface, wherein the spherically-shaped interface comprises an annular interface that defines a cone extending toward the sensing element, and wherein at least a portion of the engagement interface between the sensing element and the support is disposed within the cone.

35. The pressure transducer package of claim 34, wherein the engagement interface between the sensing element and the support is disposed entirely within the cone.

36. The pressure transducer package of claim 29, further comprising a compensator disposed between the diaphragm and the sensing element.

37. The pressure transducer package of claim 29, wherein the spherically-shaped interface comprises a first spherically-shaped surface on the housing and a second spherically shaped surface on the support.

38. The pressure transducer package of claim 37, wherein the first spherically-shaped surface is an annular surface.

39. The pressure transducer package of claim 38, wherein the second spherically-shaped surface comprises at least one portion of an annulus.

40. A pressure transducer package, comprising:

a diaphragm capable of deflecting in response to pressure detected in an environment;

a sensing element that is mechanically coupled to the diaphragm to detect deflections in the diaphragm;

a support that supports the sensing element and resists movement of the sensing element in response to deflections in the diaphragm; and

means for compensating for misalignment between the support and the sensing element to ensure that the sensing element is evenly loaded.

41. A pressure transducer package, comprising;

a housing;

a diaphragm, supported by the housing, capable of deflecting in response to pressure detected in an environment;

a sensing element that is disposed in the housing and mechanically coupled to the diaphragm to detect deflections in the diaphragm; and

a support that supports the sensing element and resists movement of the sensing element in response to deflections in the diaphragm, the support being disposed within the housing without being secured thereto and abutting the housing at a spherically-shaped interface.

42. The pressure transducer package of claim 41, wherein the spherically-shaped interface comprises a first spherically shaped surface on the housing that has a curvature that faces toward the sensing element and the diaphragm.

43. The pressure transducer package of claim 42, wherein the curvature has a center and a radius, and wherein the center of the curvature is disposed within the sensing element.

44. The pressure transducer package of claim 42, wherein the curvature has a center and a radius that defines a sphere that extends beyond an interior of the housing.

45. The pressure transducer package of claim 41, wherein the sensing element mates with the support along an engagement interface, wherein the spherically-shaped interface comprises an annular interface that defines a cone extending toward the sensing element, and wherein at least a portion of the engagement interface between the sensing element and the support is disposed within the cone.

46. The pressure transducer package of claim 45, wherein the engagement interface between the sensing element and the support is disposed entirely within the cone.

47. The pressure transducer package of claim 41, further comprising a compensator disposed between the diaphragm and the sensing element.

48. The pressure transducer package of claim 41, wherein the spherically-shaped interface comprises a first spherically-shaped surface on the housing and a second spherically shaped surface on the support.

49. The pressure transducer package of claim 48, wherein the first spherically-shaped surface is an annular surface.

50. The pressure transducer package of claim 49, wherein the second spherically-shaped surface comprises at least one portion of an annulus.