CAPACITIVE PRESSURE SENSOR ASSEMBLY

• US 20110296925A1
• Filed: 06/03/2010
• Published: 12/08/2011
• Est. Priority Date: 06/03/2010
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Miesel, Keith A., Haase, James M., Paidosh, Chris J., Janzig, Darren A., Denison, Timothy J.
• Granted Patent: US 8,397,578 B2
• Time in Patent Office: Days
• US Class Current: 73/718
• CPC Class Codes: G01L 19/142 Multiple part housings
• CPC Class Codes: G01L 19/143 Two part housings
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: H01L 2224/48472 the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/53265 with work-holder for assembly

Abstract

The disclosure is directed to a capacitive pressure sensor, and the assembly of a capacitive pressure sensor, that may be used within an implantable medical pump. In one example, a housing ferrule that encloses one capacitive plate and includes at least one protrusion for attaching a support structure of the capacitive plate. The at least one protrusion defines a smaller inner diameter as a reference point for securing the support structure while the ferrule provides a larger inner diameter to allow the support structure to tilt inside the ferrule to orient the capacitive plate into a desired plane. Despite manufacturing irregularities, the capacitive plate can be mounted in the desired plane parallel to another capacitive plate, a diaphragm, mounted to an edge of the ferrule. In another example, an assembly tool provides a stage to orient the capacitive plate and support structure within the ferrule at a desired depth.

Claims

1. A pressure sensor, comprising:

a housing ferrule defining a first inner diameter, wherein the housing ferrule is configured to receive a first capacitive plate of a capacitor; and

at least one protrusion disposed within the housing ferrule that defines a second inner diameter smaller than the first inner diameter, wherein;

the at least one protrusion is configured to provide a mounting point between the housing ferrule and a support structure of the first capacitive plate;

the housing ferrule and the support structure define a gap when the at least one protrusion is used to secure the support structure to the housing ferrule; and

the housing ferrule is configured to support a second capacitive plate substantially parallel to the first capacitive plate within the housing ferrule.

2. The pressure sensor of claim 1, wherein the gap allows the support structure to be tilted such that the first capacitive plate can be oriented in a first plane substantially parallel to a second plane of a second capacitive plate.

3. The pressure sensor of claim 1, wherein the first inner diameter is generally between 0.1 mm and 10.0 mm larger than the second inner diameter.

4. The pressure sensor of claim 3, wherein the first inner diameter is approximately 0.4 mm larger than the second inner diameter.

5. The pressure sensor of claim 1, wherein the at least one protrusion comprises less than 20 percent of a ferrule length between a proximal end and a distal end of the housing ferrule.

6. The pressure sensor of claim 1, wherein the at least one protrusion is formed integral with the housing ferrule.

7. The pressure sensor of claim 1, wherein the at least one protrusion is formed integral with the support structure.

8. The pressure sensor of claim 1, wherein the at least one protrusion comprises at least three protrusions spaced circumferentially within the housing ferrule and aligned in a plane substantially orthogonal to an axis of the housing ferrule.

9. The pressure sensor of claim 1, wherein the at least one protrusion is a substantially annular ring.

10. The pressure sensor of claim 1, wherein the support structure is configured to be welded to the at least one protrusion.

11. A method for assembling a pressure sensor, the method comprising:

placing a first capacitive plate and a support structure attached to the first capacitive plate within a housing ferrule defining a first inner diameter;

tilting the support structure within the housing ferrule to orient the first capacitive plate in a first plane substantially parallel to a second plane of a second capacitive plate;

securing the support structure to the housing ferrule via at least one protrusion, wherein the at least one protrusion defines a second inner diameter smaller than the first inner diameter; and

mounting the second capacitive plate to the housing ferrule.

12. The method of claim 11, wherein placing the first capacitive plate and the support structure attached to the first capacitive plate within the housing ferrule includes

defining a gap between the housing ferrule and the support structure, wherein the gap allows the support structure to tilt within the housing ferrule.

13. The method of claim 11, further comprising:

contacting the housing ferrule against a base plate of an assembly tool, wherein tilting the support structure comprises contacting the first capacitive plate against a stage of the assembly tool.

14. The method of claim 11, further comprising:

circumferentially orienting the first capacitive plate according to a position of a feedthrough pin coupled to the first capacitive plate and configured to extend through an aperture of a printed circuit board.

15. The method of claim 11, wherein securing the support structure to the housing ferrule includes securing the support structure via at least one protrusion integrally formed with the housing ferrule, and wherein securing the support structure to the housing ferrule comprises:

welding the support structure to the at least one protrusion within the housing ferrule.

16. The method of claim 11, wherein securing the support structure to the housing ferrule via at least one protrusion includes securing the support structure via at least one protrusion

integrally formed with the support structure, and wherein securing the support structure comprises:

welding the at least one protrusion to the housing ferrule.

17. The method of claim 11, wherein securing the support structure to the housing ferrule includes securing the support structure via at least three protrusions spaced circumferentially within the housing ferrule and aligned in a plane substantially orthogonal to an axis of the housing ferrule.

18. The method of claim 11, wherein securing the support structure to the housing ferrule includes securing the support structure via a substantially annular ring.

19. The method of claim 11, further comprising:

welding the second capacitive plate to an edge of the housing ferrule, wherein the second capacitive plate is a titanium diaphragm.

20. A pressure sensor assembly tool, the tool comprising:

a base plate; and

a stage raised from the base plate and configured to;

fit within a housing ferrule to allow an edge of the housing ferrule to pass the stage and contact a top surface of the base plate; and

set a uniform gap between a diaphragm plane defined by the edge of the housing ferrule and a capacitive plate mountable within the housing ferrule.

21. The tool of claim 20, wherein the stage height from the top surface of the base plate is generally between 0.01 mm and 0.25 mm.

22. The tool of claim 20, wherein the stage height from the top surface of the base plate is approximately 0.08 mm.

23. The tool of claim 20, wherein:

the stage is cylindrical in shape; and

a top surface of the cylindrical stage is substantially parallel to the top surface of the base plate.

24. The tool of claim 20, wherein:

the stage comprises at least three separate protrusions from the base plate; and

the at least three separate protrusions form a plane substantially parallel to the top surface of the base plate.

25. The tool of claim 20, wherein:

the capacitive plate is coupled to a support structure; and

the stage is configured to position the support structure within the housing ferrule such that the support structure can be secured to the housing ferrule via at least one protrusion within the housing ferrule.

26. A method for assembling a pressure sensor, the method comprising:

contacting an end of a housing ferrule to a base plate of an assembly tool, wherein the housing ferrule surrounds a stage of the assembly tool;

placing a first capacitive plate and attached support structure within the housing ferrule;

placing the first capacitive plate against the stage to orient the first capacitive plate in a first plane parallel to a second plane defined by the stage;

securing the support structure to the housing ferrule; and

mounting a second capacitive plate to the housing ferrule after removing the assembly tool.

27. The method of claim 26, wherein the first capacitive plate and attached support structure are configured to be tilted within the housing ferrule such that the first capacitive plate can be arranged substantially flush with the stage.

28. The method of claim 26, wherein securing the support structure to the housing ferrule comprises welding the support structure to at least one protrusion within the housing ferrule, wherein the at least one protrusion defines a second inner diameter smaller than a first inner diameter of the housing ferrule.

29. The method of claim 26, further comprising circumferentially orienting the first capacitive plate according to a location of a feedthrough pin coupled to the first capacitive plate and configured to extend through an aperture of a printed circuit board.

30. The method of claim 26, further comprising:

removing the assembly tool from the housing ferrule; and

welding a titanium diaphragm to the first end of the housing ferrule, wherein the titanium diaphragm is a second capacitive plate parallel to the first capacitive plate.