High-volume production, low cost piezoelectric transducer and method for producing same

• US 20010007403A1
• Filed: 02/02/2001
• Published: 07/12/2001
• Est. Priority Date: 09/01/1998
• Status: Active Grant

• Current Assignee: PCB Piezotronics of North Carolina, Inc. (Amphenol Corporation)
• Original Assignee: Isaak Baber, Richard Lally
• Inventors: Lally, Richard, Baber, Isaak
• Granted Patent: US 6,571,443 B2
• Time in Patent Office: Days
• US Class Current: 310/348
• CPC Class Codes: G01P 15/0915 of the shear mode type
• CPC Class Codes: H10N 30/88 Mounts; Supports; Enclosures; Casings
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/49144 by metal fusion
• CPC Class Codes: Y10T 29/49179 by metal fusion bonding

Abstract

A method of manufacture and a piezoelectric transducer are provided having a housing whose interior contains a piezoelectric element having radially spaced surfaces which undergo relative shear and produce an electrical signal in response thereto, an outer radial surface of the piezoelectric element being soldered to the interior of the housing, and an inner radial surface of the piezoelectric element is soldered to the outer surface of a stress/strain transmitting element. The solder alloy used shrinks less than →2.5% solidification. The subassembly made up of the piezoelectric element and the stress/strain transmitting element is provided with a passage to permit escape of gas from a chamber above the piezoelectric member which may be present from vapors attendant soldering.

Claims

1. A piezoelectric transducer comprising a housing and a transducer subassembly,

said transducer subassembly being secured to an inner wall of said housing;

said transducer subassembly further comprising a piezoelectric element operatively coupled to a stress/strain transmitting element;

wherein said piezoelectric element and said stress/strain transmitting element are affixed in position within said housing by a low-shrink solder whose volume changes less than about 2.5% in cooling from a liquid state to a solid state.

said transducer subassembly having a passage through said subassembly.

2. A piezoelectric transducer as recited in

claim 1

, wherein said piezoelectric element and said stress/strain transmitting element are affixed in position within said housing by a low-shrink solder whose volume changes less than about 2.3% in cooling from a liquid state to a solid state.

3. A piezoelectric transducer as recited in

claim 1

, wherein said transducer subassembly is a sensor subassembly and said sensor subassembly is so constructed and arranged that said piezoelectric element generates a signal in response to a force detected by said stress/strain transmitting element.

4. A piezoelectric transducer as recited in

claim 3

, wherein said housing is a cylindrical housing having a closed end and defining a central axis of said transducer,

wherein said stress/strain transmitting element is disposed in a central portion of said housing and is substantially surrounded by said piezoelectric element, an outer surface of said transmitting element being affixed to an inner surface of said piezoelectric element, and said piezoelectric element being affixed to an inner wall of said housing.

5. A piezoelectric transducer as recited in

claim 4

wherein said passage extending through said sensor subassembly comprises a passage extending through said stress/strain transmitting element.

6. A piezoelectric transducer as recited in

claim 4

wherein said piezoelectric element is longitudinally separated into at least two segments, and wherein said passage is defined by a channel extending in a region where said at least two segments are separated.

7. A piezoelectric transducer as recited in

claim 1

, wherein said low shrink solder is a solder alloy comprising a metal selected from the group consisting of bismuth, antimony, and a combination of bismuth and antimony.

8. A piezoelectric transducer as recited in

claim 7

, wherein said solder alloy has a composition consisting essentially of about 43% by weight lead, 43% by weight tin, and 14% by weight bismuth.

9. A piezoelectric transducer as recited in

claim 7

, wherein said solder alloy has a composition consisting essentially of about 60% by weight tin and about 40% by weight bismuth.

10. A piezoelectric transducer as recited in

claim 3

, wherein said piezoelectric element is connected to a signal conditioning circuit so constructed and arranged to develop a signal in response to a detected force.

11. A piezoelectric transducer as recited in

claim 10

, wherein said signal conditioning circuit comprises a charge amplifier disposed within said housing for developing a signal in response to a detected force.

12. A piezoelectric transducer as recited in

claim 10

, wherein said signal conditioning circuit is disposed externally of said housing, and wherein said transducer further comprises a connector operatively coupled to the piezoelectric element in said housing and extending to an exterior of said housing where said connector is operatively coupled to said signal conditioning circuit.

13. A method for fabricating a piezoelectric transducer comprising:

providing a piezoelectric element and a stress/strain transmitting element having no sealed volume of gas closed to atmosphere, and

depositing a low-shrink solder whose volume changes less than about 2.5% upon cooling from a liquid phase to a solid phase, to affix said piezoelectric element to said stress/strain transmitting element.

14. A method as recited in

claim 13

, including the further step of providing a piezoelectric element made up of at least two segments, and positioning said segments to be spaced apart from each other to define a channel therebetween, and to thereby prevent a formation of a sealed volume of gas.

15. A method as recited in

claim 13

, including the further step of fabricating said stress/strain transmitting element with a passage extending therethrough, to thereby prevent a formation of a sealed volume of gas.

16. A method as recited in

claim 13

, wherein said low-shrink solder is a solder alloy comprising a metal selected from the group consisting of bismuth, antimony, and a combination of bismuth and antimony.

17. A method as recited in

claim 16

, wherein said solder alloy consists essentially of about 43% by weight lead, about 43% by weight tin, and about 14% by weight bismuth.

18. A method as recited in

claim 16

, wherein said solder alloy consists essentially of about 60% by weight tin and about 40% by weight bismuth.