High-volume production, low cost piezoelectric transducer using low-shrink solder of bismuth or antimony alloy

• US 6,198,207 B1
• Filed: 08/31/1999
• Issued: 03/06/2001
• Est. Priority Date: 09/01/1998
• Status: Expired due to Term

• Current Assignee: PCB Piezotronics of North Carolina, Inc. (Amphenol Corporation)
• Original Assignee: Oceana Sensor Technologies
• Inventors: Baber, Isaak, Lally, Richard
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/386,472
• Time in Patent Office: 553 Days
• Field of Search: 310/333, 310/338, 310/340, 310/348, 310/349, 310/321, 310/328, 310/323.4, 310/323, 310/324
• 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% at 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 in a manner defining at least a first chamber and a second chamber within said housing on opposing sides of said transducer subassembly;

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 assembly having a passage through said subassembly permitting fluid communication between said first and said second chambers.

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

9. A piezoelectric transducer as recited in claim 1, wherein said solder is a solder alloy having 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 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 and a shear stress/strain-transmitting element operatively coupled thereto so as to operate in shear mode;

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 assembly having a passage through said subassembly.