Transducer

• US 4,047,144 A
• Filed: 08/15/1975
• Issued: 09/06/1977
• Est. Priority Date: 06/30/1971
• Status: Expired due to Term

• Current Assignee: Endevco Corporation (Illinois Tool Works Inc.)
• Original Assignee: Becton Dickinson Electronics Company (Becton, Dickinson & Co)
• Inventors: Wong, Herbert Vernon
• Primary Examiner(s): Albritton, C. L.
• Application Number:
  US05/605,120
• Time in Patent Office: 753 Days
• Field of Search: 338/2, 338/5, 338/6, 357/26, 73/88.5 SD, 29/583, 29/591
• US Class Current: 338/2
• CPC Class Codes: G01B 7/20 formed by printed-circuit technique
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

An electromechanical transducer is provided which employs a piezoresistive substrate support body of semiconductive material of which a first type N or P and a lineal resistor composed of material of a second type (P or N) formed on one surface thereof. The support body has a reduced neck intermediate two pads. The lineal resistor extends between the pads and across the neck on one side of the support body. The lineal resistor is formed by diffusing semiconductive material of the second type of conductivity into the substrate material. Strain is detected by measuring the change in resistance of the lineal resistor. When the transducer is subjected to strain, the resistance changes by an amount depending on the strain. While the electrical current flows through the resistor, heat developed in the resistors flows into the neck and then is conducted through the flaring portions of the neck to the pads and then to an object under test.

Claims

1. In an electromechanical transducer unit:

a substrate support body of semiconductive material having a first type of conductivity and having two pads separated by an intermediate reduced neck, and

a lineal resistor in the reduced neck of the substrate support body said resistor being composed of semiconductive material having a second type of conductivity, the electrical resistance of the lineal resistor varying with the relative displacement of the pads of the substrate support body, and

two relatively movable members secured to the respective pads for displacing one of the pads relative to the other.

2. An electromechanical transducer as defined in claim 1 wherein the depth and width of the lineal resistor are small fractions of the minimum thickness of the reduced neck.

3. An electromechanical transducer as defined in claim 1 wherein:

the substrate support body is reduced on all but one side at a position intermediate the two pads in order to form a neck which has one surface that is coplanar with the surfaces of the pads on one side of the substrate support body, and

the lineal resistor being in the side of the substrate support body which contains said surface.

4. An electromechanical transducer unit as defined in claim 1 wherein the substrate support body is reduced on all sides at a position intermediate the two pads in order to form a neck which has all of its surfaces recessed from all of the surface planes of the pads of the substrate support body.

5. An electromechanical transducer unit as defined in claim 1 wherein said resistor is provided with electrical terminals on said support body.

6. An electromechanical transducer unit as defined in claim 5 wherein said terminals are located on the same face of one of said pads.

7. An electromechanical transducer unit as defined in claim 1 wherein said support body is composed of a single crystal of silicon, said crystal having its [111] plane extending transversely of the longitudinal axis that passes through said pads and said neck.

8. An electromechanical transducer as defined in claim 1 wherein the transverse cross-section of the neck is larger than the cross-section of the resistor and the cross-sections of the pads are substantially greater than the cross-section of the neck, said pads being adapted to be bonded to an object undergoing test, whereby heat generated by the flow of electrical current through said resistor is conducted to said object through said neck and said pads.

9. An electromechanical transducer as defined in claim 1 wherein the first type of conductivity is N-type and the second type of conductivity is P-type.

13. An electromechanical transducer as defined in claim 9 wherein:

the transverse cross-section of the lineal resistor is substantially smaller than the transverse cross-section of the neck and the transverse cross-section and the length of the pads are substantially greater than the transverse cross-section and the length respectively of the neck;

the first type of conductivity is N-type and the second type of conductivity is P-type;

the substrate support body is reduced on all but one side at a position intermediate the two pads in order to form a neck which has one surface that is coplanar with the surfaces of the pads on one side of the substrate support body, and

the lineal resistor is in the side of the substrate support body which contains said surfaces.

10. In an electromechanical transducer unit;

a substrate support body of semiconductive material of a first type and having two pads separated by an intermediate reduced neck,

a lineal resistor composed of semiconductive material of a second type in the reduced neck of the substrate support body and extending from one of said pads to the other, one of said types being N-type, the other being P-type,

two metallic films on the substrate support body, each film contacting one of the ends of the lineal resistor respectively, the electrical resistance of the resistor varying with the relative displacement of the pads of the substrate support body, and

two relatively movable members secured to the respective pads for displacing one of the pads relative to the other.

11. A transducer as defined in claim 10 wherein said resistor is of U-shape and wherein said films are on the same face of the same pad.

12. In an electromechanical transducer:

a substrate support body of semiconductor material having a first type of conductivity and having two pads separated by an intermediate reduced neck,

a "U"-shaped line of semiconductive material of a second type of conductivity in one side of the substrate support body, one end of each leg of the "U" terminating on the same pad, the cross-member of the "U" being positioned on the other of said pads,

two metallic films on the said same pad, each respectively contacting the two ends of said legs on said same pad and adapted to be contacted by terminals, the electrical resistance of the resistor element formed by the terminals, the metallic films and the "U"-shaped line varying with the relative displacement of the pads of the substrate support body about the neck, and

two relatively movable members secured to the respective pads for displacing one of the pads relative to the other.