Membrane hydrophone for high frequency ultrasound and method of manufacture

• US 10,451,476 B2
• Filed: 08/18/2016
• Issued: 10/22/2019
• Est. Priority Date: 08/18/2015
• Status: Active Grant

• Current Assignee: FUJIFILM SonoSite, Inc. (Fujifilm Holdings Corporation)
• Original Assignee: FUJIFILM SonoSite, Inc. (Fujifilm Holdings Corporation)
• Inventors: Chaggares, Nicholas Christopher, Ivanytskyy, Oleg, Pang, Guofeng, Moszczynski, Marius
• Primary Examiner(s): Hulka, James R
• Application Number:
  US15/241,021
• Publication Number:
  US 20170052061A1
• Time in Patent Office: 1,160 Days
• Field of Search: 367149
• CPC Class Codes: A61B 8/58 Testing, adjusting or calibrating the diagnostic device
• CPC Class Codes: B06B 1/0688 with foil-type piezoelectric elements, e.g. PVDF
• CPC Class Codes: B06B 1/0696 with a plurality of electrodes on both sides
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01H 3/005 Testing or calibrating of detectors covered by the subgroups of G01H3/00 calibrating geophysical instruments, e.g. seismic receivers G01V13/00

Abstract

A membrane hydrophone for analyzing high frequency ultrasound transducers has a piezoelectric membrane with electrode patterns created on the surface of the membrane. In one embodiment, the electrode patterns are doubled on each side of the membrane except for an active area of the hydrophone. In one embodiment, the electrodes are formed by removing a conductive coating on the membrane with laser pulses. The laser is set to remove the conductive coating from the piezoelectric membrane from the same side of the membrane in order to accurately align the electrodes in the active area. In one embodiment, the active area of the hydrophone has an area in a range of 900-10,000 square microns.

Claims

1. A membrane hydrophone for measuring acoustic energy from a high frequency ultrasound transducer, comprising:

a frame;

a piezoelectric membrane having a first side and a second side that is supported by the frame and including a conductive material on both sides of the piezoelectric membrane; and

a first electrode pattern comprising a first electrode and a second electrode pattern comprising a second electrode formed within the conductive material, wherein the first electrode pattern and second electrode pattern overlap each other on opposite sides of the piezoelectric membrane to define an active area of the hydrophone;

wherein the first electrode pattern comprising the first electrode is created on both the first and second sides of the piezoelectric membrane and overlap each other except in the active area, and

wherein the second electrode pattern comprising the second electrode is created on both the first and second sides of the piezoelectric membrane and overlap each other except in the active area.

2. The membrane hydrophone of claim 1, wherein the first electrode patterns on each side of the piezoelectric membrane are electrically coupled together.

3. The membrane hydrophone of claim 2, further comprising one or more conductive vias in the piezoelectric membrane that electrically couple the first electrode patterns on each side of the piezoelectric membrane.

4. The membrane hydrophone of claim 1, further comprising a buffer amplifier to amplify the signal produced by the active area of the hydrophone, wherein an input to the buffer amplifier is capacitively coupled to the first or second electrode pattern on the membrane.

5. The membrane hydrophone of claim 1, further comprising at least one registration feature cut into the piezoelectric membrane with a laser.

6. The membrane hydrophone of claim 1, wherein the active area of the hydrophone has an area of less than 1600 square microns.

7. The membrane hydrophone of claim 1, wherein the active area of the hydrophone has an area of less than 900 square microns.

8. A method of making a membrane hydrophone for measuring acoustic energy from a high frequency ultrasound transducer, comprising:

stretching a piezoelectric membrane across a frame;

applying a conductive layer to a first side and a second side of the piezoelectric membrane; and

selectively removing a portion of the conductive layer on the piezoelectric membrane to create a first electrode pattern comprising a first electrode and a second electrode pattern comprising a second electrode that overlap in an active area of the hydrophone, wherein the first electrode pattern and the second electrode pattern are created on both the first and the second side of the piezoelectric membrane;

wherein the conductive layer is removed by applying laser energy to the conductive layer to remove a portion of the conductive layer and leaving the piezoelectric membrane intact.

9. The method of claim 8, wherein the conductive layer is selectively removed by:

applying laser energy to the conductive layer on the first side of the piezoelectric membrane to create the first electrode pattern on the first side of the membrane; and

applying laser energy to the first side of the piezoelectric membrane in a location where the conductive layer has been removed from the first side of the piezoelectric membrane to create the first electrode pattern on the second side of the piezoelectric membrane, wherein the first electrode pattern on the first and second sides of the piezoelectric membrane overlap each other except in the active area of the hydrophone.

10. The method of claim 8, wherein the conductive layer is applied with a sputtering tool.

11. The method of claim 8, wherein the electrodes are created by applying a chemical etch to the piezoelectric membrane after a portion of the conductive layer has been removed from the piezoelectric membrane with the laser.

12. The method of claim 8, wherein the electrodes are created by removing the conductive coating from the piezoelectric membrane with a combination of laser patterning of a resist layer and chemical etch.

13. The method of claim 8, further comprising creating conductive vias in the piezoelectric membrane to electrically connect the electrode patterns on each side of the piezoelectric membrane.

14. The method of claim 8, further comprising:

treating areas of the piezoelectric membrane to reduce a piezoelectric characteristic of the membrane except for the active area of the hydrophone prior to the applying of the laser energy to the conductive layer.

15. The method of claim 8, further comprising spot polling the active area of the membrane by applying a voltage to the first and second electrode patterns on the piezoelectric membrane.

16. A membrane hydrophone for measuring acoustic energy from a high frequency ultrasound transducer, comprising:

a piezoelectric membrane having a first side and a second side;

a first electrode on the first side and the second side of the piezoelectric membrane;

a second electrode on the first side and the second side of the piezoelectric membrane, whereby the first and second electrodes overlap in an area between 10-30 microns in diameter; and

at least one registration feature that is cut though the piezoelectric membrane that allows the piezoelectric membrane to be aligned with an electrode patterning tool.

17. A membrane hydrophone for measuring acoustic energy from a high

frequency ultrasound transducer, comprising:

a piezoelectric membrane having a first side and a second side;

a first plurality of electrodes on the first side of the piezoelectric membrane; and

a second plurality of electrodes on the second side of the piezoelectric membrane, whereby the first plurality and the second plurality of electrodes on the surfaces overlap in a grid-pattern of active areas.