Multilayer array ultrasonic transducers

• US 5,834,880 A
• Filed: 09/16/1997
• Issued: 11/10/1998
• Est. Priority Date: 09/04/1996
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Venkataramani, Venkat Subramaniam, Wildes, Douglas Glenn, Lewandowski, Robert Stephen
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US08/931,338
• Time in Patent Office: 420 Days
• Field of Search: 310/322, 310/334, 310/336
• US Class Current: 310/334
• CPC Class Codes: B06B 1/064 with multiple active layers
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A method for fabricating "1.5D" and "2D" multilayer ultrasonic transducer arrays employs dicing saw kerfs, which provide acoustic isolation between rows. The kerfs are metallized to provide electrical connection between surface electrode layers and buried internal electrode layers. A multilayer piezoceramic transducer element for a "1.5D" or "2D" array produced by this method has higher capacitance, and accordingly provides better transducer sensitivity, in comparison to a single layer element.

Claims

1. A transducer array having two major surfaces and comprising:

a plurality of multilayer transducer elements arranged in a two-dimensional array of rows and multiple elements in each row;

each transducer element having an external signal electrode on one surface comprising a portion of one of the array major surfaces and an external ground electrode on an opposite surface comprising a portion of the other of the array major surfaces;

each transducer element comprising an odd number of piezoelectric material layers separated by at least one internal signal electrode defining with said external signal electrode a set of signal electrodes, and at least one internal ground electrode defining with said external ground electrode a set of ground electrodes, said signal electrodes alternating with said ground electrodes;

a first set of row isolation slots extending from the one of the array major surfaces intersecting said transducer element internal signal electrodes, with conductive material in said first set of row isolation slots electrically connecting said at least one internal signal electrode of each transducer element to the corresponding external signal electrode;

a second set of row isolation slots extending from the other of the array major surfaces intersecting said transducer element internal ground electrodes, with conductive material in said second set of row isolation slots electrically connecting said internal ground electrodes to said external ground electrodes; and

a set of dicing cuts perpendicular to the row isolation slots to define the multiple elements in each row.

2. The transducer array of claim 1 wherein the first and second sets of row isolation slots comprise partial depth slots.

3. An array of multilayer ultrasonic transducer elements, comprising:

a body of piezoelectric material having two major surfaces and an internal buried conductor layer structure, the internal buried conductor layer structure including at least one ground conductor layer comprising a set of generally planar buried ground electrode precursors extending in a first coordinate direction and spaced in a second coordinate direction, and at least one signal conductor layer comprising a set of generally planar buried signal electrode precursors extending in the first coordinate direction and spaced in the second coordinate direction, the buried signal electrode precursors being staggered in the second coordinate direction with reference to the buried ground electrode precursors such that intermediate regions of the buried signal electrode precursors are in alignment with spaces between the buried ground electrode precursors and intermediate regions of the buried ground electrode precursors are in alignment with spaces between the buried signal electrode precursors;

a first set of row isolation slots extending from one of the major surfaces into the body in alignment with spaces between buried ground electrode precursors and intersecting buried signal electrode precursors to define buried signal electrode portions, and a second set of row isolation slots extending from the other of the major surfaces into the body in alignment with spaces between buried signal electrode precursors and intersecting buried ground electrode precursors to define buried ground electrode portions;

a signal electrode layer on the one of the major surfaces and buried signal electrode access conductors within the first set of row isolation slots electrically connecting the buried signal electrodes to the signal electrode layer; and

a ground electrode layer on the other of the major surfaces and buried ground electrode access conductors within the second set of row isolation slots extending from the other major surface and electrically connecting the buried ground electrodes to the ground electrode layer.

4. The array of claim 3, wherein the signal electrode layer is patterned to define isolated row signal electrodes, and at least some of the buried signal electrode access conductors are patterned to electrically isolate the buried signal electrode portions on opposite sides of the row isolation slots of the first set.

5. The array of claim 3, wherein the body is diced in the second coordinate direction to define a plurality of individual elements in each row.

6. The array of claim 3, wherein the first and second sets of row isolation slots comprise partial depth slots.

7. An array of multilayer ultrasonic transducer elements, comprising:

a body of piezoelectric material having two major surfaces and an internal buried conductor layer structure, the internal buried conductor layer structure including at least one ground conductor layer comprising a set of generally planar buried ground electrode precursors extending in a first coordinate direction and spaced in a second coordinate direction, and at least one signal conductor layer comprising a set of generally planar buried signal electrode precursors extending in the first coordinate direction and spaced in the second coordinate direction, the buried signal electrode precursors being staggered in the second coordinate direction with reference to the buried ground electrode precursors such that intermediate regions of the buried signal electrode precursors are in alignment with spaces between the buried ground electrode precursors and intermediate regions of the buried ground electrode precursors are in alignment with spaces between the buried signal electrode precursors;

at least one row isolation slot extending from one of the major surfaces into the body in alignment with spaces between buried ground electrode precursors and intersecting buried signal electrode precursors to define buried signal electrode portions;

a signal electrode layer on the one of the major surfaces and buried signal electrode access conductors within the at least one row isolation slot extending from the one major surface electrically connecting the buried signal electrodes to the signal electrode layer; and

a ground electrode layer on the other of the major surfaces and buried ground electrode access conductors electrically connecting the buried ground electrodes to the ground electrode layer.

8. The array of claim 7 and further including at least one row isolation slot extending from the other of the major surfaces into the body in alignment with spaces between buried signal electrode precursors and intersecting buried ground electrode precursors to define buried ground electrode portions, wherein the buried ground electrode access conductors are situated within the at least one row isolation slot extending from the other of the major surfaces.

9. The array of claim 8, wherein the signal electrode layer is patterned to define isolated row signal electrodes, and at least some of the buried signal electrode access conductors are patterned to electrically isolate the buried signal electrode portions on opposite sides of the row isolation slots of the first set.

10. The array of claim 8, wherein the body is diced in the second coordinate direction to define a plurality of individual elements in each row.

11. The array of claim 8, wherein each of the row isolation slots comprises a partial depth slot.