# US 10,483,453 B2 · Method of forming a multilayer acoustic impedance converter for ultrasonic transducers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,483,453 B2 - Document ID: US10483453B2 - Status: Granted - Kind: B2 - Application number: 14/875,151 - Filed: 2015-10-05 - Published: 2016-01-28 - Granted: 2019-11-19 - Earliest claimed: 2009-09-01 - Assignees: Measurement Specialties, Inc. - Applicants: Measurement Specialties, Inc. - Inventors: Minoru Toda; Mitchell L. Thompson - Web page: https://patentgrep.com/patent/US10483453B2 ## CPC - H10N 30/01: Manufacture or treatment - B06B 1/0622: {on one surface} - B06B 1/0644: {using a single piezoelectric element (B06B1/0688 takes precedence)} - B06B 1/0685: {on the back only of piezoelectric elements} - G10K 11/02: Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators - H10N 30/101: {with electrical and mechanical input and output, e.g. having combined actuator and sensor parts} - H10N 30/20: with electrical input and mechanical output, e.g. functioning as actuators or vibrators - H10N 30/30: with mechanical input and electrical output, e.g. functioning as generators or sensors - H10N 30/302: {Sensors} - A61B 2562/164: the sensor is mounted in or on a conformable substrate or carrier - H03H 3/08: for the manufacture of resonators or networks using surface acoustic waves - Y10T 29/42: Piezoelectric device making - Y10T 29/49005: Acoustic transducer - Y10T 29/49128: Assembling formed circuit to base - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R) - G10K: SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A method of forming an ultrasonic transducer comprises coupling a front polymer layer of uniform thickness to a piezoelectric element. A front metal layer is coupled to the polymer layer on a side of the front polymer layer opposite the piezoelectric element for transmitting acoustic energy between the front polymer layer and a propagation medium. The front polymer layer and the front metal layer define a front acoustic impedance converter, wherein the front polymer layer completely isolates the piezoelectric element from the front metal layer. ## Claims ### Claim 1 A method of forming an ultrasonic transducer comprising the steps of: providing a piezoelectric element having a high characteristic acoustic impedance; coupling a front polymer layer to said piezoelectric element, said front polymer layer having a continuous, uniform thickness along a length of the front polymer layer; and coupling a front metal layer to said front polymer layer on a side of said front polymer layer opposite said piezoelectric element for transmitting acoustic energy between said front polymer layer and a propagation medium having a low characteristic acoustic impedance lower than the high characteristic acoustic impedance of the piezoelectric element, wherein said front polymer layer and said front metal layer define a front acoustic impedance converter effective to convert between a characteristic acoustic impedance of the piezoelectric element and a characteristic acoustic impedance of the propagation medium, wherein said front acoustic impedance converter has an effective characteristic acoustic impedance between said piezoelectric element and said propagation medium characteristic acoustic impedances, and wherein said front polymer layer completely isolates said piezoelectric element from said front metal layer. ### Claim 2 (depends on 1) The method of claim 1, wherein said front polymer layer and said front metal layer comprise discrete continuous layers. ### Claim 3 (depends on 1) The method of claim 1, further comprising the step of coupling a backing absorber to said piezoelectric element, said backing absorber having a characteristic acoustic impedance. ### Claim 4 (depends on 1) The method of claim 1, further comprising the step of coupling a quarter wavelength matching layer to said front metal layer, said quarter wavelength matching layer configured to be in contact with said propagation medium. ### Claim 5 (depends on 1) The method of claim 1, wherein a thickness of said front metal layer (tm1) and a thickness of said front polymer layer (tp1) are substantially: tm1=ZC/(ρm2πf0); and tp1=Vp2ρp/(2πf0ZC), wherein, ZC is said effective characteristic acoustic impedance of said front acoustic impedance converter, ρm is a density of said front metal layer, f0 is a predetermined center resonant frequency, Vp is a velocity of sound in said front polymer layer, and ρp is a density of said front polymer layer. ### Claim 6 (depends on 1) The method of claim 1, wherein thicknesses of said front metal layer and said front polymer layer are selected based on densities of said front metal layer and said front polymer layer, said effective characteristic acoustic impedance of said front acoustic impedance converter, a predetermined center resonant frequency of said ultrasonic transducer, and a velocity of sound in said front polymer layer. ### Claim 7 A method of forming an ultrasonic transducer comprising the steps of: providing a piezoelectric element having a high characteristic acoustic impedance; coupling a front polymer layer to said piezoelectric element, said front polymer layer having a continuous, uniform thickness along a length of the front polymer layer; and coupling a front metal layer to said front polymer layer on a side of said front polymer layer opposite said piezoelectric element for transmitting acoustic energy between said front polymer layer and a propagation medium having a low characteristic acoustic impedance lower than the high characteristic acoustic impedance of the piezoelectric element, wherein said front polymer layer and said front metal layer define a front acoustic impedance converter effective to convert between an impedance of the piezoelectric element and an impedance of the propagation medium, wherein said front polymer layer completely isolates said piezoelectric element from said front metal layer, and wherein said thickness of said front polymer layer is less than one quarter of the wavelength of a predetermined center resonant frequency of said ultrasonic transducer. ### Claim 8 A method of forming an ultrasonic transducer comprising the steps of: providing a piezoelectric element; coupling a front polymer layer to said piezoelectric element, said front polymer layer having a continuous, uniform thickness along a length of the front polymer layer; coupling a front metal layer to said front polymer layer on a side of said front polymer layer opposite said piezoelectric element for transmitting acoustic energy between said front polymer layer and a propagation medium; wherein said front polymer layer and said front metal layer define a front acoustic impedance converter, and wherein said front polymer layer completely isolates said piezoelectric element from said front metal layer; coupling a low characteristic acoustic impedance layer having a first characteristic acoustic impedance to said front metal layer; and coupling a high characteristic acoustic impedance layer having a second characteristic acoustic impedance higher than said first characteristic acoustic impedance to said low characteristic acoustic impedance layer for being in contact with said propagation medium. ### Claim 9 (depends on 8) The method of claim 8, wherein said high characteristic acoustic impedance layer comprises at least one of a metal and a high characteristic acoustic impedance polymer. ### Claim 10 (depends on 9) The method of claim 9, wherein said high characteristic acoustic impedance polymer comprises at least one of a polyimide and polyester. ### Claim 11 (depends on 10) The method of claim 10, wherein said low characteristic acoustic impedance layer comprises at least one of rubber and latex. ### Claim 12 A method of forming an ultrasonic transducer comprising the steps of: providing a piezoelectric element; coupling a front polymer layer to said piezoelectric element, said front polymer layer having a continuous, uniform thickness along a length of said front polymer layer; and coupling a front metal layer to said front polymer layer on a side of said front polymer layer opposite said piezoelectric element for transmitting acoustic energy between said front polymer layer and a propagation medium, wherein said front polymer layer and said front metal layer define a front acoustic impedance converter, and wherein said front polymer layer completely separates said front metal layer from said piezoelectric element; and wherein said thickness of said front polymer layer is less than one quarter of a wavelength of a predetermined center resonant frequency of said ultrasonic transducer. ### Claim 13 (depends on 12) The method of claim 12, wherein said front polymer layer and said front metal layer comprise discrete continuous layers. ### Claim 14 (depends on 12) The method of claim 12, further comprising the step of coupling a backing absorber to said piezoelectric element, said backing absorber having a characteristic acoustic impedance. ### Claim 15 (depends on 12) The method of claim 12, further comprising the step of coupling a quarter wavelength matching layer to said front metal layer, said quarter wavelength matching layer configured to be in contact with said propagation medium. ### Claim 16 (depends on 12) The method of claim 12, further comprising the steps of: coupling a low characteristic acoustic impedance layer to said front metal layer; and coupling a high characteristic acoustic impedance layer to said low characteristic acoustic impedance layer for being in contact with said propagation medium. ### Claim 17 (depends on 12) The method of claim 12, wherein a characteristic acoustic impedance of said propagation medium is lower than a characteristic acoustic impedance of said piezoelectric element, and wherein said front acoustic impedance converter has an effective characteristic acoustic impedance between characteristic acoustic impedances of piezoelectric element and said propagation medium.