Process of manufacturing a piezopolymer transducer with matching layer
Inventors
Vilkomerson, David • Chilipka, Thomas
Assignees
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Publication Number
US-9166141-B2
Publication Date
2015-10-20
Expiration Date
Abstract
Matching layers improve the performance of ultrasonic transducers. Such layers have traditionally required significant effort and expense to be added to ultrasonic transducers. The present invention discloses a method of producing ultrasonic transducers with a matching layer, specifically for ultrasonic transducers utilizing piezopolymer transducer materials. Rather than the conventional method of forming the piezopolymer on a substrate and then attaching a matching layer through which the transducer emits its ultrasound energy, we teach depositing the piezopolymer on a substrate that also serves as a matching layer through which the ultrasound is emitted. We also teach depositing an additional shield layer for reducing electromagnetic interference. Methods of how to select materials and modify their ultrasonic characteristics are also discussed.
Core Innovation
The invention provides a method of forming an ultrasonic transducer for use on a medium at an operating frequency by providing a substrate layer having a front side, a back side, and a first acoustic impedance, with the back side having a uniform surface. A first electrode layer is disposed on the back side of the substrate layer, and a piezopolymer layer is deposited on the first electrode layer with the substrate layer, where the piezopolymer layer has a second acoustic impedance. A second electrode layer is disposed on the piezopolymer layer with the first electrode layer, such that the substrate layer acoustically matches the piezopolymer material layer to the medium.
In this approach, the substrate layer functions as the acoustic matching layer while the piezopolymer layer is formed directly on the electrode, rather than treating the matching layer as a separate component. The disclosed tuning concept uses electrode mass and matching of acoustic impedance for the piezopolymer/electrode composite to adjust the effective impedance relevant to matching between the piezopolymer composite and the medium. The document additionally discusses using a piezopolymer copolymer of the form P(VDFx–TrFE100–x) in examples for the piezopolymer layer.
The invention further includes a configuration that adds an EMI-reducing shield layer on the front side of the substrate layer. In the described example arrangement, the shield layer is disposed on the front side of the substrate layer while maintaining that the substrate layer acoustically matches the piezopolymer material layer to the medium. The document describes selection and thickness optimization for the shield layer relative to operating frequency and impedances, and it also discusses an optional reflective layer using silver ink disposed on the second electrode layer.
Claims Coverage
The document provides two independent method claims (two independent inventive concepts). The first independent claim covers an ultrasonic transducer formation method that uses the substrate as the acoustic matching layer by coupling substrate impedance with a piezopolymer/electrode structure. The second independent claim covers the same acoustic matching method combined with disposing a shield layer on the front side of the substrate layer, thereby adding EMI shielding while preserving acoustic matching.
Substrate acoustically matches piezopolymer to the medium using electrode-coupled impedance layers
Providing a substrate layer with a first acoustic impedance and a back side with a uniform surface; disposing a first electrode layer on the back side; depositing a piezopolymer layer on the first electrode layer with the substrate layer, the piezopolymer layer having a second acoustic impedance; and disposing a second electrode layer on the piezopolymer layer with the first electrode layer, whereby the substrate layer is acoustically matching the piezopolymer material layer to the medium.
Acoustic matching with a shield layer disposed on the substrate front side
Providing a substrate layer with a first acoustic impedance and a back side with a uniform surface; disposing a first electrode layer on the back side; depositing a piezopolymer layer on the first electrode layer with the substrate layer, the piezopolymer layer having a second acoustic impedance; disposing a second electrode layer on the piezopolymer layer with the first electrode layer; and disposing a shield layer on the front side of the substrate layer, whereby the substrate layer is acoustically matching the piezopolymer material layer to the medium.
Overall, the independent claim set centers on using the substrate layer as the acoustic matching layer through impedance-defined substrate/electrode/piezopolymer/electrode arrangement, with an additional independent concept that incorporates a shield layer on the substrate front side for electromagnetic interference reduction while preserving the acoustical matching relationship.
Stated Advantages
EMI reduction from adding an EMI-reducing shield layer while maintaining acoustic matching between the substrate and the piezopolymer material layer to the medium.
Measured increased sensitivity in the documented example arrangement.
Documented Applications
Ultrasonic transducer use on a medium at an operating frequency, including example operating frequencies discussed in the document.
Hydrophone measurements discussed for evaluating performance of the ultrasonic transducer example.
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