Patent Application
20180268796
A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C.F.R. § 1.14.
This application is a continuation of International Patent Application Number PCT/US2016/063242, filed Dec. 1, 2015, the entire contents of which are incorporated herein by reference.
The present disclosure generally relates to packaging for micromachined ultrasonic transducers (MUTs) and more particularly to packaging design for a micromachined ultrasonic transducer implementing a design of the back cavity using curved surfaces to control the resonant acoustic modes of the cavity, thereby increasing transducer performance.
Micromachined ultrasonic transducers (MUTs), and more specifically piezoelectric MUTs (pMUTs), typically consist of a released membrane structure operated at resonance and enclosed on one side by the package. In this type of structure, the design of the back-cavity on the enclosed side of the membrane has a strong effect on transducer performance, particularly the output pressure and bandwidth. Because typical packaging dimensions for MUTs are on the order of a wavelength for transducers operating at ultrasonic frequencies, standing waves are generated in the package back-cavity giving rise to acoustic resonant modes. With a traditional rectangular cavity, there are 3 degrees of freedom and multiple acoustic resonance modes in the x, y, and z dimensions as well as combination modes. The plurality of package acoustic resonance modes, if located at the incorrect frequency, can significantly reduce the output pressure and bandwidth of the transducer. In order to ensure device performance across a range of frequencies and temperatures, a method of controlling the resonant modes of the cavity is required. This invention describes a design for reducing the number of resonant modes in the back cavity of a MUT package using curved geometry to enable consistent acoustic performance of the packaged transducer.
Aspects of this disclosure relate to the package design for a pMUT utilizing curved geometry to control the presence and frequency of acoustic resonant modes in the back cavity of the transducer package. The approach consists of reducing in number and curving the reflecting surfaces present in the package cavity. Utilizing, by way of example, cylindrical or spherical geometry the resonant acoustic modes present in the package are reduced and can be adjusted to frequencies outside the band of interest.
The present disclosure may be better understood by reference to the following drawings which are for illustrative purposes only:
Although the description herein contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments, which may become obvious to those skilled in the art.
Aspects of this disclosure include a micromachined ultrasonic transducer (MUT) package, in particular a pMUT package comprised of a curved cavity to reduce the number of resonance modes present in the back cavity of a pMUT package. It will be appreciated that the following embodiments are provided by way of example only, and that numerous variations and modifications are possible. For example, while cylindrical and hemispherical embodiments are shown, the back cavity may have many different shapes utilizing curved geometry. Furthermore, while pMUTs are shown in this description, other MUTs should also be considered, such as capacitive micromachined ultrasonic transducers (cMUTs) or optical acoustic transducers. All such variations that would be apparent to one of ordinary skill in the art are intended to fall within the scope of this disclosure. It will also be appreciated that the drawings are not necessarily to scale, with emphasis being instead on the distinguishing features of the package with curved geometry for a pMUT device disclosed herein.
In an embodiment, an application specific integrated circuit (ASIC) 105 may be mounted on bottom substrate 104 and electrical connections to the ASIC 105 and pMUT 100 may be provided through the bottom substrate 104, a configuration that is known as a top-port package since the acoustic port hole is located on substrate 101 opposite the bottom substrate 104. In other embodiments, the electrical connections may be provided through substrate 101, a configuration known as a bottom-port package since the electrical connections and the acoustic port are both located on a common substrate 101.
Given that typical packaging dimensions for MUTs are on the order of a wavelength at ultrasonic frequencies, standing wave patterns are generated in the package cavity that result in acoustic resonant modes. With a traditional rectangular cavity, there are 3 degrees of freedom and multiple acoustic resonance modes in the x, y, and z dimensions as well as combination modes.
Back-cavities with rectangular geometry possess many different acoustic modes due to the plurality of reflecting surfaces. By way of example, but not limitation, the simulated acoustic frequency response of a 165 kHz pMUT packaged with a rectangular back-cavity is shown in
All cited references are incorporated herein by reference in their entirety. In addition to any other claims, the applicant(s)/inventor(s) claim each and every embodiment of the invention described herein, as well as any aspect, component, or element of any embodiment described herein, and any combination of aspects, components or elements of any embodiment described herein.
The appended claims are not to be interpreted as including means-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase “means for.” Any element in a claim that does not explicitly state “means for” performing a specified function, is not to be interpreted as a “means” or “step” clause as specified in 35 USC § 112, ¶6. In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 USC § 112, ¶6.
This application is a continuation of International Patent Application Number PCT/US15/63242 filed Dec. 1, 2015, the entire contents of which are incorporated herein by reference.
This invention was made with Government support under IIP-1346158 awarded by the National Science Foundation. The Government has certain rights in this invention. 45 CFR 650.4(f)(4)
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US15/63242 | Dec 2015 | US |
| Child | 15987824 | US |
