Patent Application
20190363241
The subject matter herein generally relates to an ultrasonic sensing device, an electronic device using the ultrasonic sensing device, and a method for making the ultrasonic sensing device.
Nowadays, more and more electronic devices have functions of fingerprint identification. A conventional fingerprint identification device generally includes an ultrasonic sensing element that is capable of identifying a fingerprint of a finger placed on the fingerprint identification device. The ultrasonic sensing element generally includes a piezoelectric material layer and two electrodes formed on opposite sides of the piezoelectric material layer. Generally, at least one electrode is made of a layer of silver paste. However, when the layer of the silver paste has a thickness greater than 15 μm, a flexible circuit board may not be lapped directly on the surface of the silver paste electrode.
Therefore, there is room for improvement within the art.
Implementations of the present technology will now be described, by way of example only, with reference to the attached figures.
It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure.
The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “comprising” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like.
As shown in
As shown in
The circuit board 130 is configured to dispose a circuit layout. As shown in
As shown in
The first electrode 111 has a thickness in a range from 0.005 μm to 1 μm and a surface roughness Ra of less than or equal to 0.1. The first electrode 111 can be made by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The first electrode 111 is made of a metal, such as copper (Cu), silver (Ag), platinum (Pt), or a metal alloy. The first electrode 111 can be used as a mask during etching process of the piezoelectric material layer 113. In one embodiment, the first electrode 111 is a copper layer having a thickness ranging from 0.005 μm to 1 μm and formed on a surface of the piezoelectric material layer 113 by vacuum evaporation, sputter coating, arc plasma plating, ion plating, or molecular beam epitaxy. The second electrode 112 may be made of indium tin oxide (ITO). The first electrode 111 has a relatively low thickness, thus the flexible circuit board 123 can be easily coupled to the first electrode 111 and the circuit board 130. The first electrode 111 has a relatively low surface roughness, thus reflection and refraction of the ultrasonic waves is less when passing through the first electrode 111, further improving the properties of the ultrasonic sensing device 100.
The ultrasonic sensing device 100 has a working cycle including a signal transmitting phase and a signal receiving phase. In the signal transmitting phase, the flexible circuit board 123 applies different voltages to the first electrode 111 and the circuit board 130, and the circuit board 130 applies the voltage signal to the second electrode 112. Thus, a voltage difference is formed on opposite sides of the piezoelectric material layer 113, and the piezoelectric material layer 113 vibrates and emits ultrasonic waves. In the signal receiving phase, the flexible circuit board 123 applies an operating voltage to the first electrode 111 and the second electrode 112, the piezoelectric material layer 113 receives the reflected ultrasonic wave and generates charges, and the second electrode 112 transmits the charges to the circuit 133 of the circuit board 130. The circuit 133 collects and analyzes charges current, and transmits the charges current to the controller through the flexible circuit board 123.
As shown in
At block S1, a circuit board is provided and piezoelectric polymer material is coated on a surface of the circuit board.
The circuit board 130 includes a substrate 131 and a circuit 133 formed on the substrate 131. A second electrode 112 is formed on the substrate 131 and electrically coupled to the circuit 133. Before coating the piezoelectric polymer material, the circuit board 130 is cleaned and dried. The piezoelectric polymer material can be coated by a conventional coating process, such as spin coating, spraying, and dipping.
At block S2, the piezoelectric polymer material is dried and crystallized to form a piezoelectric material layer.
The piezoelectric polymer material applied on the circuit board 130 is dried to remove liquid solvent and form a solid layer, annealed to crystallize the piezoelectric material, and corona polarization treated. The piezoelectric material layer completely covers the second electrode 112.
At block S3, a first electrode is formed on a surface of the piezoelectric material layer away from the circuit board.
The first electrode 111 can be made by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The first electrode 111 is made of a metal, such as copper (Cu), silver (Ag), platinum (Pt), or a metal alloy. The first electrode 111 has a thickness in a range from 0.005 μm to 1 μm and a surface roughness Ra of less than or equal to 0.1.
At block S4, the piezoelectric material layer is etched to form a piezoelectric layer by using the first electrode as a mask. Before etching, the piezoelectric material layer may not have a desired shape and size. The piezoelectric layer after the etching process may have a desired shape and size, and completely covers the second electrode 112.
At block S5, a cover is mounted to cover the first electrode. The cover covers a side of the first electrode away from the circuit board.
At block S6, a flexible circuit board is mounted to electrically couple to the first electrode and the circuit.
In one embodiment, the flexible circuit board is electrically coupled to the first electrode by one connecting pad and electrically coupled to the circuit by another connecting pad.
It is to be understood, even though information and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the present embodiments, the disclosure is illustrative only; changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present embodiments to the full extent indicated by the plain meaning of the terms in which the appended claims are expressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201810506951.4 | May 2018 | CN | national |
