Piezoelectric actuator for an ultrasonic piezoelectric pump

Abstract

The utility model discloses a kind of piezoelectric actuators for ultrasonic piezoelectric pump, including sheet metal, FPC and piezoelectric ceramic sheet, piezoelectric ceramic sheet bottom is provided with by insulating ring separation positive pole silver electrode, negative pole silver electrode, edge is equipped with flanging silver electrode, FPC is five-layer structure, metal layer thereon is provided with by insulating ring separation positive pole area, the positive pole area of FPC upper metal layer is provided with via, via inner wall is equipped with conductive material, to realize the direct electrical connection of upper metal layer positive pole area and lower metal layer, eliminate conductive silver paste, sheet metal, FPC and piezoelectric ceramic sheet are bonded by epoxy resin;In addition, the cantilever beam structure of FPC is optimized as "Z" type, to improve amplitude;The utility model simplifies assembly process, reduces cost, and improves conductive reliability and structural stability.

Description

Technical Field

[0001] This utility model relates to the field of ultrasonic piezoelectric pump technology, specifically a piezoelectric actuator for ultrasonic piezoelectric pumps, suitable for micro fluid transport scenarios. Background Technology

[0002] The piezoelectric actuator is the core driving component of an ultrasonic piezoelectric pump, and its performance directly determines the pump's fluid delivery efficiency and stability. Existing piezoelectric actuators for ultrasonic piezoelectric pumps generally employ a three-layer composite structure consisting of a metal sheet, a flexible printed circuit board (FPC), and a piezoelectric ceramic sheet. The FPC, acting as the connecting carrier, must simultaneously achieve conductive connection between the positive electrode of the metal sheet and the piezoelectric ceramic sheet, and conductive connection between the FPC and the silver-plated negative electrode of the piezoelectric ceramic sheet. This manufacturing process has significant defects. Existing FPCs require a five-layer structure (PI film - metal negative electrode - PI film separator layer - metal positive electrode - PI film). To achieve conductivity between the metal sheet and the positive electrode of the piezoelectric ceramic sheet, arrayed vias need to be machined at corresponding positions on the FPC. During assembly, conductive silver paste needs to be filled into the arrayed vias of the FPC to form a conductive path between the metal positive electrode of the FPC and the positive electrode of the piezoelectric ceramic sheet. Additionally, epoxy resin adhesive needs to be applied to enhance the adhesion strength of the three layers: metal sheet, FPC, and piezoelectric ceramic sheet. This conductive connection process is cumbersome and labor-intensive. The conductive silver paste material is expensive, and uneven filling, excessive or insufficient filling, or other problems can easily occur in the arrayed vias, leading to poor conductivity and further increasing production costs. Furthermore, the material compatibility between conductive silver paste and epoxy resin adhesive is limited. Over long-term use, differences in thermal expansion and contraction coefficients may cause interface separation, resulting in decreased conductivity or adhesion failure, affecting the lifespan of the piezoelectric actuator.

[0003] Therefore, there is an urgent need for a piezoelectric actuator to address the shortcomings of existing technologies. Utility Model Content

[0004] This invention aims to overcome the problems of existing piezoelectric actuators (FPCs) having complex structures, requiring the filling of conductive silver paste, cumbersome processes, and high costs. It provides an improved piezoelectric actuator by optimizing the array of through holes in the FPC into metallized vias, achieving direct connection between the metal layers on both sides of the FPC, eliminating the need for conductive silver paste, simplifying the assembly process, reducing material and labor costs, while ensuring conductive reliability and structural strength. In addition, changing the original FPC "I"-shaped cantilever beam to a "Z"-shaped beam can effectively increase the actuator's amplitude, thereby increasing the flow rate.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: a piezoelectric actuator for an ultrasonic piezoelectric pump, comprising a metal sheet, a flexible circuit board (FPC) and a piezoelectric ceramic sheet. The metal sheet provides support for the piezoelectric ceramic sheet and drives it to bend and vibrate. The bottom of the piezoelectric ceramic sheet is provided with a positive silver electrode and a negative silver electrode separated by an insulating ring, and its edge is provided with a flanged silver electrode that connects the negative silver electrode to the other side. The FPC has a five-layer structure, which includes, from top to bottom: an upper PI film, an upper metal layer, a PI separator layer, a lower metal layer, and a lower PI film; the upper metal layer is provided with a positive electrode region and a negative electrode region separated by an insulating ring; The FPC has a via that penetrates the upper metal layer and the PI separator layer to the lower metal layer at the position corresponding to the positive electrode region of the upper metal layer. The inner wall of the via is provided with conductive material to realize the electrical connection between the positive electrode region of the upper metal layer and the lower metal layer. The metal sheet is bonded to the surface of the lower PI film of the FPC, the bottom of the piezoelectric ceramic sheet is bonded to the surface of the upper PI film of the FPC, and the positive silver electrode of the piezoelectric ceramic sheet corresponds to and is electrically connected to the positive electrode region of the metal layer on the FPC, and the flanged silver electrode of the piezoelectric ceramic sheet corresponds to and is electrically connected to the negative electrode region of the metal layer on the FPC. The FPC and the piezoelectric ceramic sheet are partially bonded together with epoxy resin adhesive, meaning that some areas of the bonding surface between the two are not coated with epoxy resin adhesive, but the uncoated areas are bonded together to form a conductive contact surface. The metal sheet and the FPC are fully bonded together with epoxy resin adhesive to ensure structural strength.

[0006] Furthermore, the vias are uniformly distributed in the positive region of the FPC, and the overall distribution area of ​​all vias is located within the area enclosed by the insulating ring of the piezoelectric ceramic sheet, ensuring a uniform electric field and not affecting insulation.

[0007] Furthermore, the insulating ring on the metal layer of the FPC corresponds in position and shape to the insulating ring at the bottom of the piezoelectric ceramic sheet, ensuring precise alignment and insulation between the positive and negative electrodes.

[0008] Furthermore, the FPC's profile includes a cantilever beam structure, which is Z-shaped, to reduce local stiffness and increase vibration amplitude.

[0009] Furthermore, the via is coated with a metal layer (such as copper) on its inner wall by chemical plating or electroplating processes to achieve stable and reliable conductivity.

[0010] Furthermore, the epoxy resin adhesive completely bonds the metal sheet and the FPC together, ensuring structural strength; the adhesive layer between the FPC and the piezoelectric ceramic sheet is a discontinuous or partially porous surface layer, where direct contact and conductivity between the piezoelectric ceramic sheet and the FPC interface are achieved at the porous points, simplifying materials and application processes.

[0011] Compared with existing technologies, this invention offers the following advantages: It replaces the array vias with metallized vias, achieving conductive connectivity between the upper and lower metal layers of the FPC. This eliminates the need for subsequent conductive silver paste filling, reducing production steps, improving processing efficiency, and lowering both material costs (eliminating conductive silver paste) and labor costs (simplifying the process). Only epoxy resin adhesive is required for bonding, avoiding the risk of interface separation between different adhesives (conductive silver paste and epoxy resin), and eliminating the need for double adhesive application, shortening assembly time and resulting in a more stable and reliable overall structure. The metallized vias form an integrated conductive structure, offering lower contact resistance and higher stability compared to conductive silver paste filling, avoiding poor conductivity caused by uneven adhesive filling and improving product yield. Furthermore, this invention replaces the original FPC "I"-shaped cantilever beam with a "Z"-shaped beam, reducing local stiffness, effectively increasing actuator amplitude, and thus improving the flow rate of the ultrasonic piezoelectric pump. Attached Figure Description

[0012] The present invention will be further described below with reference to the accompanying drawings.

[0013] Figure 1 This is a schematic diagram of the structure of this utility model.

[0014] Figure 2 This is a schematic diagram of the lower structure of the piezoelectric ceramic sheet in this utility model.

[0015] Figure 3 This is a three-dimensional structural diagram of the present invention.

[0016] Figure 4 This is an exploded structural diagram of the FPC in this utility model.

[0017] Figure 5 This is a front view of the FPC in this utility model.

[0018] Figure 6 This is a three-dimensional structural diagram of the FPC in this utility model.

[0019] Figure 7 for Figure 6 A magnified schematic diagram of a portion of region A in the middle.

[0020] Figure 8 This is an enlarged cross-sectional view of a single through hole in the FPC of this utility model.

[0021] In the figure: 1 is a metal sheet, 2 is an FPC, 21 is an upper PI film, 22 is an upper metal layer, 23 is a PI separator layer, 24 is a lower metal layer, 25 is a lower PI film, 3 is a piezoelectric ceramic sheet, 4 is an insulating ring, 5 is an insulating ring, 6 is a via, and 7 is a cantilever beam structure. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments.

[0023] like Figures 1-8 As shown, the piezoelectric actuator of this utility model still retains the three-layer composite structure of metal sheet 1, FPC2 and piezoelectric ceramic sheet 3, specifically including: The metal sheet 1 serves as the support and vibration transmission component of the actuator. It is usually made of a metal with good elasticity (such as phosphor bronze, stainless steel, etc.). Its top is bonded to the surface of the lower PI film 25 of FPC2 with epoxy resin to transmit the vibration energy of the piezoelectric ceramic sheet 3.

[0024] The improved FPC2 still adopts a five-layer basic structure (from top to bottom: upper PI film 21, upper metal layer 22, PI separator layer 23, lower metal layer 24, and lower PI film 25). The upper metal layer 22 is formed by etching or other processes to create a positive and negative electrode region separated by an insulating ring 5. Several metallized vias 6 are machined at the positions corresponding to the positive electrode region of the upper metal layer 22 in the FPC2. These vias 6 penetrate the upper metal layer 22, the PI separator layer 23, and down to the lower metal layer 24. A metal plating layer (such as copper) is formed on the inner wall of the vias 6 through chemical plating or electroplating, thereby achieving electrical connection between the positive electrode region of the upper metal layer 22 and the lower metal layer 24. The vias 6 are uniformly distributed within the positive electrode region, and their overall distribution area is located within the area enclosed by the insulating ring 4 of the piezoelectric ceramic sheet 3. The insulating ring 5 of the upper metal layer 22 of the FPC2 corresponds precisely in position and shape to the insulating ring 4 at the bottom of the piezoelectric ceramic sheet 3. In addition, the FPC2 profile includes a “Z”-shaped cantilever beam structure 7 for connection to external circuitry and to provide appropriate flexibility, a design that helps to improve amplitude.

[0025] The piezoelectric ceramic sheet 3 is made of piezoelectric ceramic material (such as PZT piezoelectric ceramic). A positive silver electrode and a negative silver electrode are located on its bottom (the surface that contacts the FPC2), separated by an insulating ring 4. A flanged silver electrode is provided at the edge of the piezoelectric ceramic sheet 3, connecting the negative silver electrode at the bottom to the other side (usually the top surface). During assembly, the bottom of the piezoelectric ceramic sheet 3 is bonded to the surface of the upper PI film 21 of the FPC2 using epoxy resin adhesive. The positive silver electrode of the piezoelectric ceramic sheet 3 corresponds to the positive electrode region of the metal layer 22 on the FPC2 and is expected to conduct through localized gaps in the epoxy resin adhesive. Similarly, the flanged silver electrode of the piezoelectric ceramic sheet 3 corresponds to the negative electrode region of the metal layer 22 on the FPC2 and is also expected to conduct through localized gaps in the epoxy resin adhesive.

[0026] The adhesive layer uses epoxy resin (replacing the conductive silver paste and additional epoxy resin in the prior art), filling the space between the metal sheet 1 and the lower surface of FPC2, and between the upper surface of FPC2 and the piezoelectric ceramic sheet 3. Before curing, this epoxy resin has a certain degree of fluidity. After the components are pressed together, the epoxy resin layer in the electrode contact area is thin and discontinuous, forming gaps that make the contact surfaces corresponding to these gaps conductive. This simultaneously achieves conductive connection and structural bonding functions without the need for additional conductive adhesive.

[0027] The working principle of this utility model: Conductive circuit formation: An external driving power supply is connected to the pad area of ​​FPC2 (usually located at the end of cantilever beam 7) via wires, providing power to FPC2. Current flows in from the lower metal layer 24 (positive input) of FPC2, is conducted through the metal of the inner wall of via 6 to the positive region of the upper metal layer 22, and then through the conductive holes in the epoxy resin layer to the positive silver electrode of the piezoelectric ceramic sheet 3. The flanged silver electrode of the piezoelectric ceramic sheet 3 is connected to the negative region of the upper metal layer 22 of FPC2 through the perforated epoxy resin layer, and the current flows back to the power supply through this negative region, forming a complete driving circuit. This process does not require conductive silver paste or reserved holes for filling conductive silver paste.

[0028] Actuation process: When an alternating voltage is applied by the driving power supply, the piezoelectric ceramic sheet 3 generates periodic expansion and contraction vibrations under the inverse piezoelectric effect. The vibration energy is transferred to the metal sheet 1 through the FPC2. The metal sheet 1 undergoes periodic bending deformation due to the vibration of the piezoelectric ceramic sheet 3, thereby driving the fluid in the ultrasonic piezoelectric pump to achieve transportation. The "Z"-shaped cantilever beam design helps to reduce the local stiffness of the system, thereby increasing the vibration amplitude and improving the pumping efficiency.

[0029] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A piezoelectric actuator for an ultrasonic piezoelectric pump, comprising a metal sheet (1), an FPC (2), and a piezoelectric ceramic sheet (3), wherein the bottom of the piezoelectric ceramic sheet (3) is provided with a positive silver electrode and a negative silver electrode separated by an insulating ring (4), and its edge is provided with a flanged silver electrode connecting the negative silver electrode to the other side; the FPC (2) has a five-layer structure, comprising, from top to bottom: The structure comprises an upper PI film (21), an upper metal layer (22), a PI separator layer (23), a lower metal layer (24), and a lower PI film (25), wherein the upper metal layer (22) has a positive electrode region and a negative electrode region separated by an insulating ring (5), characterized in that... The FPC (2) has a via (6) at the position corresponding to the positive electrode region of the upper metal layer (22) that penetrates the upper metal layer (22) and the PI separator layer (23) to the lower metal layer (24). The inner wall of the via (6) is provided with conductive material to realize the electrical connection between the positive electrode region of the upper metal layer (22) and the lower metal layer (24). The metal sheet (1) is bonded to the surface of the lower PI film (25) of the FPC (2), the bottom of the piezoelectric ceramic sheet (3) is bonded to the surface of the upper PI film (21) of the FPC (2), and the positive silver electrode of the piezoelectric ceramic sheet (3) corresponds to and is electrically connected to the positive electrode region of the metal layer (22) on the FPC (2), and the flanged silver electrode of the piezoelectric ceramic sheet (3) corresponds to and is electrically connected to the negative electrode region of the metal layer (22) on the FPC (2); The FPC (2) and the piezoelectric ceramic sheet (3) are partially bonded together with epoxy resin adhesive to form a leak point for conductive bonding. The metal sheet (1) and the FPC (2) are fully bonded together with epoxy resin adhesive to ensure structural strength.

2. The piezoelectric actuator for an ultrasonic piezoelectric pump according to claim 1, characterized in that, The vias (6) are uniformly distributed in the positive region of the FPC (2), and the overall distribution area of ​​all vias (6) is located within the area enclosed by the insulating ring (4) of the piezoelectric ceramic sheet (3).

3. The piezoelectric actuator for an ultrasonic piezoelectric pump according to claim 1 or 2, characterized in that, The insulating ring (5) of the metal layer (22) on the FPC (2) corresponds in position and shape to the insulating ring (4) at the bottom of the piezoelectric ceramic sheet (3).

4. The piezoelectric actuator for an ultrasonic piezoelectric pump according to claim 1, characterized in that, The FPC (2) has a profile shape including a cantilever beam structure (7) which is "Z" shaped.

5. The piezoelectric actuator for an ultrasonic piezoelectric pump according to claim 1, characterized in that, The via (6) is made to form a metal coating on its inner wall by chemical plating or electroplating process to achieve conductivity.

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