Surface acoustic wave assisted mask electrodeposition device and method

Abstract

The invention discloses a surface acoustic wave assisted mask electro-deposition device and method, and the device comprises an electro-deposition tank which is filled with an electrolyte and is internally provided with an anode plate and a cathode workpiece; the surface acoustic wave resonators are fixed to the opposite side faces in the electro-deposition tank, and the sound wave radiation direction is perpendicular to the surface of the cathode workpiece; the driving circuit is connected with the surface acoustic wave resonator; the input end of the electrolyte circulating unit is connected with a liquid outlet in the bottom of the electro-deposition tank, and the output end of the electrolyte circulating unit extends into the electro-deposition tank; the anode of the pulse power supply is connected with the anode plate, and the cathode of the pulse power supply is connected with the cathode workpiece; the method can effectively improve the deposition uniformity in the manufacturing process of the metal microstructure, and is particularly suitable for electro-deposition processing of the high-precision metal microstructure.

Description

Technical Field

[0001] This invention relates to the field of microfabrication technology, and in particular to an apparatus and method for surface acoustic wave-assisted mask electrodeposition. Background Technology

[0002] Metal microstructure devices, through the precise construction of metal units at the micro- and nano-scale, have become a key enabling technology driving the development of many cutting-edge fields. Their manufacturing processes and performance directly affect the realization of their functions and the reliability of their operation. Currently, the main methods for fabricating metal microstructures include electrical discharge machining (EDM), laser processing, and mask electrodeposition. Among these, mask electrodeposition has been widely used in the field of microstructure manufacturing due to its advantages such as high-resolution patterning capabilities, high material utilization, suitability for large-scale production, and adaptability to various functional metals.

[0003] The traditional mask electrodeposition process involves covering the surface of the cathode workpiece with an insulating mask pattern, filling the space between the anode plate and the cathode workpiece with electrolyte, applying current, and then performing electrodeposition. After processing, the insulating mask is removed to obtain the metal microstructure on the workpiece surface. Currently, mask electrodeposition suffers from problems such as uneven current density distribution and uneven electrolyte flow, resulting in poor deposition uniformity, which directly affects the processing accuracy and surface quality of the metal microstructure.

[0004] To address the issue of poor surface quality in the processing of metal microstructures, invention patent CN115852451B proposes a support device for electrodeposition electrodes. This device includes multiple elastic support tubes that can radially contract and extend into a tubular electrode, supporting the electrode through restoring force. The support tubes are fixed to a connector, which is connected to an external power source and driven by a rotating assembly, thereby rotating the electrode in the electrolyte. This enhances solution agitation, resulting in a more uniform ion concentration distribution, avoiding concentration polarization, and ultimately improving the surface quality of the processed material. However, this device has a complex mechanical structure, making it unsuitable for micro-machining. Furthermore, rotation can cause vibration and uneven flow field, affecting the smoothness of the deposited layer. Invention patent CN110528035A proposes a mask jet electrodeposition device and method for improving the performance of small EDM electrodes. This invention combines jet electrodeposition and mask technology to produce a novel processing method. An electrolyte jet is directed through a nozzle towards the electrode material to be processed, forming a closed loop for processing. The jet significantly enhances electrolyte convection, reduces diffusion layer thickness, alleviates concentration polarization, and reduces bubble retention, resulting in better uniformity of the deposited layer. However, the jet energy is relatively high, intensifying liquid disturbance and potentially damaging the mask, affecting processing quality. Invention patent CN120330823A proposes a method to improve the quality of copper electrodeposition. This method places the entire electrodeposition tank within a bath-type ultrasonic generator for electrodeposition. First, an anode plate pretreatment activation process is used. Then, the electrolyte formulation is optimized by adding composite additives, and ultrasonic enhancement is employed to improve the current efficiency of the copper electrodeposition process, effectively improving the surface morphology and roughness of the copper electrodeposition. However, the propagation direction, energy distribution, and acoustic flow effects of ultrasound in the electrodeposition tank are completely disordered, random, and uncontrollable processes.

[0005] To address the aforementioned technical problems, this invention provides an apparatus and method for fabricating metal microstructures using surface acoustic wave-assisted mask electrodeposition. Summary of the Invention

[0006] The purpose of this invention is to provide an apparatus and method for surface acoustic wave-assisted mask electrodeposition to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides the following solution: The present invention provides an apparatus for surface acoustic wave-assisted mask electrodeposition, comprising: An electrodeposition tank is filled with an electrolyte and an anode plate and a cathode workpiece are installed inside the tank. The surfaces of the anode plate and the cathode workpiece to be processed are placed facing each other in the electrodeposition tank to ensure uniform primary current distribution in the deposition area.

[0008] The surface acoustic wave resonator is symmetrically fixed on the corresponding sides of the electrodeposition experimental tank to emit bidirectional or multidirectional acoustic waves to tangentially disturb the electrolyte on the surface of the cathode workpiece, thereby forming a more uniform and stable acoustic flow field and mass transfer environment, and ensuring the uniformity of the three-dimensional current distribution in the deposition area. A driving circuit, which is connected to the surface acoustic wave resonator; An electrolyte circulation unit, wherein the input end of the electrolyte circulation unit is connected to the drain port at the bottom of the electrodeposition tank, and the output end of the electrolyte circulation unit extends into the electrodeposition tank; A pulse power supply, wherein the positive terminal of the pulse power supply is connected to the anode plate, and the negative terminal of the pulse power supply is connected to the cathode workpiece; According to the apparatus for surface acoustic wave-assisted mask electrodeposition provided by the present invention, the surface acoustic wave resonator includes an excitation electrode, a substrate, an interdigital transducer, and a reflective grating.

[0009] According to the surface acoustic wave-assisted mask electrodeposition apparatus provided by the present invention, the driving circuit includes a DC power supply, a driving circuit, and a time relay connected in series, wherein the time relay is connected to the excitation electrode of the surface acoustic wave resonator. The time relay controls the timing of surface acoustic wave emission to homogenize the convection and diffusion process of the acoustic flow field.

[0010] According to the surface acoustic wave-assisted mask electrodeposition apparatus provided by the present invention, the electrolyte circulation unit includes a circulation pump and a circulation pipe. One end of the circulation pipe is connected to the drain port at the bottom of the electrodeposition tank, and the other end extends into the electrodeposition tank. The circulation pump is installed on the circulation pipe, and by continuously circulating the electrolyte, the uniformity of electrolyte concentration and temperature can be maintained.

[0011] According to the surface acoustic wave-assisted mask electrodeposition apparatus provided by the present invention, the operating frequency of the surface acoustic wave resonator should be from several megahertz to tens of megahertz. The acoustic wavelength in this frequency range matches the microstructure scale, enabling the generation of strong localized acoustic currents within the mold cavity of the microstructure to be deposited, supplementing and homogenizing ion mass transfer within the microstructure, resulting in a more uniform tertiary current distribution on the deposition surface within a single microstructure, thereby significantly improving the deposition uniformity within a single microstructure in mask electrodeposition.

[0012] A method for surface acoustic wave-assisted mask electrodeposition includes the following steps: Step 1: Clean the oil and impurities from the surfaces of the anode plate and cathode workpiece, and insulate the exposed areas of the cathode that are not deposited. Arrange the surfaces of the anode plate and cathode workpiece to be processed opposite each other to ensure uniform distribution of primary current and provide a precise workpiece position basis for electrodeposition processing. Step 2: Inject sufficient electrolyte into the electrodeposition experimental tank to ensure that the liquid surface completely submerges the anode and cathode plates; connect the input end of the electrolyte circulation unit to the drain port at the bottom of the experimental tank, extend the output end into the tank, start the circulation unit to make the electrolyte continuously circulate, avoid local ion concentration imbalance, and build a stable electrolyte environment; Step 3: Connect the positive terminal of the pulse power supply to the anode plate and the negative terminal to the cathode workpiece. Connect the drive circuit to the surface acoustic wave resonator. By setting the pulse current parameters, the operating frequency and timing of the surface acoustic wave resonator to meet the deposition requirements, and adjusting the circulation rate of the circulation unit, the overall operating parameters of the device are configured. Step 4: Trigger the drive circuit with DC power supply to make the surface acoustic wave resonator work, and use tangential surface wave disturbance to improve the flow field and the uniformity of current distribution on the macroscopic surface of the microstructure array; Simultaneously start the pulse power supply, and metal ions are deposited onto the cathode surface through the cavity of the mold to be deposited in the microstructure. Step 5: After the preset deposition time is reached, the pulse power supply, drive circuit and circulation unit are turned off in sequence; the cathode workpiece is taken out from the electrodeposition tank, the surface mask structure is removed, and a metal microstructure with uniform thickness is obtained, thus completing the entire surface acoustic wave assisted mask electrodeposition process and ensuring the accuracy and quality of the final product.

[0013] The present invention discloses the following technical effects: The surface acoustic wave generated by the surface acoustic wave resonator of this invention can enhance the flow of electrolyte on the surface of the cathode workpiece, thereby improving the local current distribution and making it more uniform on the surface of the cathode workpiece, thus improving the uniformity of the deposition layer between the macroscopic array of microstructures.

[0014] The sound source of this invention can operate at frequencies up to tens of megahertz, generating strong local acoustic flow and microscale disturbances. This can enhance the electrolyte flow within a single microstructure, thereby improving the current distribution within the microstructure and making its deposition within the microstructure more uniform. At the same time, due to the extremely small amplitude, it causes virtually no damage to the microstructure.

[0015] The device of the present invention improves the electroacoustic conversion efficiency and energy utilization by optimizing the surface acoustic wave resonant structure parameters and configuring a high-frequency matching circuit, while effectively suppressing electrical signal noise during high-frequency operation. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is an overall view of the surface acoustic wave-assisted mask electrodeposition apparatus of the present invention; Figure 2 This is a front view of the surface acoustic wave resonator in this invention; Figure 3 This is a front view of the tank portion of the surface acoustic wave-assisted mask electrodeposition apparatus of the present invention; Figure 4 Two-dimensional plot of gear thickness deposited without acoustic surface wave assistance; Figure 5 A two-dimensional plot of the gear thickness deposited under bilateral surface acoustic wave assistance.

[0018] The components include: 1. DC power supply; 2. drive circuit; 3. time relay; 4. electrodeposition tank; 5. surface acoustic wave resonator; and 6. pulse power supply. 40. Fixing block; 41. Workpiece support clip; 42. Anode plate; 43. Cathode workpiece; 44. Circulation pump; 45. Circulation pipe; 50. Excitation electrode; 51. Substrate; 52. Interdigital transducer; 53. Reflection grating. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Reference Figures 1-5 The present invention provides an apparatus for surface acoustic wave-assisted mask electrodeposition, comprising: Electrodeposition tank 4 is filled with electrolyte. An anode plate 42 and a cathode workpiece 43 are installed in the electrodeposition tank 4. The surfaces of the anode plate 42 and the cathode workpiece 43 to be processed are placed opposite each other. The surface acoustic wave resonator 5 is symmetrically fixed on two opposite sides inside the electrodeposition tank 4 by fixing blocks 40. Drive circuit 2 is electrically connected to surface acoustic wave resonator 5; The electrolyte circulation unit has its input end connected to the drain port at the bottom of the electrodeposition tank 4, and its output end extends into the electrodeposition tank 4. The positive terminal of the pulse power supply 6 is connected to the anode plate 42, and the negative terminal of the pulse power supply 6 is connected to the cathode workpiece 43. In a further optimized design, a workpiece support clip 41 is installed at the bottom of the electrodeposition tank 4, and the anode plate 42 and the cathode workpiece 43 can be fixed in the electrodeposition experimental tank 4 by the workpiece support clip 41 respectively.

[0022] The support card is fixed parallel to the bottom of the electrodeposition experimental tank 4, and the slot structure makes the anode plate 42 and the cathode workpiece 43 (mask electrodeposition substrate) to be processed face to face.

[0023] The further optimized scheme includes an excitation electrode 50, a substrate 51, an interdigital transducer 52, and a reflective grating 53.

[0024] The substrate 51 can be a lithium niobate crystal. After the excitation electrode 50 is connected to the driving circuit 2, an alternating voltage is applied to cause the interdigital transducer 52 to generate periodic mechanical vibration, converting electrical energy into surface acoustic waves (SAWs) propagating along the surface of the substrate 51. The period of the reflector grating 53 is matched with that of the interdigital transducer 52, which can reflect the SAW generated by the interdigital transducer 52 back to the propagation path, superimposing with the newly generated sound waves to form a standing wave resonance, thereby increasing the energy density of the SAW by 3-5 times and enhancing the directional disturbance effect on the electrolyte. The lower end of the SAW resonator 5 is immersed in the liquid, with its interdigital transducer 52 located near the water and not in contact with the liquid, and the reflector grating 53 located far from the water. The resonant SAW propagates along the substrate 51 to the electrolyte interface, and the sound waves drive the electrolyte molecules to move in an elliptical trajectory, forming a directional micro-amplitude acoustic current (improving the macro- and micro-current distribution).

[0025] In a further optimized scheme, the drive circuit 2 includes a DC power supply 1, the drive circuit 2 and the time relay 3 connected in series and electrically connected to the excitation electrode 50 of the surface acoustic wave resonator 5.

[0026] DC power supply 1 provides stable DC power to drive circuit 2. Drive circuit 2, through a high-frequency oscillation module and impedance matching circuit, converts the DC power into a high-frequency alternating voltage that matches the parameters of surface acoustic wave resonator 5 (piezoelectric structure), avoiding energy reflection and waste. Timing control and alternating operation: Time relay 3 is connected in series between drive circuit 2 and excitation electrode 50, controlling the on / off timing of excitation electrode 50 by setting the working cycle. The voltage regulation characteristics of DC power supply 1 can avoid output voltage fluctuations of drive circuit 2, ensuring stable surface acoustic wave amplitude; the precise timing of time relay 3 can ensure the coordinated operation of multiple resonators, further improving the uniformity of electrolyte convection.

[0027] The electrolyte circulation unit is further optimized by including a circulation pump 44 and a circulation pipe 45. One end of the circulation pipe 45 is connected to the drain port at the bottom of the electrodeposition tank 4, and the other end extends into the electrodeposition experimental tank 4. The circulation pump 44 is installed on the circulation pipe 45.

[0028] The circulating pump 44 drives the electrolyte to flow unidirectionally along the path of "bottom drain port → circulating pipe 45 → circulating pump 44 → return pipe → electrodeposition tank 4", forming forced convection. This process can replace the electrolyte in the ion-consuming zone of the tank with fresh electrolyte in the ion-enriched zone. Further optimization of the scheme: the operating frequency of the surface acoustic wave resonator 5 should be several megahertz to tens of megahertz to adapt the acoustic wavelength to the microstructure scale. The resonator can be fabricated using MEMS micromachining technology.

[0029] A method for surface acoustic wave-assisted mask electrodeposition includes the following steps: Step 1: Clean the oil and impurities from the surfaces of the anode plate 42 and the cathode workpiece 43, and insulate the exposed areas of the cathode that are not deposited. Place the surfaces to be processed of the anode plate 42 and the cathode workpiece 43 opposite each other in the electrodeposition tank 4 to provide a precise workpiece position basis for the electrodeposition process. Step 2: Inject sufficient electrolyte into electrodeposition tank 4 to ensure that the liquid surface completely submerges the anode and cathode plates; connect the input end of the electrolyte circulation unit to the drain port at the bottom of the electrodeposition tank, extend the output end into the tank, start the circulation unit to make the electrolyte continuously circulate, avoid local ion concentration imbalance, and build a stable electrolyte environment; Step 3: Connect the positive terminal of the pulse power supply 6 to the anode plate 42 and the negative terminal to the cathode workpiece 43. Connect the drive circuit 2 to the surface acoustic wave resonator 5. By setting the pulse current parameters, the operating frequency and timing of the surface acoustic wave resonator 5 to meet the deposition requirements, and adjusting the circulation rate of the circulation unit, the overall operating parameters of the device are configured. Step 4: Trigger drive circuit 2 to make surface acoustic wave resonator 5 work, using sound waves tangent to the workpiece surface to improve the uniformity of flow field and macro- and micro-electric field distribution; synchronously start pulse power supply 6, metal ions are deposited at the cathode. Step 5: After the preset deposition time is reached, the pulse power supply 6, drive circuit 2 and circulation unit are turned off in sequence; the cathode workpiece 43 is taken out from the electrodeposition tank 4, the surface mask structure is removed, and a metal microstructure with uniform thickness is obtained, thus completing the entire surface acoustic wave-assisted mask electrodeposition process and ensuring the accuracy and quality of the final product.

[0030] Step six: After machining, the thickness was measured. Taking a micro-gear structure as an example, the pitch circle of the gear was used as a reference. Two circles were equally spaced between the pitch circle and the center hole, forming three reference circles together with the pitch circle. A diameter line was taken at the tooth tip, forming six intersection points with these three circles, arranged sequentially from left to right, numbered 1, 2, 3, 4, 5, and 6. The thickness was measured at these six locations, resulting in the thickness distribution of the gear at horizontal positions as shown in Figures 4 and 5. After introducing surface acoustic waves, the uniformity of the deposited layer improved by approximately 10%. Under surface acoustic wave-assisted mask electrodeposition conditions, the thickness ratio of the deposited layer at the center and edge of the gear can reach over 90%.

[0031] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0032] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An apparatus for surface acoustic wave-assisted mask electrodeposition, characterized in that, include: An electrodeposition tank (4) is filled with an electrolyte. An anode plate (42) and a cathode workpiece (43) are installed in the electrodeposition tank (4). The surfaces of the anode plate (42) and the cathode workpiece (43) to be processed are placed facing each other in the electrodeposition tank. The surface acoustic wave resonator (5) is symmetrically fixed on opposite sides of the electrodeposition tank (4) by a fixing block (40); the acoustic wave radiation direction of the surface acoustic wave resonator is perpendicular to the surface of the cathode workpiece (43). The driving circuit (2) is connected to the surface acoustic wave resonator (5); An electrolyte circulation unit is provided, wherein the input end of the electrolyte circulation unit is connected to the drain port at the bottom of the electrodeposition tank (4), and the output end of the electrolyte circulation unit extends into the electrodeposition tank (4). A pulse power supply (6) is provided, with its positive terminal connected to the anode plate (42) and its negative terminal connected to the cathode workpiece (43).

2. The apparatus for surface acoustic wave-assisted mask electrodeposition according to claim 1, characterized in that, The anode plate (42) and the cathode workpiece (43) are fixed inside the electrodeposition tank (4).

3. The apparatus for surface acoustic wave-assisted mask electrodeposition according to claim 1, characterized in that, The surface acoustic wave resonator (5) includes an excitation electrode (50), a substrate (51), an interdigital transducer (52), and a reflective grating (53).

4. The apparatus for surface acoustic wave-assisted mask electrodeposition according to claim 3, characterized in that, The driving circuit (2) includes a DC power supply (1), a driving circuit (2) and a time relay (3) connected in series. The time relay (3) is connected to the excitation electrode (50) of the surface acoustic wave resonator (5).

5. The apparatus for surface acoustic wave-assisted mask electrodeposition according to claim 1, characterized in that, The electrolyte circulation unit includes a circulation pump (44) and a circulation pipe (45). One end of the circulation pipe (45) is connected to the drain port at the bottom of the electrodeposition tank (4), and the other end extends into the electrodeposition tank (4). The circulation pump (44) is installed on the circulation pipe (45).

6. A method for surface acoustic wave-assisted mask electrodeposition, based on the apparatus for surface acoustic wave-assisted mask electrodeposition according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Clean the oil and impurities on the surface of the anode plate (42) and the cathode workpiece (43), and insulate the exposed area of ​​the cathode that is not deposited; place the surfaces to be processed of the anode plate (42) and the cathode workpiece (43) facing each other in the electrodeposition tank (4); Step 2: Inject sufficient electrolyte into the electrodeposition tank (4) to ensure that the liquid surface completely submerges the anode and cathode plates (42); connect the input end of the electrolyte circulation unit to the drain port at the bottom of the electrodeposition tank, extend the output end into the tank, start the circulation unit, so that the electrolyte can circulate continuously, avoid local ion concentration imbalance, and build a stable electrolyte environment; Step 3: Connect the positive terminal of the pulse power supply (6) to the anode plate (42) and the negative terminal to the cathode workpiece (43). Connect the drive circuit (2) to the surface acoustic wave resonator (5). Set the pulse current parameters to suit the deposition requirements by controlling the pulse power supply (6), control the working frequency and timing of the surface acoustic wave resonator (5), and adjust the cycle rate of the cycle unit at the same time to complete the configuration of the overall device's operating parameters. Step four: By controlling the DC power supply (1), drive circuit (2), and time relay (3), the surface acoustic wave resonator (5) is activated, emitting acoustic waves to tangentially disturb the electrolyte on the cathode workpiece surface. Simultaneously, the pulse power supply (6) is activated, causing metal ions to deposit at the cathode. Step 5: After the preset deposition time is reached, the control system sequentially shuts down the pulse power supply (6), the drive circuit (2) and the circulation unit; the cathode workpiece (43) is taken out from the electrodeposition tank (4), the surface mask structure is removed, and a metal microstructure with uniform thickness is obtained, thus completing the entire surface acoustic wave-assisted mask electrodeposition process and ensuring the precision and quality of the final product.

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