Spray-flushing mixed liquid supply electroforming system and high aspect ratio metal microstructure electroforming method

Abstract

The present invention relates to a jet-and-flushing mixed liquid supply electroforming system and a high aspect ratio metal microstructure electroforming method, belonging to the field of precision device processing technology. It is characterized in that the problem of poor mass transfer in the high aspect ratio structure micro electroforming process is solved by applying a jet-and-flushing mixed flow stirring mode during the electroforming process. The liquid inlet of the jet-and-flushing mixed liquid supply is composed of a liquid spray port with a specific tilt angle and a horizontal liquid spray port. The liquid spray port with a specific tilt angle is conducive to increasing the solution renewal speed inside the high aspect ratio microstructure during the electroforming process, increasing the ion concentration inside the microstructure, thereby improving the problem of poor mass transfer in the electroforming process. The horizontal liquid spray port is conducive to balancing the flow rate inside the high aspect ratio microstructure, and improving the mass transfer imbalance inside different microstructures during the electroforming process.

Description

Technical Field

[0001] The invention belongs to the technical field of precision device processing, and in particular relates to a spray-flushing mixed liquid supply electroforming system and a high aspect ratio metal microstructure electroforming method. Background Art

[0002] With the development of micro-electromechanical system (MEMS) technology, high aspect ratio metal microstructure manufacturing technology has good application prospects in the preparation of devices such as array microelectrodes, microfluidic chips, and metal molds. Micro-electroforming technology is an atomic-scale electrodeposition process that can replicate submicron and nanometer-scale precision features. This is one of the manufacturing technologies for high aspect ratio metal microstructures. However, high aspect ratio microstructure templates pose a huge challenge to micro-electroforming technology. The internal mass transfer effect caused by the high aspect ratio microstructure template is poor, resulting in an unbalanced speed during the electroforming growth of high aspect ratio microstructures, and the problem of porous structure in the electroformed layer, which ultimately leads to manufacturing failure. Therefore, it is of great significance to study methods to improve the mass transfer performance during the electroforming process.

[0003] So far, a lot of research has been done to enhance mass transfer during electroforming to obtain defect-free microstructures, such as using various additives to change the composition of the electroforming solution, strengthening mechanical stirring, vacuum-assisted and temperature gradient electroforming, moving cathode, pulse / pulse reverse electroforming, etc. However, under the current mass transfer enhancement methods, the current density during electroforming is low, so the electroforming speed is low. Summary of the invention

[0004] In order to improve the electroforming speed of preparing high aspect ratio microstructures by micro electroforming technology, the present invention provides a spray-flushing mixed liquid supply electroforming system and a high aspect ratio metal microstructure electroforming method.

[0005] A spray-flushing mixed liquid supply electroforming system comprises a liquid storage tank, a processing tank, a constant current power supply, an anode plate, a cathode plate and a microstructure template; wherein the anode plate, the cathode plate and the microstructure template are located in the processing tank; the microstructure template is located at the part of the cathode plate to be processed, and the anode plate is located above the microstructure template; the system is characterized in that: a liquid spray inlet is arranged above the processing tank, and the liquid spray inlet is inclined at an angle of 55°-65° with the horizontal line; a flushing liquid inlet is arranged on one horizontal side of the processing tank, and a liquid outlet is arranged on the other side; the system further comprises a liquid spray magnetic pump and a flushing liquid magnetic pump; one end of the liquid spray magnetic pump is connected to the liquid storage tank, and the other end is connected to the liquid spray inlet; one end of the flushing liquid magnetic pump is connected to the liquid storage tank, and the other end is connected to the flushing liquid inlet.

[0006] The method for electroforming a high aspect ratio metal microstructure using the spray-flushing mixed liquid supply electroforming system is characterized in that: using the pattern on the microstructure template, different high aspect ratio microstructures can be prepared according to specific needs, and the aspect ratio of the microstructure is 1-8; during the electroforming process, a liquid jet magnetic pump and a liquid jet inlet are used to realize a jet flow with an inclined angle of the electroforming solution, and the jet flow velocity at the liquid jet inlet is controlled to be 1.6-3.2 m / s, and the jet flow velocity is proportional to the aspect ratio of the microstructure. The higher the aspect ratio of the microstructure, the higher the jet flow velocity; the liquid jet inlet with an inclination angle of 55°-65° with the horizontal line can be Providing a solution flow with a certain inclination angle can increase the solution renewal rate inside the microstructure template during the electroforming process, increase the ion concentration inside the microstructure template, and thus improve the poor mass transfer problem during the electroforming process; during the electroforming process, a flushing liquid magnetic pump and a flushing liquid inlet are used to achieve a horizontally incident flushing liquid flow, and the flushing liquid flow velocity at the flushing liquid inlet is controlled to be 0.1-0.4m / s. The low flow rate (0.2-0.4m / s) of the horizontal flushing liquid can eliminate the eddy current on the surface of the microstructure template to balance the flow velocity inside the microstructure template, and improve the mass transfer imbalance inside different microstructure templates during the electroforming process.

[0007] The high aspect ratio metal microstructure electroforming method using the spray-flushing mixed liquid supply electroforming system is characterized in that the microstructure template is an insulating photoresist film prepared by UV-LIGA lithography technology or a conductive template made by silicon technology, laser processing, selective corrosion and other processes.

[0008] The beneficial results of the present invention are as follows: (1) A spray-flushing mixed liquid supply electroforming system and a high aspect ratio metal microstructure electroforming method improve the solution renewal rate inside the microstructure template during the electroforming process, increase the ion concentration inside the microstructure template, improve the problems of poor mass transfer and unbalanced mass transfer during the electroforming process, and promote the further application of micro-electroforming technology in MEMS technology; (2) The electroforming liquid can be any electro-depositable metal salt solution. That is, the technology of the invention can be used in all electroforming systems, and the scope of application of the technology will not be limited by the difference in electroforming liquids. (3) The electroforming layer prepared by this technology has good surface quality and high dimensional accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A spray-flushing mixed liquid electroforming method for manufacturing high aspect ratio metal microstructures;

[0010] Figure 2 This is a simulation result diagram of a microstructure mold with a microstructure aspect ratio of 1;

[0011] Figure 3 This is a simulation result diagram of a microstructure mold with a microstructure aspect ratio of 8;

[0012] The numbers in the figure are: 1-liquid storage tank; 2-liquid spraying magnetic pump; 3-liquid spraying inlet; 4-anode plate; 5-constant current power supply; 6-processing tank; 7-flushing liquid inlet; 8-flushing liquid magnetic pump; 9-microstructure template; 10-cathode plate; 11-liquid outlet. DETAILED DESCRIPTION

[0013] The specific implementation process of the present invention is described in detail below in conjunction with the accompanying drawings. The examples are only for illustration and do not limit the scope of the present invention in any way. The following specific examples illustrate the implementation of the present invention

[0014] Example 1:

[0015] Step 1: First, prepare the electroforming copper solution, the formula of which is: CuSO4·5H2O 80 g / L, H2SO4 160 g / L. The temperature of the electroforming solution is 30°C. A microstructure mold prepared by UV-LIGA technology is selected, and the microstructure aspect ratio is 1.

[0016] Step 2: Select the jet inlet with an inclination of 55° to the horizontal line, turn on the jet magnetic pump, and adjust the flow rate to 1.6 m / s. Turn on the flushing magnetic pump and adjust the flow rate to 0.4 m / s. Turn on the power switch and set the current density to 2.5 A / dm 2 .

[0017] Step 3: Turn on the power supply, and after 16 h of electrodeposition, a micro copper column with a height of 500 um is obtained. After the electrodeposition is completed, the photoresist cathode is placed in an acetone solution for ultrasonic treatment to remove the photoresist on the cathode.

[0018] Comparative Example 1:

[0019] Step 1: First, prepare the electroforming copper solution, the formula of which is: CuSO4·5H2O 80 g / L, H2SO4 160 g / L. The temperature of the electroforming solution is 30°C. A microstructure mold prepared by UV-LIGA technology is selected, and the microstructure aspect ratio is 1.

[0020] Step 2: Turn off the jet magnetic pump. Turn on the flushing magnetic pump and adjust the flow rate to 1.6 m / s. Turn on the power switch and set the current density to 2.5 A / dm 2 .

[0021] Step 3: Turn on the power supply, and after 16 h of electrodeposition, a micro copper column with a thickness of 500 um is obtained. After the electrodeposition is completed, the photoresist cathode is placed in an acetone solution for ultrasonic treatment to remove the photoresist on the cathode.

[0022] Figure 2 This is a simulation result diagram of the ion concentration distribution inside a microstructure mold with a microstructure aspect ratio of 1. Figure 2As shown in (a), compared with Comparative Example 1 (only conventional horizontal flushing), the spray-flushing mixed liquid electroforming method in Example 1 can enhance mass transfer and obtain a higher ion concentration inside the microstructure template ( Figure 2 (b)), which can then achieve a complete array microstructure at a higher current density.

[0023] Example 2:

[0024] Step 1: First, prepare the electroforming copper solution, the formula of which is: CuSO4·5H2O 80 g / L, H2SO4 160 g / L. The temperature of the electroforming solution is 30°C. A microstructure mold prepared by UV-LIGA technology is selected, and the microstructure aspect ratio is 8.

[0025] Step 2: Select the jet inlet with an angle of 65° to the horizontal line, turn on the jet magnetic pump, and adjust the flow rate to 3.2 m / s. Turn on the flushing magnetic pump and adjust the flow rate to 0.1 m / s. Turn on the power switch and set the current density to 1.8 A / dm 2 .

[0026] Step 3: Turn on the power supply, and after 22 hours of electrodeposition, a micro copper column with a height of 500 um is obtained. After the electrodeposition is completed, the photoresist cathode is placed in an acetone solution for ultrasonic treatment to remove the photoresist on the cathode.

[0027] Comparative Example 2:

[0028] Step 1: First, prepare the electroforming copper solution, the formula of which is: CuSO4·5H2O 80 g / L, H2SO4 160 g / L. The temperature of the electroforming solution is 30°C. A microstructure mold prepared by UV-LIGA technology is selected, and the microstructure aspect ratio is 8.

[0029] Step 2: Turn off the jet magnetic pump. Turn on the flushing magnetic pump and adjust the flow rate to 3.2 m / s. Turn on the power switch and set the current density to 1.8 A / dm 2 .

[0030] Step 3: Turn on the power supply, and after 22 hours of electrodeposition, a micro copper column with a thickness of 500 um is obtained. After the electrodeposition is completed, the photoresist cathode is placed in an acetone solution for ultrasonic treatment to remove the photoresist on the cathode.

[0031] Figure 3 This is a simulation result diagram of the ion concentration distribution inside a microstructure mold with a microstructure aspect ratio of 8. Figure 3As shown in (a), in the case of comparative example 2 (only conventional horizontal flushing), the ion concentration inside the array micropores is relatively low, which will lead to slow electroforming growth of the array microcolumns or even electroforming failure, and more electroforming growth will occur in the areas on both sides. In contrast, the spray-flushing mixed liquid electroforming method in Example 2 can enhance mass transfer and obtain a higher ion concentration inside the microstructure template ( Figure 3 (b)), which can then achieve a complete array microstructure at a higher current density.

Claims

1. A spray-flushing mixed liquid supply electroforming system, comprising a liquid storage tank (1), a processing tank (6), a constant current power supply (5), an anode plate (4), a cathode plate (10) and a microstructure template (9); The anode plate (4), the cathode plate (10) and the microstructure template (9) are located in the processing groove (6); the microstructure template (9) is located at the part of the cathode plate (10) to be processed, and the anode plate (4) is located above the microstructure template (9); Features: A liquid spray inlet (3) is provided above the processing tank (6), and the liquid spray inlet is inclined at an angle of 55°-65° with the horizontal line; The processing tank (6) is provided with a flushing liquid inlet (7) on one horizontal side and a liquid outlet (11) on the other side; The system also includes a liquid spraying magnetic pump (2) and a liquid flushing magnetic pump (8); One end of the liquid spraying magnetic pump (2) is connected to the liquid storage tank (1), and the other end is connected to the liquid spraying inlet (3); One end of the flushing magnetic pump (8) is connected to the liquid storage tank (1), and the other end is connected to the flushing inlet (7).

2. A high aspect ratio metal microstructure electroforming method using the spray-flushing mixed liquid supply electroforming system of claim 1, characterized in that: The pattern on the microstructure template (9) can be used to prepare microstructures with different high aspect ratios according to specific needs, and the aspect ratio of the microstructure is 1-8; During the electroforming process, a liquid jet magnetic pump (2) and a liquid jet inlet (3) are used to realize a jet flow of the electroforming solution at an inclined angle, and the jet flow velocity at the liquid jet inlet is controlled to be 1.6-3.2 m / s; so as to increase the solution renewal speed inside the microstructure template (9) during the electroforming process, increase the ion concentration inside the microstructure template, and thus improve the poor mass transfer problem during the electroforming process; During the electroforming process, a flushing liquid magnetic pump (8) and a flushing liquid inlet (7) are used to realize a horizontally incident flushing liquid flow, and the flushing liquid flow velocity of the flushing liquid inlet (7) is controlled to be 0.1-0.4 m / s to balance the flow velocity inside the microstructure template (9) and improve the mass transfer imbalance inside different microstructure templates during the electroforming process.

3. The electroforming method according to claim 2, characterized in that: The microstructure template (9) is an insulating photoresist film prepared by UV-LIGA photolithography technology or a conductive template made by silicon technology, laser processing, selective etching and other processes.

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