Plasma electrochemical jet composite processing method and device

Abstract

The present invention relates to the technical field of composite processing, and discloses a plasma electrochemical jet composite processing method and device, wherein an electrolyte is formed into a jet through a spray device and sprayed on a workpiece, and plasma is generated on the surface of the workpiece by applying a suitable voltage, thereby breaking through the oxide film generated on the surface of the workpiece due to the electrochemical jet, realizing the combination of electrolytic plasma processing and electrochemical jet processing, and realizing the processing of chemically inert materials. A workbench is arranged on the frame of the plasma electrochemical jet composite processing device, and a fixture is arranged on the workbench. The spray device includes a nozzle, and the nozzle faces the fixture, and is used to spray the electrolyte to the workpiece; it only needs to clamp the workpiece to be processed on the fixture, connect the nozzle to the negative pole of the power supply, and connect the workpiece to the positive pole of the power supply, and spray the electrolyte on the surface of the workpiece through the nozzle, so as to realize the composite processing mode of electrolytic plasma processing and electrochemical jet processing, which has a simple structure and can effectively reduce the processing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of composite processing, and in particular to a plasma electrochemical jet composite processing method and device. Background Art

[0002] With the continuous innovation of semiconductor technology, the third generation of semiconductor materials, led by silicon carbide (SiC), have great potential in the production of high-frequency, high-temperature, radiation-resistant high-power semiconductor devices due to their advantages such as large bandgap, high breakdown electric field, and high thermal conductivity. Conventional processing methods mainly include wet etching, dry etching, electric spark, laser, chemical or electrochemical processing, etc. Chemically inert metals play an important role in high-tech fields such as aerospace, energy, and medical treatment due to their superb thermal stability, corrosion resistance and other material properties. For example, niobium (Nb) and its alloys can be used in superconducting magnets, high-temperature alloys can be used in rocket propulsion nozzles, gas turbine engines and heat-resistant and burn-resistant equipment, and titanium (Ti) can be used to manufacture medical devices. It is a good biocompatible material. However, chemically inert metals such as niobium and titanium and semiconductor materials such as silicon and silicon carbide are hard, brittle, and chemically stable, and are difficult to process by conventional methods.

[0003] Specifically, wet etching cannot accurately control the pattern, and the etchant is a dangerous strong acid or alkali such as hydrofluoric acid or potassium hydroxide; dry etching has the risk of damaging the wafer, and the equipment is complex and costly, making it unsuitable for mass production; electric spark and laser processing will produce heat-affected zones, recast layers or microcracks on the surface of the material; electrochemical processing is not suitable for chemically inert materials. For example, when materials such as niobium or silicon carbide combine with oxygen, an oxide film insulating layer will be generated on the surface to prevent the electrochemical reaction. Acidic or alkaline electrolytes are usually used to remove the oxide film, which is highly dangerous and environmentally unfriendly, thus limiting the application of conventional electrochemical jets in the processing of chemically inert materials. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a plasma electrochemical jet composite processing method that can achieve surface selective processing of chemically inert materials, and provides a plasma electrochemical jet composite processing device.

[0005] According to the first aspect of the present invention, the plasma electrochemical jet composite processing method includes: using an electrochemical jet through an injection device, spraying an electrolyte to a workpiece to be processed from the nozzle of the injection device, and applying an electric field between the nozzle and the workpiece. Under a set voltage, plasma is generated on the surface of the workpiece to break down the oxide film generated by the electrochemical jet to remove the surface material of the workpiece.

[0006] The plasma electrochemical jet composite processing method according to the embodiment of the present invention has at least the following beneficial effects: the electrolyte is formed into a jet through an injection device and sprayed onto a workpiece, and plasma is generated on the surface of the workpiece by applying a suitable voltage, thereby breaking through the oxide film on the surface of the workpiece generated by the electrochemical jet, thereby realizing the composite of electrolytic plasma processing and electrochemical jet processing, and realizing the processing of chemically inert materials.

[0007] According to some embodiments of the present invention, the electric field is applied between the nozzle and the workpiece by connecting the workpiece to a positive electrode of a power source and connecting the nozzle to a negative electrode of a power source.

[0008] According to some embodiments of the present invention, the power supply is set to a constant voltage output mode, the current waveform output by the power supply is a DC waveform or a pulse waveform, and the voltage range is 100V to 300V.

[0009] According to some embodiments of the present invention, an initial gap between the nozzle and the workpiece is 0.2 mm to 0.8 mm.

[0010] According to some embodiments of the present invention, the electrolyte is a NaNO3 aqueous solution with a mass fraction ranging from 0.5% to 20%, or the electrolyte is a neutral salt solution such as a NaCl aqueous solution.

[0011] According to some embodiments of the present invention, the movement trajectory of the nozzle relative to the surface of the workpiece is controlled to process a desired position.

[0012] The plasma electrochemical jet composite processing device according to the second aspect of the present invention comprises:

[0013] A frame, wherein a workbench is arranged on the frame, and a fixture for clamping a workpiece to be processed is arranged on the workbench;

[0014] a spraying device, comprising a nozzle, the nozzle facing the fixture, for spraying electrolyte toward the workpiece;

[0015] A power supply device, wherein the positive pole of the power supply device is connected to the workpiece, and the negative pole of the power supply device is connected to the nozzle.

[0016] The plasma electrochemical jet composite processing device according to the embodiment of the present invention has at least the following beneficial effects: it only needs to clamp the workpiece to be processed on the fixture, connect the nozzle to the negative pole of the power supply, connect the workpiece to the negative pole of the power supply, and spray the electrolyte on the surface of the workpiece through the nozzle, so as to realize the composite processing method of electrolytic plasma processing and electrochemical jet processing. The plasma electrochemical jet composite processing device according to the embodiment of the present invention can be applied to the plasma electrochemical jet composite processing method of the embodiment described above, realizes the composite processing method of electrolytic plasma processing and electrochemical jet processing, has a simple structure, and can effectively reduce the processing cost.

[0017] According to some embodiments of the present invention, the plasma electrochemical jet composite processing device further includes a driving device, which is connected to the frame and is used to drive the workbench and the nozzle to move relative to each other.

[0018] According to some embodiments of the present invention, an electrolytic tank is further provided on the workbench, the fixture is placed in the electrolytic tank, and the electrolytic tank is used to collect and discharge the electrolyte sprayed from the nozzle.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0021] Figure 1 Schematic diagram of a plasma electrochemical jet composite processing method according to an embodiment of the present invention;

[0022] Figure 2 Schematic diagram of the principle of the plasma electrochemical jet composite processing method according to an embodiment of the present invention;

[0023] Figure 3 It is a schematic diagram of a module of a plasma electrochemical jet composite processing device according to an embodiment of the present invention;

[0024] Figure 4 It is a three-dimensional structural schematic diagram of a partial structure of a plasma electrochemical jet composite processing device according to an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the formation of oxide film on the surface of chemically inert semiconductor silicon carbide;

[0026] Figure 6 for Figure 5 Schematic diagram of material removal;

[0027] Figure 7 Schematic diagram of the change process from electrochemical anodization area to plasma discharge area under different process parameters;

[0028] Figure 8 An example of machining micro-groove patterns on the surface of chemically inert semiconductor silicon;

[0029] Fig. 9 An example of machining micro-groove patterns on the surface of niobium metal;

[0030] Fig.10 Another example of machining micro-grooves patterning a semiconductor silicon surface;

[0031] Fig.11 Another example of a microgroove pattern machined into the surface of niobium metal.

[0032] Reference numerals:

[0033] Nozzle 100, electrolyte tank 110, liquid delivery pipeline 120, liquid return pipeline 130, liquid delivery device 140, filter 150, pressure gauge 160; workpiece 200, discharge 210, oxide film breakdown 220, oxide film 230, bubble 240; power supply device 300, positive power supply electrode 310, negative power supply electrode 320, oscilloscope 330; electrolyte 400; initial gap 500; workbench 600, fixture 610, electrolytic cell 620; first drive unit 710, second drive unit 720, third drive unit 730; curves L1, L2, L3, anodizing area S1, discharge area S2. DETAILED DESCRIPTION

[0034] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0035] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0036] If the first and second are described, they are only used to distinguish the technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0037] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0038] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0039] Chemically inert metals play an important role in high-tech fields such as aerospace, energy, and medicine due to their superb thermal stability, corrosion resistance, and other material properties. For example, niobium (Nb) and its alloys can be used in superconducting magnets, high-temperature alloys can be used in rocket propulsion nozzles, gas turbine engines, and heat-resistant and burn-resistant equipment. Titanium (Ti) can be used to manufacture medical devices and is a good biocompatible material. With the continuous innovation of semiconductor technology, the third-generation semiconductor materials led by silicon carbide (SiC) have great potential for development in the production of high-frequency, high-temperature, radiation-resistant high-power semiconductor devices due to their advantages such as large bandgap width, high breakdown electric field, and high thermal conductivity. However, chemically inert metals such as niobium and titanium and semiconductor materials such as silicon and silicon carbide are difficult to process by conventional methods due to their high hardness, high brittleness, and strong chemical stability.

[0040] In semiconductor technology, etching is a technique for selectively corroding or stripping the material substrate or the surface covering film according to the requirements of the mask pattern design. It is divided into two categories: wet etching and dry etching. Among them: dry etching is to use plasma to physically bombard the material surface and chemically remove the material, which can achieve anisotropic etching, but there is a risk of wafer damage due to ion bombardment, and the equipment is complex and expensive, which is not suitable for mass production. Wet etching is lower in cost than dry etching. Since silicon carbide has excellent chemical stability, conventional acid or alkaline solutions can hardly corrode it. Therefore, electric fields or ultraviolet light are generally introduced to assist wet etching. However, the lateral etching rate of wet etching is close to the longitudinal etching rate, so it is isotropic etching for silicon carbide, so the accuracy of wet etching pattern transfer is low. At the same time, the etching rate of silicon carbide wet etching is slow, which is tens to hundreds of nanometers per minute. In addition, the etchant for silicon carbide wet etching is generally high-concentration hydrofluoric acid or molten potassium hydroxide, which causes great harm to the human body and the environment.

[0041] Other machining methods such as EDM, laser, chemical or electrochemical machining are widely used, each with its own advantages and disadvantages: EDM and laser machining use heat energy to melt and evaporate to remove materials, but heat-affected zones, recast layers or microcracks will appear on the surface of the material. Electrochemical machining uses the electrochemical anodic dissolution reaction of the workpiece material in the electrolyte to achieve localized material removal, without tool loss, no heat-affected zone and residual stress after machining, and no damage to the workpiece surface. During machining, the electrolyte is sprayed onto the surface of the workpiece to be machined at high speed, and electrolytic drilling, milling, cutting and other operations can be performed. It is simple and flexible, the machining area can be controlled, and the machining flexibility is good. However, when inert materials such as niobium or silicon carbide combine with oxygen, an oxide film insulating layer will be generated on the surface to prevent the electrochemical reaction from proceeding. Therefore, the oxide film needs to be removed, which is usually achieved by using acidic or alkaline electrolytes. It is highly dangerous and environmentally unfriendly, thus limiting the application of conventional electrochemical machining in the machining of chemically inert materials.

[0042] Compared with the conventional processing methods mentioned above, the plasma electrochemical jet composite processing method provided by the present invention adopts a composite processing method of electrolytic plasma processing and electrochemical jet processing. Electrolytic plasma technology, also known as plasma electrolytic oxidation, is a composite technology that combines electrolysis and plasma discharge. It has been rapidly developed in recent years because it can significantly improve surface properties and achieve surface coatings with high environmental compatibility. In the electrolytic plasma processing process, an electric field is applied between the tool electrode and the workpiece in an electrolyte environment. Under the action of high voltage, strong ohmic heat causes the electrolytic gas on the electrode surface to precipitate and the electrolyte solution to evaporate. Discharge occurs on the electrode surface to generate plasma, generating a series of chemical, electrical and thermal reactions, thereby being able to achieve oxidation, coating, coloring, deposition and material removal such as surface polishing and cleaning on the workpiece material surface. The embodiment of the present invention adopts electrolytic plasma processing and electrochemical jet processing. The electrolyte is sprayed on the workpiece by a spray device to form a jet, and plasma is generated on the workpiece surface by applying a suitable voltage, thereby breaking through the oxide film generated by the electrochemical jet on the workpiece surface, and realizing the processing of chemically inert materials.

[0043] Figure 1 Schematic diagram of the plasma electrochemical jet composite processing method according to an embodiment of the present invention, Figure 2 The schematic diagram of the principle of the plasma electrochemical jet composite processing method according to the embodiment of the present invention is shown in FIG. - 、Na + , H2O, H2 represent ions and molecules in the electrolyte. The arrows in the figure represent the flow direction of the electrolyte. Figure 1 and Figure 2In the plasma electrochemical jet composite machining method of this embodiment, an electrochemical jet is used by a spray device, and an electrolyte 400 is sprayed toward a workpiece 200 to be machined by a nozzle 100 of the spray device, and an electric field is applied between the nozzle 100 and the workpiece 200. At this time, the electric field intensity acting on the oxide film 230 (indicated by a thick line in the figure) is very high, and a discharge 210 occurs on the electrode surface of the workpiece 200 to generate plasma. Under a set voltage, the plasma generated on the surface of the workpiece 200 can cause the oxide film 230 generated by the electrochemical jet to break down, that is, the oxide film breakdown 220 is achieved, so as to remove the surface material of the workpiece 200 and realize the selective machining of chemically inert materials.

[0044] Taking silicon carbide as an example, compared with etching technology, the plasma electrochemical jet composite processing method proposed in the present invention has the advantages of high efficiency, low cost, environmental protection and no pollution; compared with laser and electric spark machining, the plasma electrochemical jet composite processing method proposed in the present invention will not produce a heat-affected zone to reduce the surface quality, and there is no tool loss; taking niobium as an example, compared with the electrochemical jet processing method, the plasma electrochemical jet composite processing method proposed in the present invention can achieve chemically inert material removal by combining plasma discharge to remove the oxide film; compared with electrolytic plasma technology, the composite processing method proposed in the present invention has the characteristics of flexibility and convenience, and can achieve selective material removal. Therefore, through the embodiment of the present invention, by combining the electrochemical jet processing method and the electrolytic plasma technology, the advantages of each are brought into play to achieve chemically inert material processing, avoiding the constraints of the traditional etching technology, such as complex process flow, many intermediate steps, easy to cause environmental pollution and strict safety protection, reducing costs, and opening up new process methods for the preparation of related products.

[0045] In the plasma electrochemical jet composite processing method of the above embodiment, the method of applying an electric field between the nozzle 100 and the workpiece 200 is: the workpiece 200 is connected to the positive electrode 310 of the power supply, and the nozzle 100 is connected to the negative electrode 320 of the power supply. The basic principle of the plasma electrochemical jet composite processing method of this embodiment is that an electric field is applied between the anode workpiece 200 to be processed and the cathode metal nozzle 100. Due to the electrochemical oxidation-reduction reaction, a layer of oxide film 230 will be generated on the surface of the anode workpiece 200 in the processing area. At the same time, the oxide film 230 and the electrolyte 400 contact interface precipitate gas to generate oxygen bubbles 240 to form a gas film. When the applied voltage exceeds the critical value, by destroying the oxide film 230 and the electrolytic gas film formed on the surface of the workpiece 200, plasma discharge occurs in the spraying area to destroy the oxide film 230, thereby realizing electrochemical etching of the material at high temperature. In this embodiment, the power supply is set to a constant voltage output mode, and the voltage range is 100V to 300V. The specific value can be reasonably configured according to the actual processing material and processing requirements. In addition, the current waveform output by the power supply is a DC waveform or a pulse waveform. An oscilloscope probe can be used to detect the voltage and current signals during processing to monitor the current during processing.

[0046] In the plasma electrochemical jet composite processing method of the above embodiment, the electrolyte 400 is a neutral salt solution, which avoids the strong acid and alkali solutions such as hydrofluoric acid or potassium hydroxide commonly used in processing chemically inert materials, and is environmentally friendly, safe and reliable. Specifically, the electrolyte 400 can be a NaNO3 aqueous solution with a mass fraction range of 0.5% to 20%, or a NaCl aqueous solution.

[0047] In the plasma electrochemical jet composite machining method of the above embodiment, the position of the nozzle 100 is adjusted before machining to maintain an initial gap 500 between the nozzle 100 and the workpiece 200. In this embodiment, the initial gap 500 can be 0.2 mm to 0.8 mm, and can be configured accordingly according to different materials.

[0048] In the plasma electrochemical jet composite processing method of the above embodiment, a nozzle 100 with an inner diameter of 0.1 mm to 2 mm can be selected, and a stainless steel 304 material nozzle 100 can be selected. The nozzle 100 is connected to the electrolyte tank 110 through a pipeline to continuously supply the electrolyte 400. The electrolyte 400 can be pumped to the nozzle 100 by an electrolyte pump. The pipeline can be provided with a pressure gauge to measure the real-time pressure, and the pressure of the electrolyte 400 is adjusted so that the flow rate of the electrolyte 400 reaches a set value, for example, the flow rate of the electrolyte 400 can be 3.8 m / s.

[0049] In the plasma electrochemical jet composite machining method of the above embodiment, the electrolyte 400 sprayed by the nozzle 100 can be collected by the electrolytic cell, and the electrolytic cell is connected to the electrolyte tank 110, so that the electrolyte 400 in the electrolytic cell is discharged into the electrolyte tank 110. An electrolyte 400 circulation device can also be configured to realize the circulation of the electrolyte 400. Specifically, the fixture can be placed in the electrolytic cell, so when the workpiece 200 is clamped on the fixture for processing, the electrolytic cell can be used to collect and discharge the electrolyte 400 sprayed from the nozzle 100, and the electrolyte 400 circulation device includes an electrolyte tank 110, a liquid delivery pipeline, a liquid return pipeline and a liquid delivery device. The nozzle 100 is connected to the electrolyte tank 110 through the liquid delivery pipeline, and the liquid delivery device is arranged on the liquid delivery pipeline. The liquid return pipeline is connected to the electrolytic cell and is used to discharge the electrolyte 400 in the electrolytic cell into the electrolyte tank 110, and can be sent to the nozzle 100 again through the liquid delivery pipeline to realize the circulation of the electrolyte 400. A filter can be configured on the liquid return pipeline to filter the processing waste to prevent it from flowing into the electrolyte tank 110. An electrolyte pump may be connected to the liquid delivery pipeline to pump the electrolyte to the nozzle 100 . The liquid delivery pipeline may also be provided with a pressure gauge for real-time monitoring of the pressure in the liquid delivery pipeline, thereby serving as a reference for adjusting the injection flow rate of the electrolyte 400 .

[0050] In the plasma electrochemical jet composite machining method of the above embodiment, the voltage critical value for generating plasma discharge to break through the oxide film 230 is determined by factors such as the gap between the nozzle 100 and the workpiece 200 (inter-electrode gap), the concentration of the electrolyte 400 and the material properties of the workpiece 200. The specific value can be reasonably configured according to the actual processing material and processing requirements. For example, for different chemically inert materials such as niobium, silicon, and silicon carbide, by changing the process parameters such as voltage, initial gap 500, and concentration of the electrolyte 400, the plasma generation can be controlled to remove the oxide film 230 and is applicable to the processing of various materials, and has the characteristics of flexible and convenient selective removal of materials.

[0051] In the plasma electrochemical jet composite machining method of the above embodiment, by controlling the relative movement between the nozzle 100 and the workpiece 200 to be machined, a micro-groove structure can be conveniently machined on the material surface, and further changing the movement trajectory can achieve surface patterning machining.

[0052] In the plasma electrochemical jet composite machining method of the above embodiment, the workpiece 200 to be machined can be clamped by a fixture, and the relative movement between the nozzle 100 and the fixture can be achieved by adjusting the relative movement of the nozzle 100 and the fixture. In specific implementation, a mobile workbench can be set, and the fixture can be set on the mobile workbench. The movement of the workpiece 200 can be adjusted by moving the position of the workbench, which is convenient for mechanical adjustment of the position of the workpiece 200. The nozzle 100 can also be set on a driving mechanism, and the position of the nozzle 100 relative to the workpiece 200 can be adjusted by driving the driving mechanism, so that a variety of machining motion trajectories can be achieved.

[0053] The following is a processing flow of a specific embodiment of the plasma electrochemical jet composite processing method, which generally includes the following steps:

[0054] S100: The workpiece to be processed is subjected to ultrasonic degreasing treatment in acetone and ethanol in sequence, then washed with deionized water and dried with compressed air, and the workpiece to be processed is clamped with a fixture and accurately positioned;

[0055] S200: Connect the nozzle to the electrolyte pipeline and adjust the nozzle position so that the initial gap between the nozzle and the workpiece to be processed is 0.2mm to 0.8mm;

[0056] S300: Connect the workpiece to be processed to the positive pole of the power supply, connect the nozzle to the negative pole of the power supply, set the power supply constant voltage output mode, the voltage range is 100V to 300V, the current waveform is DC or pulse, and use an oscilloscope probe to detect the voltage and current signals during processing;

[0057] S400: Turn on the electrolyte pump to spray the electrolyte onto the surface of the workpiece to be processed through the nozzle, and adjust the electrolyte pressure so that the electrolyte flow rate is 3.8m / s;

[0058] S500: Start the power supply, control the machining motion trajectory, generate plasma discharge on the workpiece surface to break through the oxide film for material processing;

[0059] S600: After processing, turn off the power, turn off the electrolyte pump, and remove the workpiece.

[0060] The embodiment of the present invention further provides a plasma electrochemical jet composite processing device, Figure 3 This is a schematic diagram of a module of a plasma electrochemical jet composite processing device according to an embodiment of the present invention. Figure 4 Schematic diagram of the three-dimensional structure of the plasma electrochemical jet composite processing device according to the embodiment of the present invention, and reference is also made to Figure 3 and Figure 4 , and combined with Figure 2The plasma electrochemical jet composite processing device of the embodiment of the present invention includes a frame and a spraying device. A workbench 600 is provided on the frame. A fixture 610 for clamping a workpiece 200 to be processed is provided on the workbench 600. The fixture 610 can be a conventional three-claw or four-claw fixture 610. The spraying device includes a nozzle 100, which faces the fixture 610 and is used to spray an electrolyte 400 onto the workpiece 200. It is only necessary to clamp the workpiece 200 to be processed on the fixture 610, connect the nozzle 100 to the negative electrode 320 of the power supply, and connect the workpiece 200 to the positive electrode 310 of the power supply, spray the electrolyte 400 onto the surface of the workpiece 200 through the nozzle 100, and apply an electric field between the nozzle 100 and the workpiece 200 through the power supply to realize a composite processing method of electrolytic plasma processing and electrochemical jet processing.

[0061] When the power is turned on, an oxide film is generated on the surface of the anode workpiece 200 in the processing area due to the electrochemical redox reaction, which hinders the continuation of the electrochemical reaction. At the same time, oxygen is generated at the interface between the oxide film and the electrolyte 400. When the potential between the two electrodes reaches a critical value, the oxide film, gas film and other dielectrics at the interface are broken down to form a discharge channel, causing the surface of the workpiece 200 to instantly become hot and complex physical and chemical reactions to occur, thereby achieving surface selective processing.

[0062] The plasma electrochemical jet composite processing device of this embodiment can be applied to the plasma electrochemical jet composite processing method of the above-mentioned embodiment to realize a composite processing mode of electrolytic plasma processing and electrochemical jet processing. It has a simple structure, is flexible and convenient to operate, and can effectively reduce processing costs.

[0063] In the plasma electrochemical jet composite processing device implemented above, a power supply device 300 may also be included, the positive electrode of the power supply device 300 is connected to the workpiece 200, and the negative electrode is connected to the nozzle 100. The power supply device 300 outputs high voltage direct current, and the nozzle 100 is made of a conductive material (for example, a metal nozzle 100). The power supply device 300 can be a device that obtains energy from the power grid and provides electrical energy to one or more loads after conversion, or a device that is powered by a battery and is provided by the processing device. In this embodiment, the power supply is set to a constant voltage output mode, and the voltage range is 100V to 300V. The specific value can be reasonably configured according to the actual processing material and processing requirements. In addition, the current waveform output by the power supply is a DC waveform or a pulse waveform. The power supply device 300 is connected to an oscilloscope 330 probe to detect the voltage and current signals during processing to monitor the current during processing.

[0064] In the plasma electrochemical jet composite processing device of the above embodiment, a driving device may also be included. The driving device is connected to the frame and is used to drive the workbench 600 and the nozzle 100 to move relative to each other, so as to realize the relative movement between the workpiece 200 to be processed and the nozzle 100. The gap between the nozzle 100 and the workpiece 200 can be adjusted before processing, and the processing trajectory can be adjusted during the processing, so as to realize patterned scanning processing such as micro grooves.

[0065] Specifically, the driving device can control the motion in three directions of X, Y, and Z axes (illustrated in the figure by conventional X, Y, and Z spatial rectangular coordinate systems). For example, the driving device may include a first driving unit 710, a second driving unit 720, and a third driving unit 730, wherein the first driving unit 710 is connected to the injection device and is used to drive the injection device to move along the Z axis, thereby realizing the movement of the nozzle 100 along the Z axis; the second driving unit 720 is connected to the first driving unit 710 and is used to drive the first driving unit 710 and the injection device to move along the X axis, thereby realizing the movement of the nozzle 100 along the X axis; the third driving unit 730 is connected to the workbench 600 and is used to drive the workbench 600 to move along the Y axis, thereby realizing the movement of the workpiece 200 to be processed along the Y axis. Thus, the relative motion between the nozzle 100 and the workpiece 200 can be adjusted in three directions of X, Y, and Z axes. The first driving unit 710, the second driving unit 720, and the third driving unit 730 can select commonly used power elements such as linear motors and cylinders.

[0066] In other embodiments, the movement adjustment in the X- and Y-axis directions can also be configured on the workbench 600, and the injection device only performs movement control in the Z-axis direction. Specifically, the workbench 600 can be set as an X- and Y-axis motion platform, and the injection device is connected to the Z-axis motion mechanism, that is, a driving mechanism is set to drive the workbench 600 to move along the X- and Y-axis, and another driving mechanism is set to drive the injection device to move along the Z-axis, thereby realizing the movement of the workpiece 200 to be processed in the X- and Y-axis directions and the movement of the nozzle 100 in the Z-axis direction. Similarly, the relative movement between the nozzle 100 and the workpiece 200 can be adjusted in the three directions of the X-, Y- and Z-axis.

[0067] In other embodiments, a three-axis manipulator may be used to manipulate the nozzle 100 for adjustment in the X, Y, and Z directions, while the workbench is stationary and fixed relative to the frame, so that the relative movement between the nozzle 100 and the workpiece 200 can be adjusted in the X, Y, and Z directions.

[0068] In the plasma electrochemical jet composite processing device of the above embodiment, an electrolytic tank 620 may be further provided on the workbench 600, and the fixture 610 is placed in the electrolytic tank 620, and the electrolyte 400 sprayed by the nozzle 100 may be collected through the electrolytic tank 620, and the electrolytic tank 620 is connected to the electrolyte tank 110, so that the electrolyte 400 in the electrolytic tank 620 is discharged into the electrolyte tank 110. An electrolyte 400 circulation device may also be configured to realize the circulation of the electrolyte 400.

[0069] Specifically, the fixture 610 can be placed in the electrolytic cell 620. When the workpiece 200 is clamped on the fixture 610 for processing, the electrolytic cell 620 can be used to collect and discharge the electrolyte 400 sprayed from the nozzle 100. The electrolyte 400 circulation device includes an electrolyte tank 110, a liquid delivery pipeline 120, a liquid return pipeline 130 and a liquid delivery device 140. The nozzle 100 is connected to the electrolyte tank 110 through the liquid delivery pipeline 120. The liquid delivery device 140 is arranged on the liquid delivery pipeline 120 and can be an electrolyte pump for pumping electrolyte. A liquid discharge port can be arranged on the wall or bottom of the electrolytic cell 620. The liquid return pipeline 130 is connected to the liquid discharge port of the electrolytic cell 620, which is used to discharge the electrolyte 400 in the electrolytic cell 620 into the electrolyte tank 110, and can be sent to the nozzle 100 again through the liquid delivery pipeline 120 to realize the circulation of the electrolyte 400. The return line 130 may be provided with a filter 150 to filter the processing waste and prevent it from flowing into the electrolyte tank 110. The liquid delivery line 120 may be connected with an electrolyte pump to pump the electrolyte to the nozzle 100. The liquid delivery line 120 may also be provided with a pressure gauge 160 for real-time monitoring of the pressure in the liquid delivery line 120, so as to serve as a reference for adjusting the injection flow rate of the electrolyte 400.

[0070] In the above embodiment, the nozzle 100 can be a metal nozzle 100 with an inner diameter of 0.1 mm to 2 mm, and the material of the nozzle 100 can be stainless steel 304. The electrolyte 400 can be a NaNO3 aqueous solution with a mass fraction range of 0.5% to 20%, or other neutral salt solutions such as NaCl aqueous solution. The flow rate of the electrolyte 400 can be set to 3.8 m / s. Before processing, the initial gap 500 between the nozzle 100 and the workpiece 200 to be processed can be adjusted to 0.2 mm to 0.8 mm.

[0071] The plasma electrochemical jet composite processing device may also include a controller, which is electrically connected to the composite processing device. Specifically, the controller is used to control the operation of the electrical device in the composite processing device. It can be a PLC (Programmable Logic Controller), a single-chip microcomputer, a time-controlled switch, and a micro-processing terminal, etc. It can realize the driving of the nozzle and / or the workbench, the on and off of the power supply, the on and off of the liquid delivery device, etc. through a preset scheme, so as to realize the orderly operation of the electrical appliance. At the same time, the controller can collect and process the sensor and instrument data (such as pressure gauge, oscilloscope data) in the processing system, which is used to feedback the system operation status and provide a basis for system regulation. The process and method of the controller to realize the control can be easily realized by those skilled in the art. For example, PLC uses a programmable memory to store instructions for performing operations such as logical operations, sequential control, timing, counting and arithmetic operations, and controls various types of mechanical equipment or production processes through digital or analog input and output. It belongs to the prior art and is not the main point of the invention of the present invention, so it will not be repeated here.

[0072] The general steps of processing using the above plasma electrochemical jet composite processing device are as follows:

[0073] 1. Place the workpiece to be processed in the electrolytic cell of the machine tool, clamp it with a fixture and accurately position it. The workpiece to be processed can be pre-treated first: ultrasonic degreasing treatment in acetone and ethanol in sequence, then washed with deionized water and dried with compressed air;

[0074] 2. Install a metal nozzle on the spindle of the processing device, connect the nozzle to the electrolyte pipeline, and adjust the nozzle position to maintain the initial gap between the nozzle and the workpiece to be processed;

[0075] 3. Connect the workpiece to be processed to the positive pole of the power supply device, connect the nozzle to the negative pole of the power supply device, set the power supply device to constant voltage output mode, the voltage range is 100V ~ 300V, the current waveform is DC or pulse, and use an oscilloscope probe to detect the voltage and current signals during processing;

[0076] 4. Turn on the electrolyte pump to spray the electrolyte onto the surface of the workpiece to be processed through the nozzle, and adjust the electrolyte pressure so that the electrolyte flow rate is 3.8m / s;

[0077] 5. Start the power supply of the driving device, control the relative movement of the workpiece and the nozzle to adjust the machining motion trajectory, generate plasma discharge on the surface of the workpiece to break through the oxide film for material processing;

[0078] 6. After processing, turn off the power of the drive device, turn off the electrolyte pump, and remove the workpiece.

[0079] Two specific application examples of the plasma electrochemical jet composite processing method and the plasma electrochemical jet composite processing device according to the embodiments of the present invention are as follows:

[0080] Taking silicon carbide, a chemically inert semiconductor material, as an example, Figure 5 Schematic diagram of the formation of oxide film on the surface of chemically inert semiconductor silicon carbide. Figure 6 for Figure 5 Schematic diagram of material removal in Figure 5 The 1μm and Figure 6 The 200 μm marked in the lower left corner is the scale bar. Figure 7 The schematic diagram of the change process from the anodizing area to the plasma discharge area under different process parameters. The ordinate represents the current density (A / cm 2 ), the horizontal axis represents voltage (V), curve L1 represents Si (0.001-0.01Ω·cm), and curve L2 represents Nb (1.25×10 -9 Ω·cm), and curve L3 represents SiC (0.015-0.028Ω·cm). Figures 5 to 7 During the specific processing, the workpiece to be processed is an n-type 4H-SiC (0001) sample with a size of 10×10mm, a thickness of 350μm, a resistivity of 0.015~0.028Ω·cm, and a surface treated with chemical mechanical polishing. Before the experiment, the sample was ultrasonically degreased in acetone and ethanol in turn, then cleaned with deionized water and dried with compressed air. The cathode is a stainless steel 304 nozzle with an inner diameter of 0.31mm. The electrolyte is a NaNO3 aqueous solution with a certain mass fraction in the range of 0.5% to 20%. The electrolyte flow rate is 3.8m / s, the initial electrode gap is 0.2mm~0.8mm, and the power supply adopts a constant voltage output mode with a voltage range of 200V~300V. The current waveform is DC or pulse, and an oscilloscope probe is used to obtain the voltage and current signals. By Figure 5 and Figure 6 By comparison, it can be seen that at a voltage of 200V, the surface undergoes an electrochemical anodic oxidation process. When the voltage continues to rise and reaches a critical value, plasma discharge will occur to break through the oxide film, and micromachining of chemically inert materials can be achieved under the thermal mechanism. Figure 6 As shown in the figure, under the conditions of voltage 220V and processing time 14s, plasma discharge is generated to break through the oxide film to remove the material and leave a radial micro-pit. The diameter of the micro-pit and its affected area is 633μm, which is about twice the diameter of the nozzle. The dotted line in the figure indicates the affected area of ​​the micro-pit. Figure 7It can be seen that when the electrolyte mass fraction is 20wt.%, the initial machining gap is 200μm, and in the anodized area S1, the current density increases linearly with the increase of voltage. Beyond a certain voltage critical value, plasma discharge occurs and the current density rises at a higher rate, as shown in the curve plasma discharge area S2 in the figure. Depending on the electrolyte concentration, the corresponding critical voltage separating the two areas is in the range of 200V to 260V and a higher electrolyte concentration corresponds to a lower critical voltage.

[0081] Taking chemically inert semiconductor silicon and metallic niobium as examples, Figures 8 to 11 Several examples of microgroove patterns processed on the surfaces of chemically inert semiconductor silicon and metal niobium. The scale bars marked in the lower left corner of the figure are 200μm and 400μm. During the specific processing, the relative movement between the metal nozzle and the workpiece to be processed is controlled to process the microgroove pattern structure on the material surface. The anode workpiece during processing is a p-type Si (100) sample with a size of 10×10mm, a thickness of 460μm, a resistivity of 0.001~0.01Ω·cm, and a surface treated with chemical mechanical polishing; the niobium sample has a size of 10×10mm, a thickness of 400μm, and a resistivity of 1.25×10 -9 Ω·cm. Before the experiment, the sample was ultrasonically degreased in acetone and ethanol, then cleaned with deionized water and dried with compressed air. The cathode was a stainless steel 304 nozzle with an inner diameter of 0.31mm. The electrolyte used was a 20% mass fraction NaNO3 aqueous solution with an electrolyte flow rate of 3.8m / s. The initial electrode gap was 200μm. The power supply adopted a constant voltage output mode with a voltage of 160V. The relative movement speed between the metal nozzle and the workpiece to be processed was 0.3mm / s. Figure 8 and Fig.10 In order to obtain micro-grooves with good dimensional accuracy on the silicon surface using this method, Fig. 9 and Fig.11 Figure 2 shows the microgrooves obtained on the niobium surface using this method.

[0082] The plasma electrochemical jet composite machining method and the plasma electrochemical jet composite machining device of the embodiment of the present invention continuously remove the newly generated oxide film by continuously discharging plasma induced by voltage on the workpiece electrode surface and the charged particles inside the plasma, thereby realizing localized and efficient removal of chemically inert materials, and have good application prospects and advantages. The plasma electrochemical jet composite machining method and the device of the embodiment of the present invention can be applied to composite electrolytic machining machine tools, superconducting magnetic levitation equipment, gas turbine engines, surgical equipment, power semiconductor devices, etc.

[0083] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. Plasma electrochemical jet composite processing method, characterized in that: include: An electrochemical jet is used by a spray device, and an electrolyte is sprayed toward a workpiece to be processed by a nozzle of the spray device, and the workpiece is connected to the positive electrode of a power supply, and the nozzle is connected to the negative electrode of a power supply, and an electric field is applied between the nozzle and the workpiece. Under a set voltage, an electrochemical oxidation-reduction reaction causes an oxide film to be generated on the surface of the workpiece, and gas is precipitated at the contact interface between the oxide film and the electrolyte to generate oxygen bubbles to form an air film. The voltage is continuously increased until the applied voltage exceeds a critical value, and plasma is generated on the surface of the workpiece to break down the oxide film and the air film generated by the electrochemical jet, so as to remove the surface material of the workpiece.

2. The plasma electrochemical jet composite processing method according to claim 1, characterized in that: Set the power supply to constant voltage output mode. The output current waveform is a DC waveform or a pulse waveform. The voltage range is 100 V to 300 V.

3. The plasma electrochemical jet composite processing method according to claim 1, characterized in that: The initial gap between the nozzle and the workpiece is 0.2 mm to 0.8 mm.

4. The plasma electrochemical jet composite processing method according to claim 1, characterized in that: The electrolyte is a neutral salt solution.

5. The plasma electrochemical jet composite processing method according to claim 4, characterized in that: The electrolyte is a NaNO3 aqueous solution with a mass fraction ranging from 0.5% to 20%, or the electrolyte is a NaCl aqueous solution.

6. The plasma electrochemical jet composite processing method according to any one of claims 1 to 5, characterized in that: The movement trajectory of the nozzle relative to the surface of the workpiece is controlled to process the desired position and achieve localized material removal.

7. A plasma electrochemical jet composite processing device for implementing the plasma electrochemical jet composite processing method according to any one of claims 1 to 6, characterized in that: include: A frame, wherein a workbench is arranged on the frame, and a fixture for clamping a workpiece to be processed is arranged on the workbench; a spraying device, comprising a nozzle, the nozzle facing the fixture, for spraying electrolyte toward the workpiece; A power supply device, wherein the positive pole of the power supply device is connected to the workpiece, and the negative pole of the power supply device is connected to the nozzle.

8. The plasma electrochemical jet composite processing device according to claim 7, characterized in that: It also includes a driving device, which is connected to the frame and is used to drive the workbench and the nozzle to move relative to each other.

9. The plasma electrochemical jet composite processing device according to claim 7 or 8, characterized in that: An electrolytic tank is also provided on the workbench, the fixture is placed in the electrolytic tank, and the electrolytic tank is used to collect and discharge the electrolyte sprayed from the nozzle.

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