CN110539044B - Method and device for chemically etching microstructure by spark assistance - Google Patents
Method and device for chemically etching microstructure by spark assistance Download PDFInfo
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- CN110539044B CN110539044B CN201910918224.3A CN201910918224A CN110539044B CN 110539044 B CN110539044 B CN 110539044B CN 201910918224 A CN201910918224 A CN 201910918224A CN 110539044 B CN110539044 B CN 110539044B
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H11/00—Auxiliary apparatus or details, not otherwise provided for
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H5/00—Combined machining
- B23H5/02—Electrical discharge machining combined with electrochemical machining
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Abstract
The invention discloses a method and a device for chemically etching a microstructure by spark assistance, wherein the method for chemically etching the microstructure by spark assistance comprises the following steps: providing a pulse power supply, wherein the positive electrode of the pulse power supply is connected with the anode, and the negative electrode of the pulse power supply is connected with the tool electrode; providing a working fluid system, wherein the working fluid system supplies electrolyte, and the anode and the tool electrode are arranged in the electrolyte; and switching on the pulse power supply, wherein the pulse power supply outputs a pulse direct-current voltage, and the pulse direct-current voltage has forward bias. The invention can restrain the consumption of the tool electrode by applying the pulse direct current with forward bias, the workpiece does not need to be connected with a power supply, and the workpiece is not influenced by the conductivity of the workpiece material, so that the high-efficiency, high-precision and high-surface-quality processing of the conductive material and the non-conductive material can be realized.
Description
Technical Field
The invention relates to the field of microstructure processing, in particular to a method and a device for chemically etching a microstructure by spark assistance.
Background
At present, the microstructure is widely applied in the fields of biomedical treatment, microreactors, microelectronic chips, high-end clock covers and the like. Taking a microfluidic chip in biomedical treatment as an example, a large number of elongated micro-grooves with uniform cross sections are formed in the microfluidic chip, so that hundreds of samples can be analyzed simultaneously in a few minutes or less, and the flow of liquid is controllable, and the consumption of samples and reagents is extremely low. However, as the substrate material of the microfluidic chip is usually glass (the main component of SiO 2), the glass has the characteristics of high hardness and good chemical stability, so that the surface micro-groove processing is very difficult.
Common methods for glass surface micro-groove processing include mechanical milling, hot-melt processing, wet etching, spark-assisted chemical etching, and the like. The mechanical milling is a mechanical processing method for processing the surface of a workpiece by taking a rotary multi-edge milling cutter as a cutter, has the characteristics of convenient operation, high processing efficiency and good size consistency, and is a main processing method for processing glass materials. However, since the tool used in machining requires a hardness higher than that of the workpiece material, and the mohs hardness of the glass itself reaches about 8, it is necessary to use diamond or cubic boron nitride having a higher hardness as the tool, and the tool is worn in machining, so that the cost of mechanical milling of the glass is high. In addition, as glass is a hard and brittle material, defects such as edge breakage, microcracks and the like are easy to generate in mechanical processing, and therefore, the processing method has certain limitation in application; the high-temperature hot-melting processing is a processing mode of heating a workpiece to a (liquid) melting point and then forming or connecting, and has the advantages of stable processing, long service life, difficult corrosion and the like. However, the glass has a higher melting point, is generally above 1000 ℃, has poor portability in operation under a high-temperature environment, is easy to generate thermal stress, is easy to generate thermal deformation after being cooled, and therefore has poor processing precision and limitation in application; wet etching is a technique of immersing etching material in etching liquid to carry out etching, is pure chemical etching, and has the characteristics of good etching surface quality, high etching efficiency and stability. However, since the chemical characteristics of the glass are stable, only hydrofluoric acid (HF) or sodium hydroxide (NaOH) can be used as an etching solution, and wet etching is used for microstructural processing, so that a mask is required for selective material removal, and the mask preparation process is complex and tedious, the wet etching has the same limitation in application. The spark-assisted chemical etching (SPARK ASSISTED CHEMICAL ENGRAVING, SACE) is a process of composite electrolytic machining (ECD) and electric spark machining (EDM), wherein a stable air film is formed on the surface of a cathode through electrochemical reaction, then breakdown occurs when the voltage reaches a critical value, and the workpiece material is selectively removed by combining the high temperature and high pressure generated during breakdown with the etching characteristic of the electrolyte on the workpiece. The spark-assisted chemical etching glass surface microstructure has the characteristics of stable processing, low processing cost, high processing precision and good processing surface quality, and is very suitable for processing the glass surface microstructure.
In recent years, insulating materials or semiconductor materials such as spark-assisted chemical etching glass and the like have become hot problems of research, and a great deal of research results are also obtained by conducting intensive research on the technology by using the technology, but at present, holes are punched in quartz glass and zirconia ceramics, but the technology is a process of reversely copying on the surface of a workpiece due to tool electrode loss (cathode loss) in the processing process, and the taper formed by the tool loss is necessarily reflected on the surface of the workpiece, so that the problem that the processed holes have low roundness and overlarge taper angle can be caused. In general, the shortcomings of current spark-assisted chemical etching are mainly reflected in: (1) The technology has the advantages that when a constant direct current power supply is used, the over-cut amount of the side wall of the micro groove is large, and the accurate control of the machining precision is affected; (2) The undercut of the micro-groove side wall is suppressed when pulsed direct current is used, but the electrode is lost, so that the uniformity of the cross-section dimension is poor when long grooves are processed.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method and a device for chemically etching a microstructure by spark assistance, which can achieve the effect of effectively inhibiting the loss of a tool electrode.
The technical scheme adopted by the invention is as follows:
The invention provides a method for chemically etching a microstructure by spark assistance, which comprises the following steps:
Providing a pulse power supply, wherein the positive electrode of the pulse power supply is connected with the anode, and the negative electrode of the pulse power supply is connected with the tool electrode;
Providing a working fluid system, wherein the working fluid system supplies electrolyte, and the anode and the tool electrode are arranged in the electrolyte;
and switching on the pulse power supply, and outputting a pulse direct-current voltage by the pulse power supply, wherein the pulse direct-current voltage has forward bias, and etching a workpiece by using the tool electrode.
The pulse direct current voltage output by the pulse power supply has forward bias, namely the output pulse direct current voltage has forward voltage bias compared with the standard direct current voltage. In operation, the anode, tool electrode and electrolyte form a passageway, and the tool electrode is used to etch the workpiece. When the existing spark-assisted chemical etching process uses standard pulse direct-current voltage, tool electrode loss can occur when the potential of the standard pulse direct-current voltage in a negative half period is 0V, the tool electrode loss can be restrained by forward biasing the standard pulse direct-current voltage, the time and the loss amount of the tool electrode can be controlled by controlling the time and the bias voltage amount of forward biasing the standard pulse direct-current voltage, and then the micro-grooves with variable cross-section shapes can be processed independently and selectively.
Preferably, the voltage bias of the forward bias is greater than the absolute value of the equilibrium potential of the tool electrode in the electrolyte. The absolute value of the equilibrium potential of the tool electrode in the electrolyte is denoted as |equilibrium potential|, and when the voltage bias amount for forward biasing the standard pulse dc voltage is larger than the |equilibrium potential|, the tool electrode loss can be completely suppressed.
Further preferably, the voltage bias amount of the forward bias > (absolute value of the equilibrium potential of the tool electrode in the electrolyte +1v).
The invention also provides a device for chemically etching the microstructure by spark assistance, which comprises:
The power supply system comprises a pulse power supply, wherein the pulse power supply can output a pulse direct-current voltage, the pulse direct-current voltage is provided with a forward bias, the positive electrode of the pulse power supply is connected with the anode, and the negative electrode of the pulse power supply is connected with the tool electrode;
The working solution system comprises a processing tank, wherein the processing tank is used for containing electrolyte, and the anode and the tool electrode are both positioned in the electrolyte when in a working state. Preferably, the pulse power supply is an arbitrary waveform power supply.
Preferably, the pulse power supply comprises a pulse direct-current voltage output module and a bias voltage output module which are connected through a circuit, wherein the pulse direct-current voltage output module is used for outputting standard pulse direct-current voltage, and the bias voltage output module is used for biasing the standard pulse direct-current voltage.
Preferably, the tool electrode is a group electrode consisting of at least two electrodes. The group electrode can be an array electrode formed by at least two single electrodes, and by arranging the group electrode, the synchronous processing of the group holes or the milling processing of the group grooves can be realized.
Preferably, the tool electrode further comprises a feed adjusting device, wherein the feed adjusting device is connected with the tool electrode and used for adjusting movement of the tool electrode. The feed adjustment device includes, but is not limited to, a machine tool motion platform.
Preferably, the working fluid system further includes an electrolyte circulation tank, and the electrolyte circulates between the processing tank and the electrolyte circulation tank.
Preferably, a workpiece support frame is arranged in the processing groove.
The beneficial effects of the invention are as follows:
In conventional spark-assisted chemical etching, a standard pulsed DC voltage is used, which at a potential of 0V causes the tool electrode to react, resulting in electrode wear. The invention provides a method for spark-assisted chemical etching of a microstructure, which can inhibit the consumption of a tool electrode by applying a pulse direct current with forward bias, and can control the time and the loss of the tool electrode by controlling the time and the bias voltage of forward bias on a standard pulse direct current voltage, thereby autonomously and selectively processing micro-grooves with variable cross-section shapes. In addition, the high-temperature plasma formed in the existing electric spark machining technology acts on two electrodes, so that electrode loss is formed on the two electrodes, and the workpiece is required to be made of a conductive material, so that only the conductive material can be machined. In the further beneficial effect, the aim of completely inhibiting the tool electrode loss can be achieved by limiting the voltage bias of the forward bias to be larger than the equilibrium potential of the tool electrode reaction.
Drawings
FIG. 1 is a graph showing the polarization curve of a tungsten electrode in a 6mol/L NaOH solution in example 1;
FIG. 2 is a graph showing the output waveforms of the pulse power supply used in the experiment in example 1;
FIG. 3 is a schematic diagram of the structure of the apparatus for spark-assisted chemical etching of microstructures in example 2;
FIG. 4 is a schematic diagram showing the breakdown of the gas film in the processing region when the tool electrode is used to process the workpiece in example 2;
FIG. 5 is a graph showing the characterization of a tungsten electrode after spark-assisted chemical etching using a standard pulsed DC and a pulsed DC biased at 2V in example 2;
fig. 6 is a graph depicting tungsten electrodes and resulting micro-trenches after spark-assisted chemical etching in example 3.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
Example 1
The embodiment of the invention provides a method for chemically etching a microstructure by spark assistance, which comprises the following steps:
(1) Providing a pulse power supply, wherein the positive electrode of the pulse power supply is connected with the anode, and the negative electrode of the pulse power supply is connected with the tool electrode;
(2) Providing a working fluid system, wherein the working fluid system supplies electrolyte, and the anode and the tool electrode are arranged in the electrolyte;
(3) And switching on the pulse power supply, wherein the pulse power supply outputs a pulse direct-current voltage, and the pulse direct-current voltage has forward bias.
In the embodiment, the pulse power supply is an arbitrary waveform power supply, a pulse direct-current voltage of 2V forward bias is output in the experiment, the anode is a graphite electrode, the tool electrode is a tungsten electrode, and the electrolyte is 6mol/L NaOH.
As shown in fig. 1, the polarization curve of the tungsten electrode (connected with the positive electrode to form an anode) in 6mol/L NaOH (i.e., the electrolyte in the spark-assisted chemical etching microstructure test in this example) was studied, and it can be seen from the polarization curve that the equilibrium potential U 0 of the tungsten electrode is-0.9V under the above processing conditions, i.e., the tungsten undergoes an anodic oxidation reaction when the anode voltage is greater than-0.9V, and the ionic reaction equation is as follows:
W+8OH-→WO4 2-+4H2O+6e-
When the tungsten electrode undergoes an anodic oxidation reaction, the electrode material is consumed, i.e., electrode loss is formed.
Unlike the electrode connection method in making the polarization curve, when the spark-assisted chemical etching microstructure is performed, the tungsten electrode is connected with the negative electrode, and the pulse power supply is connected for etching, and the experiment adopts the pulse power supply output waveform shown in fig. 2. When the connected pulse power source outputs a standard pulse direct current voltage, as shown in fig. 2 (a), the whole pulse period of the standard pulse direct current voltage is ρ, the direct current voltage output in the positive half period t 1 is ρ, the voltage output in the negative half period t 0 is f =0, and the |equilibrium potential U 0 |= | -0.9v| is drawn above the coordinate axis zero line because the negative potential of the voltage waveform actually causes the tungsten electrode to undergo oxidation reaction. In electrochemical machining, the equilibrium potential is actually the zero line where the oxidation-reduction reaction occurs, so that the potential below the equilibrium potential (0V) in fig. 2 (a) will cause the tungsten electrode to undergo anodic oxidation reaction, resulting in electrode loss, which also explains the reason for electrode loss in conventional standard pulsed dc spark-assisted chemical etching. In order to overcome the above-mentioned drawbacks, the embodiment of the present invention proposes forward biasing the output standard pulse dc voltage, so as to realize suppression of the consumption of the tool electrode, and when the voltage amount U t' of the forward bias is greater than the absolute value of the equilibrium potential of the tool electrode in the electrolyte (2V is greater than-0.9V), as shown in the voltage waveform of fig. 2 (b), no potential line below the equilibrium potential is present, and no anodic oxidation reaction occurs to the tungsten electrode, so that the electrode loss can be completely suppressed.
Example 2
Referring to fig. 3, the device comprises a pulse power supply 1, the pulse power supply 1 can output pulse direct current voltage, the pulse direct current voltage is provided with forward bias, the positive electrode of the pulse power supply 1 is connected with an anode 3, the negative electrode of the pulse power supply 1 is connected with a tool electrode 4, the device further comprises a working fluid system, the working fluid system comprises a processing tank 2, electrolyte 7 is contained in the processing tank 2 in a working state, the anode 3 and the tool electrode 4 are placed in the electrolyte 7 to form a passage, and the tool electrode 4 is used for etching a workpiece 5. The pulse power supply 1 can be any waveform power supply; the pulse direct current voltage output module can generate standard pulse direct current voltage, and the bias voltage output module can bias the standard pulse direct current voltage so that the pulse power supply finally outputs the pulse direct current voltage with forward bias, the pulse direct current voltage output module is of an existing structure such as an existing pulse direct current power supply, and the bias voltage output module is of an existing structure such as a direct current voltage deflection circuit mentioned in CN 1881785A. In this embodiment, the pulse power source 1 is an arbitrary waveform power source, the anode 3 is a graphite electrode, and the tool electrode 4 is a tungsten electrode. In order to facilitate the control of the adjustment of the distance between the tool electrode 4 and the workpiece 5, the device for spark-assisted chemical etching of microstructures may further comprise in a preferred embodiment a feed adjustment device 8, in particular the feed adjustment device 8 may be a machine tool motion platform, which is connected to the tool electrode 4 via an electrode mounting clamp 9, thereby controlling the adjustment of the movement of the tool electrode 4. In some preferred embodiments, a workpiece support 6 is also provided in the processing tank 2 for supporting the workpiece 5. In some preferred embodiments, the working fluid system further comprises an electrolyte circulation tank 10, in which in the working state electrolyte 7 is pumped from the processing tank 2 into the electrolyte circulation tank 10 by means of an electrolyte outflow pump 11, and electrolyte 7 is pumped from the electrolyte circulation tank 10 by means of an electrolyte inflow pump 12, through a filter 13 and into the processing tank 2.
The etching was performed using the apparatus for spark-assisted chemical etching of microstructures of fig. 3, using the following steps:
1. Clamping: the workpiece 5 is arranged on a workpiece support frame 6, is pressed by external mechanical force and is fixed, and the liquid level of electrolyte 7 is 1-3mm higher than the upper surface of the workpiece 5, wherein the workpiece 5 is glass in the embodiment; the graphite electrode is soaked in the electrolyte 7; the tungsten electrode is clamped on the electrode mounting clamp 9, and the electrode mounting clamp 9 is connected with a machine tool moving platform and can carry out XYZ axis movement. For other types of feeding adjustment devices, for example, the upper part only performs Z-axis feeding, the lower part performs XY-direction movement, and the lower part performs other movement control modes such as XYZ-direction movement, and finally, the XYZ-axis movement control can be realized.
2. Determining an initial machining gap: the Z-axis height is adjusted to determine the distance between the tungsten electrode and the workpiece 5, namely the initial machining gap, and the gap can be adjusted according to the process so as to achieve the optimal machining effect.
3. And (3) electrolyte circulation: starting an electrolyte inflow pump 12, pumping the electrolyte 7 from the electrolyte circulation tank 10, passing through a filter 13, flowing into the processing tank 2, and then pumping the electrolyte 7 back into the electrolyte circulation tank 10 under the action of an electrolyte outflow pump 11 to form electrolyte circulation, wherein the liquid level of the electrolyte 7 is kept to be 1-3mm higher than the upper surface of the workpiece 5 in the whole process by controlling the flow between the two pumps, and the electrolyte 7 is 6mol/LNaOH in the embodiment.
4. The power connection mode is as follows: the positive electrode of the pulse power supply 1 is connected with a graphite electrode, and the negative electrode is connected with a tungsten electrode.
5. Spark assisted chemical etching of microstructures: setting a target waveform on the arbitrary waveform power supply, and starting the arbitrary waveform power supply and the double pumps. Fig. 4 is a schematic diagram showing the breakdown of the gas film in the processing area when the tool electrode is used to process a workpiece, as shown in fig. 4, the electrolyte is electrolyzed under the action of an electric field to generate a large amount of hydrogen bubbles 14, the soaking section of the tungsten cathode soaked in the electrolyte (the area ratio of the soaking section of the graphite electrode soaked in the electrolyte to the soaking section of the tungsten electrode soaked in the electrolyte is greater than 100) is rapidly surrounded by the bubbles, the gas film is finally formed as the bubbles grow and gather, and when the voltage reaches a critical value, the arc 15 breaks down. When the arc 15 breaks down, a plasma channel with a certain temperature (the temperature is 300-500 ℃) is formed, and the working fluid is extruded by instant high-temperature expansion, so that bubbles are cavitated, and a hydraulic effect is generated. The local high temperature and the hydraulic action induced by the tungsten electrode tip strengthen the etching of the electrolyte to the glass, and the holes and the grooves are punched and milled on the glass along with the movement and the feeding of the tool electrode 4.
Process verification is carried out on standard pulse direct current and offset 2V pulse direct current spark auxiliary chemical etching respectively, and the parameters of the standard pulse direct current voltage adopted in comparative example 1 are as follows: the pulsed dc voltage used in this example 2 was forward biased by 2V at the standard pulsed dc voltage of the comparative example, the other parameters were the same, the electrolyte used for process verification was 6mol/L NaOH, the tool electrode tungsten electrode diameter was 300 μm, immersed by 1mm, and the tungsten electrodes used in comparative example 1 and this example 2 were characterized after 60s of processing, as shown in fig. 5, wherein (a) in fig. 5 represents a tungsten electrode diagram after spark-assisted chemical etching by the standard pulsed dc voltage of comparative example 1; fig. 5 (b) shows a tungsten electrode pattern after spark assisted chemical etching using a pulsed dc voltage of 2V forward bias in example 1. It can be seen from the figure that there is a significant loss of tungsten electrode at standard pulse direct current, the electrode diameter is reduced from 300 μm to 221 μm, while the loss of tungsten electrode is completely suppressed at pulse direct current using forward bias of 2V, and the electrode diameter remains unchanged at 300 μm.
In the present embodiment, a single tungsten electrode is used as an example, and when a group electrode composed of two or more electrodes is used as a tool electrode, the group hole synchronous machining or the group groove milling machining can be realized, and the group electrode can be repeatedly used. In the embodiment, the pulse power supply outputs the pulse direct current voltage with forward bias in the whole pulse period, the voltage bias quantity of the forward bias is larger than the absolute value of the balance voltage of the working electrode, the loss of the tool electrode is restrained, and the time of forward bias and the voltage bias quantity of the forward bias on the standard pulse direct current waveform can be controlled according to actual requirements in the actual operation process, so that the time of the loss and the loss quantity of the tool electrode are controlled, and further the processing of the microstructure with the variable cross section shape is realized.
Example 3
In this embodiment, the device of fig. 3 for spark-assisted chemical etching of the microstructure is used for etching, and parameters of the pulse dc power supply are as follows: direct current voltage=50v, frequency=1khz, duty ratio=50wt%, forward bias voltage amount=2v, electrolyte used is 6mol/LNaOH, tool electrode used is tungsten electrode with diameter of 300 μm, workpiece is quartz glass, workpiece is immersed in 1mm, initial gap between tool electrode and workpiece is 10 μm, draft is 100 μm, machining length is 1mm, workpiece feeding speed is 1 μm/s. The pulse direct current with the bias of 2V is utilized to carry out spark auxiliary chemical etching on the surface of quartz glass, the processed tungsten electrode and micro-grooves generated on the quartz glass are characterized, as shown in fig. 6, the (a) in fig. 6 shows the processed tungsten electrode, no electrode loss can be seen, the diameter of the tungsten electrode is kept 300 mu m, the (b) in fig. 6 shows the micro-grooves generated after processing, the width of the micro-grooves processed by the pulse direct current with the bias of 2V is 345 mu m, the single-side over-cutting amount is 22.5 mu m, the dimensional consistency in the length direction of the grooves is good, the width error is less than 5 mu m, and the processed surface is smooth due to the grooves processed by the chemical etching.
Claims (9)
1. A method of spark assisted chemical etching of microstructures comprising the steps of: providing a pulse power supply, wherein the positive electrode of the pulse power supply is connected with the anode, and the negative electrode of the pulse power supply is connected with the tool electrode; providing a working fluid system, wherein the working fluid system supplies electrolyte, and the anode and the tool electrode are arranged in the electrolyte; switching on the pulse power supply, and outputting a pulse direct-current voltage with forward bias by the pulse power supply, and etching a workpiece by using the tool electrode; the voltage bias of the forward bias is greater than the absolute value of the equilibrium potential of the tool electrode in the electrolyte.
2. The method of spark-assisted chemical etching of a microstructure of claim 1 wherein the forward biased voltage bias (absolute value of the tool electrode's equilibrium potential in the electrolyte +1v).
3. An apparatus for spark assisted chemical etching of microstructures comprising: the power supply system comprises a pulse power supply, wherein the pulse power supply can output a pulse direct-current voltage, the pulse direct-current voltage is provided with a forward bias, the positive electrode of the pulse power supply is connected with the anode, and the negative electrode of the pulse power supply is connected with the tool electrode; the working solution system comprises a processing tank, wherein the processing tank is used for containing electrolyte, and the anode and the tool electrode are both positioned in the electrolyte when in a working state; the voltage bias of the forward bias is greater than the absolute value of the equilibrium potential of the tool electrode in the electrolyte.
4. A device for spark-assisted chemical etching of microstructures as in claim 3 wherein said pulsed power source is an arbitrary waveform power source.
5. A device for spark-assisted chemical etching of microstructures as in claim 3 wherein said pulsed power supply comprises a pulsed dc voltage output module and a bias voltage output module in circuit connection, said pulsed dc voltage output module to output a standard pulsed dc voltage, said bias voltage output module to bias said standard pulsed dc voltage.
6. The apparatus for spark-assisted chemical etching of a microstructure according to any one of claims 3 to 5, wherein the tool electrode is a group electrode consisting of at least two electrodes.
7. The apparatus for spark-assisted chemical etching of a microstructure according to any one of claims 3 to 5, further comprising a feed adjustment device coupled to the tool electrode for adjusting movement of the tool electrode.
8. The apparatus for spark-assisted chemical etching of a microstructure according to any one of claims 3 to 5, wherein the working fluid system further comprises an electrolyte circulation tank, the electrolyte circulating between the processing tank and the electrolyte circulation tank.
9. The apparatus for spark-assisted chemical etching of a microstructure according to any one of claims 3 to 5, wherein a workpiece support is provided in the processing tank.
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