Plasma voltage characteristic on-line monitoring device and method

Abstract

The embodiment of the invention provides a plasma voltage characteristic on-line monitoring device and method, and the device comprises a detection handle assembly, a shielding cable, a monitoring host, a signal processing module employing a resistance-capacitance voltage division and operational amplification architecture with AC amplitude-frequency characteristic compensation, and a full-scale linear non-step ADC sampling module. And in combination with a sliding window type transient voltage capture algorithm, plasma voltage signals are acquired, processed and monitored. By means of the technical scheme, full-scale high-precision online detection of the plasma voltage characteristics within the bandwidth ranging from-500 V to + 500 V and 0-2 MHz can be achieved, data support is provided for performance calibration and closed-loop adjustment of plasma cleaning equipment, and the risk of electrical damage to workpieces in the plasma cleaning process is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of plasma detection technology, specifically to an online monitoring device and method for plasma voltage characteristics. Background Technology

[0002] Plasma treatment technology, with its advantages of being clean, efficient, pollution-free, and adaptable to a wide range of materials, is widely used in the surface cleaning and modification processes of workpieces such as PCBs, PCBAs, semiconductor wafers, and glass. However, under actual working conditions, affected by equipment operating parameters and environmental factors, the plasma generated by the nozzles of plasma cleaning equipment is prone to deviating from electrical neutrality, forming an AC voltage with specific frequency characteristics, and even containing high-amplitude transient impulse voltages, causing irreversible electrical damage to workpieces with highly sensitive electrical characteristics.

[0003] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the Invention

[0004] This application provides an online monitoring device and method for plasma voltage characteristics to solve or alleviate one or more of the technical problems mentioned above.

[0005] As a first aspect of the present application, the present application provides an online monitoring device for plasma voltage characteristics, including a detection handle assembly, a shielded cable, and a monitoring host; The detection handle assembly includes an insulated handle, a plasma receiving plate, and a heat-resistant insulating component. The plasma receiving plate is used to receive the plasma jet non-contactly to couple its voltage signal. It is attached to the upper surface of the heat-resistant insulating component, which is fixedly connected to the insulated handle. The shielded cable is electrically connected between the plasma receiving board and the monitoring host. The monitoring host is equipped with an ADC sampling module, a signal processing module, and a microprocessor. The signal processing module includes a resistor-capacitor voltage divider unit and an operational amplifier unit. The RC voltage divider unit includes the upper arm resistor. and the lower arm resistor of the voltage divider And the upper arm compensation capacitor C used to compensate for AC amplitude-frequency characteristics. in1 and the voltage divider lower arm compensation capacitor C in2 Among them, the upper arm resistor of the voltage divider The input terminal is connected to the plasma receiving plate, and its output terminal is connected to the lower arm resistor of the voltage divider. The input terminal is connected; the equivalent resistance of the shielded cable is Rs, and the equivalent capacitance is Cs; the compensation unit satisfies the amplitude-frequency characteristic compensation formula: × = ×(Cs+ The voltage divider resistors satisfy +Rs>> .

[0006] In one implementation, the upper arm resistor of the voltage divider One end is electrically connected to the output end of the shielded cable, and the upper arm resistor of the voltage divider is... The other end is connected to the lower arm resistor of the voltage divider. One end is electrically connected to the input terminal of the operational amplifier unit, and the lower arm resistor of the voltage divider is connected. The other end is grounded; Voltage divider upper arm compensation capacitor C in1 With the upper arm resistor of the voltage divider Parallel connection, voltage divider lower arm compensation capacitor C in2 With the lower arm resistor of the voltage divider in parallel; Among them, the upper arm resistor of the voltage divider Voltage divider lower arm resistor The equivalent resistance Rs of the cable satisfies the following relationship: .

[0007] In one embodiment, the operational amplifier unit includes an operational amplifier U1.1, a feedback resistor R4, a gain resistor R5, and a matching resistor R3. The non-inverting input of the operational amplifier U1.1 is electrically connected to the output of the RC voltage divider unit, and the inverting input is electrically connected to one end of the feedback resistor R4 and one end of the gain resistor R5. The other end of the feedback resistor R4 is grounded, and the other end of the gain resistor R5 is electrically connected to the output of the operational amplifier U1.1. The matching resistor R3 is connected in series between the non-inverting input of the operational amplifier U1.1 and the output of the RC voltage divider unit. The feedback resistor R4, the gain resistor R5, and the matching resistor R3 are all high-precision, low-temperature drift resistors. Output voltage of operational amplifier unit Input voltage acquired by the plasma receiving plate The following relationship must be satisfied: .

[0008] In one implementation, the equivalent resistance of the shielded cable Much smaller than the resistance of the upper arm of the voltage divider Electrical characteristics, output voltage of operational amplifier unit Input voltage collected by the plasma receiving plate Furthermore, the following relationship must be satisfied: .

[0009] In one embodiment, the plasma receiving plate is a metal plate with nickel plating on a brass substrate, and the heat-resistant insulating component is an alumina ceramic component. The detection surface of the plasma receiving plate is positioned directly opposite the nozzle of the plasma cleaning equipment, and the detection spacing is 2mm to 20mm. It also includes a grounding terminal for connecting to the grounding terminal of the plasma cleaning equipment.

[0010] In one implementation, the signal processing module has the characteristics of high input impedance and low input capacitive reactance, with an input impedance ≥ 10. 8 Ω, input capacitive reactance ≤10pF; the sampling bandwidth of the signal processing module is 0~2MHz, the voltage measurement range is -500V~+500V, and the ADC sampling module adopts a full-range linear non-segmented sampling architecture.

[0011] In one implementation, the microprocessor is equipped with a transient voltage capture algorithm, which performs the following steps: Using the sampling period of the ADC sampling module as the unit, the voltage values ​​of N consecutive sampling points are sorted by sliding window, and the voltage peak and valley values ​​within the window are extracted. The peak and valley values ​​are compared with the extreme values ​​of the previous window. When the difference exceeds a preset threshold, it is marked as a transient voltage event and the complete sampling data at the corresponding time is stored. Here, N is a positive integer and satisfies N≥2 times the number of Nyquist sampling points corresponding to the sampling bandwidth.

[0012] In one embodiment, the microprocessor includes a storage module and a display module. The storage module is used to store the maximum voltage value, minimum voltage value, and transient voltage extreme value collected within a preset time period. The display module is used to display the plasma voltage waveform and the collected values.

[0013] In one embodiment, a high-voltage protection circuit is also included, with its input terminal connected to the plasma receiving plate and its output terminal connected to the signal processing module. This circuit clamps the input terminal of the signal processing module to a safe voltage range when a transient high voltage exceeding a preset threshold is received.

[0014] As a second aspect of the embodiments of this application, this application provides a method for online monitoring of plasma voltage characteristics, implemented based on any of the above embodiments' online monitoring devices for plasma voltage characteristics, including: Align the detection surface of the plasma receiving plate with the center of the nozzle of the plasma cleaning equipment, adjust the detection spacing to 2mm to 20mm, and connect the plasma receiving plate to the monitoring host through a shielded cable. Start the plasma cleaning equipment, and direct the plasma jet from the nozzle toward the plasma receiving plate; The monitoring host collects signals, analyzes and processes the data, and displays the real-time voltage characteristic data of the plasma through the display module.

[0015] The embodiments of this application employ the above-described technical solution to monitor the real-time voltage characteristics of plasma, thereby achieving observability of plasma voltage characteristics and providing data support for closed-loop regulation of plasma, thus avoiding product damage caused by surface cleaning. Attached Figure Description

[0016] The accompanying drawings exemplify embodiments and form part of the specification, serving together with the textual description to explain exemplary implementations of the embodiments. The illustrated embodiments are for illustrative purposes only and do not limit the scope of the claims. Throughout the drawings, the same reference numerals refer to similar but not necessarily identical elements.

[0017] Figure 1 A schematic diagram of a plasma voltage characteristic monitoring device according to an embodiment of this application is shown. Figure 2 The schematic diagram illustrates the module configuration of a plasma voltage characteristic monitoring device according to an embodiment of this application.

[0018] Figure 3 A flowchart illustrating a plasma voltage characteristic monitoring method according to an embodiment of this application is shown schematically. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0020] It should be noted that the descriptions involving "first," "second," etc., in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0021] In the description of this application, it should be understood that the numerical labels before the steps do not indicate the order of the steps, but are only used to facilitate the description of this application and to distinguish each step, and therefore should not be construed as a limitation of this application.

[0022] This application provides an online monitoring device for plasma voltage characteristics, such as... Figures 1 to 2 As shown, the online plasma voltage characteristic monitoring device includes a non-invasive detection handle 1 assembly, a high-fidelity shielded cable 4, and an intelligent monitoring host 5.

[0023] The detection handle 1 assembly includes an insulated handle 1, a plasma receiving plate 2, and a heat-resistant insulating component 3. The plasma receiving plate 2 is used to receive plasma jets in a non-contact manner to couple their voltage signals. The plasma receiving plate 2 adopts a composite metal structure with a brass substrate plated with nickel, which has both high conductivity and plasma corrosion resistance. It is attached to the upper surface of the heat-resistant insulating component 3 made of alumina ceramic material. The heat-resistant insulating component 3 is fixedly connected to the insulated handle 1.

[0024] During monitoring, the detection surface of the plasma receiving plate 2 is positioned directly opposite the nozzle of the plasma cleaning equipment, with a detection spacing of 2mm to 20mm, achieving non-contact and safe detection and avoiding interference with the plasma flow field caused by the invasive detection of traditional vacuum chamber built-in probes.

[0025] One end of the shielded cable 4 is electrically connected to the plasma receiving plate 2, and the other end is connected to the monitoring host 5.

[0026] The RC voltage divider unit includes the upper arm resistor. and the lower arm resistor of the voltage divider And the upper arm compensation capacitor C used to compensate for AC amplitude-frequency characteristics. in1 and the voltage divider lower arm compensation capacitor C in2 Among them, the upper arm resistor of the voltage divider The input terminal is connected to the plasma receiving plate 2, and its output terminal is connected to the lower arm resistor of the voltage divider. The input terminal is connected; the equivalent resistance of the shielded cable 4 is Rs, and the equivalent capacitance is Cs; the compensation unit satisfies the amplitude-frequency characteristic compensation formula: ×C in1 = ×(Cs+C in2 The voltage divider resistors satisfy +Rs>> .

[0027] Because plasma can generate high transient voltages (e.g., ±500V), a voltage divider with a large attenuation is constructed using Rin1 and Rin2 to ensure the safety of subsequent circuits and expand the measurement range. To guarantee the stability and safety of the circuit operation when measuring high transient voltages, the values ​​of Rin1 and Rin2 must satisfy the relationship (Rin1 + Rs) >> Rin2. Since Rs is typically very small (in the milliohm range), this condition ensures that the vast majority of the voltage drop occurs across Rin1.

[0028] To compensate for the response characteristics of the voltage divider circuit at different frequencies, especially the attenuation of high-frequency signals by the parasitic capacitance Cs of the shielded cable 4, the RC voltage divider circuit also includes a voltage divider upper arm compensation capacitor C. in1 and the voltage divider lower arm compensation capacitor C in2 C in1 With R in1 Parallel, C in2 With R in2 Parallel connection. The capacitor values ​​satisfy the impedance matching relationship: ×C in1 = ×(Cs+C in2 When this relationship holds, the voltage division ratio formed by resistors is equal to that formed by capacitors, thus making the entire voltage divider network a distortion-free broadband attenuator, ensuring the flatness of the amplitude-frequency characteristics over a wide bandwidth, and achieving accurate compensation for AC components.

[0029] The monitoring host 5 has a built-in wideband signal processing module, a full-range linear ADC sampling module, and a microprocessor, which are electrically connected in sequence. The microprocessor is electrically connected to the display module, storage module, and communication interface module, respectively. The communication interface module is externally connected to the communication interface terminal 6. The monitoring host 5 has a grounding terminal 7, a power interface 8, a USB interface 9, and a display screen on its casing. The grounding terminal 7 is used to electrically connect to the grounding terminal of the plasma cleaning equipment under test to ensure common ground reference and eliminate ground loop interference.

[0030] The monitoring device provided in this application fills the technical gap in online monitoring of plasma voltage characteristics. Through the cooperation of the non-invasive detection handle 1 and the high-fidelity shielded cable 4, it realizes the in-situ acquisition of plasma voltage characteristics at the nozzle outlet, providing a high-quality raw signal source for subsequent signal processing and data processing, and laying the hardware foundation for the observability of plasma voltage characteristics.

[0031] In one implementation, the upper arm resistor of the voltage divider One end is electrically connected to the output end of shielded cable 4, and the upper arm resistor of the voltage divider is... The other end is connected to the lower arm resistor of the voltage divider. One end is electrically connected to the input terminal of the operational amplifier unit, and the lower arm resistor of the voltage divider is connected. The other end is grounded; Voltage divider upper arm compensation capacitor C in1 With the upper arm resistor of the voltage divider Parallel connection, voltage divider lower arm compensation capacitor C in2 With the lower arm resistor of the voltage divider in parallel; Among them, the upper arm resistor of the voltage divider Voltage divider lower arm resistor The equivalent resistance Rs of cable 4 satisfies the following relationship: .

[0032] This embodiment employs a high-impedance front-mounted approach to the receiving board 2, placing the main voltage divider impedance near the front end of the plasma receiving board 2. This reduces the attenuation effect of the parasitic capacitance Cs of the shielded cable 4 on the transient voltage signal. Simultaneously, the upper arm compensation capacitor C... in1 , Lower arm compensation capacitor C in2 4. Equivalent capacitance of cable Cs, upper arm resistance of voltage divider Voltage divider lower arm resistor Satisfy the AC amplitude-frequency characteristic compensation relationship: ×C in1 = ×(Cs+C in2 This compensation relationship precisely offsets the phase distortion and amplitude attenuation of high-frequency signals caused by the distributed capacitance of cable 4, ensuring the consistency of signal amplitude-frequency characteristics within the 0-2MHz bandwidth.

[0033] The resistor-capacitor voltage divider design provided in this application breaks through the bottleneck of high-frequency signal distortion caused by parasitic parameters of cable 4 in traditional detection schemes, and realizes the attenuation-free transmission of nanosecond-level transient impact voltage signals in plasma. It provides signal fidelity assurance for capturing the core causes of damage to electrically sensitive workpieces such as PCBs and PCBAs, and improves the observability and accuracy of plasma voltage characteristics.

[0034] In one embodiment, the operational amplifier unit includes an operational amplifier U1.1, a feedback resistor R4, a gain resistor R5, and a matching resistor R3. The non-inverting input terminal of the operational amplifier U1.1 is electrically connected to the output terminal of the RC voltage divider unit, and the inverting input terminal is electrically connected to one end of the feedback resistor R4 and one end of the gain resistor R5, respectively. The other end of the feedback resistor R4 is grounded, and the other end of the gain resistor R5 is electrically connected to the output terminal of the operational amplifier U1.1. The matching resistor R3 is connected in series between the non-inverting input terminal of the operational amplifier U1.1 and the output terminal of the RC voltage divider unit.

[0035] Output voltage of operational amplifier unit Input voltage collected by plasma receiving plate 2 The following relationship must be satisfied: .

[0036] This amplifier circuit amplifies the voltage-divided signal by a fixed factor of (1 + R5 / R4), and the output signal is used for sampling by the subsequent ADC. The fixed-rate amplification achieves linear, range-free sampling across the entire measurement range, ensuring signal continuity and measurement consistency throughout the entire range (e.g., -500V to +500V).

[0037] In one embodiment, the equivalent resistance of the shielded cable 4 Much smaller than the resistance of the upper arm of the voltage divider The electrical characteristics of the operational amplifier unit, and the output voltage of the operational amplifier unit. Input voltage collected by plasma receiving plate 2 Furthermore, the following relationship must be satisfied: .

[0038] In one embodiment, the signal processing module has the characteristics of high input impedance and low input capacitive reactance, with an input impedance ≥ 10. 8 Ω, input capacitive reactance ≤10pF; the sampling bandwidth of the signal processing module is 0~2MHz, the voltage measurement range is -500V~+500V, and the ADC sampling module adopts a full-range linear non-segmented sampling architecture.

[0039] In this embodiment, the weak plasma voltage signal collected by the receiving board 2 is processed into a standard analog signal, coupled with a high input impedance (≥10). 8 The circuit design with low input capacitance (≤10pF) ensures the integrity of the measurement signal, avoids the load effect and signal distortion of the plasma electric field caused by traditional low input impedance schemes, provides a high signal-to-noise ratio analog signal for subsequent digital sampling, and ensures accurate reproduction of the dynamic waveform of plasma AC voltage.

[0040] By selecting high-precision, low-temperature drift resistors and strictly matching capacitors, the signal processing module achieves a measurement error of ≤±5% across the full range of -500V to +500V, with a measurement accuracy better than 0.5V, which can meet the process monitoring requirements of most sensitive components.

[0041] The ADC sampling module adopts a full-range linear, non-segmented sampling architecture, directly digitizing the standard analog signal output from the operational amplifier unit. The sampling bandwidth is 0–2MHz, and the voltage measurement range is -500V to +500V. This architecture eliminates the measurement dead zone, switching delay, and accuracy loss caused by traditional multi-range switching, achieving high-precision, high-consistency measurement across the entire range, ensuring signal continuity, and exhibiting excellent dynamic response characteristics.

[0042] The fully linear, non-segmented sampling scheme solves the problems of segmented switching errors and blind spots, enabling the device to continuously capture the complete dynamic process of plasma voltage from steady state to transient state, including all characteristic parameters such as positive and negative overshoot and oscillation decay under abnormal charging conditions. This continuous and observable voltage characteristic data provides complete data support for identifying abnormal states of plasma deviating from electrical neutrality, and is a key data foundation for realizing real-time closed-loop adjustment of the operating parameters of plasma cleaning equipment.

[0043] In one embodiment, the plasma receiving plate 2 is a metal plate with nickel plating on a brass substrate, and the heat-resistant insulating component 3 is an alumina ceramic component. The detection surface of the plasma receiving plate 2 is positioned directly opposite the nozzle of the plasma cleaning equipment, and the detection spacing is 2mm to 20mm.

[0044] In one embodiment, the storage module is used to store the maximum voltage value, minimum voltage value and transient voltage extreme value collected within a preset time period, the display module is used to display the plasma voltage waveform and collected values ​​in real time, and the communication interface module includes a wired communication unit and a wireless communication unit for data interaction with a PC host computer.

[0045] In one embodiment, the power interface has a power supply range of DC7.5V to 36V and a rated input current of ≤1A. The USB interface is electrically connected to the microprocessor and is used for upgrading the device firmware.

[0046] The analog signal, after being processed by the signal processing module, is sent to the high-speed ADC sampling module. This module features a high sampling rate and high resolution, for example, a sampling rate of no less than 10 MSPS and a resolution of no less than 12 bits, to ensure that it can capture nanosecond-level transient voltage changes. After the ADC converts the analog signal into a digital signal, it is sent to the microprocessor (MCU).

[0047] In this embodiment, the microprocessor (MCU) is the core of the entire monitor's control and computation. It executes programs stored in internal or external memory to perform the following functions: parsing and processing digital signals from the ADC; calculating in real-time characteristic data such as the effective voltage value, peak value, and valley value of the current plasma; capturing and recording transient peak values, valley values, and extreme values ​​such as maximum and minimum values ​​from a continuous data stream over a period of time; storing this data in a connected storage module (such as an SD card or Flash chip); controlling the display module to display data; and exchanging data with external devices (such as a host PC) through a communication interface module. The communication interface module supports wired methods (such as RS-232, RS-485, USB, Ethernet, etc.) and / or wireless methods (such as Wi-Fi, Bluetooth, etc.).

[0048] The display module, such as a TFT color LCD screen, is used to intuitively display measurement results in various forms. It can not only plot the voltage change over time in real time, allowing users to observe the dynamic characteristics of the plasma, but also simultaneously or separately display historically captured voltage extreme values ​​(such as the maximum positive peak value and the maximum negative peak value) and statistical data over a period of time on the same interface or in paginated interfaces, providing comprehensive data support for users to evaluate the stability and consistency of plasma equipment.

[0049] To further ensure the safety of the monitor under abnormally high voltage conditions, this embodiment also includes a high-voltage protection circuit. The input of this high-voltage protection circuit is connected to the plasma receiving board 2, and the output is connected to the input of the signal processing module (i.e., the input of the upper arm resistor Rin1 of the voltage divider). Internally, it can be composed of a pair of reverse-connected transient voltage suppressor diodes (TVS) or gas discharge tubes. When a transient high-voltage spike exceeding a preset safety threshold (e.g., ±600V) is received, it can quickly clamp the input of the subsequent circuit to a safe voltage range, thereby preventing damage to the expensive signal conditioning and sampling circuits.

[0050] In addition, the monitor host is equipped with a grounding terminal 7, which is used to connect to the grounding terminal of the monitored plasma cleaning equipment via a wire during use. This allows the monitor and the plasma equipment to share a common ground, forming an equipotential reference point, which can effectively eliminate common-mode interference caused by the difference in grounding potential between the two and ensure the accuracy of the measurement data.

[0051] In terms of power supply, the monitor integrates a wide-voltage input power module with an input voltage range of DC 7.5V to 36V and a rated current of no more than 1A. This allows the monitor to flexibly adapt to different power supply standards in various industrial environments (such as 12V and 24V DC power supplies) without the need for additional voltage conversion equipment.

[0052] The microprocessor is equipped with an adaptive transient voltage capture algorithm. This algorithm sorts the voltage values ​​of N consecutive sampling points in a sliding window (N≥2 times the number of Nyquist sampling points corresponding to the sampling bandwidth) using the sampling period of the ADC sampling module as the unit. It extracts the voltage peak and valley values ​​within the window, compares the peak and valley values ​​with the extreme values ​​of the previous window, and marks them as transient voltage events when the difference exceeds a preset dynamic threshold and stores the complete sampling data at the corresponding time.

[0053] In the PCB plasma cleaning process, the device monitors the plasma voltage characteristics at the nozzle exit in real time. When a transient impulse voltage amplitude exceeds a preset safety threshold (e.g., ±300V) or the AC voltage frequency deviates from the standard range, the microprocessor uploads the abnormal data to a PC-based host computer in real time via a communication interface module (e.g., Modbus, TCP / IP, WiFi protocol). Based on the continuous and observable voltage characteristic data, the host computer automatically adjusts the operating parameters of the plasma cleaning equipment, such as the RF power, gas flow rate, or pulse duty cycle, to restore the plasma to an electrically neutral state. Simultaneously, the storage module employs a circular buffer storage mechanism to save the maximum, minimum, and transient voltage extreme values ​​within a preset time period, forming a process quality traceability data chain.

[0054] This algorithm and closed-loop control mechanism enable proactive identification and rapid response to abnormal plasma charging states, transforming the traditional passive mode of "post-event detection of workpiece damage" into a proactive protection mode of "real-time monitoring-early warning-adjustment." By providing continuous and high-precision dynamic voltage data support for plasma cleaning equipment, it effectively avoids irreversible electrical damage to electrically sensitive workpieces such as PCBs and PCBAs caused by abnormally charged plasma, significantly reducing workpiece scrap rates and improving the safety and consistency of plasma processing.

[0055] The power interface adopts a wide voltage supply design, with a power supply range of DC7.5V to 36V and a rated input current of ≤1A, adapting to various power supply environments in industrial sites. The USB interface is electrically connected to the microprocessor, supporting online firmware upgrades and function expansion. The display module uses real-time waveform refresh technology to display the plasma voltage waveform and acquired values ​​on the screen in real time, facilitating on-site maintenance personnel to intuitively judge the equipment status.

[0056] In one example, the detection handle 1 component can be flexibly adjusted to maintain a detection distance (2mm to 20mm) from the nozzle, acquiring plasma voltage characteristic curves at different spray distances to provide a quantitative basis for equipment calibration. In on-site operation and maintenance scenarios, the non-invasive detection method can quickly complete the sampling inspection of the energized status of multiple equipment models without affecting production cycle time. In process consistency control scenarios, the detection data is connected to the MES system through the communication interface module, enabling traceability of plasma voltage characteristic data throughout the entire production process.

[0057] like Figure 3 As shown, this application provides a method for online monitoring of plasma voltage characteristics, implemented based on any of the above embodiments of an online plasma voltage characteristic monitoring device, including: S410, align the detection surface of the plasma receiving plate with the center of the nozzle of the plasma cleaning equipment, adjust the detection spacing to 2mm~20mm, and connect the plasma receiving plate to the monitoring host through a shielded cable. S420, start the plasma cleaning equipment, the plasma jet ejected from the nozzle is directed toward the plasma receiving plate; The S430 monitoring host collects signals, analyzes and processes the data, and displays the real-time voltage characteristic data of the plasma through the display module.

[0058] The microprocessor (MCU) uploads real-time voltage characteristic data and historical extreme value data to a host PC via a wired or wireless connection through a communication interface module. The host PC can then perform more in-depth analysis, modeling, and long-term storage of the received data. More importantly, this real-time, precise voltage characteristic data can serve as feedback signals, forming a closed-loop control system with the plasma equipment's control system (such as power sources and gas flow meters). For example, when the plasma voltage deviates from the set process window or a dangerous transient high voltage is detected, the host computer software can immediately send commands to the plasma equipment to automatically adjust its output power or trigger protection mechanisms, thereby achieving precise control of the plasma process and effectively preventing product damage caused by voltage anomalies.

[0059] The detection method provided in this application embodiment achieves full-dimensional, online, and high-precision detection of the plasma voltage characteristics at the nozzle outlet through a complete technical chain of "acquisition-conditioning-digitalization-intelligent processing-closed-loop regulation". It solves the technical bottlenecks of existing technologies that cannot monitor the energized state of the nozzle outlet of atmospheric pressure plasma cleaning equipment, cannot capture transient impact voltage, and cannot provide continuous dynamic data support, thus providing a systematic solution for the safety and consistency of plasma processing technology.

[0060] The following specific embodiments illustrate the online monitoring process of plasma voltage characteristics provided in this application.

[0061] Example 1 This embodiment uses the aforementioned online plasma voltage characteristic monitoring device to detect the voltage characteristics of the nozzle plasma in an atmospheric pressure radio frequency plasma cleaning equipment. The specific implementation parameters and process are as follows: In this embodiment, the core component parameters of the device are set as follows: upper arm resistor of voltage divider Voltage divider lower arm resistor Feedback resistor Gain resistor Equivalent resistance of shielded cable Equivalent capacitance of shielded cable Voltage divider upper arm compensation capacitor voltage divider lower arm compensation capacitor .

[0062] First, verify the voltage divider safety condition by substituting the parameters and calculating: , ,satisfy The design requirements stipulate that safe voltage division of high-voltage signals can be achieved, while ensuring that the input impedance of the device is not lower than [a certain value]. .

[0063] Next, verify the AC amplitude-frequency characteristic compensation relationship by substituting the parameters for calculation: Left side: ; Right side: ; The values ​​on the left and right sides are equal, which meets the amplitude-frequency response compensation requirements and can guarantee... Consistent voltage division ratio within the bandwidth eliminates amplitude-frequency attenuation of high-frequency signals.

[0064] In this embodiment, the magnification factor of the operational amplifier unit... The calculation is as follows: ; partial pressure ratio The calculation is as follows: ; Therefore, the sampling voltage With input voltage The relationship is: ; The formula for calculating the input voltage is as follows: ; The detection process in this embodiment is as follows: Align the detection surface of the plasma receiving plate with the center of the nozzle of the plasma cleaning equipment, and adjust the detection spacing to... The plasma receiving board is electrically connected to the monitoring host via a shielded cable, and the grounding terminal of the monitoring host is reliably connected to the grounding terminal of the plasma cleaning equipment to activate the power supply. Power on the plasma cleaning equipment, start the plasma cleaning system, and set the equipment output power to [value missing]. The nozzle ejects plasma into contact with the receiving plate.

[0065] During the detection process, the sampling voltage acquired by the ADC sampling module Peak value Substituting into the above formula, the peak input voltage of the plasma is calculated. for: ; The microprocessor, through a transient voltage capture algorithm, captured the peak transient voltage during this detection process. It displays the voltage waveform and value in real time, and simultaneously stores the detected data in the storage module and uploads it to the PC host computer.

[0066] Example 2 This embodiment applies to plasma voltage detection in an atmospheric pressure plasma cleaning equipment for PCB board surface cleaning. The specific implementation process is as follows: The system parameters are configured as follows: upper arm resistor of voltage divider Values Voltage divider upper arm compensation capacitor Values Voltage divider lower arm resistor Values voltage divider lower arm compensation capacitor The value is 1950 The equivalent resistance of shielded cables Values Equivalent capacitance The value is 5 In the signal amplification circuit Values , Values .

[0067] Verification calculation of amplitude-frequency response compensation formula: ; ; The values ​​on both sides are equal, which meets the amplitude-frequency characteristic compensation requirements.

[0068] Voltage divider resistor condition verification: ; Much larger This meets the requirements for high input impedance voltage division.

[0069] Signal amplification factor calculation: ; Calculation of partial pressure ratio: ; The relationship between the sampled signal voltage and the input voltage is as follows: ; The actual voltage conversion formula is: ; During implementation, the axial distance between the plasma receiving plate and the nozzle was set to 10mm. The grounding terminal of the monitoring system was connected to the grounding terminal of the plasma cleaning equipment. A DC 24V power supply was then connected, and the plasma cleaning equipment was started. The plasma input voltage collected by the plasma receiving plate... for After processing by the signal conditioning module, the output sampled signal voltage is... After the high-speed ADC sampling module acquires the voltage value, it transmits it to the microprocessor (MCU), which then converts it into the actual voltage value. The measurement value is consistent with the actual input value, and the measurement error is 0.

[0070] The microprocessor (MCU) sets a sliding time window of 1 second, iterates through the continuously sampled data, and captures the maximum voltage value within the window. The minimum value is The transient peak extreme value is The display module shows the corresponding waveforms and data in real time, the storage module records the corresponding data, and the data is uploaded to the PC via the WiFi communication module.

[0071] The embodiments of this application realize the real-time acquisition, processing, analysis and storage of plasma voltage signals, and complete the visualization and quantifiable monitoring of plasma voltage characteristics. It provides a dedicated technical means for the research and control of plasma charging characteristics, and solves the problem of workpiece damage caused by abnormal plasma charging during plasma cleaning from the detection level.

[0072] This application employs a signal processing architecture combining a resistive-capacitive voltage divider unit with an operational amplifier unit, along with an AC amplitude-frequency characteristic compensation circuit design. This ensures the consistency of the voltage division ratio and amplification factor across the entire sampling bandwidth of 0–2MHz, eliminating amplitude-frequency attenuation and waveform distortion during high-frequency signal transmission. Through a front-end design with high input impedance and low input capacitive reactance, the attenuation effect of cable parasitic parameters on transient voltage signals is significantly reduced, ensuring complete acquisition of high-voltage transient signals. The use of a full-range linear, non-segmented sampling scheme eliminates the switching errors and measurement blind spots inherent in traditional segmented sampling, achieving high-precision continuous measurement across the entire range of -500V to +500V. Combined with a sliding window transient voltage capture algorithm, it enables accurate identification and complete storage of nanosecond-level transient voltage events, significantly improving the device's detection accuracy and response performance for plasma voltage anomalies. This application's embodiment possesses excellent engineering adaptability, perfects the quality control system for the entire plasma cleaning process, and provides data support for precise optimization of the plasma cleaning process and closed-loop equipment control. The device structure of this application embodiment is adaptable to various application scenarios of plasma cleaning equipment, including those operating under normal pressure and vacuum. The high-temperature resistant and corrosion-resistant receiving plate design and insulation protection structure ensure the reliability and operational safety of the device in plasma environments. The potential reference design, sharing a common ground with the cleaning equipment, eliminates measurement errors caused by ground potential differences in industrial settings, ensuring measurement stability under different operating conditions. Furthermore, this application embodiment achieves bidirectional interaction of detection data through a standardized communication interface, providing quantitative feedback data for closed-loop adjustment of operating parameters such as power and gas pressure of the plasma cleaning equipment. It can also be applied to multiple industrial processes, including factory performance calibration of plasma cleaning equipment, on-site operation and maintenance testing, and process consistency control, expanding the engineering application boundaries of plasma charge characteristic detection technology.

[0073] Obviously, those skilled in the art should understand that the modules or steps of the embodiments of this application described above can be implemented using general-purpose computer devices. They can be centralized on a single computer device or distributed across a network of multiple computer devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computer device. In some cases, the steps shown or described can be performed in a different order than those presented here, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the embodiments of this application are not limited to any particular combination of hardware and software.

[0074] It should be noted that the above are merely preferred embodiments of this application and do not limit the scope of patent protection of this application. Any equivalent structural or procedural changes made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A plasma voltage characteristic online monitoring device, characterized in that, This includes the testing handle assembly, shielded cable, and monitoring host; The detection handle assembly includes an insulating handle, a plasma receiving plate, and a heat-resistant insulating component. The plasma receiving plate is used to receive the plasma jet in a non-contact manner to couple its voltage signal. It is attached to the upper surface of the heat-resistant insulating component, and the heat-resistant insulating component is fixedly connected to the insulating handle. The shielded cable is electrically connected between the plasma receiving board and the monitoring host. The monitoring host is equipped with an ADC sampling module, a signal processing module and a microprocessor. The signal processing module includes a resistor-capacitor voltage divider unit and an operational amplifier unit. The resistor-capacitor voltage divider unit includes the upper arm resistor of the voltage divider. and the lower arm resistor of the voltage divider And the upper arm compensation capacitor C used to compensate for AC amplitude-frequency characteristics. in1 and the voltage divider lower arm compensation capacitor C in2 The upper arm resistor of the voltage divider The input terminal is connected to the plasma receiving plate, and its output terminal is connected to the lower arm resistor of the voltage divider. The input terminal is connected; the equivalent resistance of the shielded cable is Rs, and the equivalent capacitance is Cs; the compensation unit satisfies the amplitude-frequency characteristic compensation formula: ×C in2 = ×(Cs+C in1 The voltage divider resistors satisfy +Rs>> .

2. The online plasma voltage characteristic monitoring device according to claim 1, characterized in that, The upper arm resistor of the voltage divider One end is electrically connected to the output end of the shielded cable, and the upper arm resistor of the voltage divider is... The other end is connected to the lower arm resistor of the voltage divider. One end is electrically connected to the input terminal of the operational amplifier unit, and the lower arm resistor of the voltage divider is connected. The other end is grounded; The voltage divider upper arm compensation capacitor C in1 With the upper arm resistor of the voltage divider The lower arm compensation capacitor C is connected in parallel. in2 With the lower arm resistor of the voltage divider in parallel; Among them, the upper arm resistor of the voltage divider Voltage divider lower arm resistor The equivalent resistance Rs of the cable satisfies the following relationship: 。 3. The online plasma voltage characteristic monitoring device according to claim 2, characterized in that, The operational amplifier unit includes an operational amplifier U1.1, a feedback resistor R4, a gain resistor R5, and a matching resistor R3. The non-inverting input of the operational amplifier U1.1 is electrically connected to the output of the RC voltage divider unit, and the inverting input is electrically connected to one end of the feedback resistor R4 and one end of the gain resistor R5. The other end of the feedback resistor R4 is grounded, and the other end of the gain resistor R5 is electrically connected to the output of the operational amplifier U1.

1. The matching resistor R3 is connected in series between the non-inverting input of the operational amplifier U1.1 and the output of the RC voltage divider unit. The feedback resistor R4, the gain resistor R5, and the matching resistor R3 are all high-precision, low-temperature-drift resistors. The output voltage of the operational amplifier unit Input voltage collected by the plasma receiving plate The following relationship must be satisfied: 。 4. The online plasma voltage characteristic monitoring device according to claim 3, characterized in that, The equivalent resistance of the shielded cable Much smaller than the resistance of the upper arm of the voltage divider The electrical characteristics of the operational amplifier unit, and the output voltage of the operational amplifier unit. Input voltage collected by the plasma receiving plate Furthermore, the following relationship must be satisfied: 。 5. The online plasma voltage characteristic monitoring device according to claim 1, characterized in that, The plasma receiving plate is a brass substrate plated with nickel, and the heat-resistant insulating component is an alumina ceramic component. The detection surface of the plasma receiving plate is positioned facing the nozzle of the plasma cleaning equipment, and the detection spacing is 2mm to 20mm. It also includes a grounding terminal for connecting to the grounding terminal of the plasma cleaning equipment.

6. The online plasma voltage characteristic monitoring device according to claim 1, characterized in that, The signal processing module features high input impedance and low input capacitive reactance, with an input impedance ≥ 10. 8 Ω, input capacitive reactance ≤10pF; the sampling bandwidth of the signal processing module is 0~2MHz, the voltage measurement range is -500V~+500V, and the ADC sampling module adopts a full-range linear non-segmented sampling architecture.

7. The online plasma voltage characteristic monitoring device according to claim 6, characterized in that, The microprocessor is equipped with a transient voltage capture algorithm, which performs the following steps: Using the sampling period of the ADC sampling module as the unit, the voltage values ​​of N consecutive sampling points are sorted by sliding window, the voltage peak and valley values ​​within the window are extracted, and the peak and valley values ​​are compared with the extreme values ​​of the previous window. When the difference exceeds the preset threshold, it is marked as a transient voltage event and the complete sampling data at the corresponding time is stored. Where N is a positive integer, and satisfies N≥2 times the number of Nyquist sampling points.

8. The online plasma voltage characteristic monitoring device according to claim 7, characterized in that, The microprocessor includes a storage module and a display module. The storage module is used to store the maximum voltage value, minimum voltage value and transient voltage extreme value collected within a preset time period. The display module is used to display the plasma voltage waveform and the collected values.

9. The online monitoring device for plasma voltage characteristics according to claim 1, characterized in that, It also includes a high-voltage protection circuit, whose input terminal is connected to the plasma receiving plate and whose output terminal is connected to the signal processing module. When a transient high voltage exceeding a preset threshold is received, the input terminal of the signal processing module is clamped to a safe voltage range.

10. A method for online monitoring of plasma voltage characteristics, characterized in that, Based on the plasma voltage characteristic online monitoring device according to any one of claims 1 to 9, it includes: Align the detection surface of the plasma receiving plate with the center of the nozzle of the plasma cleaning equipment, adjust the detection spacing to 2mm to 20mm, and connect the plasma receiving plate to the monitoring host through a shielded cable. Start the plasma cleaning equipment and direct the plasma jet from the nozzle toward the plasma receiving plate; The monitoring host collects signals, analyzes and processes the data, and displays the real-time voltage characteristic data of the plasma through the display module.

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