A method and system for pump filter linkage control in a circuit board cleaning pre-process

Abstract

The application discloses a kind of line board cleaning front process pump filter linkage control method and system, including in PLC controller preset pump filter linkage control parameter set;Real-time process data is synchronously collected by pressure, flow, concentration and liquid level sensing unit;Current filter differential pressure, differential pressure change rate, normalized differential pressure index NDI and flow deviation rate are calculated, and real-time clogging state of filter device is evaluated;According to the numerical interval where NDI and flow deviation rate are located, four linkage control strategies of normal operation, mild clogging compensation, severe clogging protection or limit protection are executed, and cleaning pump speed is adaptively adjusted;According to the comparison result of concentration real-time value and target range, liquid supplementing pump and water supplementing valve are automatically controlled;According to liquid level real-time value, safety linkage protection is executed.The application realizes intelligent linkage control of pump-filter-valve trinity, and improves the stability and energy efficiency level of cleaning process.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board manufacturing, and specifically relates to a pump-filter linkage control method and system for the pre-cleaning process of circuit boards. Background Art

[0002] In the manufacturing process of printed circuit boards (PCBs), the PCB surface needs to be cleaned before processes such as solder resist ink coating, legend printing, and surface treatment, so as to remove contaminants such as copper surface oxide layers, grease, fingerprints, and dust particles. The pre-cleaning process usually adopts a spray cleaning method, in which a cleaning pump pressurizes the cleaning solution and sprays it onto the PCB surface through nozzles, and the waste cleaning liquid is recycled after impurities are removed by a filtering device.

[0003] Current technical solutions related to pump and filter control for the pre-cleaning process of circuit boards have the following deficiencies: First, the cleaning pump and the filtering device operate independently of each other. The output parameters of the pump are based on preset fixed values, and cannot be dynamically adjusted according to the real-time clogging state of the filtering device. When the filtering device is gradually clogged, the pump still maintains the original output, resulting in abnormally increased pipeline pressure or insufficient nozzle flow, which affects the cleaning quality and accelerates the wear of the pump. In the multi-stage filtration circulation system disclosed in Chinese patent CN214513237U, each filtration pump operates independently, and there is no linkage control strategy based on filtration pressure difference or flow rate. In the cleaning device disclosed in Chinese patent CN101652029A, there is only a start-stop linkage relationship between the pump and the filtering device, which cannot dynamically adjust the output of the pump according to the clogging state of the filtering device.

[0004] Second, no fusion analysis is performed on the data of each sensor. Although some solutions introduce a single sensor such as a pressure sensor, a liquid level sensor, or a concentration sensor, they cannot form a complete closed loop from perception to execution. In the circulating water-saving device disclosed in Chinese patent CN210546650U, the state of the filter screen cannot be perceived in real time, and the operating parameters of the water pump cannot be adaptively adjusted according to the clogging degree of the filter screen.

[0005] Third, the perception and prediction capabilities of the filtration state are insufficient. The perception of the state of the filtering device in the prior art mainly relies on manual inspection or threshold alarm, and lacks a prediction model based on the change trend of pressure difference. In the intelligent filter tank flushing control system disclosed in Chinese patent CN108107829A, the control logic is triggered by a switch value threshold, and does not have predictive control capability based on the change trend of pressure difference. The automatic control oil filter disclosed in Chinese patent CN118122000A only realizes monitoring and alarm rather than linkage control.

[0006] Fourth, the operation of the pump, the maintenance of the filtration device, and the switching of pipeline valves are treated as three independent processes, lacking a unified control framework to coordinate them. In actual production, there is a coupling relationship between the pump's operating efficiency, the filtration efficiency of the filtration device, and the opening degree of the pipeline valves, requiring coordinated optimization.

[0007] Fifth, there is a lack of dynamic management of the cleaning solution concentration. The concentration of the cleaning solution during the pre-cleaning process directly affects the cleaning quality of the PCB board surface and the roughness of the copper surface. Current technology lacks a linkage mechanism to feed back online concentration monitoring data in real time to pump speed adjustment and replenishment valve control, resulting in large fluctuations in the cleaning solution concentration between batches.

[0008] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] The technical problem to be solved by this invention is: in view of the current situation where the cleaning pump and the filter device operate independently and lack intelligent linkage control in the pre-cleaning process of circuit boards, a pump-filter linkage control method and system for the pre-cleaning process of circuit boards is provided. Through data fusion analysis of multi-dimensional sensing network and PLC controller, a pump-filter-valve linkage control model is established to realize adaptive adjustment of cleaning pump speed, prediction and early warning of filter blockage status, and automatic control of cleaning solution concentration.

[0010] To address the aforementioned technical problems, this invention provides a method and system for controlling the pump-filter linkage in the pre-cleaning process of circuit boards.

[0011] A method for pump-filter linkage control in the pre-cleaning process of circuit boards includes the following steps: S1: A set of pump-filter linkage control parameters is preset in the PLC controller. The parameter set includes the rated speed of the cleaning pump. Rated flow rate Initial differential pressure threshold of the filtration device Filter device early warning differential pressure threshold Filter device ultimate pressure difference threshold Target concentration of cleaning solution and allowable deviation range [ , Pressure difference change rate warning threshold and sampling period T; S2: Within each sampling period T, real-time process data is synchronously collected by pressure sensing units, flow sensing units, concentration sensing units, and level sensing units arranged in the cleaning pipeline. The real-time process data includes the pump inlet pressure. Pump post-pressure Filtration pressure Pipeline flow rate F, cleaning fluid concentration C, and storage tank level L; S3: The PLC controller calculates the status evaluation index of the filtration device based on the real-time process data. The status evaluation index includes the current filtration pressure difference. Pressure difference change rate Normalized differential pressure index (NDI) and flow deviation rate ,in = - NDI = ( - ) / ( - ), =|F- | / ; S4: The PLC controller determines the normalized differential pressure index (NDI) and the flow deviation rate based on the normalized differential pressure index (NDI) and the flow deviation rate. Within the given numerical range, select one of the following linkage control strategies to adjust the cleaning pump speed: normal operation mode, mild blockage compensation mode, severe blockage protection mode, or limit protection mode. S5: The PLC controller compares the cleaning fluid concentration C with the target concentration range [ , The comparison is performed, and the opening and closing of the replenishment pump and / or water replenishment valve are controlled according to the comparison results to maintain the concentration of the cleaning solution within the target concentration range; S6: The PLC controller compares the liquid level L in the storage tank with the liquid level safety threshold, and executes liquid level safety linkage protection based on the comparison result.

[0012] Preferably, the linkage control strategy described in step S4 specifically includes: When NDI < 0.5 and When the value is <0.1, the normal operation mode is executed, and the cleaning pump maintains its rated speed. run; When 0.5 ≤ NDI < 0.75, or 0.1 ≤ When the flow rate is less than 0.2, a mild blockage compensation mode is implemented, using PID control to adjust the cleaning pump speed so that the pipeline flow rate F returns to the rated flow rate. Pump speed adjustment increment ΔN = ×( -F)+ ×Σ( -F)×T+ ×( - ) / T, of which , , These are PID control parameters; When 0.75 ≤ NDI < 1.0, or When the value is ≥0.2, the severe blockage protection mode is activated, reducing the cleaning pump speed to a safe speed. And trigger an alarm; When NDI≥1.0, the limit protection mode is executed, the cleaning pump is stopped and the pipeline valves are closed.

[0013] As a preferred option, data recording and trend prediction steps are also included: The PLC controller records sensor data and linkage control operations to a historical database and generates a trend analysis report at a fixed period. The trend analysis report includes a trend curve of the filter differential pressure changing over time and an estimate of the remaining service life of the filter element based on the trend of differential pressure change. When the remaining service life of the filter element is lower than a preset threshold, the PLC controller pushes a replacement reminder through the human-machine interface or the host computer management system.

[0014] Preferably, when the system is configured with a main filter branch and a backup filter branch, in the severe blockage protection mode, the PLC controller first opens the solenoid valve of the backup filter branch, and after the flow sensing unit confirms that the flow of the backup branch is stable, the solenoid valve of the main filter branch is then closed, so as to achieve filter branch switching without interrupting the cleaning production.

[0015] Preferably, the concentration sensing unit is a conductivity sensor or a sound velocity sensor, and the conductivity value or sound velocity value is converted into the cleaning solution concentration value through a calibration curve.

[0016] A pre-process pump-filter system for circuit board cleaning includes: Cleaning pumps and their frequency converters; At least one filter device; Multiple sensors, including a pre-pump pressure sensor, a post-pump pressure sensor, a post-filtration pressure sensor, a flow sensor, a concentration sensor, and a level sensor; replenishment pump and replenishment valve; A PLC controller is electrically connected to the frequency converter, the sensor, the replenishment pump, and the water replenishment valve. The PLC controller stores a control program, which, when executed, implements the method according to any one of claims 1 to 8.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Improved cleaning quality stability: When the filter device gradually gets clogged, the PLC controller automatically compensates the pump speed to maintain a constant nozzle outlet flow rate, ensuring that the impact pressure and flow rate of the cleaning fluid on each PCB board are consistent, thus avoiding insufficient cleaning or excessive corrosion caused by filter blockage.

[0018] (2) Reduction of unplanned downtime: Based on the filter cartridge remaining life prediction and early warning mechanism based on the pressure difference change trend, combined with the automatic switching function of the backup filter branch, unplanned downtime caused by filter blockage can be greatly reduced.

[0019] (3) Energy consumption optimization: In the mild clogging compensation mode, the pump speed is finely adjusted by PID to avoid energy waste caused by fixed high speed operation. When the filter element is close to the end of its life, the system automatically reduces the speed for protection, avoiding the surge in energy consumption caused by the decrease in pump efficiency under high back pressure conditions.

[0020] (4) Reduced cleaning fluid consumption: The linkage control of online concentration monitoring and automatic fluid replenishment keeps the cleaning fluid concentration in the optimal range, avoiding the problems of excessive or untimely fluid replenishment under manual replenishment.

[0021] (5) Extended equipment life: The adaptive adjustment of pump speed and automatic protection shutdown under extreme conditions effectively reduce the pump's operating time under harsh conditions such as high back pressure and idling, and extend the service life of pump mechanical seals, bearings and other vulnerable parts. Detailed Implementation

[0022] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0023] Example 1: Pump-Filter Linkage Control under Single Filter Branch Configuration This embodiment uses a horizontal spray cleaning pretreatment line in a PCB factory as an example. The cleaning solution is an acidic micro-etching solution, mainly composed of a mixed solution of sulfuric acid and sodium persulfate, used to remove the oxide layer on the copper surface and roughen the copper surface before solder resist application.

[0024] The cleaning line is configured as follows: the cleaning pump has a rated power of 5.5kW, a rated flow rate of 200L / min, and a rated speed of 2900rpm, driven by a frequency converter; the filtration device is a single-stage PP cotton filter cartridge with a filtration accuracy of 10μm and an initial clean pressure differential of 0.05MPa; sensors include a pressure sensor before the pump. (Measuring range 0-1.0MPa), downstream pressure sensor (Measuring range 0-1.0MPa), Post-filter pressure sensor (Measuring range 0-1.0MPa), electromagnetic flowmeter F (measuring range 0-300L / min), conductivity-type concentration sensor C, ultrasonic level sensor L; the controller is a PLC controller with a touch screen; the replenishment system includes a replenishment pump and a water replenishment solenoid valve.

[0025] The preset linkage parameter in the PLC controller is: = 0.05MPa. =0.30MPa, =0.45MPa, =5.0% (calibrated based on conductivity value). =4.5%, =5.5%, =2.0L, =0.10MPa / h, sampling period T=1s.

[0026] After the system is running, during 8 hours of continuous production, the PLC controller collects data from each sensor in real time and executes linkage control.

[0027] At 5 hours and 30 minutes into the operation, the PLC controller detected that the NDI index reached 0.52 ( =0.28MPa), triggering the mild blockage compensation mode. The PLC controller automatically increases the pump speed gradually from 2900rpm to 3050rpm, restoring the flow rate to 198L / min (deviation rate less than 1%), and at the same time displays the prompt message "Filter device is mildly blocked, pump speed has been automatically compensated" on the touch screen.

[0028] At 7 hours and 15 minutes into the run, the NDI index reached 0.78 ( =0.38MPa), triggering the severe blockage protection mode. The PLC controller reduces the pump speed to 2000rpm (safe speed), issues an audible and visual alarm, and displays a red warning message on the touchscreen indicating that the filter element is about to fail. Upon receiving the alarm, the operator must replace the filter element within 5 minutes. After replacement, the PLC controller detects... The pressure is restored to 0.06MPa, the protection mode is automatically exited, the pump speed is restored to the rated 2900rpm, and normal production is resumed.

[0029] Throughout the 8-hour production cycle, concentration sensor C monitored a gradual decrease in the cleaning fluid concentration from the initial 5.0%, dropping to 4.4% and 4.3% in the 3rd and 6th hours respectively (below [a certain threshold]). =4.5%), the PLC controller automatically started the replenishment pump to inject 2.0L of concentrate into each, and the concentrations were restored to 5.1% and 4.9% respectively after replenishment. A total of 3 automatic water replenishment operations were performed within 8 hours, and none triggered the liquid level alarm. The cleaning quality inspection results for the entire batch of PCB boards were: copper surface roughness Ra = 0.30-0.35μm (within the control range), and the cleanliness was all qualified.

[0030] Example 2: Seamless switching under dual-filter branch redundancy configuration This embodiment adds a backup filtration branch to the existing embodiment 1. The backup PP cotton filter cartridge has the same specifications as the main filter. Solenoid valves are installed at the inlet and outlet of both the main filter and the backup filter. Automatic switching logic is added to the PLC controller program.

[0031] When the NDI index of the main filter reaches 0.75, the PLC controller first opens the solenoid valve of the standby filter branch. After the flow rate in the standby branch stabilizes (confirmed by the flow sensor F after approximately 3 seconds), the solenoid valve of the main filter branch is then closed, achieving a seamless "open-then-close" switching. After the switching is complete, the PLC controller notifies the operator that the main filter has been automatically isolated and is scheduled for replacement, ensuring uninterrupted cleaning production. Flow rate fluctuations during the switching process do not exceed 5% and do not affect the cleaning quality.

[0032] Example 3: Pressure Difference Sudden Change Detection and Emergency Protection This embodiment demonstrates the triggering scenario of the differential pressure surge emergency mode. During a normal production process, a sudden change in the upstream process caused large copper shavings to fall into the cleaning fluid, quickly clogging the inlet of the filter device. The PLC controller detected a sudden increase in ΔP from 0.15 MPa to 0.52 MPa within two consecutive sampling cycles (2 seconds). =0.185MPa / h, greater than (0.10MPa / h). The PLC controller immediately activated the emergency mode: stopped the cleaning pump, closed the nozzle supply valve, and triggered a red emergency alarm. Upon arrival, operators found that the filter inlet was blocked by large copper shavings. After clearing the blockage, the system reset and returned to normal operation. This emergency protection effectively prevented the risk of pipeline overpressure rupture.

[0033] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for pump-filter linkage control in the pre-cleaning process of circuit boards, characterized in that, Includes the following steps: S1: Preset a set of pump-filter linkage control parameters in the PLC controller. The parameter set includes the rated speed of the cleaning pump. Rated flow rate Initial differential pressure threshold of the filtration device Filter device early warning differential pressure threshold Filter device ultimate pressure difference threshold Target concentration of cleaning solution and allowable deviation range [ , Pressure difference change rate warning threshold and sampling period T; S2: Within each sampling period T, real-time process data is synchronously collected by pressure sensing units, flow sensing units, concentration sensing units, and level sensing units arranged in the cleaning pipeline. The real-time process data includes the pump inlet pressure. Pump post-pressure Filtration pressure Pipeline flow rate F, cleaning fluid concentration C, and storage tank level L; S3: The PLC controller calculates the status evaluation index of the filtration device based on the real-time process data. The status evaluation index includes the current filtration pressure difference. Pressure difference change rate Normalized differential pressure index (NDI) and flow deviation rate ,in = - NDI = ( - ) / ( - ), =|F- | / ; S4: The PLC controller determines the normalized differential pressure index (NDI) and the flow deviation rate based on the normalized differential pressure index (NDI) and the flow deviation rate. Within the given numerical range, select one of the following linkage control strategies to adjust the cleaning pump speed: normal operation mode, mild blockage compensation mode, severe blockage protection mode, or limit protection mode. S5: The PLC controller compares the cleaning fluid concentration C with the target concentration range [ , The comparison is performed, and the opening and closing of the replenishment pump and / or water replenishment valve are controlled according to the comparison results to maintain the concentration of the cleaning solution within the target concentration range; S6: The PLC controller compares the liquid level L in the storage tank with the liquid level safety threshold, and executes liquid level safety linkage protection based on the comparison result.

2. The method for pump-filter linkage control in the pre-cleaning process of circuit boards according to claim 1, characterized in that, The linkage control strategy mentioned in step S4 specifically includes: When NDI < 0.5 and When the value is <0.1, the normal operation mode is executed, and the cleaning pump maintains its rated speed. run; When 0.5 ≤ NDI < 0.75, or 0.1 ≤ When the flow rate is less than 0.2, a mild blockage compensation mode is implemented, using PID control to adjust the cleaning pump speed so that the pipeline flow rate F returns to the rated flow rate. Pump speed adjustment increment ΔN = ×( -F)+ ×Σ( -F)×T+ ×( - ) / T, of which , , These are PID control parameters; When 0.75 ≤ NDI < 1.0, or When the value is ≥0.2, the severe blockage protection mode is activated, reducing the cleaning pump speed to a safe speed. And trigger an alarm; When NDI≥1.0, the limit protection mode is executed, the cleaning pump is stopped and the pipeline valves are closed.

3. The method for pump-filter linkage control in the pre-cleaning process of circuit boards according to claim 2, characterized in that, It also includes an emergency mode for sudden pressure changes: When the pressure difference change rate Exceeding the aforementioned differential pressure change rate warning threshold In such cases, the PLC controller prioritizes emergency shutdown protection, including stopping the cleaning pump, recording process data snapshots before and after the sudden change, and triggering an emergency alarm; The differential pressure change emergency mode has a higher priority than the normal operation mode, mild blockage compensation mode, severe blockage protection mode, and ultimate protection mode.

4. The method for pump-filter linkage control in the pre-cleaning process of circuit boards according to claim 1, characterized in that, The concentration linkage control in step S5 specifically includes: When C < When the time comes, the PLC controller starts the replenishment pump to inject a preset volume of concentrate into the cleaning solution storage tank; When C> At this time, the PLC controller opens the water supply valve to inject deionized water to dilute the cleaning solution; The concentration linkage control is decoupled from the pump-filter linkage control in step S4, and the concentration adjustment operation does not interrupt the execution of the pump-filter linkage control strategy.

5. The method for pump-filter linkage control in the pre-cleaning process of circuit boards according to claim 1, characterized in that, The liquid level safety linkage protection mentioned in step S6 specifically includes: When L < low liquid level threshold When the liquid level is too low, the cleaning pump stops running and the replenishment valve is opened for emergency replenishment. When L > high liquid level threshold When the liquid level is too high, an alarm is triggered, and the replenishing valve and water supply valve are closed to prevent overflow.

6. The method for pump-filter linkage control in the pre-cleaning process of circuit boards according to claim 1, characterized in that, It also includes data recording and trend forecasting steps: The PLC controller records sensor data and linkage control operations to a historical database and generates a trend analysis report at a fixed period. The trend analysis report includes a trend curve of the filter differential pressure changing over time and an estimate of the remaining service life of the filter element based on the trend of differential pressure change. When the remaining service life of the filter element is lower than a preset threshold, the PLC controller pushes a replacement reminder through the human-machine interface or the host computer management system.

7. The method for pump-filter linkage control in the pre-cleaning process of circuit boards according to claim 2, characterized in that, When the system is configured with a main filter branch and a backup filter branch, in the severe blockage protection mode, the PLC controller first opens the solenoid valve of the backup filter branch. After the flow sensing unit confirms that the flow of the backup branch is stable, the solenoid valve of the main filter branch is then closed, so as to achieve filter branch switching without interrupting the cleaning production.

8. The method for pump-filter linkage control in the pre-cleaning process of circuit boards according to claim 1, characterized in that, The concentration sensing unit is a conductivity sensor or a sound velocity sensor, which converts the conductivity value or sound velocity value into the cleaning solution concentration value through a calibration curve.

9. A pre-process pump-filter system for circuit board cleaning, characterized in that, include: Cleaning pumps and their frequency converters; At least one filter device; Multiple sensors, including a pre-pump pressure sensor, a post-pump pressure sensor, a post-filtration pressure sensor, a flow sensor, a concentration sensor, and a level sensor; replenishment pump and replenishment valve; A PLC controller is electrically connected to the frequency converter, the sensor, the replenishment pump, and the water replenishment valve. The PLC controller stores a control program, which, when executed, implements the method according to any one of claims 1 to 8.

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