Dry ice plasma cleaning apparatus and method

Abstract

The present application relates to motor accessory assembling technical field, particularly to a dry ice plasma cleaning device and method, including cleaning spray head, pedestal, plasma generating module and dry ice cleaning module, the first end of cleaning spray head is provided with nozzle, the second end is used for installing pedestal, the pedestal is opposite to nozzle;Plasma generating module includes plasma generating element and power connection element which is arranged on the pedestal and electrically connected with plasma generating element, one end of plasma generating element is arranged on the pedestal, the other end passes through the air element and extends to the gas flow guide cavity;The shaft center of plasma generating element is hollowly provided with through hole, dry ice cleaning module is provided with high-temperature-resistant pipeline for passing through broken dry ice, high-temperature-resistant pipeline is arranged on the pedestal, one end passes through the through hole and extends to the port of nozzle.The present application optimizes the generation and distribution environment of plasma, so that the effect of dry ice cleaning and plasma stress relief reaches the best balance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor accessory assembly, in particular to a dry ice plasma cleaning device and method. BACKGROUND

[0002] In the field of electronic manufacturing, cleaning of PCBA (Printed Circuit Board Assembly) boards is of great importance. With the development of electronic products towards miniaturization and high performance, the components on PCBA boards are becoming increasingly sophisticated. During the production process, PCBA boards inevitably come into contact with various contaminants, such as flux residue, dust, oil stains, etc. If these contaminants are not removed in a timely manner, they will affect the electrical performance of the circuit board, leading to problems such as short circuits, poor contact, etc., thereby reducing the stability and reliability of the product and shortening its service life. Traditional dry ice cleaning is a way of cleaning PCBA boards. It utilizes the sublimation characteristics of dry ice, through high-speed injection of dry ice particles to impact contaminants, causing them to freeze rapidly and fall off. However, this cleaning method has obvious drawbacks. In the instant of high-speed impact of dry ice particles on the PCBA board, a large stress is generated. This stress may cause potential damage to the delicate components on the board, such as deformation of component pins, loosening of solder joints, and even possible damage to the internal structure of fragile electronic components. Therefore, after traditional dry ice cleaning, effective stress relief measures must be taken to ensure that the quality and performance of the PCBA board are not affected. SUMMARY

[0003] To solve the above problems, the present application optimizes the generation and distribution environment of plasma, so that the effects of dry ice cleaning and plasma stress relief reach the best balance. Through the coordinated work of each module and structure, a dry ice plasma cleaning device and method for efficient removal of residues and stress relief in the field of PCBA board cleaning is achieved.

[0004] The technical solution adopted by the present application is: a dry ice plasma cleaning device, comprising a cleaning nozzle, a base, a plasma generation module, and a dry ice cleaning module, the first end of the cleaning nozzle is provided with a nozzle, the second end is used for installing the base, the base is opposite to the nozzle, the cleaning nozzle is provided with a gas compression cavity and a gas flow guide cavity, a gas passage element is arranged between the gas compression cavity and the gas flow guide cavity, the base is provided with a gas supply element for supplying gas to the gas compression cavity; the plasma generation module comprises a plasma generation element for generating kilovolt voltage and an electricity connection element arranged on the base and electrically connected with the plasma generation element, one end of the plasma generation element is arranged on the base, the other end passes through the gas passage element and extends towards the gas flow guide cavity; a through hole is hollowly arranged at the axis of the plasma generation element, the dry ice cleaning module is provided with a high-temperature-resistant pipeline for passing through the broken dry ice, one end of the high-temperature-resistant pipeline is arranged on the base, the other end passes through the through hole and extends to the port of the nozzle.

[0005] Further improvement of the above scheme is that the cleaning nozzle comprises an upper shell, a lower shell and an inner shell, the inner shell is arranged between the upper shell and the lower shell, the upper shell is provided with a first connecting part, the lower shell is provided with a second connecting part, and the first connecting part and the second connecting part are connected by threads; the lower shell is provided with a support step, and one end of the inner shell abuts on the support step.

[0006] Further improvement of the above scheme is that the upper shell is provided with a third connecting part, the base is provided with an assembly step, the inner shell is provided with a fourth connecting part, one end of the assembly step abuts on the third connecting part, and the other end abuts on the fourth connecting part, so as to fix the base; the outer periphery of the assembly step is provided with a sealing groove, the sealing groove is used for installing a sealing ring, and the sealing groove is used for sealing the inner wall of the gas compression cavity; the end of the lower shell is provided with a fifth connecting part, and the fifth connecting part is used for connecting the nozzle.

[0007] Further improvement of the above scheme is that the nozzle is provided with a tapered part, the end of the tapered part is provided with a spouting part, the spouting part is coaxial with the high-temperature-resistant pipeline, and the end of the high-temperature-resistant pipeline extends out of the port of the spouting part.

[0008] Further improvement of the above scheme is that the gas supply element comprises an air inlet channel arranged on the base, the air inlet channel is provided with an air inlet interface, the air inlet interface is used for gas supply of the gas compression cavity, and the air inlet interface is used for conveying gas from the gas compression cavity to the gas flow guide cavity.

[0009] Further improvement of the above scheme is that the base is provided with a pipeline fixing part, and the pipeline fixing part is used for clamping and fixing the high-temperature-resistant pipeline on the base.

[0010] Further improvement of the above scheme is that the base is provided with a fixing groove below the pipeline fixing part, the fixing groove is provided with an internal fixing part, the internal fixing part is used for fixing the power connection element and the high-temperature-resistant pipeline, and the base is provided with a locking fixing part below the internal fixing part, the locking fixing part is used for fixing the end of the plasma generating element on the base, and the locking fixing part is used for electrically connecting the power connection element and the plasma generating element.

[0011] Further improvement of the above scheme is that the inner diameter of the air passage element is connected with the plasma generating element, and the outer diameter of the air passage element is arranged between the gas compression cavity and the gas flow guide cavity; the air passage element is provided with a plurality of air passage holes, and the plurality of air passage holes are evenly distributed in a ring shape around the plasma generating element as the axis.

[0012] Further improvement of the above scheme is that the air passage hole penetrates through the thickness direction of the air passage element in a diagonal direction, so that the gas flows in a ring shape when entering the gas flow guide cavity from the gas compression cavity.

[0013] Further improvement of the above scheme is that the power element is AGG silica gel high-voltage flexible cord, and the high-temperature-resistant pipeline is high-temperature-resistant glass pipeline.

[0014] A cleaning method comprises the dry ice plasma cleaning device, and the cleaning method comprises the following steps:

[0015] Step S1, dry ice preparation stage: liquid CO2 is prepared into dry ice particles with a particle size of 80-150 μm through an expansion granulator, the particle roundness is controlled to be greater than or equal to 85%, and the dry ice particles are stored in a constant-temperature container at-78 ℃;

[0016] Step S2, pretreatment stage: the PCBA board is pre-cleaned by using ultrasonic waves with a frequency of 40 kHz to remove loose surface contaminants;

[0017] Step S3, primary cleaning stage: the dry ice particles are sprayed out from the high-temperature-resistant pipeline at a pressure of 0.8-1.5 MPa through a two-stage booster system, the spraying angle is adjusted to 30°-60°, the impact speed reaches 150-200 m / s, and the micro-explosion effect generated by the phase change sublimation of the dry ice is used to strip the dense surface contaminants;

[0018] Step S4, plasma treatment stage: oxygen-containing mixed gas is introduced immediately after the dry ice is sprayed, a high-frequency electric field with an electron density of 1×10¹ 0 -5×10¹¹ cm⁻³ is generated by a radio frequency power supply, and the treatment time is 30-90 seconds;

[0019] Step S5, stress relief stage: the plasma working voltage is adjusted to 800-1200 V, the protective gas with an argon-nitrogen ratio of 4:1 is introduced, and a stress buffer layer with a thickness of 10-30 nm is formed on the surface of the PCBA;

[0020] Step S6, post-treatment stage: a pulse vacuum adsorption system is used to recycle residual dry ice and contaminants, and the adsorption pressure is maintained at-50 kPa to-80 kPa.

[0021] Further improvement of the above scheme is that step S3 and step S4 are controlled by time sequence coupling, the dry ice spraying period is set to 10-30 seconds, the plasma treatment period is set to 5-15 seconds, 3-5 cycles of alternation are performed, and the alternation interval time is not more than 2 seconds;

[0022] In the time sequence coupling control, the dry ice spraying pressure changes in a gradient manner in the alternation process, the initial pressure is 1.2-1.5 MPa, the pressure decreases by 0.2-0.3 MPa in each cycle, and the plasma treatment power increases by 10-15% in amplitude synchronously;

[0023] Further improvement of the above scheme is that the oxygen-containing mixed gas in step S4 is composed of oxygen, argon and carbon tetrafluoride in a volume ratio of 3:6:1, the gas flow is controlled at 8-12 L / min, and the ionization zone temperature is kept at 40-60℃.

[0024] Further improvement of the above scheme is that the two-stage pressurization system in step S3 comprises:

[0025] a first-stage screw propelling mechanism with a rotating speed controlled at 800-1200 rpm;

[0026] a second-stage Venturi accelerator with a throat diameter to outlet diameter ratio of 1:3-1:5;

[0027] a built-in piezoelectric sensor for real-time monitoring of particle speed and feedback adjustment of propelling pressure;

[0028] Further improvement of the above scheme is that the stress buffer layer forming process in step S5 comprises:

[0029] step a, injection of atomized silane coupling agent in a plasma environment, with an atomized particle size controlled at 5-10 μm;

[0030] step b, directional arrangement of the coupling agent molecules by electric field guidance, with a 50-100 V bias voltage applied;

[0031] step c, pulse annealing process, with a temperature rising rate of 10-15℃ / s to 80-100℃ and then quenching.

[0032] The present application has the following advantages:

[0033] Compared with the existing dry ice cleaning device, in the aspect of dry ice residue removal function, one end of the high-temperature-resistant pipeline of the dry ice cleaning module is stably arranged on the base, the other end accurately penetrates the through hole at the axis of the plasma generating element, and extends to the nozzle port. Ensure that the broken dry ice can smoothly pass through the high-temperature-resistant pipeline and reach the cleaning position. The dry ice sublimates rapidly in the normal temperature environment, and the strong impact force generated in the phase change process can effectively remove various stubborn residues on the surface of the PCBA board. Whether it is the residual flux, dust particles or other impurities after welding, they can be completely removed under the high-efficiency impact of dry ice, greatly improving the cleanliness of the surface of the PCBA board, and providing reliable guarantee for the subsequent production process or use performance. The plasma assisted stress relief function, when the plasma generating module works, the plasma generating element can generate kilovolt voltage, and the power supply element ensures stable power supply of the whole system. One end of the plasma generating element is fixed on the base, and the other end penetrates the air passage element and extends towards the gas flow guide cavity. In this process, plasma is generated in a specific area and interacts with the surface of the PCBA board. The high-energy characteristics of the plasma can effectively change the stress distribution inside the PCBA board. During the manufacturing, processing and use of the PCBA board, internal stress will inevitably accumulate, which may cause problems such as deformation and cracking of the board, affecting its performance and service life. Through the action of plasma, the internal stress of the PCBA board can be released and redistributed, eliminating potential stress concentration points, thereby enhancing the structural stability and reliability of the PCBA board. The setting of the gas compression cavity and the gas flow guide cavity, and the air passage element between the two, cooperate with the gas supply element on the base, can accurately control the gas flow and pressure entering the cleaning area. It can optimize the generation and distribution environment of plasma, so that the effects of dry ice cleaning and plasma stress relief reach the best balance. Through the cooperative work of each module and structure, efficient residue removal and stress relief are realized in the field of PCBA board cleaning, which provides strong support for improving the quality and performance of the PCBA board.

[0034] The cleaning method, in the dry ice preparation stage, accurately controls the particle size of the dry ice particles in 80-150pm and the roundness is greater than or equal to 85%, and is stored in a -78°C constant temperature container, which provides high-quality cleaning medium for subsequent cleaning. The high-quality dry ice particles can play a more effective role in the primary cleaning stage. The dry ice is sprayed out of the high-temperature-resistant pipeline at a pressure of 0.8-1.5MPa, an impact speed of 150-200m / s, and a spray angle of 30°-60°, which can accurately impact the surface of the PCBA board. The micro-explosion effect generated by the phase change sublimation of dry ice can efficiently strip the dense contaminants on the surface, while the excellent residue removal function of dry ice is retained, ensuring that the physical impurities on the surface of the PCBA board are effectively removed. The pretreatment stage adopts 40kHz ultrasonic wave for pre-cleaning, which can remove the loose contaminants on the surface in advance, lay a good foundation for subsequent deep cleaning, and make the whole cleaning process more efficient. In the plasma treatment stage, oxygen-containing mixed gas is introduced immediately after the dry ice spraying, and a high-frequency electric field of 13.56MHz is generated to form a low-temperature plasma with a specific electron density. This not only helps to further clean the surface of the PCBA board. By adjusting the plasma working voltage and introducing specific proportion of argon and nitrogen protective gas, a uniform and appropriate thickness stress buffer layer can be formed on the surface of the PCBA board, effectively eliminating the stress generated during the cleaning process, ensuring the performance stability of the PCBA board, and avoiding the damage or performance degradation of electronic components caused by stress problems. In the post-treatment stage, the pulse vacuum suction system can efficiently recover residual dry ice and pollutants under the adsorption pressure of -50kPa to -80kPa, keep the working environment clean, and prevent secondary pollution of the PCBA board caused by residual pollutants. The whole cleaning method comprehensively utilizes the characteristics of dry ice and plasma, realizes the multiple goals of efficient cleaning, stress elimination and environmental friendliness, and significantly improves the cleaning quality and reliability of the PCBA board. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 FIG. 1 is a schematic diagram of a dry ice plasma cleaning device according to the present application;

[0036] Figure 2 FIG. 2 is a schematic diagram of the dry ice plasma cleaning device according to the present application; Figure 1

[0037] Figure 3 FIG. 4 is a sectional view of A-A in the dry ice plasma cleaning device according to the present application; Figure 2

[0038] Figure 4 FIG. 6 is a schematic diagram of the internal structure of the dry ice plasma cleaning device according to the present application; Figure 1

[0039] Figure 5 Figure 1 ​​​​Schematic diagram of part structure of the middle dry ice plasma cleaning device

[0040] Figure 6 Flowchart of the cleaning method of the present application.

[0041] Legend: cleaning nozzle 1, nozzle 11, conical part 111, spray part 112, gas compression cavity 12, gas flow guide cavity 13, air passage element 14, air passage hole 141, upper shell 15, first connecting part 151, third connecting part 152, lower shell 16, second connecting part 161, support step 162, fifth connecting part 163, inner shell 17, fourth connecting part 171, base 2, gas supply element 21, gas inlet channel 211, gas inlet interface 212, assembly step 22, sealing groove 221, pipe fixing part 23, fixing groove 24, built-in fixing part 241, locking fixing part 242, plasma generation module 3, plasma generation element 31, through hole 311, power connection element 32, dry ice cleaning module 4, high-temperature-resistant pipe 41. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present application, the present application will be described in more detail below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0043] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments of the present application, and is not intended to limit the present application. As used herein, Figures 1 to 5As shown, in an embodiment of the present application, a dry ice plasma cleaning device includes a cleaning nozzle 1, a base 2, a plasma generation module 3, and a dry ice cleaning module 4. The first end of the cleaning nozzle 1 is provided with a nozzle 11, and the second end is used to install the base 2. The base 2 is opposite to the nozzle 11. The cleaning nozzle 1 is provided with a gas compression cavity 12 and a gas flow guide cavity 13. A gas passage element 14 is arranged between the gas compression cavity 12 and the gas flow guide cavity 13. The base 2 is provided with a gas supply element 21 for supplying gas to the gas compression cavity 12. The plasma generation module 3 includes a plasma generation element 31 for generating kilovolt voltage and an electrical connection element 32 arranged on the base 2 and electrically connected to the plasma generation element 31. One end of the plasma generation element 31 is arranged on the base 2, and the other end extends through the gas passage element 14 and towards the gas flow guide cavity 13. A through hole 311 is hollowly arranged at the axis of the plasma generation element 31. The dry ice cleaning module 4 is provided with a high-temperature-resistant pipeline 41 for passing the broken dry ice. One end of the high-temperature-resistant pipeline 41 is arranged on the base 2, and the other end extends through the through hole 311 and reaches the port of the nozzle 11. In terms of dry ice residue removal function, in this embodiment, one end of the high-temperature-resistant pipeline 41 of the dry ice cleaning module 4 is stably arranged on the base 2, the other end accurately passes through the through hole 311 at the axis of the plasma generation element 31, and extends to the port of the nozzle 11. It is ensured that the broken dry ice can smoothly pass through the high-temperature-resistant pipeline 41 and reach the cleaning site. The dry ice rapidly sublimates in the normal temperature environment, and the strong impact force generated in the phase change process can effectively remove various stubborn residues on the surface of the PCBA board. Whether it is residual flux, dust particles or other impurities after welding, they can be completely removed under the high-efficiency impact of dry ice, greatly improving the cleanliness of the surface of the PCBA board and providing reliable protection for subsequent production processes or use performance. The plasma-assisted stress elimination function is realized by the working of the plasma generation module 3. The plasma generation element 31 can generate kilovolt voltage, and the electrical connection element 32 ensures stable power supply of the whole system. One end of the plasma generation element 31 is fixed on the base 2, and the other end extends through the gas passage element 14 and towards the gas flow guide cavity 13. In this process, plasma is generated in a specific area and interacts with the surface of the PCBA board. The high-energy characteristics of the plasma can effectively change the stress distribution inside the PCBA board. During the manufacturing, processing and use of the PCBA board, internal stress will inevitably accumulate, which may cause problems such as deformation and cracking of the board, affecting its performance and service life. Through the action of plasma, the internal stress of the PCBA board can be released and redistributed, eliminating potential stress concentration points, thereby enhancing the structural stability and reliability of the PCBA board.The gas compression cavity 12 and the gas flow guide cavity 13, and the air supply element 14 between the two, in cooperation with the air supply element 21 on the base 2, include the air inlet channel arranged on the base, which can accurately control the gas flow and pressure entering the cleaning area. The generation and distribution environment of the plasma can be optimized to achieve the best balance of dry ice cleaning and plasma stress relief effect. Through the coordinated work of each module and structure, efficient residue removal and stress relief are realized in the field of PCBA board cleaning, which provides strong support for improving the quality and performance of the PCBA board.

[0045] The cleaning nozzle 1 comprises an upper shell 15, a lower shell 16 and an inner shell 17, the inner shell 17 is arranged between the upper shell 15 and the lower shell 16, the upper shell 15 is provided with a first connecting part 151, the lower shell 16 is provided with a second connecting part 161, and the first connecting part 151 and the second connecting part 161 are connected through threads; the lower shell 16 is provided with a support step 162, and one end of the inner shell 17 abuts on the support step 162. In the embodiment, the design of the threaded connection of the upper and lower shells 16 not only ensures the stability of the structure, but also facilitates disassembly and installation during maintenance and repair of the equipment, greatly improving the convenience of operation and reducing the maintenance cost. Secondly, one end of the inner shell 17 abuts on the support step 162 of the lower shell 16, which provides stable support for the inner shell 17 and ensures the stability of the internal structure of the nozzle, thereby ensuring the stability and reliability of the cleaning process. When cleaning the PCBA board, the function of removing residues by dry ice is fully retained. When the dry ice contacts the surface of the PCBA board, it sublimates rapidly, effectively removes stubborn residues by using the impact force generated by sublimation, and ensures that the surface of the circuit board reaches high cleanliness. The interaction of the plasma and the surface of the PCBA board can effectively release the stress accumulated in the board due to manufacturing, processing and other processes, avoiding the adverse effects of stress concentration on the performance of the PCBA board.

[0046] The upper shell 15 is provided with a third connecting portion 152, the base 2 is provided with a fitting step 22, the inner shell 17 is provided with a fourth connecting portion 171, one end of the fitting step 22 is in abutment with the third connecting portion 152, and the other end is in abutment with the fourth connecting portion 171, so as to fix the base 2; the outer periphery of the fitting step 22 is provided with a sealing groove 221, which is used to install a sealing ring, so as to seal the inner wall of the gas compression cavity 12; the end of the lower shell 16 is provided with a fifth connecting portion 163, which is used to connect the nozzle 11. In this embodiment, the base 2 is stably fixed through the cooperation of the third connecting portion 152, the fitting step 22 and the fourth connecting portion 171, and this precise connection mode ensures the stability of the overall structure of the device, and provides a solid foundation for subsequent efficient cleaning work. The design of the outer peripheral sealing groove 221 of the fitting step 22 and the sealing ring effectively seals the gas compression cavity 12, ensures the stability of the pressure in the cavity, and enables the dry ice to participate in the cleaning work in the compression cavity in the best state, thereby enhancing the cleaning ability of the dry ice on the residues on the PCBA board and ensuring that stubborn stains can be completely removed. The device retains the core function of dry ice residue removal. The strong impact force generated by the sublimation of dry ice can quickly strip and remove various impurities on the surface of the PCBA board.

[0047] The nozzle 11 is provided with a tapered portion 111, the end of the tapered portion 111 is provided with a spraying portion 112, the spraying portion 112 is coaxial with the high-temperature-resistant pipeline 41, and the end of the high-temperature-resistant pipeline 41 protrudes out of the port of the spraying portion 112. In this embodiment, the tapered portion 111 of the nozzle 11 has the function of optimizing the airflow. During the process of spraying plasma from the nozzle 11, the tapered portion 111 can guide the airflow to gradually converge, so that the plasma beam is more concentrated, and the energy density of the plasma is improved. This helps to enhance the impact and stripping ability on the surface contaminants of the cleaning object, and can more efficiently remove stubborn dirt, impurities and the like. The spraying portion 112 is coaxial with the high-temperature-resistant pipeline 41, which ensures that the dry ice and plasma can be stably sprayed along an accurate path. This reduces the scattering and energy loss of the plasma during transmission, ensures the uniformity and stability of the plasma, and further improves the consistency of the cleaning effect, so that the entire cleaning area can be uniformly treated. The end of the high-temperature-resistant pipeline 41 protrudes out of the port of the spraying portion 112, which on the one hand protects the spraying portion 112 from direct heat impact of the high-temperature plasma, prolonging the service life of the spraying portion 112. On the other hand, this structure can play a certain restraining role on the sprayed dry ice plasma, further optimizing the spraying form of the plasma, making the cleaning effect more accurate, and effectively improving the performance of the dry ice plasma cleaning device when processing complex shapes or high-precision cleaning tasks.

[0048] The gas supply element 21 comprises an air inlet channel 211 provided on the base 2, which is provided with an air inlet interface 212 for supplying the gas compression cavity 12 with gas to transport the gas from the gas compression cavity 12 to the gas flow guiding cavity 13. Specifically, the base 2 is provided with a pipe fixing member 23 for clamping and fixing the high-temperature-resistant pipe 41 on the base 2; the base 2 is provided with a fixing groove 24 below the pipe fixing member 23, which is provided with an internal fixing member 241 for fixing the power connection element 32 and the high-temperature-resistant pipe 41; the internal fixing member 241 is provided with a locking fixing member 242 below, which is used to fix the end of the plasma generating element 31 on the base 2 and electrically connect the power connection element 32 with the plasma generating element 31. In this embodiment, the provision of the air inlet channel 211 and the air inlet interface 212 can stably and efficiently supply the gas compression cavity 12 with gas, ensuring smooth transportation of the gas from the gas compression cavity 12 to the gas flow guiding cavity 13, providing a stable gas source basis for the generation and transmission of plasma, which helps to improve the uniformity and stability of dry ice plasma cleaning, and ensures the consistency of cleaning effect. The pipe fixing member 23 and the internal fixing member 241 in the fixing groove 24 cooperate with each other to firmly fix the high-temperature-resistant pipe 41 on the base 2, which not only prevents the pipe from shaking and shifting during the operation of the device, ensuring the stability of gas transmission, but also provides good protection for the pipe, prolonging its service life. At the same time, the stable fixation of the internal fixing member 241 to the power connection element 32 ensures the stability of the circuit connection and reduces the problem of poor contact caused by loose elements. The locking fixing member 242 reliably fixes the end of the plasma generating element 31 on the base 2 and realizes good electrical connection between the power connection element 32 and the plasma generating element 31, so that the plasma generating element 31 can work stably and efficiently generate plasma.

[0049] The inner diameter of the ventilation element 14 is connected with the plasma generating element 31, and the outer diameter is arranged between the gas compression cavity 12 and the gas flow guide cavity 13. A plurality of ventilation holes 141 are arranged on the ventilation element 14, and the plurality of ventilation holes 141 are evenly distributed in a ring shape around the plasma generating element 31. Specifically, the ventilation holes 141 are obliquely penetrated along the thickness direction of the ventilation element 14, so that the gas flows in a ring shape when entering the gas flow guide cavity 13 from the gas compression cavity 12. In this embodiment, the inner diameter of the ventilation element 14 is connected with the plasma generating element 31, and the outer diameter is arranged between the gas compression cavity 12 and the gas flow guide cavity 13. This layout ensures the accuracy and stability of the gas transmission path, so that the gas can flow orderly from the compression cavity to the flow guide cavity, providing a stable gas source supply basis for the subsequent plasma cleaning process. The design of the plurality of ventilation holes 141 evenly distributed in a ring shape around the plasma generating element 31 greatly optimizes the distribution of the gas. When the gas passes through the ventilation holes 141, it enters the gas flow guide cavity 13 in a ring shape, which makes the gas distribution in the flow guide cavity more uniform. Uniform gas distribution helps to form a stable and uniform plasma field in the plasma generating area, improving the generation efficiency and quality of the plasma. The design of the ventilation holes 141 obliquely penetrating along the thickness direction of the ventilation element 14 further enhances the ring flow effect of the gas. The oblique penetration mode promotes the rotation and diffusion of the gas when entering the flow guide cavity, which not only helps to mix more fully with the dry ice particles, but also forms a more complex and effective gas flow pattern in the cleaning area. The complex gas flow pattern can more comprehensively and deeply act on the surface of the object to be cleaned, thereby significantly improving the cleaning effect of the dry ice plasma cleaning device.

[0050] The power connection element 32 is an AGG silicone high-voltage flexible wire, and the high-temperature resistant pipe 41 is a high-temperature resistant glass pipe. In this embodiment, the AGG silicone high-voltage flexible wire has good electrical insulation performance and high-voltage resistance characteristics, which can ensure the stable and reliable power transmission of the dry ice plasma cleaning device during operation, effectively reduce the faults and safety hazards caused by power connection problems, and ensure that the device can work continuously and efficiently. The application of the high-temperature resistant glass pipe can adapt to the high-temperature environment generated during the dry ice plasma cleaning process, ensure the structural integrity and chemical stability of the pipe, and avoid deformation or damage of the pipe due to temperature effects. On the other hand, the glass pipe has good visibility, which facilitates the operator to observe the cleaning situation inside the device in real time and adjust the parameters in time, thereby improving the cleaning effect and precision and optimizing the entire dry ice plasma cleaning operation process.

[0051] Referring to Figures 1 to 6As shown, a cleaning method includes a dry ice plasma cleaning device for PCBA board cleaning, the cleaning method comprising the following steps: step S1, dry ice preparation stage: liquid CO2 is prepared into dry ice particles with a particle size of 80-150 μm through an expansion granulator, the particle roundness is controlled to be ≥85%, and the dry ice particles are stored in a constant temperature container at-78℃; step S2, pretreatment stage: the PCBA board is pre-cleaned by using ultrasonic waves with a frequency of 40 kHz to remove loose surface contaminants; step S3, primary cleaning stage: the dry ice particles are sprayed out from a high-temperature-resistant pipeline 41 at a pressure of 0.8-1.5 MPa through a two-stage booster system, the spraying angle is adjusted to be 30°-60°, the impact speed reaches 150-200 m / s, and the micro-explosion effect generated by the phase change sublimation of the dry ice is used to strip the dense surface contaminants; step S4, plasma treatment stage: oxygen-containing mixed gas is introduced immediately after the dry ice spraying, a high-frequency electric field with an electron density of 1×10¹ 0- low temperature plasma of 5x10 11 cm -3, treatment time 30-90 seconds; step S5, stress relief phase: adjusting the plasma working voltage to 800-1200V, passing in the protective gas of argon and nitrogen in a ratio of 4:1 to form a stress buffer layer of 10-30nm thickness on the surface of the PCBA; step S6, post-processing phase: using a pulsed vacuum adsorption system to recover residual dry ice and pollutants, the adsorption pressure is maintained at -50kPa to -80kPa. In the dry ice preparation stage of this embodiment, the particle size of the dry ice particles is accurately controlled to be 80-150μm and the roundness is ≥85%, and is stored in a -78℃ constant temperature container, providing a high quality cleaning medium for subsequent cleaning. High quality dry ice particles can play a more effective role in the primary cleaning stage, sprayed out of the high-temperature-resistant pipeline 41 at a pressure of 0.8-1.5MPa, an impact speed of 150-200m / s, and a spray angle of 30°-60°, which can accurately impact the surface of the PCBA board. Using the micro-explosion effect generated by the phase change sublimation of dry ice, it can efficiently strip the dense contaminants on the surface, while retaining the excellent residue removal function of dry ice, ensuring that the physical impurities on the surface of the PCBA board are effectively removed. The pretreatment stage uses 40kHz ultrasonic waves for pre-cleaning, which can remove loose surface contaminants in advance, laying a good foundation for subsequent deep cleaning and making the entire cleaning process more efficient. The plasma treatment stage immediately passes in oxygen-containing mixed gas and generates a 13.56MHz high-frequency electric field after dry ice spraying, forming a low-temperature plasma with a specific electron density. This not only helps to further clean the surface of the PCBA board. Adjusting the plasma working voltage and passing in a specific ratio of argon and nitrogen protective gas can form a uniform and appropriately thick stress buffer layer on the surface of the PCBA board, effectively eliminating the stress generated during the cleaning process, ensuring the performance stability of the PCBA board, and avoiding damage or performance degradation of electronic components due to stress problems. In the post-processing stage, the pulsed vacuum adsorption system can efficiently recover residual dry ice and pollutants at an adsorption pressure of -50kPa to -80kPa, keeping the working environment clean, while preventing secondary pollution of the PCBA board by residual pollutants. The entire cleaning method combines the characteristics of dry ice and plasma to achieve the multiple goals of efficient cleaning, stress relief, and environmental friendliness, significantly improving the cleaning quality and reliability of the PCBA board.

[0052] Step S3 and step S4 are controlled by time sequence coupling, the dry ice spraying period is set to 10-30 seconds, the plasma treatment period is 5-15 seconds, and the two are alternately performed for 3-5 cycles, and the alternating interval time is not more than 2 seconds; in this embodiment, the dry ice spraying period and the plasma treatment period are accurately set by time sequence coupling control, and the two are alternately performed for a specific cycle, which effectively plays the advantages of the two cleaning methods. Dry ice spraying can use low temperature impact and sublimation characteristics to quickly remove large area loose contaminants, while cooling the cleaned surface to reduce the risk of thermal damage. Plasma treatment can further remove stubborn stains and microscopic impurities by chemical reaction of active particles to improve surface activity. Alternating multiple cycles can gradually and deeply remove different types of contaminants. The alternating interval time of not more than 2 seconds ensures the continuity and efficiency of the entire cleaning process, and avoids the re-attachment of contaminants due to too long interval.

[0053] The oxygen-containing mixed gas in step S4 is composed of oxygen, argon and carbon tetrafluoride in a volume ratio of 3:6:1, the gas flow is controlled at 8-12L / min, and the ionization zone temperature is maintained at 40-60℃. In this embodiment, oxygen, argon and carbon tetrafluoride are combined in a volume ratio of 3:6:1, which can effectively play the characteristic advantages of each gas. Oxygen can react with pollutants to remove organic impurities; argon has good electrical conductivity and chemical stability, which helps to maintain a stable plasma environment and improve cleaning efficiency; carbon tetrafluoride can enhance the dissolution and stripping ability of specific pollutants. The gas flow is controlled in the range of 8-12L / min, which can ensure that the gas is fully ionized in the ionization zone to form a plasma with sufficient density and activity, and uniformly and efficiently clean the surface of the dry ice and the surface of the object to be cleaned. The ionization zone temperature is maintained at 40-60℃, which helps to maintain the activity and stability of the plasma, avoids abnormal plasma generation due to too high or too low temperature, ensures the stability and reliability of the cleaning process, and improves the cleaning quality, thereby achieving efficient removal of various complex contaminants.

[0054] The double-stage pressurization system in step S3 comprises: a first-stage spiral propulsion mechanism, the rotating speed of which is controlled at 800-1200 rpm; and a second-stage Venturi accelerator, the throat diameter to outlet diameter ratio of which is 1:3-1:5; a built-in piezoelectric sensor is used to monitor the particle speed in real time and feedback adjust the propulsion pressure; in this embodiment, the first-stage spiral propulsion mechanism is precisely controlled at 800-1200 rpm, which can stably and efficiently deliver dry ice particles, providing sufficient and uniform material supply for the subsequent cleaning process, and ensuring the continuity and stability of the cleaning operation. The unique throat diameter to outlet diameter ratio (1:3-1:5) design of the second-stage Venturi accelerator effectively improves the acceleration effect of the dry ice particles, so that the particles obtain higher kinetic energy. When the high-speed dry ice particles cooperate with the plasma, they can more deeply and comprehensively impact the surface of the object to be cleaned, significantly enhancing the removal ability of stubborn stains and impurities. The built-in piezoelectric sensor monitors the particle speed in real time and feedback adjusts the propulsion pressure, realizing intelligent dynamic control of the entire cleaning process.

[0055] The formation process of the stress buffer layer in step S5 comprises: step a, injecting atomized silane coupling agent in a plasma environment, the atomized particle size is controlled at 5-10 μm; step b, directional arrangement of the coupling agent molecules by electric field guidance, a bias voltage of 50-100 V is applied; step c, pulse annealing process is adopted, the temperature is raised to 80-100℃ at a rate of 10-15℃ / s and then quenched. In this embodiment, dry ice plasma cleaning can effectively remove impurities and pollutants on the surface of the material, providing a clean and active surface suitable for the formation of the subsequent stress buffer layer, which helps the atomized silane coupling agent to better adhere and react, and improves the uniformity of the distribution of the coupling agent on the surface of the material. During the formation of the stress buffer layer, the directional arrangement of the coupling agent molecules in combination with the good foundation created by the dry ice plasma cleaning can form a more ordered and stable structure, enhancing the stress buffering capacity. The pulse annealing process under such conditions can further optimize the microstructure of the stress buffer layer, making its performance more stable. Precise control of the temperature rising and quenching process in combination with the surface state after dry ice plasma cleaning improves the bonding force between the stress buffer layer and the material substrate, ensuring that the stress buffer layer can play a lasting role in complex environments, and improving the overall reliability and stability of the material.

[0056] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that, for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A dry ice plasma cleaning device, characterized in that: The system includes a cleaning nozzle, a base, a plasma generating module, and a dry ice cleaning module. The cleaning nozzle has a nozzle at one end and a base at the other, with the base opposite the nozzle. The cleaning nozzle has a gas compression chamber and a gas guiding chamber, with a venting element between the gas compression chamber and the gas guiding chamber. The base has a gas supply element for supplying gas to the gas compression chamber. The plasma generating module includes a plasma generating element for generating kilovolts and a connecting element disposed on the base and electrically connected to the plasma generating element. One end of the plasma generating element is disposed on the base, and the other end passes through the venting element and extends toward the gas guiding chamber. A through hole is hollowed out at the center of the plasma generating element. The dry ice cleaning module has a high-temperature resistant pipe for passing crushed dry ice through it. One end of the high-temperature resistant pipe is disposed on the base, and the other end passes through the through hole and extends to the nozzle port. The inner diameter of the ventilation element is connected to the plasma generating element, and the outer diameter is located between the gas compression chamber and the gas guiding chamber; the ventilation element is provided with multiple ventilation holes, which are evenly distributed circumferentially around the plasma generating element as the axis; The vent hole is obliquely penetrating along the thickness direction of the vent element so that the gas flows in a circumferential manner when it enters the gas guiding cavity from the gas compression chamber. The electrical connection element is an AGG silicone high-voltage flexible wire, and the high-temperature resistant pipe is a high-temperature resistant glass pipe.

2. The dry ice plasma cleaning apparatus according to claim 1, characterized in that: The cleaning nozzle includes an upper housing, a lower housing, and an inner housing. The inner housing is disposed between the upper housing and the lower housing. The upper housing is provided with a first connecting part, and the lower housing is provided with a second connecting part. The first connecting part and the second connecting part are connected by threads. The lower housing is provided with a supporting step, and one end of the inner housing abuts against the supporting step.

3. The dry ice plasma cleaning apparatus according to claim 2, characterized in that: The upper housing is provided with a third connecting part, the base is provided with an assembly step, and the inner housing is provided with a fourth connecting part. One end of the assembly step abuts against the third connecting part and the other end abuts against the fourth connecting part to fix the base. A sealing groove is provided on the outer periphery of the assembly step for installing a sealing ring to seal the inner wall of the gas compression chamber. A fifth connecting part is provided at the end of the lower housing for connecting a nozzle.

4. The dry ice plasma cleaning apparatus according to claim 1, characterized in that: The nozzle is provided with a tapered portion, and the end of the tapered portion is provided with a spraying portion. The spraying portion and the high-temperature resistant pipe are on the same axis; the end of the high-temperature resistant pipe extends out of the port of the spraying portion.

5. The dry ice plasma cleaning apparatus according to claim 1, characterized in that: The gas supply element includes an air inlet channel disposed on the base, the air inlet channel being provided with an air inlet interface, the air inlet interface being used to supply gas to the gas compression chamber, so as to transport gas from the gas compression chamber toward the gas guide chamber.

6. The dry ice plasma cleaning apparatus according to claim 5, characterized in that: The base is provided with a pipe fixing component, which is used to clamp and fix the high-temperature resistant pipe on the base; The base is provided with a fixing groove below the pipe fixing component. An internal fixing component is provided in the fixing groove. The internal fixing component is used to fix the electrical connection element and the high-temperature resistant pipe. A locking fixing component is provided below the internal fixing component. The locking fixing component is used to fix the end of the plasma generating element to the base and to electrically connect the electrical connection element to the plasma generating element.

7. A cleaning method, characterized in that: The dry ice plasma cleaning apparatus according to any one of claims 1 to 6 is used for cleaning PCBA boards, and the cleaning method includes the following steps: Step S1, Dry ice preparation stage: Liquid CO2 is used to prepare dry ice particles with a particle size of 80-150μm through an expander granulator, and the particle roundness is controlled to be ≥85%, and stored in a constant temperature container at -78℃. Step S2, Pre-treatment stage: The PCBA board is pre-cleaned using ultrasonic waves at a frequency of 40kHz to remove loose contaminants from the surface. Step S3, primary cleaning stage: Dry ice particles are sprayed from high-temperature resistant pipes at a pressure of 0.8-1.5MPa through a dual-stage pressurization system. The spray angle is adjusted to 30°-60° and the impact speed reaches 150-200m / s. The micro-explosion effect generated by the phase change sublimation of dry ice is used to peel off dense contaminants on the surface. Step S4, Plasma Treatment Stage: Immediately after dry ice spraying, an oxygen-containing mixed gas is introduced, and a 13.56MHz high-frequency electric field is generated by a radio frequency power supply, forming an electron density of 1×10¹. 0 Low-temperature plasma of -5×10¹¹cm⁻³, processing time 30~90 seconds; Step S5, stress relief stage: Adjust the plasma working voltage to 800-1200V, introduce a protective gas with an argon to nitrogen ratio of 4:1, and form a stress buffer layer with a thickness of 10-30nm on the PCBA surface. Step S6, post-treatment stage: The residual dry ice and pollutants are recovered using a pulsed vacuum adsorption system, and the adsorption pressure is maintained at -50kPa to -80kPa.

8. The cleaning method according to claim 7, characterized in that: Steps S3 and S4 are controlled by time-series coupling. The dry ice spraying cycle is set to 10-30 seconds and the plasma treatment cycle is set to 5-15 seconds. The two are alternated for 3-5 cycles, and the alternation interval does not exceed 2 seconds. In the time-coupled control, the dry ice injection pressure changes in a gradient during the alternation process. The initial pressure is 1.2-1.5 MPa, and it decreases by 0.2-0.3 MPa in each cycle. The plasma processing power increases synchronously by 10-15%. The oxygen-containing mixed gas in step S4 is composed of oxygen, argon and carbon tetrafluoride in a volume ratio of 3:6:1, with the gas flow rate controlled at 8-12 L / min and the ionization zone temperature maintained at 40-60℃.

9. The cleaning method according to claim 7, characterized in that: The two-stage supercharging system described in step S3 includes: The first-stage screw propulsion mechanism has a rotational speed controlled at 800-1200 rpm; The second-stage Venturi accelerator has a throat diameter to outlet diameter ratio of 1:3 to 1:

5. Built-in piezoelectric sensor monitors particle velocity in real time and adjusts propulsion pressure accordingly; The process of forming the stress buffer layer in step S5 includes: Step a: Inject atomized silane coupling agent into a plasma environment, with the atomized particle size controlled at 5-10 μm; Step b: The coupling agent molecules are oriented and aligned by an electric field, and a bias voltage of 50-100V is applied. Step c involves using a pulse annealing process, heating the temperature to 80-100℃ at a rate of 10-15℃ / s and then rapidly cooling it.

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