A laser-dry ice hybrid cleaning method

Abstract

This invention discloses a laser-dry ice hybrid cleaning method. The workpiece with an adhering layer on its surface is placed on a platform. A laser device and a dry ice blasting cleaning device are controlled and activated, causing the dry ice particles ejected from the dry ice nozzle and the laser beam emitted from the laser head to move synchronously and simultaneously act on the same area of ​​the adhering layer. Through the synergistic effect of the dry ice particles and the laser, the adhering layer is removed along a preset cleaning path, thus achieving efficient and high-quality surface cleaning. This invention solves the problems of poor cleaning efficiency, low cleaning quality, and poor process adaptability in existing cleaning technologies.

Description

Technical Field

[0001] This invention relates to the technical field of cleaning methods, and more particularly to a laser-dry ice hybrid cleaning method. Background Technology

[0002] During the production process, industrial molds accumulate various layers of deposits, including mold release agent residues and metal oxides. These contaminants shorten the mold's lifespan and affect product quality. Cleaning electronic equipment requires removing microparticles and organic contaminants while ensuring no damage to electronic components. Traditional cleaning methods, such as chemical cleaning, ultrasonic cleaning, and mechanical cleaning, often involve environmental pollution, material damage, and insufficient cleaning precision. While dry ice cleaning is environmentally friendly, its ability to remove stubborn contaminants or residual adhesives is limited. Laser cleaning, although highly precise, can cause thermal damage to materials with low heat resistance.

[0003] Existing technologies employ a step-by-step cleaning approach that combines multiple cleaning methods, using different methods sequentially to achieve further cleaning. However, this step-by-step approach simply utilizes the characteristics of each method and fails to fundamentally overcome its limitations, resulting in poor cleaning effectiveness for complex, mixed contaminants. Furthermore, the time required for this type of step-by-step cleaning approach is the sum of the times for each sequential cleaning method, which actually reduces cleaning efficiency and makes it difficult to achieve high-efficiency cleaning. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a laser-dry ice hybrid cleaning method that can efficiently remove various types of contaminants while avoiding the risks of thermal damage and surface damage.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A laser-dry ice hybrid cleaning method, comprising:

[0007] The workpiece to be cleaned is placed on a platform, and the surface of the workpiece to be cleaned has an adhesion layer.

[0008] The laser device and dry ice jet cleaning device are regulated and activated so that the dry ice particles ejected by the dry ice nozzle and the laser beam spot emitted by the laser head move synchronously and always act on the same area of ​​the adhesion layer at the same time. The adhesion layer is removed along the preset cleaning path through the synergistic effect of the dry ice particles and the laser.

[0009] Optionally, the laser head is configured to irradiate the workpiece vertically and to defocus the laser beam spot on the surface of the workpiece to be cleaned.

[0010] Optionally, the vertical distance between the laser head and the surface of the workpiece to be cleaned is 5.0cm-30.0cm, the diameter of the spot in the defocused state is 0.02mm-0.5mm, and the laser energy density of the laser beam irradiating the surface of the workpiece to be cleaned is 10 mJ / mm²-200mJ / mm².

[0011] Optionally, the laser device employs lasers of different wavelengths, such as continuous, long-pulse, and short-pulse lasers, and adjusts process parameters such as laser power, repetition frequency, beam type, spot size, cleaning speed, and cleaning path to adapt to the material to be removed from the deposited layer. The beam type is controlled through optical components and can be selected as a flat-top beam, vortex beam, radial beam, angular beam, Bessel beam, or linearly polarized laser beam. The spot shape can be selected as a circular spot, square spot, rectangular spot, or linear spot. The optical components include DOE, ROE, SLM, optical elements, and metasurface optical elements, which directly control the output laser beam, thereby achieving beam shaping and optical field manipulation.

[0012] Optionally, the dry ice nozzle is configured to spray dry ice particles onto the surface of the workpiece to be cleaned at an angle α, where 30° ≥ α > 0°. Here, the angle of inclination refers to the angle between the dry ice nozzle and the vertical direction (i.e., the laser emission direction).

[0013] Optionally, the dry ice nozzle has a spray distance of 10-12 cm from the surface of the workpiece to be cleaned, and the nozzle diameter is 0.5 cm-2 cm.

[0014] Optionally, when the dry ice particles and the laser beam spot act on the surface of the workpiece to be cleaned, the center of the spot coincides with the center of the dry ice spray coverage area by ≥95%.

[0015] Optionally, the substrate of the workpiece to be cleaned includes, but is not limited to, materials such as metal, glass, and semiconductors, or their composite structures. The adhesion layer is a composite layer comprising at least two types of adhering substances, with different adhering substances having different material compositions; for example, a composite of mold release agent residue and metal oxide dirt, or a composite of organic contaminants and microparticle dirt.

[0016] Optionally, the laser device is an infrared pulsed laser; the dry ice nozzle moves synchronously with the laser head, and the moving speed is set to allow the output pulsed light spots to overlap, with the overlap degree controlled between 40% and 80%.

[0017] Optionally, the dry ice nozzle and the laser head move synchronously through a synchronous movement module, which includes a rigid connecting arm that links the dry ice nozzle and the laser device.

[0018] Optionally, the laser device and the dry ice jet cleaning device are started synchronously through a synchronization triggering module. The synchronization triggering module includes a differential signal triggering unit, a pre-calibration compensation unit, and a real-time status monitoring unit. The differential signal triggering unit is used to output a synchronous start or stop signal; the pre-calibration compensation unit is used to eliminate the inherent delay of the equipment; and the real-time status monitoring unit is used to provide feedback on the cleaning status.

[0019] The laser beam and dry ice particles act simultaneously on the surface to be cleaned, and their synergistic mechanism includes:

[0020] Synergistic thermal expansion and contraction peeling: The laser acts directly on the adhesion layer in the air medium, causing the organic components (such as release agents) to heat up and expand instantly. Simultaneously sprayed -78.5℃ dry ice particles cause the adhesion layer to cool down and contract rapidly, forming cyclic thermal stress. This causes dense microcracks to be generated inside the adhesion layer, thereby reducing the adhesion to the substrate.

[0021] Laser-enhanced dry ice micro-explosion: The laser spot completely overlaps with the center of the dry ice jet. The dry ice particles absorb the laser energy before impact, and a gaseous CO2 layer quickly forms on the surface. This causes the gaseous layer to expand rapidly at the moment of impact, thereby enhancing the impact kinetic energy of the dry ice.

[0022] Energy coupling enhancement: Laser energy not only acts on the adhesion layer, but also directly stimulates the phase change potential of dry ice particles, causing dry ice to rapidly transform from a solid state to a supercritical state. The volume expansion factor during impact is increased by 2 times compared to step-by-step cleaning, and the penetration of dense mixed adhesion layers is significantly enhanced.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) This invention utilizes the effective synergistic effect of laser and dry ice to keep the surface to be cleaned in a state of thermal expansion and contraction, further enhancing the application effect of the physical properties of dry ice and laser on the difference in thermal expansion coefficients between the sample material and the adhering substance, greatly reducing the adhesive effect between the sample substrate layer and the adhering layer. At the same time, compared with the disadvantages of laser cleaning, which is prone to thermal ablation damage to the sample material, and dry ice cleaning, which is difficult to remove oil stains and other adhering substances, the two methods can be used in combination to achieve good complementarity, and can achieve good cleaning effect on workpieces with multiple mixed adhering layers and adhering substances of different thicknesses.

[0025] (2) Compared with the laser-dry ice step-by-step cleaning scheme, which requires the combined time of laser cleaning and dry ice cleaning, the synchronous laser-dry ice hybrid cleaning performs both simultaneously, requiring less time and being more efficient. Moreover, during cleaning, the laser energy synchronously triggers the sublimation and expansion of dry ice particles, generating shock waves, which are superimposed with the plasma shock waves generated by the laser, thereby accelerating the peeling of the adhesion layer and achieving a stronger cleaning effect without damaging the substrate.

[0026] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0027] Figure 1 A schematic diagram of the system used in the laser-dry ice hybrid cleaning method of the embodiment;

[0028] Figure 2 The images show the surface of the samples after cleaning using the methods of Example 1 and the comparative example. From left to right, they are dry ice cleaning, laser cleaning, and laser-dry ice hybrid cleaning of Example 1.

[0029] Figure 3A This is a SEM image of the sample surface after dry ice cleaning. Figure 3B This is a SEM image of the sample surface after laser cleaning. Figure 3C Here is a SEM image of the sample surface after laser-dry ice hybrid cleaning in Example 1;

[0030] Figure 4A This is an EDS image of the sample surface after dry ice cleaning. Figure 4B This is an EDS image of the sample surface after laser cleaning. Figure 4C This is an EDS image of the sample surface after laser-dry ice hybrid cleaning in Example 1. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] The laser-dry ice hybrid cleaning method in the embodiment uses a cleaning system such as... Figure 1 As shown, the system includes a platform 1, a laser device 2, a dry ice blasting cleaning device 3, a synchronous movement module 4, and a synchronous triggering module 5. The laser head 21 of the laser device 2 and the dry ice nozzle 31 of the dry ice blasting cleaning device 3 are located above the platform 1 and move synchronously via the synchronous movement module 4. The laser head 21 is vertically positioned relative to the platform 1, while the dry ice nozzle 31 is tilted, ensuring that the emitted laser beam and the ejected dry ice particles land in the same area. The laser device 2 and the dry ice blasting cleaning device 3 are synchronously started and stopped via the synchronous triggering module 5. This laser-dry ice hybrid cleaning method includes:

[0033] The workpiece 6 to be cleaned is placed on the platform 1, and the surface of the workpiece 6 to be cleaned has an adhesive layer.

[0034] The laser device 2 and the dry ice jet cleaning device 3 are activated by the synchronous trigger module 5, so that the dry ice particles ejected by the dry ice nozzle 31 and the laser beam spot emitted by the laser head 21 move synchronously and always act on the same area of ​​the attached layer at the same time. The attached layer is removed along the preset cleaning path through the synergistic effect of the dry ice particles and the laser.

[0035] The workpiece 6 to be cleaned is placed horizontally on platform 1 and temporarily fixed using, for example, a clamp to prevent it from moving relative to platform 1, ensuring alignment accuracy. The horizontal position of the surface of platform 1 is calibrated using a level. The substrate of the workpiece 6 to be cleaned includes, but is not limited to, materials such as metal, glass, and semiconductors, and its adhering layer is a composite dirt containing at least two types of contaminants, such as a composite dirt of mold release agent residue and metal oxides, or a composite dirt of organic contaminants and microparticles, which are difficult to remove. The laser head 21 is vertically positioned. The vertical distance between the laser head 21 and the surface of the workpiece 6 is adjusted according to the thickness of the workpiece 6, so that the laser beam irradiates vertically and the spot is defocused on the surface of the workpiece 6, ensuring that the laser energy acts on the adhering layer without damaging the workpiece substrate. The vertical distance between the laser head 21 and the surface of the workpiece 6 is 5.0cm-30.0cm, the spot diameter in the defocused state is 0.02mm-0.5mm, and the laser energy density irradiated on the cleaning surface is 10 mJ / mm²-200mJ / mm².

[0036] The laser device used is not limited to lasers of different wavelengths, such as continuous, long-pulse, and short-pulse lasers. The laser cleaning process parameters, including laser power, repetition rate, beam type, spot size, cleaning speed, and cleaning path, are adjusted according to the properties of the deposited layer and the cleaning requirements. The laser power must ensure effective removal of the deposited material without damaging the substrate. The spot size and repetition rate together determine the laser cleaning speed. The beam type is controlled by DOE, ROE, SLM, optical elements, metasurface optical elements, etc., and can be adjusted to a flat-top beam, vortex beam, radial beam, angular beam, Bessel beam, linearly polarized laser beam, etc., depending on the properties of the material to be removed. The spot shape can be adjusted to a circular spot, square spot, rectangular spot, linear spot, etc. The cleaning path is the scanning path trajectory of the laser beam on the surface of the workpiece to be cleaned.

[0037] The dry ice nozzle 31 is configured to spray dry ice particles onto the surface of the workpiece 6 to be cleaned at an angle α, where 30° ≥ α > 0°. Here, the angle refers to the angle between the dry ice nozzle and the vertical direction (i.e., the laser emission direction). The angle can be adjusted using a robotic arm or similar structure. The spray distance from the dry ice nozzle 31 to the surface of the workpiece 6 is 10-12 cm, and the nozzle diameter is 0.5 cm-2 cm. The dry ice cleaning process parameters are adjusted according to the properties of the deposited layer and the cleaning requirements to ensure effective synergy between the laser and dry ice cleaning processes. The dry ice nozzle 31 can be angled using a protractor with the laser head 21 as a reference to adapt to the removal of the deposited layer, ensuring that when the dry ice particles and the laser beam spot act on the surface of the workpiece, the center of the laser spot coincides with the center of the dry ice spray coverage area by ≥95%.

[0038] The synchronous movement module 4 is used to achieve synchronous movement of the dry ice nozzle 31 and the laser head 21 to ensure that the sprayed dry ice particles and the laser beam always act on the same area. The synchronous movement module 4 includes a rigid connecting arm, through which the dry ice nozzle is linked and fixed to the laser device; when the laser head 21 moves along the cleaning path, its displacement is synchronously transmitted to the dry ice nozzle 31 through the rigid connecting arm, causing the dry ice nozzle 31 to follow the laser head 21 and move along the same trajectory and at the same speed; the rigid connecting arm compensates for vibration deviations during the movement in real time, ensuring that the spraying area of ​​the dry ice nozzle 31 and the beam action area of ​​the laser head 21 always coincide, with an overlap of not less than 95%.

[0039] The synchronization trigger module 5 is used to synchronously start and stop the dry ice nozzle 31 and the laser head 21 to ensure that the sprayed dry ice particles and the laser beam always act simultaneously. The synchronization trigger module 5 includes a differential signal trigger unit, a pre-calibration compensation unit, and a real-time status monitoring unit. The differential signal trigger unit outputs a synchronous start or stop signal; the pre-calibration compensation unit eliminates inherent equipment delays; and the real-time status monitoring unit provides feedback on the cleaning status. After receiving the start or stop command from the cleaning system, the synchronization trigger module 5 synchronously generates a laser trigger signal and a dry ice spray trigger signal. The differential signal trigger unit converts the two trigger signals into anti-interference differential pulse signals, which are transmitted to the laser emission controller of the laser head 21 in the laser device and the spray control valve of the dry ice nozzle 31 in the dry ice spray cleaning device, respectively, ensuring that they always act synchronously. The pre-calibration compensation unit eliminates the inherent response delay of the laser and dry ice devices. By pre-calibrating the action delay of the two systems and setting the compensation amount, it ensures that the laser thermal effect and the dry ice mechanical impact on the substrate surface are precisely synchronized in the time domain, ensuring that the coupling effect of the collaborative cleaning is fully utilized. The real-time status monitoring unit is used to provide feedback on the cleaning status. By collecting operating parameters such as laser power and dry ice spray pressure in real time, it verifies the synchronous execution effect of the two systems, promptly reports fluctuations in operating conditions and equipment abnormalities, and ensures the stability and reliability of the cleaning process.

[0040] When dry ice particles and a laser beam act simultaneously on the adhesion layer on the surface of a workpiece to be cleaned, their effective synergistic effects include:

[0041] Firstly, the laser beam and dry ice particles act simultaneously on the area to be cleaned. The laser provides instantaneous thermal energy, causing the chemical bonds of the adhesive layer to break and the structure to loosen. The dry ice particles impact the surface to be cleaned at high speed, directly peeling off the adhesive through momentum transfer. At the same time, the sublimation temperature of the dry ice embrittles the adhesive layer, further enhancing the peeling effect. The thermal effect of the laser loosens and embrittles the adhesive layer, reducing the impact threshold of the dry ice particles and making the physical peeling of dry ice more efficient. The low temperature characteristics of dry ice suppress the overheating of the substrate caused by the laser, avoiding damage to the substrate. At the same time, the heat absorbed by the sublimation of dry ice further increases the temperature difference between the adhesive layer and the substrate, making the adhesive layer more prone to cracking and detachment under thermal stress. In addition, part of the laser directly acts on the dry ice particles. After absorbing the laser energy, the micro-explosion effect produced by the dry ice particles impacting the sample surface is stronger, improving the cleaning effect of the dry ice particles.

[0042] Secondly, because the impact area of ​​dry ice particles is relatively large, there are areas where laser cleaning is performed after dry ice cleaning. In this case, the impact of dry ice removes the loose oxides on the surface of the deposited layer and freezes and embrittles any remaining dirt, thereby accelerating the "thermal stripping" of the dirt by the subsequent laser beam.

[0043] Example 1

[0044] Based on the above cleaning system, the laser device in Example 1 uses an infrared wavelength, short-pulse laser with a power of 30W. The output laser beam is directly controlled through an optical element group, resulting in a linearly polarized laser beam with a circular spot. After shaping, the spot energy uniformity is ≥90%, the edge steepness is ≥85%, and the energy density fluctuation range is reduced from ±35% to ±5%, avoiding damage to the substrate from excessively high local energy. The infrared laser parameters are adjusted to a power of 40%-100% and a repetition frequency of 10-30 kHz. The spot size (defocused spot size) is calculated based on the given theoretical focused spot diameter or spot edge length, and then, according to the defocusing distance, the actual defocused spot size is calculated to be 50μm-100μm. The moving speed (i.e., cleaning speed) is determined by both the spot size and the repetition frequency, and is set to allow the output pulsed spots to superimpose, with the superposition degree controlled between 40%-80%. This superposition degree is the ratio of the center-to-center distance between two spots to that of a single spot.

[0045] The workpiece to be cleaned is an aluminum alloy painted sample, whose surface has an untreated oxide layer, an adhesive primer layer, and an adhesive topcoat layer.

[0046] The laser-dry ice hybrid cleaning method includes the following steps:

[0047] Step 1: Place the aluminum alloy painted sample horizontally on the platform and fix it with clamps;

[0048] Step 2: Adjust the vertical distance between the laser head and the sample surface to 17cm based on the thickness of the aluminum alloy paint sample.

[0049] Step 3: Adjust the laser cleaning process parameters as follows: linearly polarized circular spot, power 65%, frequency 30kHz, lateral scanning path, overlap 50%, and cleaning twice.

[0050] Step 4: Adjust the process parameters of dry ice cleaning. Fix the dry ice cleaning nozzle at a 75° angle to the horizontal (i.e., α is 25°) 15cm directly above the sample surface, with a mass flow rate of 0.55kg / min.

[0051] Step 5: The laser and dry ice are activated simultaneously, causing the sprayed dry ice particles to move synchronously with the laser beam spot and act on the surface of the aluminum alloy painted sample, thereby completing efficient and high-quality surface cleaning.

[0052] To facilitate observation of the cleaning effect, dry ice cleaning and laser cleaning under the same parameters were used as comparative examples. Surface images after cleaning by the three methods are shown below. Figure 2 As shown, dry ice cleaning alone results in a dull, incompletely cleaned surface, while laser cleaning and the combined cleaning method produce a metallic luster. SEM images of the surfaces after cleaning using the three methods are shown below. Figure 3A , Figure 3B and Figure 3C As shown, the EDS plot is as follows Figure 4A , Figure 4B and Figure 4C As shown in the figure. The comparison revealed that dry ice cleaning yielded the highest result for element F, followed by laser cleaning, with laser-dry ice cleaning showing the lowest. This indicates that the cleaning effect improves progressively. Because the aluminum alloy substrate already has an oxide layer on its surface exposed to air before the coating is applied, and dry ice cleaning is incomplete, it misses this oxide layer. Laser cleaning, due to over-cleaning, damages the oxide layer. Laser-dry ice combined cleaning causes less damage to the oxide layer. Therefore, element O shows the highest result for dry ice cleaning, followed by laser-dry ice combined cleaning, and the lowest result for laser cleaning, with a significant difference between the two.

[0053] The above embodiments are only used to further illustrate a laser-dry ice hybrid cleaning method of the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A laser-dry ice hybrid cleaning method, characterized in that, include: The workpiece to be cleaned is placed on a platform, and the surface of the workpiece to be cleaned has an adhesion layer. The laser device and dry ice jet cleaning device are regulated and activated so that the dry ice particles ejected by the dry ice nozzle and the laser beam spot emitted by the laser head move synchronously and always act on the same area of ​​the adhesion layer at the same time. The adhesion layer is removed along the preset cleaning path through the synergistic effect of the dry ice particles and the laser.

2. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that, The laser head is configured to irradiate the workpiece vertically and to defocus the laser beam spot on the surface of the workpiece to be cleaned.

3. The laser-dry ice hybrid cleaning method according to claim 2, characterized in that: The vertical distance between the laser head and the surface of the workpiece to be cleaned is 5.0cm-30.0cm, the diameter of the spot in the defocused state is 0.02mm-0.5mm, and the laser energy density of the laser beam irradiating the surface of the workpiece to be cleaned is 10 mJ / mm²-200mJ / mm².

4. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that: The dry ice nozzle is configured to spray dry ice particles onto the surface of the workpiece to be cleaned at an angle α, where 30° ≥ α > 0°, and the angle α is the angle between the dry ice nozzle and the laser emission direction.

5. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that: The dry ice nozzle has a spray distance of 10 cm to 12 cm from the surface of the workpiece to be cleaned, and the nozzle diameter is 0.5 cm to 2 cm.

6. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that: When the dry ice particles and the laser beam spot act on the surface of the workpiece to be cleaned, the center of the spot coincides with the center of the dry ice spray coverage area by ≥95%.

7. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that: The adhesion layer is a composite layer comprising at least two types of adhesion substances.

8. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that: The laser device is an infrared pulsed laser; the dry ice nozzle moves synchronously with the laser head along a preset cleaning path, and the moving speed is set to allow the output pulse spots to overlap, with the overlap degree controlled between 40% and 80%.

9. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that: The dry ice nozzle and the laser head move synchronously through a synchronous movement module, which includes a rigid connecting arm that links the dry ice nozzle and the laser device.

10. The laser-dry ice hybrid cleaning method according to claim 1, characterized in that: The laser device and the dry ice jet cleaning device are started synchronously through a synchronization triggering module. The synchronization triggering module includes a differential signal triggering unit, a pre-calibration compensation unit, and a real-time status monitoring unit. The differential signal triggering unit is used to output a synchronization start or stop signal; the pre-calibration compensation unit is used to eliminate the inherent delay of the equipment. The real-time status monitoring unit is used to provide feedback on the cleaning status.

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