A cleaning process for circulating cleaning of PFA pipe fittings by using peristaltic pump

Abstract

The application discloses a cleaning process for cleaning PFA pipe fittings by using a peristaltic pump, which comprises the following steps: step one, oxidative circulation cleaning by mixing ammonia water and hydrogen peroxide; step two, first pure water circulation flushing; step three, circulation cleaning by mixing hydrochloric acid and hydrogen peroxide; step four, second pure water circulation flushing; step five, dilute nitric acid cleaning circulation; and step six, final pure water circulation flushing. By virtue of the low shear force, non-pollution and circulation driving characteristics of the peristaltic pump, and the three-stage chemical synergistic effect of "oxidative cleaning-complexing cleaning-acid cleaning and passivation", the metal ions and micro-nano particles on the inner wall of the PFA pipe fitting can be efficiently removed.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing and precision cleaning technology for components. Specifically, it relates to a circulating cleaning process that uses a peristaltic pump as a circulating power source to efficiently remove metal ions and micro / nano particles from the inner wall of PFA (perfluoroalkoxy) pipe fittings. Background Technology

[0002] PFA (perfluoroalkoxy resin) is a high-performance fluoropolymer with a carbon-fluorine bond structure in its main chain. It possesses excellent chemical inertness, extremely low exudation, resistance to high and low temperatures, and high insulation strength. Compared to PTFE, PFA has better melt processing properties, enabling the fabrication of thin-walled, smooth, and high-purity tubing products. In semiconductor manufacturing processes, PFA tubing is widely used to transport ultra-high-purity chemicals (such as photoresists, etching solutions, cleaning solutions, solvents, etc.), ultrapure water, and high-purity gases, making it a key piping material in high-purity fluid transport systems for semiconductors.

[0003] In the ultra-precision fabrication of semiconductor devices, any trace contaminants on the inner wall of the delivery pipeline can migrate into the process chemicals, and then come into contact with the wafer surface, leading to the following serious consequences:

[0004] Metal ion contamination: Metal ions (such as Al, Ca, Cr, Cu, Fe, K, Na, etc.) may diffuse into the wafer during subsequent processes, causing reliability issues such as device leakage, breakdown voltage drop, and threshold voltage drift.

[0005] Particulate matter contamination: Micro and nano particles may directly scratch the wafer surface, causing physical masking defects, or adhere to circuit patterns due to electrostatic adsorption, leading to short circuits or open circuits.

[0006] During the manufacturing (extrusion molding, cutting, flaring, etc.) and transportation and storage processes, PFA pipe fittings inevitably accumulate processing debris, environmental dust, grease, or metal ion contaminants on their inner walls. Furthermore, polymerization residues in the PFA material itself (such as catalyst residues and oligomers) can also contribute to contamination.

[0007] Existing cleaning processes for PFA pipe fittings mainly have the following problems:

[0008] Traditional soaking methods are not thorough in cleaning: In conventional static soaking processes, the chemical solution has poor flow in the inner cavity of slender pipes, and contaminants at the root of the inner wall of the pipe, elbows, flared ends and other parts cannot fully come into contact with the chemical solution, resulting in cleaning blind spots.

[0009] One-way flushing method consumes a lot of chemical solution: The method of flushing pipes with chemical solution by pumping chemical solution in one direction (that is, the chemical solution flows through the pipes and is then discharged) can produce a flow flushing effect, but the amount of chemical solution used is large, the cost is high, and the effect is limited when the flushing time is insufficient.

[0010] Ultrasonic cleaning is not suitable for slender pipes: Ultrasonic cleaning is effective for the outer surface and simple inner cavity of pipes, but for the inner cavity of slender pipes with a large length-to-diameter ratio, the ultrasonic cavitation effect is severely attenuated inside the cavity, resulting in poor cleaning effect.

[0011] The evaluation of cleaning effect is limited to a single dimension: existing processes mostly use particle count (LPC) as the evaluation indicator, ignoring the control requirements of metal ions (ICP-MS), which cannot meet the dual standards of high-end semiconductor manufacturing for the cleanliness of pipeline materials.

[0012] Therefore, developing a precision cleaning process that can simultaneously and efficiently remove metal ions and micro / nano particles from the inner wall of PFA pipe fittings, is applicable to slender pipe structures, and is cost-effective is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0013] To address the problems existing in the prior art, the present invention provides a cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning, which solves at least one of the above-mentioned technical problems.

[0014] The technical solution of this invention is: a cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning, comprising the following steps:

[0015] Step 1: Oxidative cyclic cleaning using a mixture of ammonia and hydrogen peroxide;

[0016] Connect the PFA fitting to the cleaning circulation system and use a peristaltic pump to drive the mixed solution of NH4OH, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulation rinsing. The segmented circulation rinsing is as follows: after rinsing for 1 minute, pause and repeat the operation at least 4 times; then seal both ends of the PFA fitting and let it stand and soak for 1 hour.

[0017] Step two, first pure water circulation rinse;

[0018] A peristaltic pump is used to drive ultrapure water to circulate and flush the PFA fittings to remove residual alkali.

[0019] Step 3: Circulate and clean with a mixture of hydrochloric acid and hydrogen peroxide;

[0020] A peristaltic pump is used to drive a mixed solution of HCl, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation at least 4 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour.

[0021] Step four: Second pure water circulation rinsing;

[0022] A peristaltic pump is used to drive ultrapure water to circulate and flush the PFA fittings to remove residual acid.

[0023] Step 5: Acid washing with dilute nitric acid in a circulating cycle;

[0024] A peristaltic pump is used to drive a dilute nitric acid solution to circulate in the inner cavity of the PFA pipe fitting for segmented circulatory flushing. The segmented circulatory flushing is as follows: after circulatory flushing for 1 minute, pause, and repeat this operation at least 4 times; then seal both ends of the PFA pipe fitting and let it stand and soak for 2-4 hours.

[0025] Step six: Final rinse with pure water circulation;

[0026] A peristaltic pump is used to drive ultrapure water to thoroughly circulate and flush the PFA fittings to remove residual acid and stripped contaminants.

[0027] Further preferred, the volume ratio of NH4OH, H2O2 and ultrapure water is NH4OH : H2O2 : H2O = 1 : 1 : 5.

[0028] More preferably, the peristaltic pump has a circulation flow rate of 0.5-5 L / min, and the pump head material is PTFE or PFA.

[0029] To avoid secondary pollution.

[0030] In a further preferred embodiment, in step two, the rinsing time is not less than 5 minutes, or until the conductivity of both the outlet and return water of the cleaning circulation system is stable at 0.08 μS / cm, at which point the rinsing is considered complete.

[0031] In a further preferred embodiment, in step three, the volume ratio of HCl, H2O2 and ultrapure water is HCl : H2O2 : H2O = 1 : 1 : 5.

[0032] In a further preferred embodiment, in step five, the volume fraction of dilute nitric acid is 5%.

[0033] Further preferably, steps one, two, three, four, five, and six are all performed at room temperature.

[0034] In a further preferred embodiment, the static soaking in steps one, three, and four must ensure that the solution completely fills the inner cavity of the PFA pipe fitting to avoid air bubbles remaining and affecting the cleaning effect.

[0035] Further preferably, after step six, the metal ion content on the inner wall surface of the PFA pipe fitting meets the following standard: Al ≤ 2 μg / m 2Ca ≤ 2 μg / m 2 Cr ≤ 0.1 μg / m 2 Cu ≤ 0.2 μg / m 2 Fe ≤ 1.5 μg / m 2 K ≤ 1 μg / m 2 Mg ≤ 0.5 μg / m 2 Na ≤ 2 μg / m 2 Ni ≤ 0.1 μg / m 2 Zn ≤ 0.5 μg / m 2 Furthermore, Co, Li, Mn, and Ti were not detected (ND).

[0036] Further preferably, after step six, the number of particles on the inner wall surface of the PFA pipe fitting meets the following standard: the number of particles with a diameter ≥ 0.1 μm is not higher than 3600 particles / cm². 2 The number of particles with a diameter ≥ 0.15 μm is no higher than 1600 particles / cm. 2 .

[0037] A cleaning process for PFA pipe fittings using a peristaltic pump for circulation cleaning includes the following steps:

[0038] Step 1: Oxidative cyclic cleaning using a mixture of ammonia and hydrogen peroxide;

[0039] Prepare a mixed solution in a drug storage tank with a volume ratio of NH4OH : H2O2 : H2O = 1 : 1 : 5;

[0040] Connect the PFA fitting to the cleaning circulation system. One end of the PFA fitting is connected to the outlet of the peristaltic pump through a PFA hose, and the other end of the PFA fitting is connected to the return port of the drug storage tank through a PFA hose, forming a closed circulation loop.

[0041] Start the peristaltic pump and set the circulation flow rate to 2 L / min;

[0042] A peristaltic pump is used to drive a mixed solution of NH4OH, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation at least 4 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour.

[0043] Step two, first pure water circulation rinse;

[0044] Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank.

[0045] Use a peristaltic pump to circulate and flush the PFA fittings with ultrapure water with a resistivity ≥18 MΩ·cm for 10 minutes to remove residual alkali.

[0046] Step 3: Circulate and clean with a mixture of hydrochloric acid and hydrogen peroxide;

[0047] Drain the ultrapure water from the drug storage tank and prepare a mixed solution in the drug storage tank with a volume ratio of HCl : H2O2 : H2O = 1 : 1 : 5;

[0048] A peristaltic pump is used to drive a mixed solution of HCl, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation at least 4 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour.

[0049] Step four: Second pure water circulation rinsing;

[0050] Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank.

[0051] A peristaltic pump is used to drive the circulation of ultrapure water with a resistivity ≥18 MΩ·cm in the inner cavity of the PFA fitting to remove residual acid.

[0052] Step 5: Acid washing with dilute nitric acid in a circulating cycle;

[0053] Drain the ultrapure water and prepare a 5% (v / v) dilute nitric acid solution in the drug storage tank;

[0054] A peristaltic pump is used to drive a dilute nitric acid solution to circulate in the inner cavity of the PFA pipe fitting for segmented circulatory flushing. The segmented circulatory flushing is as follows: after circulatory flushing for 1 minute, pause, and repeat this operation at least 4 times; then seal both ends of the PFA pipe fitting and let it stand and soak for 2-4 hours.

[0055] Step six: Final rinse with pure water circulation;

[0056] Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank.

[0057] Rinse continuously for 20 minutes;

[0058] The inner cavity of the pipe fittings is dried using high-purity nitrogen, and then double-layered clean packaging is performed in a Class 100 clean environment before being sent for testing.

[0059] In a further preferred embodiment, in step six, after 20 minutes of cyclic rinsing, the conductivity of both the outlet and return outlet of the ultrapure water storage tank is found to be stable at 0.08 μS / cm, indicating that the rinsing is complete.

[0060] If there is a discrepancy, continue rinsing for 5 minutes. If the conductivity of both the outlet and return outlet of the ultrapure water storage tank is stable at 0.08 μS / cm, the rinsing is considered complete.

[0061] The inner diameter and length of PFA fittings directly affect the resistance to chemical circulation, the effective cleaning area, and the total contaminant load, thus influencing the optimal cleaning parameters. This invention further provides recommended process parameter adjustment ranges for different specifications of PFA fittings, as shown in Table 1.

[0062] 1 / 4 inch (6.35mm) x 1 meter Approximately 200 1.0 - 2.0 4 times 2.0 1 / 4 inch (6.35mm) x 2 meters Approximately 400 2.0 - 3.0 5 times 3.0 1 / 2 inch (12.7 mm) x 1 meter Approximately 400 2.0 - 3.0 5 times 3.0 1 / 2 inch (12.7mm) x 2 meters Approximately 800 3.0 - 5.0 6 times 4.0 3 / 8 inch (9.525 mm) x 1.5 meters Approximately 450 2.5 - 3.5 5 times 3.0

[0063] When the PFA fitting specifications (inner diameter × length) are 1 / 4 inch (6.35 mm) × 1 meter, the peristaltic pump circulation flow rate is 1.0 - 2.0 L / min, the number of segmented circulations in steps one, three and five is 4, and the standing soaking time of dilute nitric acid is 2 hours.

[0064] When the PFA fitting specifications (inner diameter × length) are 1 / 4 inch (6.35 mm) × 2 meters, the peristaltic pump circulation flow rate is 2.0 - 3.0 L / min, the number of segmented circulations in steps one, three and five is 5, and the standing soaking time in dilute nitric acid is 3 hours.

[0065] When the PFA fitting specifications (inner diameter × length) are 1 / 2 inch (12.7 mm) × 1 meter, the peristaltic pump circulation flow rate is 2.0 - 3.0 L / min, the number of segmented circulations in steps one, three and five is 5, and the standing soaking time in dilute nitric acid is 3 hours.

[0066] When the PFA fitting specifications (inner diameter × length) are 1 / 2 inch (12.7 mm) × 2 meters, the peristaltic pump circulation flow rate is 3.0 - 5.0 L / min, the number of segmented circulations in steps one, three and five is 6, and the standing soaking time in dilute nitric acid is 4 hours.

[0067] When the PFA fitting specifications (inner diameter × length) are 3 / 8 inch (9.525 mm) × 1.5 m, the peristaltic pump circulation flow rate is 2.5 - 3.5 L / min, the number of segmented circulations in steps one, three and five is 5, and the standing soaking time in dilute nitric acid is 3 hours.

[0068] Beneficial effects:

[0069] This invention utilizes the low shear force and pollution-free cyclic drive characteristics of a peristaltic pump, combined with the synergistic effect of a three-stage chemical process of "oxidative cleaning—complexation cleaning—acid pickling and passivation," to achieve highly efficient removal of metal ions and micro / nano particles from the inner wall of PFA pipe fittings. Testing showed that after cleaning using this invention, the concentration of metal ions (Al, Ca, Cr, Cu, Fe, K, Mg, Na, Ni, Zn) on the inner surface of PFA pipe fittings was controlled at 2 μg / m³. 2 Co, Li, Mn, and Ti were not detected, and the surface particle count (≥0.1 μm) was as low as 3586 particles / cm. 2 It meets the stringent cleanliness requirements of high-end semiconductor manufacturing for ultra-high purity fluid delivery pipelines.

[0070] In step one, NH4OH and H2O2 work synergistically (the principle of SC-1 cleaning solution) to decompose organic contaminants through strong oxidation, while simultaneously stripping away micro- and nano-particles adhering to the inner wall of the pipe fittings. The peristaltic pump's circulatory drive ensures the solution flows continuously and evenly through every part of the pipe fitting's interior, including elbows, flared sections, and straight sections, avoiding dead zones. Segmented operation (1 min × 5 times) ensures that each fresh solution flushes the pipe wall, while allowing sufficient time for contaminants to detach from the surface during pauses.

[0071] Step three has a dual function: ① HCl provides an acidic environment and chloride ions, which form soluble complexes with metal ions (such as FeCl4). - AlCl4 - (etc.), desorbing and dissolving metallic contaminants from the inner wall of the pipe fittings; ② The oxidation of H2O2 helps decompose residual organic matter, while oxidizing low-valence metal ions to high-valence states (such as Fe). 2+ →Fe 3+ It is easier to complex and remove.

[0072] In step five, the strong acidity and oxidizing properties of dilute nitric acid can: ① further dissolve residual metal oxides (especially Al and Cr oxides that are difficult to remove with the SC-1 / SC-2 combination); ② chemically passivate the inner wall of PFA pipe fittings, reducing the risk of metal precipitation during subsequent use; ③ remove the residue of specific metal ions (such as Ag, Cu, etc.). Attached Figure Description

[0073] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0074] A batch of PFA tubing (1 / 4 inch inner diameter, 2 meters long, 210 cm² surface area) to be used in semiconductor processes 2The pipe fitting is the target for cleaning. After extrusion molding and cutting processes, the inner wall of the fitting contains potential metal ions and micro / nano particle contaminants. Cleaning is performed according to the process of this invention.

[0075] Condition before cleaning: This PFA fitting is a new fitting and has not undergone any cleaning treatment. Catalyst residues (such as Al and Fe compounds) may have been introduced during the extrusion molding process, and machining particles may have been introduced during the cutting and flaring processes.

[0076] See Figure 1 A cleaning process for PFA pipe fittings using a peristaltic pump for circulation cleaning includes the following steps:

[0077] Step 1: Oxidative cyclic cleaning using a mixture of ammonia and hydrogen peroxide;

[0078] Prepare a mixed solution in a drug storage tank with a volume ratio of NH4OH : H2O2 : H2O = 1 : 1 : 5;

[0079] Connect the PFA fitting to the cleaning circulation system. One end of the PFA fitting is connected to the outlet of the peristaltic pump through a PFA hose, and the other end of the PFA fitting is connected to the return port of the drug storage tank through a PFA hose, forming a closed circulation loop.

[0080] Start the peristaltic pump and set the circulation flow rate to 2 L / min;

[0081] A peristaltic pump is used to drive a mixed solution of NH4OH, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation 5 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour.

[0082] Step two, first pure water circulation rinse;

[0083] Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank.

[0084] Use a peristaltic pump to circulate and flush the PFA fittings with ultrapure water with a resistivity ≥18 MΩ·cm for 10 minutes to remove residual alkali.

[0085] Step 3: Circulate and clean with a mixture of hydrochloric acid and hydrogen peroxide;

[0086] Drain the ultrapure water from the drug storage tank and prepare a mixed solution in the drug storage tank with a volume ratio of HCl : H2O2 : H2O = 1 : 1 : 5;

[0087] A peristaltic pump is used to drive a mixed solution of HCl, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation 5 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour.

[0088] Step four: Second pure water circulation rinsing;

[0089] Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank.

[0090] Use a peristaltic pump to circulate and flush the PFA fittings with ultrapure water with a resistivity ≥18 MΩ·cm for 10 minutes to remove residual acid.

[0091] Step 5: Acid washing with dilute nitric acid in a circulating cycle;

[0092] Drain the ultrapure water and prepare a 5% (v / v) dilute nitric acid solution in the drug storage tank;

[0093] A peristaltic pump is used to drive a dilute nitric acid solution to circulate within the PFA pipe fitting for segmented rinsing. The segmented rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation 5 times. Then, both ends of the PFA pipe fitting are sealed and left to soak for 3 hours.

[0094] Step six: Final rinse with pure water circulation;

[0095] Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank.

[0096] Rinse continuously for 20 minutes;

[0097] The inner cavity of the pipe fittings is dried using high-purity nitrogen, and then double-layered clean packaging is performed in a Class 100 clean environment before being sent for testing.

[0098] In a further preferred embodiment, in step six, after 20 minutes of cyclic rinsing, the conductivity of both the outlet and return outlet of the ultrapure water storage tank is found to be stable at 0.08 μS / cm, indicating that the rinsing is complete.

[0099] If there is a discrepancy, continue rinsing for 5 minutes. If the conductivity of both the outlet and return outlet of the ultrapure water storage tank is stable at 0.08 μS / cm, the rinsing is considered complete.

[0100] The specific method for sealing both ends of the PFA tubing is as follows: In the cleaning circulation system, both ends of the PFA tubing are connected to the outlet of the peristaltic pump and the return port of the chemical solution storage tank via PFA hoses, respectively. Corrosion-resistant PFA shut-off valves or diaphragm valves are installed at the inlet and outlet ends of the PFA tubing. When static soaking is required, both valves are closed, forming a closed cavity inside the tubing, ensuring the chemical solution is completely filled and not connected to the external circulation pipeline. This method effectively prevents chemical solution loss or concentration changes, while also preventing the entry of external contaminants. After soaking, the valves are reopened to resume circulation rinsing.

[0101] The test results are as follows:

[0102] (1) Testing equipment:

[0103] ICP-MS: Inductively Coupled Plasma Mass Spectrometer (for detecting metal ions, model: AN14 package)

[0104] Table 2: Metal Ion Content (ICP-MS)

[0105] 1 Al 1.08 8 K 0.76 2 Ca 1.13 9 Li ND(<0.01) 3 Co ND(<0.08) 10 Mg 0.20 4 Cr 0.07 11 Mn ND(<0.20) 5 Cu 0.11 12 Na 1.70 6 Fe 1.32 13 Ni 0.03 7 Ti ND(<0.04) 14 Zn 0.21

[0106] Note: The inner surface area of ​​the pipe fitting is 210 cm². 2 Provided by the customer. Calculated based on fluid contact area, conforming to the surface area calculation method for pipe fittings in the SEMI standard.

[0107] (2) Detection equipment: Liquid particle counter (SWTC-VIII-005-J / SWTC-XIII-005-J)

[0108] The test results are shown in Table 3 below:

[0109] ≥0.1 μm 3586 ≥0.15 μm 1553 ≥0.2 μm 1289 ≥0.3 μm 430 ≥0.45 μm 159 ≥0.5 μm 123 ≥0.8 μm 49 ≥1.0 μm 33

[0110] (3) Results Analysis

[0111] The above test results show that the metal ion control effect is excellent.

[0112] All detected metal ions (Al, Ca, Cr, Cu, Fe, K, Mg, Na, Ni, Zn) were controlled at extremely low levels (≤1.70 μg / m³). 2 Co (detection limit 0.08), Li (detection limit 0.01), Mn (detection limit 0.20), and Ti (detection limit 0.04) were all not detected (ND), indicating that the process of the present invention has achieved a level below the detection limit for the removal of these trace metal ions.

[0113] Compared with semiconductor industry standards (such as SEMI F57-1018 requirements for metal precipitation in polymer materials), the metal residue of PFA pipes after cleaning by the process of this invention is far below the standard limit, which can meet the most stringent requirements for the transportation of high-purity chemicals.

[0114] Excellent particulate matter control effect:

[0115] The number of surface particles (≥0.1 μm) is as low as 3586 particles / cm. 2 It is far superior to the Class 10,000 level of conventional cleaning processes.

[0116] The number of particles decreased significantly with increasing particle size, with only 33 particles / cm remaining for large particles ≥1.0 μm. 2 This indicates that the present invention has a good removal effect on particulate matter of various particle size ranges.

[0117] Verification of the advantages of peristaltic pump circulation cleaning:

[0118] In this embodiment, compared to traditional soaking processes, it is difficult to ensure sufficient contact of the cleaning solution within the pipe cavity. However, this process utilizes a peristaltic pump for circulation, achieving continuous flow and renewal of the cleaning solution in bends and straight pipe sections, thus avoiding blind spots in cleaning. The segmented circulation design (1min × 5 times) ensures that each fresh solution effectively flushes the pipe wall while allowing sufficient time for contaminants to detach during the pauses in the immersion process.

[0119] Synergistic effect of three-stage chemical cleaning:

[0120] Ammonia / Hydrogen peroxide (SC-1 type): Effectively removes organic matter and particulate matter. Hydrochloric acid / Hydrogen peroxide (SC-2 type): Highly efficient at complexing and removing metal ions. Dilute nitric acid pickling: Further passivates the surface and removes specific metal oxides that are difficult to remove with the SC-1 / SC-2 combination. The three-stage chemical cleaning sequence is scientifically sound, with alternating use of acids and alkalis, and isolated by rinsing with pure water in between, avoiding cross-neutralization of the solutions.

[0121] in conclusion

[0122] This embodiment fully demonstrates that the metal ion and particulate matter removal process for PFA pipe fittings provided by this invention, utilizing the low shear force and pollution-free circulation drive characteristics of the peristaltic pump, combined with the three-stage chemical synergistic cleaning process of "ammonia / hydrogen peroxide oxidation—hydrochloric acid / hydrogen peroxide complexation—dilute nitric acid pickling" and the time sequence optimization of "circulating rinsing + static soaking," achieves highly efficient synergistic removal of metal ions and micro / nano particles from the inner wall of PFA pipe fittings. PFA pipe fittings treated by this process exhibit industry-leading levels of metal ion content and particle count on their inner surface, stably meeting the stringent cleanliness requirements of high-end semiconductor manufacturing for ultra-high purity fluid transport pipelines, and possessing extremely high industrial application value and market prospects.

[0123] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning, comprising the following steps: Step 1: Oxidative cyclic cleaning using a mixture of ammonia and hydrogen peroxide; Connect the PFA fitting to the cleaning circulation system and use a peristaltic pump to drive the mixed solution of NH4OH, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulation rinsing. The segmented circulation rinsing is as follows: after rinsing for 1 minute, pause and repeat the operation at least 4 times; then seal both ends of the PFA fitting and let it stand and soak for 1 hour. Step two, first pure water circulation rinse; A peristaltic pump is used to drive ultrapure water to circulate and flush the PFA fittings to remove residual alkali. Step 3: Circulate and clean with a mixture of hydrochloric acid and hydrogen peroxide; A peristaltic pump is used to drive a mixed solution of HCl, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation at least 4 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour. Step four: Second pure water circulation rinsing; A peristaltic pump is used to drive ultrapure water to circulate and flush the PFA fittings to remove residual acid. Step 5: Acid washing with dilute nitric acid in a circulating cycle; A peristaltic pump is used to drive a dilute nitric acid solution to circulate in the inner cavity of the PFA pipe fitting for segmented circulatory flushing. The segmented circulatory flushing is as follows: after circulatory flushing for 1 minute, pause, and repeat this operation at least 4 times; then seal both ends of the PFA pipe fitting and let it stand and soak for 2-4 hours. Step six: Final rinse with pure water circulation; A peristaltic pump is used to drive ultrapure water to thoroughly circulate and flush the PFA fittings to remove residual acid and stripped contaminants.

2. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: The volume ratio of NH4OH, H2O2 and ultrapure water is NH4OH : H2O2 : H2O = 1 : 1 :

5.

3. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: The peristaltic pump has a circulation flow rate of 0.5-5 L / min, and the pump head is made of PTFE or PFA.

4. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: In step two, the rinsing time shall be no less than 5 minutes, or until the conductivity of both the outlet and return water of the cleaning circulation system is stable at 0.08 μS / cm, at which point the rinsing is considered complete.

5. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: In step three, the volume ratio of HCl, H2O2 and ultrapure water is HCl : H2O2 : H2O = 1 : 1 :

5.

6. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: In step five, the volume fraction of dilute nitric acid is 5%.

7. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: Steps one, two, three, four, five, and six were all performed at room temperature.

8. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: After step six, the metal ion content on the inner wall surface of the PFA pipe fitting meets the following standard: Al ≤ 2 μg / m 2 Ca ≤ 2 μg / m 2 Cr ≤ 0.1 μg / m 2 Cu ≤ 0.2 μg / m 2 Fe ≤ 1.5 μg / m 2 K ≤ 1 μg / m 2 Mg ≤ 0.5 μg / m 2 Na ≤ 2 μg / m 2 Ni ≤ 0.1 μg / m 2 Zn ≤ 0.5 μg / m 2 Furthermore, Co, Li, Mn, and Ti were not detected (ND).

9. The cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning according to claim 1, characterized in that: After step six, the particle count on the inner wall surface of the PFA pipe fitting must meet the following standard: the number of particles with a diameter ≥ 0.1 μm must not exceed 3600 particles / cm. 2 The number of particles with a diameter ≥ 0.15 μm is no higher than 1600 particles / cm. 2 .

10. A cleaning process for PFA pipe fittings using a peristaltic pump for circulating cleaning, comprising the following steps: Step 1: Oxidative cyclic cleaning using a mixture of ammonia and hydrogen peroxide; Prepare a mixed solution in a drug storage tank with a volume ratio of NH4OH : H2O2 : H2O = 1 : 1 : 5; Connect the PFA fitting to the cleaning circulation system. One end of the PFA fitting is connected to the outlet of the peristaltic pump through a PFA hose, and the other end of the PFA fitting is connected to the return port of the drug storage tank through a PFA hose, forming a closed circulation loop. Start the peristaltic pump and set the circulation flow rate to 2 L / min; A peristaltic pump is used to drive a mixed solution of NH4OH, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation at least 4 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour. Step two, first pure water circulation rinse; Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank. Use a peristaltic pump to circulate and flush the PFA fittings with ultrapure water with a resistivity ≥18 MΩ·cm for 10 minutes to remove residual alkali. Step 3: Circulate and clean with a mixture of hydrochloric acid and hydrogen peroxide; Drain the ultrapure water from the drug storage tank and prepare a mixed solution in the drug storage tank with a volume ratio of HCl : H2O2 : H2O = 1 : 1 : 5; A peristaltic pump is used to drive a mixed solution of HCl, H2O2 and ultrapure water to circulate in the inner cavity of the PFA fitting for segmented circulatory rinsing. The segmented circulatory rinsing is performed by rinsing for 1 minute, pausing, and repeating this operation at least 4 times. Then, the two ends of the PFA fitting are sealed and left to soak for 1 hour. Step four: Second pure water circulation rinsing; Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank. Use a peristaltic pump to circulate and flush the PFA fittings with ultrapure water with a resistivity ≥18 MΩ·cm for 10 minutes to remove residual acid. Step 5: Acid washing with dilute nitric acid in a circulating cycle; Drain the ultrapure water and prepare a 5% (v / v) dilute nitric acid solution in the drug storage tank; A peristaltic pump is used to drive a dilute nitric acid solution to circulate in the inner cavity of the PFA pipe fitting for segmented circulatory flushing. The segmented circulatory flushing is as follows: after circulatory flushing for 1 minute, the operation is paused and repeated at least 4 times. Then, the two ends of the PFA pipe fitting are sealed and left to soak for 3 hours. Step six: Final rinse with pure water circulation; Drain the medicine from the medicine storage tank, and introduce ultrapure water into the medicine storage tank to switch the medicine storage tank to an ultrapure water storage tank. Rinse continuously for 20 minutes; The inner cavity of the pipe fittings is dried using high-purity nitrogen, and then double-layered clean packaging is performed in a Class 100 clean environment before being sent for testing.

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