Cleanness testing method

Abstract

The invention relates to a cleanliness testing method. The method comprises the following steps: an impurity collection step (10): collecting impurity particles on a to-be-detected part on a first carrier made of a water-soluble material; a carrier dissolving step (20) of completely dissolving the first carrier and dispersing the impurity particles in an aqueous solution to form a particle solution when the first carrier together with the impurity particles collected thereon is placed in the aqueous solution; an impurity recollection step (30): collecting impurity particles in the particle solution by using a second carrier; and an impurity analysis step (40): detecting and analyzing the impurity particles on the second carrier. The method is particularly suitable for the application that an aerostatic press is adopted to collect impurity particles on a to-be-detected component onto a first carrier in a filter paper form and a microscope is adopted to detect and analyze impurity particles on a second carrier in a filter paper form. The component to be detected may be a fuel cell.

Description

Technical Field

[0001] This application relates to the field of cleanliness testing, and particularly to a method for testing the cleanliness of a fuel cell. Background Art

[0002] With the development of science and technology, consumers have higher and higher requirements for the performance of products. Non-compliance with cleanliness standards during the processing or assembly of product parts may directly affect the quality and performance of the products.

[0003] For example, if there are too many impurity particles in the small holes during the manufacturing process of the hydrogen supply system of a fuel cell and the cleanliness does not meet the standard, the small holes may be blocked. If the particles are metal conductive particles, a short circuit may also occur, which are all undesirable. For another example, for some components that have relative movement with adjacent components (such as an air compressor), if the cleanliness of the contact surface does not meet the standard and there are large or too many impurity particles, it may lead to an increase in friction and jamming of the relative movement between the two, affecting the function. Therefore, it is very necessary to detect the cleanliness of some important components.

[0004] For some components (such as the hydrogen supply pipeline of a fuel cell), common methods for cleanliness testing include: blowing air through its surface with a pneumatic machine and blowing the impurity particles on the surface onto a filter paper arranged downstream of it. The air flows through the filter paper, and the impurity particles are retained on the filter paper to complete the collection of the impurity particles. Finally, the impurity particles on the filter paper are usually analyzed using a microscope. However, the filter paper usually cannot be properly placed on the microscope platform, and improper placement may also cause some impurity particles to fall off, resulting in inaccurate test results. Summary of the Invention

[0005] The purpose of this application is to solve at least one of the above problems.

[0006] To this end, this application provides a method for cleanliness testing, including: an impurity collection step: collecting the impurity particles on the component to be detected on a first carrier made of a water-soluble material; a carrier dissolution step: when the first carrier together with the impurity particles collected thereon is placed in an aqueous solution, making the first carrier completely dissolve and the impurity particles disperse in the aqueous solution to form a particle solution; an impurity re-collection step: collecting the impurity particles in the particle solution with a second carrier; and an impurity analysis step: detecting and analyzing the impurity particles on the second carrier.

[0007] The cleanliness test method provided by this application first uses a first carrier made of a water-soluble material (for example, it can be in the form of filter paper, filter bag or filter element, etc.) to collect impurity particles from the component to be detected. Then, the first carrier with the collected impurity particles is placed in an aqueous solvent. After the first carrier is completely dissolved, a second carrier (usually filter paper, also called filter membrane) is used to collect the impurity particles in the solution again. Finally, the impurity particles on the second carrier are detected and analyzed. In the scenario where the form or specification (such as size) of the first carrier cannot adapt to the detection and analysis steps of the final impurity particles, especially for the analysis instrument (such as a microscope), this application solves this problem perfectly by dissolving the first carrier in an aqueous solution and dispersing the impurity particles in the aqueous solution, and then using a new second carrier suitable for the detection and analysis steps of the impurity particles to re-collect the impurity particles dispersed in the solution.

[0008] On the one hand, especially in the case of using a pneumatic machine to collect impurity particles on the first carrier and using a microscope for impurity detection and analysis, the first carrier in this method can be selected or designed to have a relatively large size suitable for matching with the pneumatic machine (the air flow pipeline of which has a relatively high air flow speed and pressure due to flushing the surface or inner cavity of the sample), and the second carrier can be selected or designed to have a relatively small size suitable for placing on the platform of the microscope. The method of this application has a wide range of application fields and is also applicable to components to be detected that cannot disperse impurity particles in an aqueous solution by immersion in the aqueous solution and then collect them. On the other hand, since this method does not include the step of soaking the component to be detected in an aqueous solution, the problem of the component to be detected being scrapped due to soaking is avoided. Especially for expensive components with complex manufacturing and high precision, this method has the advantage of avoiding waste. In addition, the re-collection of the impurity particles in this application from the aqueous solution is achieved by filtering with filter paper, without particle loss, which can ensure the accuracy and precision of the cleanliness detection, and can also be used for failure analysis of products and optimization of the design or production process based on this. Description of the Drawings

[0009] Figure 1 is a flowchart of the cleanliness test method of this application.

[0010] Figure 2 is a simplified schematic diagram of some steps of the cleanliness test method of this application. Detailed Description of the Invention

[0011] Overall, the cleanliness test of a component generally includes an impurity collection step of collecting impurity particles on the component onto a carrier and an impurity analysis step of placing the collected impurity particles on or in an analytical instrument using the carrier to detect, measure, analyze, photograph, etc. the impurity particles. The cleanliness test method of the present application aims to solve the situation where the carrier used in the impurity collection step is not suitable or cannot be used together with the analytical instrument for the impurity analysis step, which is usually because the size (or other specification parameters) of the carrier is incompatible with the analytical instrument (for example, most simply, it does not match the size of the platform of the analytical instrument that supports the carrier). For this reason, the present application provides a strategy for replacing the carrier between the impurity collection step and the impurity analysis step, that is, replacing the first carrier used in the impurity collection step but not suitable for the impurity analysis step with a second carrier that can be used for the impurity analysis step and is compatible with the analytical instrument.

[0012] More specifically, the present application adopts the method of dissolving the first carrier used in the impurity collection step in an aqueous solution, so that the collected impurity particles are dispersed in the aqueous solution, and then collecting the impurity particles dispersed in the aqueous solution again with a second carrier compatible with the analytical instrument. Thus, as Figure 1 shown in the flowchart, the cleanliness test method of the present application essentially mainly includes the following four steps: First is the impurity collection step 10, in which all impurity particles on the component to be detected are collected using a first carrier made of a soluble material; then is the carrier dissolution step 20, in which the first carrier together with the collected impurity particles is placed in a pre-prepared aqueous solution to dissolve the first carrier completely; then is the impurity re-collection step 30, in which all impurity particles in the solution are re-collected with a second carrier; finally is the impurity analysis step 40 of detecting and analyzing the impurity particles on the second carrier.

[0013] The inventors recognize that examples of the water-soluble material used to form the first carrier include, but are not limited to: granulated sugar, calcium alginate wool or fluff, porous gelatin, polyvinylpyrrolidone, polyvinyl alcohol, rice paper.

[0014] This method may include a first carrier preparation step 12 of forming the first carrier from a water-soluble material (such as at least one of those listed above) before the impurity collection step 10. Depending on the requirements of the impurity collection step 10, the first carrier may be in the form of a (filter) paper (or membrane) in a substantially sheet form, or a (filter) bag in a substantially pocket form, or a (filter) element in a substantially three-dimensional form, or a combination form of any two or all three.

[0015] In some embodiments, the impurity collection step 10 may be performed by repeatedly wiping the component to be detected with the first carrier.

[0016] In some embodiments, the impurity collection step 10 can be carried out by using a pneumatic machine to blow a strong air flow over the component to be detected, blowing the impurity particles thereon onto the first carrier. At this time, the method can further include a carrier fixing step 14 of fixing the first carrier to a position downstream of the pneumatic machine and the component to be detected (such as a bracket arranged downstream) before the impurity collection step 10. Preferably, the first carrier is oriented such that its receiving surface is substantially perpendicular to the direction of the air flow blown out from the air flow duct of the pneumatic machine, and when the first carrier is in the form of a filter paper, its size is designed to be large enough to avoid being blown out by the high-pressure and high-flow air flow from the pneumatic machine. In the embodiment where the impurity collection step 10 is implemented by using a pneumatic machine, the first carrier in the form of a filter paper can have an outer diameter size greater than 70 mm, such as about 100 mm, and a single layer or multiple layers of filter paper can be selected according to requirements to adjust the structural strength and passing rate of the first carrier (or called the filter unit). Optionally, an air suction system (such as a vacuum suction system) can be used instead of the pneumatic machine in the blowing form to perform the impurity collection step 10, and the placement form or position of the first carrier can be changed accordingly.

[0017] After the impurity collection step 10 is completed, the method of the present application can further include a carrier transfer step 22 of transferring the first carrier with impurity particles collected thereon to the position where the carrier dissolution step is performed before performing the carrier dissolution step 20. The carrier transfer step 22 can include the following sub-steps: providing a packaging container (such as a packaging bag) whose interior meets the cleanliness requirements (according to industry requirements, such as VDA19-1 in the automotive industry, the pollution brought by the container should not affect the test results of the sample); loading the first carrier into the packaging container and sealing it well; optionally, writing information such as the specification size, material, packaging date, and name of the tester on the packaging container; and transferring the packaging container to the position where the carrier dissolution step is performed.

[0018] The cleanliness test method of the present application can further include a solution preparation step 24 before performing the carrier dissolution step 20. In this step, an appropriate amount of aqueous solution is prepared in a test container (such as a graduated beaker), and the mass of the prepared aqueous solution is preferably 50 to 200 times the mass of the first carrier. The solution used in the cleanliness test method of the present application can be deionized water. Optionally, an ionic or non-ionic surfactant with a concentration of 0.1% - 1.0% can be added to the deionized water. Available ionic surfactants such as sodium dodecyl sulfate. In some other embodiments, the aqueous solution used can be an alcohol solvent with a concentration of 1% - 10%, such as ethanol, isopropanol, etc., which can accelerate the dissolution process of the first carrier made of water-soluble materials.

[0019] The cleanliness test method of the present application may further include a solution heating step 26 after the solution preparation step 24. In this step, the aqueous solution can be heated to 40 to 80 degrees Celsius to facilitate the more rapid dissolution of the first carrier.

[0020] After the carrier transfer step 22, the solution preparation step 24, and the optional solution heating step 26 are completed, the method can start the carrier dissolution step 20. During this step, the first carrier is taken out of the transfer container and placed in the prepared aqueous solution until the first carrier is completely dissolved. At this time, the impurity particles collected from the component to be detected will be completely dispersed in the aqueous solution.

[0021] The dissolution process of the first carrier can be achieved by standing still. For example, the beaker can be placed on any known particle size or cleanliness test bench in the art. Due to the different materials of the carrier and the components of the solution, the entire dissolution process may last from 15 minutes to 60 minutes.

[0022] Preferably, the carrier dissolution step 20 may include additional measures to accelerate the dissolution for the beaker or the dissolution process occurring therein. The additional measures to accelerate the dissolution may include placing the beaker in a heat preservation device so that the temperature of the liquid in the beaker remains substantially at 40 to 80 degrees Celsius during the dissolution process of the first carrier, or it can be raised to 90 degrees. The additional measures to accelerate the dissolution may include applying mechanical stirring to the solution in the beaker to speed up the dissolution process. The additional measures to accelerate the dissolution may also include applying ultrasonic oscillation to the beaker to speed up the dissolution process. For example, the beaker in which the first carrier is dissolving can be placed in an ultrasonic vibrator, and the beaker can be continuously or intermittently oscillated to facilitate the faster and more complete dissolution of the first carrier. As an example, the ultrasonic vibrator can be an ultrasonic cleaning machine available on the market. The additional measures to accelerate the dissolution may not be limited to the several listed above, and one of them can be adopted alone or several different measures to accelerate the dissolution can be applied simultaneously. In the case of applying the additional measures to accelerate the dissolution, the dissolution process of the first carrier can be accelerated from, for example, a maximum of about 60 minutes to, for example, a minimum of about 10 minutes.

[0023] The completion of the carrier dissolution step 20 can be determined by visual observation. For example, when no obvious flocs and floating insoluble substances are observed in the beaker, it can be determined that the dissolution is completed.

[0024] After the filter paper dissolution step 20, the cleanliness method of the present application performs an impurity re-collection step 30 of re-collecting the impurity particles in the solution with a second carrier. The form, size or specification of the second carrier used at this time is selected according to the analytical instrument used in the subsequent impurity analysis step 40. Usually, the second carrier is in the form of a conventional filter paper, for example, it can be a filter paper made of materials such as nitrocellulose, polypropylene, nylon, etc. Of course, although the dissolution operation is no longer performed, the second carrier used at this time can also be made of the same or different water-soluble materials as the first carrier.

[0025] The re-collection of impurities can be performed by filtering the solution formed in the filter paper dissolution step 20 with a second carrier in the form of a filter paper. The re-collection step performed by filtering the solution basically does not lose any impurity particles, ensuring the accuracy of this test method to the greatest extent.

[0026] After the impurity re-collection step 30, the cleanliness test method of the present application further includes a drying step 32 of drying the second carrier with the filtered impurity particles thereon. This step can be achieved by leaving the second carrier to dry for a certain time or placing it in a dryer.

[0027] Finally, the second carrier (along with the impurity particles thereon) is placed in an analytical instrument to perform the impurity analysis step 40. The impurity analysis step is known in the art and includes, but is not limited to, the following operations: optically or electronically scanning the impurity particles on the second carrier, detecting and analyzing the quantity, particle size, composition, etc. of the impurity particles on the second carrier, statistically calculating the results of the detection and scanning, obtaining the cleanliness of the component to be detected based on the detection and analysis of the impurity particles, and forming a cleanliness test report, etc. The analytical instrument used in this step can be a particle detection device such as the following: optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), or atomic force microscope (AFM), etc. This step can adopt analytical methods such as the following: energy dispersive X-ray analysis (EDX), electron energy loss spectroscopy (EELS), or X-ray photoelectron spectroscopy (XPS). These devices and methods are not the focus of the present application and will not be described in detail here.

[0028] It should be noted that due to the limitations of the platform size of various microscopes used in the impurity analysis step 40, the outer diameter size of the second carrier should be appropriately selected. For example, usually, the outer diameter of the second carrier in the form of a filter paper is not greater than 50 mm. In some embodiments, the second carrier can have an outer diameter of 25 mm or 47 mm.

[0029] The above describes the entire process of the cleanliness test method of the present application. As can be seen from the above description, the method of the present application is particularly suitable for applications where the first carrier used in the impurity collection step 10 cannot be used in the final impurity analysis step 40 (for example, it is not compatible with or incompatible with the analytical instrument). The carrier dissolution step 20 and the impurity re-collection step 30 of the present application perfectly solve this problem.

[0030] In particular, the method of the present application is particularly advantageous for the part to be detected that can only be collected on the first carrier by using gas as a medium (e.g., using an air compressor) in the impurity collection step 10 and the size of the analytical instrument used in the impurity analysis step 40 is strictly limited (e.g., the platform size is particularly small, such as a microscope). The method can select or design the specifications or size or any other detailed parameters of the first carrier used in the impurity collection step 10 according to the requirements of the impurity collection step 10, and select or design the specifications or size or any other detailed parameters of the second carrier used in the impurity recollection step 30 according to the requirements of the analytical instrument in the impurity analysis step 40. According to the principle of the present application, except that the forming material of the first carrier must be a water-soluble material, other details of the first carrier and the second carrier can be the same or different, and these details include, but are not limited to: the form, size (e.g., the thickness and outer diameter of the filter paper, etc.), porosity, average pore size, etc. of the carrier.

[0031] More specifically, the present application can be applied to all applications in which foreign particles are collected from a component to be inspected using an air press and inspected or analyzed using a microscope, but the large size of filter paper suitable for the air press is not compatible with the subsequent microscope. On the one hand, the first carrier can be a filter paper with a relatively large outer diameter (e.g., about 100 mm). The larger outer diameter provides a larger surface area, so that the airflow with a very large impact and strength mixed with impurity particles output by the air compressor can continuously and smoothly pass through the filter paper and intercept the impurity particles without blowing the filter paper apart; on the other hand, the second carrier can be a filter paper with a relatively small outer diameter (e.g., about 25 mm or 47 mm). This smaller outer diameter can be placed on a limited-size platform of a microscope device for performing impurity analysis, so that the analysis step can be performed smoothly, solving the problem that the filter paper is too large to be placed on the microscope platform, so that the analysis step cannot be performed smoothly, and solving the problem that the analysis result is not accurate enough due to the loss of some impurity particles (e.g., being blocked and not detected, or even falling off the microscope platform or filter paper) caused by the filter paper being placed on the microscope platform in an inaccurate and uneven manner. For example, the component to be detected can be an air compressor in a fuel cell.

[0032] As described above, the cleanliness test method of the present application is particularly advantageous for the above application of using a pneumatic machine in the impurity collection step and a microscope in the impurity analysis step. In addition to the above advantages, the advantages of this method also lie in its application field standardization or generality, and it can be applied to all types of components to be tested. For example, the components for which cleanliness tests are to be performed can be divided into two categories: those for which the impurity particles can be dispersed in a liquid by directly immersing the component in an aqueous solution; those for which the impurity particles on the component cannot be dispersed in the solution by directly immersing the component in an aqueous solution. For example, direct contact of such components with an aqueous solution will cause them to be scrapped and no longer usable. For the first category of components, as described above, their cleanliness can be detected by directly immersing them in an aqueous solution, and of course this method can also be used, or the cleanliness test can be carried out by omitting the impurity collection step 10 and the carrier dissolution step 20; this method can particularly perform cleanliness tests on all the second category of components to be tested, specifically by collecting the impurity particles on such components on a first carrier in any feasible manner (the above step 10), and then dissolving the first carrier in an aqueous solution (so that all the impurity particles are dispersed in the aqueous solution, the above step 20). Such components can include: air compressors, membrane electrodes, hydrogen supply systems, reactors, entire engines, etc. of fuel cell products in the automotive field; complex integrated circuit boards in the field of electronic products, and other high-value electronic products that are scrapped after being immersed in a solution; gas turbine engines, hydrogen supply and oxygen supply systems, control systems, etc. in the field of aerospace. For these components that cannot be immersed in an aqueous solution, especially those with complex processing and high costs, the invention of this method can avoid waste to the greatest extent.

[0033] Although some preferred embodiments of the present invention have been described in detail, it should be understood that various changes and modifications can be made thereto without departing from the spirit and scope of the appended claims.

Claims

1. A cleanliness test method, comprising: An impurity collection step (10): collecting impurity particles on a component to be detected on a first carrier made of a water-soluble material; A carrier dissolution step (20): when the first carrier together with the impurity particles collected thereon is placed in an aqueous solution, causing the first carrier to completely dissolve and the impurity particles to disperse in the aqueous solution to form a particle solution; An impurity re-collection step (30): collecting the impurity particles in the particle solution with a second carrier; And An impurity analysis step (40): detecting and analyzing the impurity particles on the second carrier.

2. The cleanliness test method according to claim 1, wherein The first carrier is at least one of a filter paper, a filter bag, and a filter element, and the second carrier is a filter paper.

3. The cleanliness test method according to claim 2, wherein, The first carrier has a first outer diameter dimension, and the impurity collection step (10) is performed by a pneumatic press. Preferably, the first outer diameter dimension is between 80 and 120 mm; The second carrier has a second outer diameter dimension smaller than the first outer diameter dimension, and the impurity analysis step (40) is performed using a microscope. Preferably, the second outer diameter dimension is 25 mm or 47 mm.

4. The cleanliness test method according to claim 1, wherein The water-soluble material is one of the following: granulated sugar, calcium alginate wool or fluff, porous gelatin, polyvinylpyrrolidone, polyvinyl alcohol, rice paper.

5. The cleanliness test method according to claim 1, wherein, The impurity collection step (10) is achieved by one of the following: blowing the impurity particles on the component to be detected onto the first carrier using a blowing system; sucking the impurity particles on the component to be detected onto the first carrier using a suction system; wiping the component to be detected with the first carrier.

6. The cleanliness test method according to claim 1, further comprising a preparation step (24) of preparing an aqueous solution in a container before the carrier dissolution step (20), and the mass of the prepared aqueous solution is 50 to 200 times the mass of the first carrier; Preferably, it further comprises a heating step (26) of heating the aqueous solution to between 40 and 80 degrees Celsius.

7. The cleanliness test method according to claim 6, wherein, The container is a beaker, and the impurity dissolution step (20) is carried out on a workbench or in an ultrasonic cleaner.

8. The cleanliness test method according to claim 6, wherein, The aqueous solution is deionized water. Preferably, the deionized water contains an ionic or non-ionic surfactant with a concentration of 0.1% - 1.0%; or The aqueous solution is an alcohol solvent with a concentration of 1% - 10%. Preferably, the alcohol solvent is ethanol or isopropanol.

9. The cleanliness test method according to claim 1, wherein, The method further comprises a carrier transfer step (22) of transferring the first carrier collecting the impurity particles into the aqueous solution using a container with a satisfactory internal cleanliness.

10. The cleanliness test method according to claim 7, wherein, The carrier dissolution step (20) is achieved by standing still, or The carrier dissolution step (20) includes one or more of the following auxiliary measures: mechanically stirring the aqueous solution; maintaining the aqueous solution within a specific temperature range; applying ultrasonic vibration to the beaker.

11. The cleanliness test method according to claim 1, wherein, The impurity re-collection step (30) is achieved by filtering the particle solution with a second carrier in the form of a filter paper.

12. The cleanliness test method according to claim 1, wherein, The impurity analysis step (40) is performed using an optical microscope, a scanning electron microscope, a transmission electron microscope, or an atomic force microscope; and / or detecting or analyzing impurity particles on the second carrier using energy-dispersive X-ray analysis, electron energy loss spectroscopy, or X-ray photoelectron spectroscopy.

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