Sample preparation method for coating thickness detection

Abstract

The invention relates to a sample preparation method for coating thickness detection, which comprises the following steps: circularly heating and cooling a base material to obtain a weakly combined base material with a base material body and a coating locally separated; and forming a cut extending along the thickness direction of the coating in a local separation area of the coating of the weak combination base material to obtain a coating section sample vertical to the surface of the base material. Due to the difference of linear cutting expansion coefficients of a base material body and a coating, alternating thermal stress is initiated at the interface of the base material body and the coating through cyclic heating and cooling processes, so that the base material and the coating are controllably and locally separated, a weakly combined base material is obtained, and a cut extending in the thickness direction is prepared in the surface of the locally separated coating. A coating section sample perpendicular to the surface of the base material can be obtained through simple mechanical separation. The method can be used for efficiently preparing a coating sample with clear section and good integrity at low cost on the premise of not depending on expensive or high-damage equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of material mechanical property testing methods, in particular to a sample preparation method for coating thickness detection. BACKGROUND

[0002] In the fields of cutting tools, molds, semiconductors, aerospace and medical devices, etc., very thin coatings such as physical vapor deposition coatings have been widely used, and the thickness of the coatings has a direct impact on the performance, service life and cost-effectiveness of the coatings. At present, there are many existing technical solutions for the thickness detection of such very thin coatings, but all have certain limitations.

[0003] For example, the X-ray fluorescence method calculates the thickness by measuring the characteristic X-ray intensity of the coating elements, but the measurement error of this method is large, usually between ±5% and 10%, and it needs to rely on standard sample calibration, and the detection sensitivity for light elements such as carbon is low.

[0004] The ball mill method measures the cross-sectional thickness by mechanically grinding a bevel and then using a microscope, which also has the problems of large measurement error and significant manual operation error, and is usually only suitable for rough measurement.

[0005] Although the scanning electron microscope cross-section method has high precision, the sample preparation process is complex, often requiring the use of focused ion beams or precision polishing equipment, and such equipment is expensive and has high investment costs, limiting its widespread application.

[0006] The atomic force microscope step method measures the thickness by scanning the step height between the coating and the substrate with a probe, although it has high precision, but the detection speed is slow, and the equipment is expensive, which is not suitable for the needs of fast and low-cost detection in conventional laboratories.

[0007] Overall, the existing technical solutions have obvious shortcomings in terms of equipment investment, sample preparation complexity, measurement accuracy and operational convenience, etc. SUMMARY

[0008] The embodiments of the present application provide a sample preparation method for coating thickness detection to solve the problem of obvious shortcomings in terms of equipment investment, sample preparation complexity, measurement accuracy and operational convenience, etc. when measuring the thickness of the coating in the related art.

[0009] In a first aspect, a sample preparation method for coating thickness detection is provided, which includes the following steps: The substrate is subjected to a cyclic heating and cooling treatment to obtain a weakly bonded substrate with the substrate body and the coating partially separated; A slit extending in the thickness direction of the coating is formed in the coating partially separated region of the weakly bonded substrate to obtain a coating cross-section sample perpendicular to the surface of the substrate.

[0010] In some embodiments, the cyclically heating and cooling the substrate comprises: heating to a preset high temperature and holding; cooling to a preset low temperature and holding; repeating the heating and cooling steps until the substrate body and the coating layer partially separate.

[0011] In some embodiments, the preset high temperature is higher than a critical temperature caused by the difference in the thermal expansion coefficients of the substrate body and the coating material.

[0012] In some embodiments, the partial separation of the substrate body and the coating layer in the weakly-bonded substrate is characterized by forming cracks, bubbles or warping in the edge region or the central region of the coating layer.

[0013] In some embodiments, the forming of the slit extending along the thickness direction of the coating layer in the partial separation region of the coating layer of the weakly-bonded substrate comprises: forming the slit along the thickness direction of the coating layer with the cracks, bubbles or warping region in the edge region or the central region of the coating layer as a positioning reference.

[0014] In some embodiments, the forming of the slit extending along the thickness direction of the coating layer in the partial separation region of the coating layer of the weakly-bonded substrate further comprises: pasting an adhesive material to the slit and tearing along the slit direction to obtain a coating cross-section sample perpendicular to the substrate surface.

[0015] In some embodiments, the adhesive material is a flexible adhesive material.

[0016] In some embodiments, the coating cross-section sample perpendicular to the substrate surface comprises: a coating cross-section sample pasted to the adhesive material, and / or a coating cross-section sample left on the substrate.

[0017] In some embodiments, the forming of the slit extending along the thickness direction of the coating layer in the partial separation region of the coating layer of the weakly-bonded substrate comprises: using a cutting tool to draw the slit on the coating layer surface.

[0018] In some embodiments, the thickness of the coating layer is 0.01-10 μm.

[0019] The embodiment of the present application provides a sample preparation method for coating thickness detection. Due to the difference between the base material body and the coating in linear expansion coefficient, alternating thermal stress is caused at the interface between the two through a cyclic heating and cooling process. In the heating stage, the material with higher linear expansion coefficient expands faster, thereby generating shear stress; in the cooling stage, the material also shrinks more quickly, thereby generating tensile stress. After multiple thermal cycles, stress is concentrated at the interface defects and induces microcracks, thereby effectively weakening the interface bonding force, enabling the base material and the coating to be locally separated, and obtaining a weakly bonded base material. Subsequently, a slit extending in the thickness direction is prepared on the surface of the locally separated coating, and a coating cross-section sample perpendicular to the surface of the base material can be obtained through simple mechanical separation.

[0020] The present application realizes coating separation at the interface through non-contact thermal stress, and can efficiently and at low cost prepare a coating sample with clear and complete cross-section without relying on expensive or high-damage equipment. The sample can truly reflect the original thickness and structure of the coating, effectively avoids cross-section damage or deformation caused by traditional mechanical methods, provides a reliable basis for subsequent high-precision thickness detection using a scanning electron microscope, an optical microscope and the like, and significantly improves the accuracy and repeatability of measurement. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 The coating interface sample (10000X) prepared by the sample preparation method for coating thickness detection provided by the embodiment of the present application; Figure 2 The coating interface sample (70000X) prepared by the sample preparation method for coating thickness detection provided by the embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] The embodiment of the present application provides a sample preparation method for coating thickness detection, which can solve the problems of obvious deficiencies in equipment investment, sample preparation complexity, measurement accuracy and operation convenience when measuring the coating thickness in the related art.

[0025] A sample preparation method for coating thickness detection comprises the following steps: The base material is subjected to cyclic heating and cooling treatment to obtain a weakly-bonded base material with the base material body and the coating partially separated; A slit extending along the thickness direction of the coating is formed in the coating partially-separated region of the weakly-bonded base material to obtain a coating cross-section sample perpendicular to the surface of the base material.

[0026] The embodiment of the present application provides a sample preparation method for coating thickness detection, which can solve the problems of obvious deficiencies in equipment investment, sample preparation complexity, measurement accuracy and operation convenience when measuring the coating thickness in the related art.

[0027] The present application can efficiently and low-costly prepare a coating sample with clear cross-section and good integrity by realizing coating separation at the interface through non-contact thermal stress without relying on expensive or high-damage equipment. The sample can truly reflect the original thickness and structure of the coating, effectively avoiding the cross-section damage or deformation caused by the traditional mechanical method, providing a reliable foundation for subsequent high-precision thickness detection using a scanning electron microscope, an optical microscope and the like, and significantly improving the accuracy and repeatability of measurement.

[0028] Further, the cyclic heating and cooling treatment of the base material comprises: heating to a preset high temperature and holding; cooling to a preset low temperature and holding; repeating the heating and cooling steps until the base material body and the coating are partially separated.

[0029] Further, the preset high temperature is higher than the critical temperature caused by the difference in thermal expansion coefficients of the base material body and the coating material.

[0030] Specifically, first, the sample is rapidly heated to 300 degrees Celsius at a rate of 10 to 30 degrees Celsius per minute, and kept at this temperature for 30 minutes; then, the sample is rapidly transferred to a low-temperature environment of minus 30 to 50 degrees Celsius, and kept at this temperature for 5 minutes. After each cycle, the surface of the coating is checked for signs of separation, such as peeling, warping, or cracking. If obvious peeling is observed, the cycle is terminated; if no effective separation is observed, the above heating and cooling steps are repeated. Generally, effective separation of the coating can be achieved after at most 3 to 4 cycles.

[0031] When the substrate is subjected to cyclic heating and cooling treatment to achieve local separation of the substrate body and the coating, the preset high temperature is higher than the critical temperature at which the substrate body and the coating material produce effective stress due to the difference in thermal expansion coefficient. When the preset high temperature exceeds the critical value, the difference in thermal expansion coefficient between the substrate body and the coating can be fully amplified - the material with high linear expansion coefficient expands rapidly during heating, and the material with low linear expansion coefficient expands slowly, thereby forming a stable and sufficient shear stress at the interface between the two. At the same time, it is necessary to avoid excessive temperature leading to structural damage of the coating or degradation of the substrate performance, to ensure the authenticity of the coating thickness in subsequent testing is not affected by the sample preparation process.

[0032] Rapid heating to a preset high temperature at a certain rate and holding can reduce uneven heat transfer inside the substrate, avoid coating peeling caused by local overheating, and allow the shear stress at the interface to accumulate fully, so that the stress can accurately act on the micro defects originally existing at the interface, such as bonding gaps and impurity sites, laying a foundation for subsequent stress concentration leading to cracking. After the high-temperature stage is completed, the substrate and the coating are transferred to a preset low-temperature environment and kept at this temperature. Under the low-temperature environment, the material with high linear expansion coefficient shrinks much faster than the material with low linear expansion coefficient. At this time, the interface will produce tensile stress in the opposite direction to the heating stage, which will further increase the stress concentration degree at the defect, promote the gradual expansion of the interface cracks, and ensure that the stress is fully transmitted to avoid stress residues affecting the subsequent cycle effect due to incomplete cooling.

[0033] After that, the above heating and cooling steps are repeated, and after each cycle, the surface coating is checked by naked eye or microscope for peeling or peeling tendency, and usually 3-4 cycles can achieve local separation of the substrate body and the coating. Such cycle number design can not only ensure that the interfacial bonding force is effectively reduced through multiple stress accumulation, ensuring the separation effect, but also avoid excessive cycles that can cause the coating to crack or the substrate to be damaged due to repeated thermal expansion and cold contraction, affecting the integrity of the sample. Through such a cycle of heating and cooling treatment above the critical temperature, without relying on expensive special equipment such as focused ion beam (FIB) and atomic force microscope (AFM), only using a heating furnace such as a muffle furnace that can be equipped in a conventional laboratory, the operation can be completed, which greatly reduces the equipment investment cost of sample preparation. At the same time, the whole process is clear and easy to operate, compared with the complex polishing process of scanning electron microscope (SEM) cross-section method or the tedious process of FIB sample preparation, the time consumption is significantly shortened, and the sample preparation efficiency is improved. More importantly, by controlling the temperature, rate, holding time and cycle number, the original structure and thickness state of the coating are maximized while the separation is achieved, avoiding additional damage to the coating during sample preparation, ensuring that the coating cross-section obtained by hand tearing with adhesive tape can truly reflect the actual thickness of the coating, solving the precision problem of the existing X-ray fluorescence method and ball mill method, and the high cost and low efficiency problem of the FIB and AFM method. Let the general laboratory or detection room prepare high-quality detection samples without expensive equipment, which provides convenience for the development of basic research related to coating thickness detection, and significantly saves experimental funds.

[0034] Further, the substrate is a metal material or a ceramic / graphite material. The present application covers metal materials (such as stainless steel, titanium alloy, nickel alloy, copper alloy, aluminum alloy) and ceramic / graphite materials (such as silicon wafer, tool steel, graphite). The selected substrate has high temperature resistance and will not deform during the cycle heating process, can stably withstand the stress caused by temperature change, ensures the integrity of the substrate structure, avoids the influence of the substrate deformation on the coating interface state, provides a reliable basis for the subsequent operation of forming stress concentration at the coating bonding site by using the difference in linear expansion coefficient between the substrate and the coating to weaken the bonding force, and does not need to be pre-treated for high temperature resistance. Simplify the operation process while ensuring the stability of sample preparation.

[0035] Further, the coating material can be selected from a physical vapor deposition (PVD) coating. The coating is limited to a physical vapor deposition (PVD) coating (such as titanium nitride (TiN), aluminum titanium nitride (AlTiN), tungsten carbide (WC), oxide monolayer or multilayer, etc.). First, the PVD coating has excellent thin film density and uniformity. When the coating is formed by a physical vapor deposition process, the particle deposition process on the substrate surface is controllable, and a very thin coating with uniform thickness distribution and dense structure can be formed. The coating has few internal defects and tight interlayer bonding. In the process of weakening the interfacial bonding force of the substrate and the coating by cyclic heating and cooling in the present application, the coating itself is not easy to crack or delaminate in advance due to loose internal structure, and can maintain the integrity of the coating form, laying a foundation for subsequent clear fracture obtained by hand tearing with adhesive tape, avoiding the situation that the fracture is irregular and cannot accurately reflect the true thickness due to the structure problem of the coating itself. Second, the PVD coating has stable physical and chemical properties, and its high temperature resistance is outstanding. In the process of cyclic heating and cooling, the coating will not melt, oxidize or change its chemical properties, but will only physically expand and contract with temperature changes, forming a difference in linear expansion coefficient with the substrate, and then generating stress concentration at the interface. There is no need to worry about the performance degradation of the coating in the temperature cycle affecting the sample preparation effect. Third, the PVD coating has suitable mechanical strength and brittle balance characteristics. It has high hardness but also has a certain breaking strength. When the substrate and coating interface are cracked by temperature cycling in the present application, the shear force of ordinary conductive adhesive can overcome the breaking strength of the coating, realize the complete peeling and tearing of the coating, and neither crack in the tearing process due to too low coating strength nor be difficult to tear due to too high strength to obtain a cross section.

[0036] Further, the coating thickness is 0.01-10 μm. When the coating thickness is within the range of 0.01-10 μm, the difficulty of sample preparation caused by too thin coating below 0.01 μm can be avoided. The too thin coating is easy to crack due to too low strength after cyclic heating and cooling, and it is difficult to obtain a complete fracture by hand tearing with adhesive tape. The peeling and delamination problem caused by too thick coating above 10 μm can also be avoided. The too thick coating is easy to separate between layers during the interface cracking and peeling process, and cannot truly reflect the overall coating thickness.

[0037] Further, in the weakly bonded substrate, the local separation of the substrate body and the coating is characterized by forming cracks, bubbles or warping in the edge or center region of the coating. Without the help of complex detection equipment, the staff can preliminarily observe whether the coating edge is slightly warped by naked eye, or further confirm whether there are hidden cracks in the center region of the coating, or whether there are bubbles or bumps in the local area by using an ordinary optical microscope, to quickly judge whether the interfacial bonding force has been weakened to the extent that the subsequent hand tearing operation can be performed, avoiding the operation delay caused by the need to rely on professional instrument detection of the interface state in traditional sample preparation, and shortening the sample preparation judgment period.

[0038] Further, in the partial separation area of the weakly bonded coating of the substrate, a slit is formed extending along the thickness direction of the coating, specifically: taking the crack, bubble or lifting area of the edge or center area of the coating as the positioning reference, a slit is made along the thickness direction of the coating.

[0039] The crack or bubble area is a position where the interfacial bonding force has been significantly weakened, and the slit is made based on this reference, which not only makes the positioning operation more accurate and intuitive, but also facilitates direct observation and confirmation by visual or optical microscope, and more importantly, it reduces the external force required for forcibly making a slit on the intact coating. This can effectively avoid problems such as irregular cracks or even damage to the substrate caused by excessive force.

[0040] Through this guided and controllable slit, it can be ensured that during subsequent peeling with adhesive tape, the fracture can extend along a preset path that is basically perpendicular to the surface of the substrate. This is crucial for obtaining a smooth and clear coating cross-section that truly reflects the thickness direction of the coating, improving the success rate of sample preparation and the quality of the cross-section, and laying a reliable foundation for subsequent high-precision thickness measurement by microscope.

[0041] Specifically, for linear cracks, first observe the extension trajectory of the crack by visual or optical microscope, and confirm that the crack has no branches or only a small number of small branches, then keep the blade of the utility knife collinear or parallel to the extension direction of the existing crack.

[0042] For bubble areas, if the bubble is regular circular or elliptical, prefer to plan the slit path along the diameter direction of the bubble, which can cover the center and edge areas of the bubble to the greatest extent, and the interfacial separation degree in the diameter direction of the bubble is more uniform, so that the weak interfacial separation in the center of the bubble and the transition area at the edge can be penetrated simultaneously during the slit; if the bubble shape is irregular or there are local cracking signs at the edge, then choose the most prominent raised part of the bubble edge as the starting point of the slit, where the separation gap between the coating and the substrate is the largest due to the raised part, and the interfacial bonding force is the weakest, so that cutting from this point can quickly penetrate the coating to the substrate surface, while avoiding falling into the hollow area inside the bubble.

[0043] For lifting areas, first determine the extension direction and height of the lifting edge, which usually forms a clear step-like structure, and the slit is cut from the starting end of the lifting edge and extended in the direction towards the intact area of the coating, specifically the distance between the slit and the lifting edge should be controlled within 0.5-1 mm, which not only takes advantage of the weakened interfacial bonding force at the lifting edge to reduce the difficulty of the slit, but also avoids the coating from breaking due to being too close to the lifting edge during the slit.

[0044] Further, after forming the slit extending along the thickness direction of the coating layer in the local separation area of the weakly bonded coating layer, the method further comprises: pasting an adhesive material to the slit and tearing along the slit direction to obtain a coating cross-section sample perpendicular to the substrate surface.

[0045] In the method, after forming the slit extending along the thickness direction of the coating layer in the local separation area of the weakly bonded coating layer, an adhesive material such as a conductive tape is pasted to the slit and torn along the slit direction. The adhesive material can apply a uniform and extensive surface pressure to the coating layer during pasting, ensuring that the coating layer surface is fully and closely contacted, effectively avoiding problems such as coating layer fragmentation, delamination or inclined section caused by uneven stress, thereby successfully obtaining a complete coating cross-section with neat edges, regular shape and substantially perpendicular to the substrate. The cross-section can truly and clearly expose the complete thickness and microstructure of the coating layer from the surface to the interface, minimizing the deformation or damage introduced during sample preparation, and providing a reliable observation sample for subsequent high-precision thickness measurement and morphology analysis by microscope.

[0046] Further, the adhesive material is a flexible adhesive material. The flexible material can closely fit the coating layer surface, even on the micro-uneven places, to ensure uniform distribution of the adhesive force. During the tearing process, the flexibility allows the stress to be concentrated in a relatively moderate and controllable manner at the front of the slit, rather than producing an instantaneous rigid impact, which can effectively guide the crack to expand through the coating thickness, and maximally avoid the risk of accidental fragmentation of the coating layer, secondary cracks or irregular peeling from the substrate caused by excessive stress concentration.

[0047] Further, the coating cross-section sample perpendicular to the substrate surface comprises: a coating cross-section sample pasted to the adhesive material, and / or a coating cross-section sample left on the substrate.

[0048] The method of the present application can obtain two forms of cross-section samples after the tearing step is completed: one adheres to the adhesive material, and the other remains on the original substrate surface. In actual observation, researchers can observe and select the coating fracture for thickness analysis for measurement with a magnifying glass or optical magnifier according to specific equipment conditions and analysis requirements, or can perform comparative analysis on both. This double-sample acquisition mechanism greatly improves the success rate of sample preparation, effectively avoiding the failure of the entire sample preparation process due to accidental damage to a single sample during preparation. The cross-section adhering to the adhesive material can be more convenient for fixing and observing under a specific microscope, while the cross-section remaining on the substrate maintains the original spatial positional relationship. The two samples serve as backups and supplements for each other, not only improving the fault tolerance of the method, but also providing more possibilities for cross-validation of measurement results and ensuring the accuracy and reliability of thickness data, thereby further enhancing the practicality and reliability of the rapid sample preparation method.

[0049] Further, the coating surface partially separated from the weakly bonded substrate forms a slit extending in the thickness direction of the coating, comprising: using a cutting tool to draw a slit on the coating surface.

[0050] On the coating surface that has completed partial weakening, a slit extending in the thickness direction is manually drawn using a cutting tool such as a craft knife, effectively avoiding the problems of irregular fragmentation, inclined cross-section, or excessive peeling area of the coating caused by random crack propagation during the tearing process. By actively guiding the slit drawn by the craft knife, an edge that is neat and a surface that is flat can be artificially drawn.

[0051] Further, it also includes surface cleaning treatment of the substrate before the cyclic heating and cooling treatment.

[0052] By pre-cleaning, the distortion of the thickness measurement value caused by interface impurities and the misreading of the microstructure are fundamentally avoided, ensuring that the cross-section morphology observed under the microscope purely reflects the coating thickness information, thereby ensuring the accuracy and reliability of the final thickness detection data.

[0053] Example 1: A metal bipolar plate with a TiN coating of about 800 nanometers thick deposited on the surface was used as a sample, and the specific sample preparation process was as follows: S1: First, the metal bipolar plate sample was pretreated to ensure that the surface was free of oil stains, dust, and other impurities, and then the sample was placed in a muffle furnace, the muffle furnace heating program was set, heated to 300℃ at a rate of 15℃ per minute, and then immediately transferred to a low-temperature environment of minus 50 degrees Celsius for 5 minutes. S2: The sample treated in S1 step is taken out from the low temperature environment, and after its temperature rises to room temperature, the coating surface is comprehensively inspected. By visual observation, the edge area of the coating is checked for obvious lifting, local cracks or bubbles on the surface, and other signs of interface separation; if no effective separation features are found by visual observation, the sample needs to be heated and cooled again according to the parameters in S1 step until the interface separation features appear on the coating surface, and the temperature cycle is immediately terminated; S3: A sharp art knife is prepared, and the edge lifting, local cracks or bubbles on the coating surface are cut open. When cutting, the art knife is kept perpendicular to the coating surface, and a length of about 5-8 mm and a depth of just penetrating the coating to the substrate surface are cut along the thickness direction of the coating. Then a conductive adhesive with a width matching the length of the cut is taken, and its one side edge is aligned with one end of the cut, and is slowly pasted on the coating surface along the cut direction. During the pasting process, the conductive adhesive is pressed with fingers to remove the bubbles between the adhesive layer and the coating, and to ensure that the two are closely attached. After the conductive adhesive is firmly pasted, the end of the conductive adhesive not pasted is pinched, and the conductive adhesive is torn along the cut direction at a uniform and stable speed, and a sample for coating thickness detection is obtained.

[0054] The application also provides a coating thickness detection method adapted to the above sample preparation method, and the specific operation is as follows: The two types of coating samples prepared according to the foregoing steps are fixed on the microscope stage, and the angle of the substrate is adjusted so that the coating fracture is directly opposite the microscope objective.

[0055] Subsequently, a microscope suitable for observing extremely thin coatings is selected, and the initial magnification can be set to 10000 times to quickly locate the fracture area (as shown in Figure 1 The subsequent step is gradually adjusted to 70000 times to clearly present the coating thickness boundary (as shown in Figure 2 First, the coating fracture remaining on the original substrate surface is observed: the stage is moved to find the area with flat and undeformed fracture, and the thickness values at 3-5 different positions are measured along the direction perpendicular to the substrate surface (i.e. the thickness direction of the coating) by the scale function of the microscope. The measurement results are recorded and the average value is calculated as the basic thickness data of the sample.

[0056] Then, the coating fracture sample attached to the adhesive material is observed with the same microscope parameters, and 3-5 measurement points are also selected in the complete fracture area, and the measurement is completed along the thickness direction of the coating and the data is recorded, and the average thickness of this kind of sample is calculated. Then, the average thickness of the two kinds of samples is compared, if the deviation is within ± 2%, it is determined that the sample preparation and detection result is effective, and the arithmetic mean of the average values of the two kinds of samples is taken as the final coating thickness detection value; if the deviation exceeds ± 2%, it is necessary to recheck whether the fracture of the two kinds of samples is damaged, whether the measurement position is selected improperly, or to select other fracture samples in the same sample preparation process for supplementary measurement until the deviation of the two average values meets the requirements, so as to ensure that the detection result can truly reflect the actual thickness of the TiN coating on the metal bipolar plate surface, and avoid the detection error caused by accidental defects of a single sample. The whole detection process does not need to rely on expensive equipment such as FIB and AFM, and can be completed only through a conventional microscope, and through the cross comparison of the two kinds of samples, the accuracy and reliability of the thickness detection are further improved, which is suitable for the operation scene of ordinary laboratory or detection room.

[0057] In summary, the thin coating thickness detection cross-section sample rapid preparation method provided by the application can solve the problem of preparing high-quality coating cross-section without special and expensive equipment, and the obtained cross-section sample can truly reflect the coating thickness. The test cost is saved, and the widespread development of basic research is facilitated.

[0058] In the description of the present application, it should be noted that the positions or position relationships indicated by the terms "upper", "lower" and the like are based on the positions or position relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0059] It should be noted that, in the present application, the relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0060] The foregoing is merely illustrative of the principles of the application and various modifications can be made by those skilled in the art without departing from the spirit and scope of the application. The above embodiments are illustrative, and not restrictive, of the scope of the application.

Claims

1. A sample preparation method for coating thickness detection, characterized in that, It includes the following steps: The substrate is subjected to cyclic heating and cooling treatment to obtain a weakly bonded substrate in which the substrate body and coating are partially separated. In the partially separated area of ​​the coating on the weakly bonded substrate, a slit extending along the coating thickness direction is formed to obtain a coating cross-section sample perpendicular to the substrate surface.

2. The sample preparation method for coating thickness detection as described in claim 1, characterized in that: The cyclic heating and cooling treatment of the substrate includes: Heat to the preset high temperature and maintain the temperature; Cool to the preset low temperature and maintain the temperature; Repeat the heating and cooling steps until the substrate body and coating partially separate.

3. The sample preparation method for coating thickness detection as described in claim 2, characterized in that: The preset high temperature is a critical temperature higher than the difference in thermal expansion coefficients between the substrate and the coating material.

4. The sample preparation method for coating thickness detection as described in claim 1, characterized in that: In the weakly bonded substrate, the local separation between the substrate body and the coating is characterized by the formation of cracks, blistering, or peeling in the coating edge or central region.

5. The sample preparation method for coating thickness detection as described in claim 1, characterized in that: In the locally separated areas of the coating on the weakly bonded substrate, a slit extending along the coating thickness direction is formed, specifically: Using the cracks, bubbles, or peeling areas at the edge or center of the coating as a positioning reference, make a slit along the coating thickness direction.

6. The sample preparation method for coating thickness detection as described in claim 1, characterized in that: After forming a slit extending along the coating thickness direction in the locally separated region of the coating on the weakly bonded substrate, the process further includes: The adhesive material is applied to the slit and then torn along the slit direction to obtain a coating cross-section sample perpendicular to the substrate surface.

7. The sample preparation method for coating thickness detection as described in claim 6, characterized in that: The adhesive material is a flexible adhesive material.

8. The sample preparation method for coating thickness detection as described in claim 6, characterized in that: The coating cross-section sample perpendicular to the substrate surface includes: A cross-sectional sample of the coating applied to the adhesive material. And / or a cross-sectional sample of the coating remaining on the substrate.

9. The sample preparation method for coating thickness detection as described in claim 1, characterized in that: A slit extending along the coating thickness direction is formed on the coating surface where the weakly bonded substrate has partially separated, including: Use a cutting tool to make slits on the coating surface.

10. The sample preparation method for coating thickness detection as described in claim 1, characterized in that: The coating thickness is 0.01-10 μm.

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