Method for detecting surface of copper foil

Abstract

The invention provides a copper foil surface detection method. The copper foil surface detection method comprises black body grafting operation and surface detection operation. The black body grafting operation comprises the step of grafting a first functional group modified on the surface of a copper foil by using a black body material, so that the black body material is grafted on the first functional group. Wherein the surface of the black body material is modified with a second functional group, and the second functional group can be grafted with the first functional group. The surface detection operation comprises the step of detecting the surface of the copper foil grafted with the black body material by using an infrared thermal imager so as to obtain an infrared thermal image, and the distribution state of the first functional group modified on the surface of the copper foil can be correspondingly displayed by imaging the black body material. Therefore, an effective method is provided for evaluating the modified deposition state (such as uniformity) of the silane coupling agent on the surface of the copper foil in the process of the copper foil substrate.

Description

Technical Field

[0001] This application relates to a detection method, and more particularly to a method for detecting the surface of copper foil. Background Technology

[0002] With the advancement of high-performance and networked electronic products, the trend towards higher signal frequencies has a significant impact on copper foil laminates (CCLs). CCLs are manufactured by heating and pressurizing an insulating resin substrate and copper foil, playing a crucial role in high-frequency, high-speed applications. To reduce signal transmission losses, these applications require substrates with low dielectric constant (Low Dk) and low dielectric loss (Low Df). However, these characteristics also weaken the bonding between the copper foil and the substrate due to a reduction in the number of highly polar molecular functional groups.

[0003] Furthermore, copper foil substrates require low surface roughness for high-frequency applications. Under high-frequency conditions, current tends to accumulate in a thin layer on the conductor surface (i.e., the skin effect); however, the roughness of the copper foil interface significantly impacts signal standing waves and reflections. Therefore, reducing the roughness of the copper foil interface is a crucial measure to mitigate this effect.

[0004] To improve the adhesion between copper foil and insulating resin substrate, silane coupling agents are typically used to modify the surface of the copper foil bonding surface, forming a siloxane cross-linked structure and enhancing chemical bonding. However, there are challenges in using silane coupling agents for modification. For example, silane coupling agents may agglomerate in solvents depending on the compatibility of their functional groups and solvent properties, affecting the uniformity of modification and interfacial adhesion on the copper foil. Furthermore, the degree of hydrolysis of the silane coupling agent also affects its bonding with the copper foil, but currently, there is a lack of effective methods to evaluate the deposition uniformity or amount of silane coupling agent modification on the copper foil surface.

[0005] Therefore, when the parameters of the copper foil modified by the silane coupling agent are different, it is currently impossible to know whether there are differences in the deposition uniformity or deposition amount of the silane coupling agent. It is generally believed that the difference in deposition amount will affect the bonding force between the copper foil and the insulating resin substrate.

[0006] Therefore, the applicant believes that the above-mentioned defects can be improved. So, the applicant has devoted himself to research and applied scientific principles, and finally proposed a design that is reasonable and effectively improves the above-mentioned defects. Summary of the Invention

[0007] The technical problem to be solved by this application is to provide a method for detecting the surface of copper foil, which addresses the shortcomings of the prior art.

[0008] To address the aforementioned technical problems, one technical solution adopted in this application is a method for detecting the surface of a copper foil, comprising: providing a copper foil; wherein a surface of the copper foil is modified with a first modifier to create a first functional group on the surface of the copper foil; performing a blackbody grafting operation, comprising: grafting a blackbody material onto the first functional group on the surface of the copper foil to modify the first functional group, thereby grafting the blackbody material onto the first functional group; wherein the surface of the blackbody material is modified with a second functional group, which can be grafted onto the first functional group; and performing a surface detection operation, comprising: using an infrared thermal imager to detect the surface of the copper foil grafted with the blackbody material to obtain an infrared thermal image; wherein the infrared thermal image, by imaging the blackbody material, correspondingly displays the distribution state of the first functional group modified on the surface of the copper foil.

[0009] Optionally, the first modifier is an aminosilane coupling agent, and the first functional group is an aminosilane functional group derived from the aminosilane coupling agent; wherein, the blackbody material is at least one of carbon black, graphene, and carbon nanotubes; wherein, the second functional group is at least one of a carboxyl group (-COOH group) and a hydroxyl group (-OH group).

[0010] Optionally, the second functional group is a carboxyl group, which can generate an electrostatic interaction with an amino terminus of the first functional group, so that the blackbody material is grafted onto the first functional group on the surface of the copper foil through the second functional group.

[0011] Optionally, the surface of the copper foil has a first emissivity, the blackbody material has a second emissivity, and the second emissivity is greater than the first emissivity.

[0012] Optionally, the first emissivity is not greater than 0.8, the second emissivity is not less than 0.8, and the ratio of the second emissivity to the first emissivity is not less than 2.

[0013] Optionally, the first emissivity is between 0.01 and 0.2, the second emissivity is between 0.8 and 1.0, and the ratio of the second emissivity to the first emissivity is not less than 8.

[0014] Optionally, in the blackbody grafting operation, the copper foil modified with the first functional group is grafted onto the first functional group by immersing it in a dispersion liquid containing the blackbody material modified with the second functional group.

[0015] Optionally, the concentration of the second functional group-modified blackbody material in the dispersion liquid is 0.01 to 0.1 wt%, and the average particle size of the dispersion is 10 nanometers to 200 nanometers.

[0016] Optionally, the copper foil is immersed in the dispersion liquid for 10 to 20 minutes.

[0017] Optionally, the concentration of the second functional group-modified blackbody material in the dispersion liquid is 0.02 to 0.03 wt%, and the average particle size of the dispersion is 10 nanometers to 50 nanometers, and the immersion time of the copper foil in the dispersion liquid is 13 to 17 minutes.

[0018] The beneficial effect of this application is that the copper foil surface detection method provided by this application can achieve the following: "providing a copper foil; wherein a surface of the copper foil is modified with a first modifier to create a first functional group on the surface of the copper foil" and "performing a blackbody grafting operation, including: grafting a blackbody material onto the first functional group on the surface of the copper foil to modify the first functional group, thereby grafting the blackbody material onto the first functional group; wherein the surface modification of the blackbody material creates a second functional group that can interact with the copper foil surface." The technical solutions of "grafting modification of the first functional group" and "performing a surface inspection operation, including: using an infrared thermal imager to inspect the surface of the copper foil grafted with the blackbody material to obtain an infrared thermal image; wherein the infrared thermal image, by imaging the blackbody material, correspondingly displays the distribution state of the first functional group modified on the surface of the copper foil" provide an effective method to evaluate the deposition state (e.g., uniformity) of silane coupling agent on the surface of the copper foil during the copper foil substrate process.

[0019] The other effects and embodiments of this application are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of a copper foil surface inspection method according to an embodiment of this application;

[0022] Figures 2A to 2C These are schematic diagrams of steps S110 to S130 of the copper foil surface detection method according to embodiments of this application;

[0023] Figure 3 This is an experimental photograph of an infrared thermal image of the copper foil surface in one embodiment of this application, obtained by an infrared thermal imager.

[0024] Figure 4 This is an experimental infrared thermal image of the copper foil surface in a comparative example of this application, obtained by an infrared thermal imager. Detailed Implementation

[0025] The following specific embodiments illustrate the implementation of the "Method for Detecting the Surface of Copper Foil" disclosed in this application. Those skilled in the art can understand the advantages and effects of this application from the content disclosed in this specification. This application can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this application. Furthermore, the accompanying drawings in this application are for simple illustrative purposes only and are not depictions based on actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this application in detail, but the disclosed content is not intended to limit the scope of protection of this application.

[0026] It should be understood that although terms such as "first," "second," and "third" may be used in this article to describe various materials or parameters, these materials or parameters should not be limited by these terms. These terms are mainly used to distinguish one material from another, or one parameter from another.

[0027] [Methods for inspecting the surface of copper foil]

[0028] Please see Figure 1 and Figures 2A-2C As shown, this application provides a method for detecting the surface of copper foil, which is applicable to the technical field of copper foil substrate (CCL) preparation in printed circuit boards.

[0029] More specifically, the copper foil surface detection method provided in this application includes steps S110, S120, and S130. It should be noted that the order of the steps and the actual operation method described in this embodiment can be adjusted according to needs and are not limited to those described in this embodiment.

[0030] like Figure 1 and Figure 2AAs shown, step S110 includes: providing a copper foil 1. The surface 11 (e.g., the bonding surface) of the copper foil 1 is modified with a first modifier to create a first functional group FN1 on the surface 11. The copper foil 1 is in the form of a thin sheet.

[0031] In some embodiments of this application, the copper foil 1 may be, for example, an electrolytic copper foil or a rolled copper foil. For instance, the copper foil 1 is an electrolytic copper foil. Furthermore, regarding the thickness range, the thickness of the copper foil 1 may be, for example, between 3 micrometers and 50 micrometers, and optionally between 5 micrometers and 40 micrometers, but this application is not limited to this.

[0032] In the embodiments of this application, the first modifier is an aminosilane coupling agent, and the first functional group FN1 is an aminosilane functional group derived from the aminosilane coupling agent, which has an amino group (-NH2) at its end.

[0033] For example, the aminosilane coupling agent may be, for instance, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (ETAS), but this application is not limited thereto.

[0034] The surface 11 of the copper foil 1 can be modified with the first functional group FN1 (i.e., aminosilane functional group) by immersing it in an aqueous solution containing an aminosilane coupling agent (the concentration of the aminosilane coupling agent is about 0.1 to 10 V / V%). It is worth mentioning that the surface modification of the copper foil can be, for example, a pretreatment for preparing a copper foil laminate (CCL) in a printed circuit board process (e.g., a pretreatment operation performed on the copper foil before laminating it with an insulating resin substrate).

[0035] like Figure 1 and Figure 2B As shown, step S120 includes: performing a blackbody grafting operation, which includes: using a blackbody material 2 to perform a grafting modification reaction on the first functional group FN1 (i.e., aminosilane functional group) on the surface 11 of the copper foil 1, so that the blackbody material 2 is grafted onto the first functional group FN1 (e.g., amino terminus), thereby marking the position of the first functional group FN1 by the blackbody material 2.

[0036] In some embodiments of this application, the blackbody material 2 is at least one of carbon black, graphene, and carbon nanotubes. For example, the blackbody material 2 is a multi-walled carbon nanotube (MWCNT), but it is not limited thereto.

[0037] Furthermore, the surface modification of the blackbody material 2 includes a second functional group FN2. In some embodiments of this application, the second functional group FN2 is at least one of a carboxyl group (-COOH group) and a hydroxyl group (-OH group).

[0038] For example, the second functional group FN2 is a carboxyl group, which can generate an electrostatic interaction with the amino terminus of the first functional group FN1, so that the blackbody material 2 is grafted onto the first functional group FN1 modified on the surface 11 of the copper foil 1 through its second functional group FN2.

[0039] More specifically, when the detection method of this application embodiment is applied to the preparation of copper foil substrate (CCL), the blackbody grafting operation includes taking at least a portion of the sheet material as a test sample from the copper foil 1 with the first functional group FN1 modified on the surface provided by step S110, and using the blackbody material 2 to graft and modify the first functional group FN1 on the surface 11 of the taken test sample copper foil 1, so that the second functional group FN2 (such as carboxyl group) of the blackbody material 2 is grafted with the first functional group FN1.

[0040] In some embodiments of this application, the surface 11 of the copper foil 1 is a polished surface with a first emissivity ε1. The blackbody material 2 has a second emissivity ε2, and the second emissivity ε2 is greater than the first emissivity ε1. Therefore, the modified first functional group FN1 on the surface 11 of the copper foil 1 can achieve high resolution in infrared thermography through target calibration of the blackbody material 2. For example, the first emissivity ε1 is not greater than 0.8 and can be selected from 0.01 to 0.2. The second emissivity ε2 is not less than 0.8 and can be selected from 0.8 to 1.0. Wherein, ε2 / ε1 is not less than 2 and can be selected to be not less than 8, to effectively improve resolution.

[0041] If the modified first functional group FN1 on the surface 11 of the copper foil 1 has not been grafted onto the blackbody material 2, it will have low resolution under infrared thermography and cannot be detected by infrared thermography.

[0042] It should be noted that the first emissivity ε1 and the second emissivity ε2 mentioned above refer to the emissivity (ε) of the material measured by infrared thermometry using an infrared pyrometer within a temperature range of 20°C to 100°C (e.g., 25°C), but this application is not limited to this.

[0043] Furthermore, the copper foil 1 with the first functional group FN1 modified on the surface can be grafted onto the first functional group FN1 by, for example, immersing it in a dispersion liquid containing a carboxyl-modified blackbody material 2 (e.g., carbon nanotubes, concentration of about 0.01 to 0.1 wt%, average particle size of about 10 nanometers to 200 nanometers), so as to facilitate subsequent detection of the copper foil surface by infrared thermography.

[0044] like Figure 1 and Figure 2C As shown, step S130 includes: performing a surface inspection operation, which includes: using an infrared thermal imager (IR imager) to inspect the surface 11 of the copper foil 1 grafted with blackbody material 2 to obtain an infrared thermal image R. The infrared thermal image R, by imaging the blackbody material 2, correspondingly displays the distribution state of the first functional group FN1 (i.e., aminosilane functional group) modified on the surface 11 of the copper foil 1, thereby assisting in evaluating the quality of the silane coupling agent modification, such as the uniformity or concentration of the silane coupling agent modification on the copper foil surface.

[0045] For example, uniformity can be evaluated by assessing the color temperature distribution of an infrared thermal image R.

[0046] Infrared thermal imagers can only detect high emissivity materials (i.e., blackbody material 2), and blackbody material 2 grafted with a second functional group FN2 (such as a carboxyl group) can only interact with the first functional group FN1 (such as an amino functional group) on the surface 11 of copper foil 1, and will not interact with the unmodified copper foil surface.

[0047] In the aminosilane-modified copper foil samples, the blackbody material 2 grafted with the second functional group FN2 could only be deposited on the amino-functionalized surface and emitted bright light in infrared images, while the bare copper foil surface appeared dull. Related experimental photos are shown below. Figure 3 and Figure 4 As shown.

[0048] Figure 3 The image shown is an experimental photograph of the copper foil surface as detected by an infrared thermal imager in one embodiment of this application. In the left region R1, the color temperature falls entirely within the range of 40 to 60°C without significant variation, indicating the presence of uniformly distributed aminosilane functional groups. However, the color temperature of the right region R2 is entirely below 40°C, indicating that it is unmodified and contains no aminosilane functional groups. Furthermore... Figure 4 The images shown are experimental photographs of copper foil surfaces as a proportion of this application, obtained by infrared thermal imaging. The color temperature of most (90%) of the copper foil surfaces is below 40°C, indicating that the copper foil surfaces do not have uniformly distributed aminosilane functional groups.

[0049] In another embodiment of this application, the uniformity assessment method can be, for example, by extracting a predetermined number of color temperature value points within a unit area from an infrared thermal image R, and calculating the average value and standard deviation of these value points. If the average value and standard deviation fall within a certain value range (e.g., not greater than 2, and optionally not greater than 0.5), the uniformity of the silane coupling agent modification on the copper foil surface is assessed as uniform. If the average value and standard deviation exceed the ideal value range, the uniformity of the silane coupling agent modification on the copper foil surface is assessed as non-uniform. For example, if the average value and standard deviation fall within a certain value range, it means that blackbody material is evenly dispersed within the unit area, which corresponds to the silane coupling agent being uniformly modified on the surface of the copper foil.

[0050] However, it should be noted that the above are merely illustrative examples of evaluation methods, and this application is not limited to them.

[0051] In general, the copper foil surface inspection method provided in this application first provides copper foil whose surface has been modified with a silane coupling agent. Before laminating the copper foil with an insulating resin substrate (e.g., CCL lamination), at least a portion of the copper foil is taken out as a test sample. Next, the modified silane coupling agent on the surface of the taken copper foil is grafted onto it using a blackbody material (e.g., carbon black, graphene, or carbon nanotubes). Finally, the surface of the copper foil is inspected using thermal imaging technology to evaluate the quality of the silane coupling agent modification, such as the uniformity of the modification on the copper foil surface. If the evaluation result is uniform, the remaining copper foil material is sent to the subsequent lamination process to be laminated with the insulating resin substrate, thereby ensuring the reliability of subsequent lamination processes (e.g., the bonding between the copper foil and the substrate).

[0052] It is worth noting that the low emissivity of polished copper foil leads to low resolution in infrared thermography (e.g., unclear silane modification). The detection method provided in this application employs a high-emissivity blackbody material grafted onto silane on the copper foil. Targeted calibration is achieved through the specific interaction between the COOH groups on the blackbody material and the NH2 groups on the silane, thereby reducing the detection time to less than ten minutes. The detection method provided in this application is highly feasible, improves the process yield of copper foil substrates (CCL), and helps reduce production costs.

[0053] Furthermore, in order to effectively improve the grafting modification efficiency of the second functional group FN2 (e.g., carboxyl group) of the blackbody material 2 onto the first functional group FN1 (i.e., aminosilane functional group) on the surface 11 of the copper foil 1, and to effectively pinpoint the position of the first functional group FN1 on the surface 11 of the copper foil 1, the embodiments of this application have more optional implementation methods for the preparation method of the blackbody material 2 and the grafting modification conditions for the first functional group FN1, but this application is not limited to the implementation methods exemplified below.

[0054] The preparation method of the blackbody material 2 in this application embodiment includes: adding 0.1 to 0.3 grams, and optionally 0.15 to 0.25 grams, of the blackbody material (such as multi-walled carbon nanotubes, MWCNTs) to a solution formed by mixing sulfuric acid (H2SO4) and nitric acid (HNO3) to form a reaction solution. The volume of sulfuric acid is 14 to 28 ml (optionally 20 to 22 ml), the volume of nitric acid is 5 to 9 ml (optionally 6 to 8 ml), and the volume ratio of sulfuric acid to nitric acid is 2 to 4:1 (optionally 2.5 to 3.5:1).

[0055] The reaction solution is then heated to 60–80°C (optionally 65–75°C) and ultrasonically treated for 2–4 hours (optionally 2.5–3.5 hours), wherein the ultrasonic oscillation frequency may be, for example, between 40–45 kHz.

[0056] Therefore, the blackbody material (i.e., carbon nanotubes) can be modified with carboxyl groups to form carboxyl-modified blackbody materials (e.g., CNT-COOH).

[0057] After the reaction is complete, the solid reactants (i.e., carboxyl-modified blackbody material) in the reaction solution are separated and washed with deionized water until the filtrate becomes neutral (pH ~ 7). The solid reactants are then dried to complete the modification of the blackbody material. The dried carboxyl-modified blackbody material is collected to facilitate subsequent detection operations.

[0058] Next, the dried carboxyl-modified blackbody material can be further dispersed in a solvent to form a dispersion liquid (e.g., CNT-COOH dispersed liquid).

[0059] In one embodiment of this application, the solvent may be liquid water (H2O), which has a more stable dispersion effect on carboxyl-modified blackbody materials compared to organic solvents (such as isopropanol, IPA) (e.g., no solid precipitate or phase separation is generated after three days of storage).

[0060] Regarding concentration, the concentration of the carboxyl-modified blackbody material in a solvent (e.g., liquid water) can be, for example, from 0.01 wt% to 0.1 wt%, and optionally from 0.020 wt% to 0.030 wt%.

[0061] In one preparation method, 38 mg of carboxyl-modified blackbody material can be dispersed in 38 mL of liquid water, but this application is not limited thereto.

[0062] To improve the dispersibility of the carboxyl-modified blackbody material in a solvent, the dispersion liquid can be treated with ultrasound for 1 to 6 hours (optionally 3 to 5 hours), wherein the ultrasonic oscillation frequency can be, for example, between 40 and 45 kHz.

[0063] In terms of particle size, the dispersed particle size of the carboxyl-modified blackbody material in the solvent is 10 nanometers to 200 nanometers, and optionally between 10 nanometers and 50 nanometers, so as to effectively and individually mark the position of each aminosilane functional group on the copper foil surface.

[0064] Then, the copper foil with aminosilane functional groups modified on its surface is immersed in a dispersion liquid containing a carboxyl-modified blackbody material, so that the carboxyl-modified blackbody material can graft and modify the aminosilane functional groups. The immersion time of the copper foil in the dispersion liquid can be 1 to 30 minutes, preferably 10 to 20 minutes, and particularly preferably 13 to 17 minutes.

[0065] After soaking, the copper foil is removed and its surface (e.g., CNT-COOH modified Cu-foil) is dried with an air gun to facilitate subsequent testing.

[0066] It is worth mentioning that if the copper foil surface is modified with aminosilane functional groups, the copper foil soaked in the dispersion liquid will show black areas, but the surface of the copper foil that is not modified with aminosilane functional groups will still show the color of copper foil.

[0067] The above technical solution can effectively improve the grafting modification efficiency of carboxyl-based aminosilane functional groups on the surface of copper foil in blackbody materials, and effectively pinpoint the position of aminosilane functional groups on copper foil.

[0068] [Beneficial Effects of the Examples]

[0069] The beneficial effect of this application is that the copper foil surface detection method provided by this application can achieve the following: "providing a copper foil; wherein a surface of the copper foil is modified by a first modifier to create a first functional group on the surface of the copper foil" and "performing a blackbody grafting operation, including: grafting a blackbody material onto the first functional group on the surface of the copper foil to create a blackbody material grafted onto the first functional group; wherein the surface modification of the blackbody material creates a second functional group that can interact with the first functional group." The technical solution of "grafting modification" and "performing a surface inspection operation, including: using an infrared thermal imager to inspect the surface of the copper foil grafted with the blackbody material to obtain an infrared thermal image; wherein the infrared thermal image, by imaging the blackbody material, correspondingly displays the distribution state of the first functional group modified on the surface of the copper foil", can provide an effective method to evaluate the deposition state (e.g., uniformity of modification distribution) of silane coupling agent on the surface of the copper foil during the copper foil substrate process.

[0070] The embodiments and / or implementation methods described above are merely preferred embodiments and / or implementation methods for implementing the technology of this application, and are not intended to limit the implementation methods of the technology of this application in any way. Any person skilled in the art may make some modifications or alterations to other equivalent embodiments without departing from the scope of the technical means disclosed in this application, but these should still be regarded as the technology or embodiments that are substantially the same as those of this application.

Claims

1. A method for detecting the surface of copper foil, characterized in that, The detection method for the surface of the copper foil includes: A copper foil is provided; wherein a surface of the copper foil is modified with a first modifier to modify the surface of the copper foil to have a first functional group. Performing a blackbody grafting operation includes: grafting a first functional group on the surface of the copper foil with a blackbody material to graft the blackbody material onto the first functional group; wherein the surface modification of the blackbody material includes a second functional group that can be grafted onto the first functional group; and Performing a surface inspection operation includes: using an infrared thermal imager to inspect the surface of the copper foil grafted with the blackbody material to obtain an infrared thermal image; wherein the infrared thermal image, by imaging the blackbody material, correspondingly displays the distribution state of the first functional group modified on the surface of the copper foil.

2. The method for detecting the surface of copper foil according to claim 1, characterized in that, The first modifier is an aminosilane coupling agent, and the first functional group is an aminosilane functional group derived from the aminosilane coupling agent; wherein the blackbody material is at least one of carbon black, graphene, and carbon nanotubes; wherein the second functional group is at least one of carboxyl and hydroxyl groups.

3. The method for detecting the surface of copper foil according to claim 2, characterized in that, The second functional group is a carboxyl group, which can generate an electrostatic interaction with an amino terminus of the first functional group, so that the blackbody material is grafted onto the first functional group on the surface of the copper foil through the second functional group.

4. The method for detecting the surface of copper foil according to claim 1, characterized in that, The surface of the copper foil has a first emissivity, the blackbody material has a second emissivity, and the second emissivity is greater than the first emissivity.

5. The method for detecting the surface of copper foil according to claim 4, characterized in that, The first emissivity is not greater than 0.8, the second emissivity is not less than 0.8, and the ratio of the second emissivity to the first emissivity is not less than 2.

6. The method for detecting the surface of copper foil according to claim 4, characterized in that, The first emissivity is between 0.01 and 0.2, the second emissivity is between 0.8 and 1.0, and the ratio of the second emissivity to the first emissivity is not less than 8.

7. The method for detecting the surface of copper foil according to claim 3, characterized in that, In the blackbody grafting operation, the copper foil modified with the first functional group is grafted onto the first functional group by immersing it in a dispersion liquid containing the blackbody material modified with the second functional group.

8. The method for detecting the surface of copper foil according to claim 7, characterized in that, The concentration of the blackbody material modified by the second functional group in the dispersion liquid is 0.01 to 0.1 wt%, and the average particle size of the dispersion is 10 nanometers to 200 nanometers.

9. The method for detecting the surface of copper foil according to claim 8, characterized in that, The copper foil is immersed in the dispersion liquid for 10 to 20 minutes.

10. The method for detecting the surface of copper foil according to claim 9, characterized in that, The concentration of the blackbody material modified by the second functional group in the dispersion liquid is 0.02 to 0.03 wt%, the average particle size of the dispersion is 10 nanometers to 50 nanometers, and the immersion time of the copper foil in the dispersion liquid is 13 to 17 minutes.

Images